"But seeing they could not See; hearing they could not Hear"
“The views expressed herein are those of the author and do not necessarily represent those of the National Weather Service or affiliate/related organizations. Please consult .gov sites for official information”

"From its chamber comes the whirlwind, and cold from the scattering winds." - Job 37:9.

"The wind blows to the south and turns to the north; round and round it goes, ever returning on its course".

Monday, October 31, 2011

Chance of Elevated Rotating Storm, Coastal Mini-Rain Event Through 2pm

FORECAST helicity of over 450 m2/s2 Advecting Toward East Central Florida late morning through early afternoon

TODAY: Fairly complex situation evolving this morning as expected. For this morning so far, tossing the GFS since it has quick evolution of a surface low, whereas the trends of the short term RUC and the latest NAM hold off on that formation until later.

NOW: Appears a weak warm front just above the surface is stretched from off shore Ft. Myers toward Melbourne. Strong NE wind at Canaveral north of this feature back more toward the east and decreasing further south.

Instability from the Gulf Stream advecting on shore from Ft. Pierce toward MLB and south to Miami, and expect this could work on shore toward the Tip of the Cape by mid-late morning. The RUC and to some degree the NAM shows a variety of surface lows to form from near Miami to offshore Ft. Pierce to offshore the Cape with just above the deck a more concentric and larger area of low pressure forms along the warm front elongated as stated above through late morning all within the base of a 700mb trough. The warm front should be able to get as far west and north as Port St. John and NNE toward the North side of the Cape by noon as a slightly negatively tilted upper level trough moves through the Deep South and crosses the North Half of Florida.  

Increasing Bulk Shear from the surface to 500mb, Helicity of 400-500 m2/s2 (very high), and CAPE of 400-750 (which is weak) combined with continued on shore flow in the "northeast quadrant' of a developing 925-850mb low centered near the NW side of Lake Okeechobee resulting in onshore flow, with winds veering to S to SSW-SW- W aloft and vorticity moving in with the upper level trough could set up a coastal rain event, all combined with the fact that all of the south half of the state will be within the left exit region of a strengthen upper level jet resulting in increasing upper level divergence and increasing lift  could rationalize this rainfall and possibly some elevated rotating storms...but tornadoes do not look likely.

Worst case would be heavy rainfall along coastal Brevard to Vero Beach, but on the other-hand...if the factors all add up just a few miles further to the east and more quickly (per the GFS)...then light to moderate rain will be the rule ...with the better chance of moderate rainfall nearest the coast.

 An urban flood statement was issued earlier for MLB and south, and with sunrise and greater progression/formation of mid level features with the approach of the upper level trough rain chances/amounts could increase especially near the coast where the low level winds meet upper level SW winds. There could be thunder by mid morning where all the ingredients meet and rotation in the mid-levels results in heavy down pours. It would not surprise me if additional flood statements are issued, and maybe a tornado warning..but believe any rotation to reach the ground would occur offshore.

The big questions are 
1. Where will the 925mb low form and equally as important, when?
2. How far north will the 70F degree dew-points get. All models agree the Beach Line zone toward Tampa, the "Magic Dividing Line". Highest helicity will be right along the 70F dew-point line dividing the state in half..again along the "Magic Dividing line".

Easterly winds are resulting in good coastal convergence, so additional rainfall could occur all the way toward JAX near and east of I-95, but instability will be near zero north of Port Canaveral.
Vort maxes are still on the approach in the mid and upper levels with the heavier rain already occurring despite the fact that this energy and colder air aloft has not yet arrived.
Vorticity arriving. Note that it will base out along the northern extent of the 70F dew-point isothern and cross along the Beach Line where the best helicity will be. This will aid in keeping good isentropic lift type precipitation going north of the warm front. Along the east coast, this lift will be enhanced due to the proximity of warmer ocean waters south of the tip of the CAPE combined with weak instability. As I type, Melbourne is reporting 'Heavy Rain".

The other big question is depending on where the mid level and surface features align, how far north will the heaviest coastal rain get? Guidance is indicating any mid-level convection to make it as far north as KSC with better flat out rain further north. It showed a brief lull in the activity early this morning as a ripple in the 700mb flow might be creating the rains currently occurring, but as the main mid-upper level trough approaches, this area lifts further north toward KSC to the beach line and west toward MCO (Orlando) with the best convergence at the beaches over the Barrier Islands of Brevard from 10am-2pm.

FURTHER SOUTH: It appears the rain has ended for South Florida for the time being, perhaps being 'capped' by warm air aloft over running an otherwise more unstable atmosphere. Whether any storms will impact this area later is a bit questionable, dependent on where the surface low develops, or more appropriately the low just above the surface. If it forms offshore, the resultant pseudo-cold frontal trough will form off shore, and this area will already by behind the front, thus...very little more rain. On the other hand, if the warm front turns into a cold front (rather than a front forming along the Gulf Stream), then South Florida could have another round of heavier rain and thunder after 3pm until around 6pm.  South Florida will need to be monitored during the course of the afternoon to see how things evolve for their second shot of rainfall.

IT'S HALLOWEEN, WHEN DOES IT END?: Looks like rainfall will taper off and end with the setting sun everywhere, with some light rain possibly continuing from time to time until 8pm near the coast somewhere from Brevard to Miami contingent upon where the surface low strengthens to the east of the coastline (and back wash moisture wraps around the north side of it)...This day is standing up to its "Trick or Treating" by Mother Nature reputation. A rotating storm passed off shore north of the Port (Canaveral) on this day in 1997.

BEYOND: Briefly, continued NE winds rule the roost with another frontal boundary to cross near Friday but have no impacts but to enhance NE flow once it passes. Coastal showers (sprinkles) possible by Wednesday. There are TWO opportunities setting up for a Nor'easter like set up along the SE U.S> coast in the first 10 days of November which would be mainly an erosion issue, but the details are yet to be ironed out. 

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Sunday, October 30, 2011

Rainfall For Tonight Remains "Up in the Air"

The Great Model Debate - How Far South will the Polar Jet Coming Down from Canada Dig as well as how far  west will it bottom out in the next 18 hours. Areas to consider for substantial rainfall Monday are between the lavender lines and south of the green line (South Florida) for rains on Monday OR both areas under the Green Line (north Florida).

SHORT POST AT NOON: Keeping this post fairly short today after looking at overnight model runs, including the SREF, two version of the FIM, the overnight GFS, the latest NAM, the ECMWF, and the GGEM....taking all of these and comparing to actuals and latest trends at the ground.

One big problem seems to be the record snowfall (of over 30" in the mountains of New England yesterday and overnight. High pressure is strengthening behind the low pressure system that is well out of the picture by now near Nova Scotia, and the snow covered ground left behind is likely creating persist colder temperatures at the ground over a boarder than expected expanse and thus strengthening surface high pressure all the down the eastern seaboard. During the past couple of hours pressures have been rising over the state with brisky ENE-NNE winds continuing. Diurnally, this would occur, but the are occurring more than what would be expected under the circumstances portrayed by yesterday's model runs.

The effect of the strengthening high pressure is that the surface front over the Florida straits is making no northward expansion if not pressing further south. Any rainfall that was to occur by now per some models over South Florida is not happening, or rather is occurring offshore with steering in the mid-levels in this area from the WSW (away from shore). Only low topped showers emanating down wind of the Bahamas will be able to make it to shore in this area and those are not able to materialize due to extensive cloud cover.

LATEST VISIBLE SATELLITE and LDIS REAL TIME SHOWS an inverted mid level trough extending from the Yucatan into the South Central Gulf. This COULD be a big player for the North Half of the state on Monday. Snow can be seen in this image over Pennsylvania, SE NY, and New England likely helping to strengthen the surface high due to cold air at the surface. Yellow arrows show the southern branch jet and new approaching polar jet behind low pressure near Wisconsin seen in the clouds there but not drawn in.

One school of thought is that the inverted trough of low pressure will continue to enhance. Strengthening high pressure over the mid Atlantic into the Southeast States will create a temporary 'block' and allow the jet stream from the poles to drop toward the North Central Gulf and pick this area up and swoop this area across All of North Central from JAX to Port Canaveral, creating rainfall due to isentropic lift. But will the jet phase with the southern branch and allow this to happen, or will they phase and stay further north and never pick up whatever is developing in the central gulf...OR, will they never phase at all?!

The other school of thought is that what is in the GULF has no effect, but rather general lifting of the lower pressure from the old frontal boundary and southward into the Caribbean brings that boundary  further north toward Lake Okeechobee.  This in turn takes all the rainfall to the southern 1/3 of the state, quite the opposite result. 

And finally, another school of thought shows neither to occur, possibly because the surface high pressure building south which would be indicative of the rising surface pressures and a low temperature in Crestview, Florida this morning of 32F, colder than that of where it snowed in White Plains , NY and NYC...would preclude the surface front over the Florida Straits from lifting north significantly as well as from allowing the digging upper level trough coming out of Canada to have a substantial affect with the already very stable low level layer in place across Florida (and dry to boot).

In either case, there is a chance of rain showers almost anywhere tonight through sunset Monday but where any low level boundaries will be in place and how much moisture at the NECESSARY levels of the atmosphere for rain to occur coincident with any vort maxes coming either out of the NW Caribbean (South Florida) or the Gulf (North Florida) remains   big questions.

For these reasons, I'm not actually forecasting any bulls eye's for big rains as of noon on this Sunday, October 30th. Another post will follow toward evening as more morning model runs become available. To state 'a case'.

Especially since by  now big changes in the atmosphere over Florida are not forecast to begin until after 8PM no matter which model is used. In short, the Record Snow Event for the far Northeast States might have had bigger impacts than models figured it would, namely because so much snow fell. This would not be accounted for in even the morning model runs, and might not be fully accounted for until runs become available until the 8pm soundings are made and correlated with the latest trends at the surface during daylight.  ..with the models containing that information not being available until well past midnight. By that time, whatever is going to happen (or not happen) will already have become evident on radar and satellite imagery. 

The only trend verifying so far as of noon is that some better moisture is working north in the lower levels, but in order for any substantially workable moisture to get north of South Florida it has to figuratively 'go around the block, in the back door, then re-enter through the front door' to get further north...a very long a drawn out process..will this process be able to take place before the upper level trough by passes the state altogether? 

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Saturday, October 29, 2011

Continued Cloudy Through Sunset, Possible Thunder Southeast

915AM Surface chart from Melbourne's Local Data Integration System shows a surface low over North Central Brevard County with a temporarily stationary surface front located as shown. This low is gradually stacking up into the mid-levels through 10,000 and will waver near the location of this low until mid-afternoon. Drizzle could occur over East Central from time to time with a better chance of rain shown in green  and thunder in the white area after noon time through  5pm.   The color coding is surface temperatures with the key shown toward the right side.
At 850mb,   the same low with the fronts shown in black at this level also is noted. The green lines indicating plentiful moisture remaining in the low levels. This moistures will slowly erode from the West later today, with clearing from the NW to ESE during the afternoon. Also noted above is that there was a tornado warning issued around 827AM this morning for a small but rotating storm east of Lake Okeechobee which has since moved offshore. So far, it does not look like a re-occurrence of this type of activity will occur over South Florida later today based on the wind fields taking shape. 

The low over East Central Florida should strengthen a bit more as it moves to the east during the early afternoon, abetted by upper level divergence. This divergence should be able to keep the cloud cover in place as well, especially since PWAT continues over 2" over Central and South Florida, and even where it is not that moist, there is ample moisture in the critical area between the LCL, Lifted Condenstation Level, and LFC, Level of Free Convection,  to generate clouds. These have already formed well to the west and north once the sun came up where it was previously clear.

Latest visible satellite image shows the abundant cloud cover. Most of the region from JAX to Gainvesville should start to clear out later this afternoon after peak heating, with the clearing line making it toward Central by Sunset ..but the areas along US1 from Volusia and South toward Lake Okeechobee and South Florida could remain mostly cloudy at least. 

OVERNIGHT: Big rains with thunder occurred over South Florida as two or more vorticity maxes crossed this area and Central. The one over South Florida had warmer dewpoint air and thus more instability to work with, thus the lightning. Further north toward Central, the air was more stable resulting in more of an over running stratiform type rain. Very early this morning another vort max crossed Central and exited near Port Canaveral, producing a second round of moderate to heavy rainfall in tandem with another further south.

TODAY: Mostly cloudy, with some drizzle possible in isolated fashion with more bona fide showers and possible thunder over SE Florida east and south of Lake Okeechobee and into the Everglades as well as over the Keys. The surface and mid-level low will pull off the east and NE later today. ..meanwhile, a strengthening low off the coast of Maryland will 'bomb out', with increasing winds, moisture, and cold air in place resulting in Snow across Eastern PA, SE NY, and New England with temperatures holding in the 30Fs. This low will parallel the NE coast with snows spreading toward Maine tomorrow. While this low is deepening, the surface front further south will be quasi-stationary until that low further north starts to move north and east a bit.

Meanwhile, the front will clear Central Brevard between the hours of 1:30-300pm in earnest, followed by a burst of NNW wind nearly parallel to the coast running down Flagler, Volusia and North Brevard by late afternoon. This surge could induce another shot of brief rain east of US1 in North Brevard toward far Eastern SE Volusia. Meanwhile, South Florida will be have a chance of thunderstorms about that same time. Highs today remaining in the lower 70Fs falling into the mid-upper 60Fs north of Port Canaveral by mid-afternoon. Highs in South Florida could reach the low 80Fs if there are enough cloud breaks. The front should clear Miami by 7pm give or take an hour, with thunder chances over by 6pm. Rain clears this area for the time being until tomorrow.

SUNDAY: Overnight, winds will remain steady and breezy from the NNW gradually veering to the N to NNE. Moisture could remain in place from Southern Brevard and South to Key Large and the Keys, so cloudy skies could remain a problem. There will still be enough moisture in the lower levels, especially as the wind becomes more NE-ENE later in the day for scattered to broken cloud cover further north toward the Magic Dividing line running form Port Canaveral to Orlando to Tampa as well. .with highs possibly only in the upper 60Fs to lower 70Fs, north of the Beach Line but warming toward the upper 70Fs South Florida with lower to mid-70Fs up and down A1A from Volusia and South, but fingers crossed on that one (fearing upper 60Fs). Only chance of rain on Sunday earlier will be over the Keys but as winds become more NE-ENE during the day some sprinkles could re-emerge under the clouds almost anywhere.

SUNDAY OVERNIGHT/MONDAY:  Thinking cap time once again. Not going to touch on the finer details for this time frame since although model guidance is close on the timing of a retrogression back to Peninsular pattern similar to last night, there are some finer details regarding where the best chance of rain will occur. The GFS is showing an area of rain developing near the SE Coast and working north as another low pressure area develops...with the highest rainfall totals over Martin/St. Lucie/toward Indian River Counties..with a newer run now showing  as far north as extreme eastern Brevard to the Port. The GFS handled the events of last night fairly well, whereas both the short term Rapid Update Cycle model and the NAM showed the highest rainfall to occur over a band across Central Florida. Much of this was likely due to the temperature profiles of the atmosphere, with the latter two stressing isentropic lift whereas the GFS was based more upon thermodynamics, which ended up being the better option. So far, the NAM is again showing Central for the highest rainfall on Monday. and the GFS is playing a repeat of last night. I'm not so sure that will be the case just yet, but chances probably will favor the GFS solution if for no other reason than how well this model has done the past few months over Florida vs. the NAM which I refused to acknowledge once it proved to have a bad track record by Mid-July .  This model did quite well last winter so I keep going back to it to see when it might start to strike gold again.

It did well with all the other features such as wind fields and temperatures, it is the placement of precipitation that has been the bust. It was surprising to the see the short term RUC bust as well, so can't knock it all that had something going, but it never happened in reality.

OTHERWISE: In either case, rain chances increase from south to north over night Sunday, with the bulk of the rainfall on Monday in either case to occur along and South of I-4. Both models now intersect though that the east coast from North Brevard to Miami will have rain in some form or another. Thunder could again come into play (elevated), but low level instability will likely be lacking every where other than in Dade County due to continued cloud cover. This instability would be advected into Dade and perhaps Broward by the closer proximity of the warmer Gulf Stream waters around South Florida. On the other hand, the NAM believes it will be the colder air aloft over Central mixing in the mid-levels along a mid-level boundary that will cause the rains over Central.

BEYOND: Either way, Monday's rain will be a daytime event, ending shortly before dark or toward mid-evening. On shore winds from the NNE-NE following almost immediate with no big cool down except over North Florida. Lows along the East Coast in the mid 60Fs, but upper 60Fs toward Central Brevard and 70Fs further South neat the Coast.  Continued breezy onshore winds gradually veering to ENE through Wednesday into Thursday and 'deceasing'  by Friday with a chance of coastal sprinkles almost anytime after sunrise Wednesday through Friday as temperatures slowly warm, with 70Fs prevalent along the east coast round the 24 hour clock, with lower 80Fs inland and west.  

Rain chances decrease and temperatures warm toward next weekend...
with possible big changes in store, especially toward the Texas Gulf Coast/Eastern Texas/and parts of the Deep South heading into the second week in November. Indicators are pointing toward a potential severe weather event in the next 7-10 days.. 

No big cool downs are shown by the latest GFS way out in dreamland time zone, but that could change. So far, it is showing nothing but warmer air for the Southern 2/3rds of the state heading toward mid-November.   

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Friday, October 28, 2011

Continued Cloudy With Rain Chance Today/Tonight

Image shows Depression Rina near the NE Tip of the Yucatan, which looks less than a depression this hour. The heavier rain and some thunder is well to the NNE of what was Rita. It looks more like that is what is left of the upper portions of Rita is this activity further north with only a surface circulation left behind further south. More on Rita below.
Otherwise, cold front is moving through the NW Gulf of Mexico. Area of inverted low pressure in the Central Gulf ahead of the front where sea surface temperatures are warmest with a tiny circulation on the north end well south of Mobile, AL.

TODAY: Considerable cloudiness across the peninsula especially all central portions, less so South Florida. The upper level portion of Rita has detached (or de-coupled) from the surface circulation and based on some of the 'other' tracking models, will cross Central or South Central tonight if it gets that far. Area of convection in the Gulf is occurring over the warmest Gulf waters in an area of better low level convergence..with Deep Layer Mean winds aloft steering the cloud tops across the Florida Peninsula into an area of upper level divergence. This activity has been slowly crawly  north and eastward, but not sure how long this will last before reaching land..but I suspect it will cease tonight. Otherwise, temperatures are in the mid-80Fs over South FLorida with mainly mid-upper 70Fs elsewhere.

Taking the optimistic 'less rain' slant today based on trends and disregarding all of the models as far as rain fields goes. Overall, South Florida is the most unstable from near Port Charolette to West Palm and South for storms. However, lapse rates in this area are horrible (some warmer air aloft) as well as a dry mid-layer region per the MIA sounding with no apparent triggers to set storms off. If that aspect of the atmosphere down in this region changes, thunder could easily occur. BUT, high clouds from the Gulf could stabilize the atmosphere here, so my line of thinking is that although thunder is possible here, it might not occur. Latest Meso analysis on the SPC website definitely would give cause to reason at least the chance though if it is correct.  

Rina is the lavender "L". Note the convergence is all to the north of the circulation shown by those light blue lines. This is where storms have been going up. All the divergence is over Florida though..perfect ingredients over the state for cirrus clouds. Rina has nothing going for it now, and would expect it will be close to gone by tonight unless it races toward the SSE, but even so, it still has a loft of upper level shear to contend with, so not expecting a rebirth.

Elsewhere, convective inhibition and a stable environment will yield mainly only elevated light rain fall in patches.  Note the area of low pressure in the Gulf. This will be forced eastward and become involved with the actual cold frontal boundary tonight which will press  across the Panhandle and into Central Florida by late morning on Saturday. Thus, at least a chance of rain remains across Central where the most northern extent of the deeper moisture managed to advect.  Best chance of rain between 6pm toinght through noon Saturday seems to be in the area in Green shown in the first  image (although, it might need to another 50 miles further north on the north side),  rain eneding from north to south from sunrise to noon,  reaching South Central portions solely by early afternoon. Rainfall tapering off the further south the front goes after 4pm, with the actual front clearing South Florida shortly after sunset Saturday.

Behind the front, temperatures will be in the mid-upper 60Fs for lows (cooler west of I-95), with highs in the 70Fs. Might not be much clearing over South Florida on Sunday, with a much better chance from Brevard County and north, although some strato cumulus clouds could advect in along the coast accompanied by some alto-cumulus along with breezy N-NNE winds by Sunday afternoon.

Sunday night, the next system in the gravy train of impulses will bottom out well north of the state, with the Southern Branch jet still across Central Florida. Net result will be to buckle north the low level flow bringing a return to moisture as far north as a line running from North Volusia toward Brooksville, with the deeper moisture running South of I-4 in Volusia to the north side of Orlando and toward North Tampa Bay.

It appears the best chance of rain with this moisture surge will be along a line running along the Beach line, through Orlando and on  to Tampa Bay because by this time upper level temperatures will have cooled with passage of the earlier cold front (the upper level heights will have lowered), yet surface temperatures will remain relatively warm. Moderate mid-level lift could induce some moderate rainfall here with some rumbles once the moisture works north and under the cooler air aloft toward sunset Sunday night through mid-afternoon Monday. Another impulse to the north will push this region southward but rain chances should decrease toward Lake Okeechobee due to continued warmer air aloft in this area.

BEYOND: N-NNE winds and breezy Monday becoming more NE-ENE Tuesday into Wednesday. Cooler inland temperatures in the 50Fs, but closer to the mid-upper 60Fs closer to the coast. Afternoon highs in the 70Fs possibly warming to the lower 80Fs late week. Mostly clear mornings with near shore stratocumulus clouds advecting into the coast at times, most likely by Wednesday morning through Thursday night. Perhaps a coastal sprinkle toward Thursday.

NEXT FRONT appears on the backdoor near next Friday. With the wind shift ahead of that boundary rain chances end as the front goes through dry..maybe yet another front after this one as well two days later, which goes through 'dry' as well. No big temperature departures with these fronts, as the Southern Branch jet which will merge with the northern branch at times..both remaining over far North Florida and Georgia.  Continued re-enforcing cold shots though in the NE states with some snows tomorrow then followed by cold rain later in the week, followed by more cold. Looks very negative NAO (North Atlantic Oscillation), being counter-acted by strong La Nina.        

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Thursday, October 27, 2011

Questions Regarding Second Half of Weekend's Wet Weather Chance

Latest satellite imagery shows weakened Hurricane Rita near the Yucatan. Yellow shows the moisture field in the Caribbean expanding north today. Ridge axis across Central Florida and cold front as shown from Virginia to South Central Texas. Note all the clouds (moisture) behind the front.

Very good weather forecast model agreement this morning with the evolution of events through Mid-Day Saturday. It is from there that the NAM/ECMWF vs. GFS differ in one (going on two) significant aspects which could greatly affect the umbrella requirement of the forecast from Central Floridians late Saturday and much of Sunday. For South Florida, there really is no impact (keep an umbrella handy for starters as it looks now). The overall differentiation between these models being the amount of moisture behind the surface cold front and how far south the front actually gets.  The other key aspect is how the GFS treats what is left of Rita in the Western Gulf. 

The GFS refuses to give up on the ship on the storm, and as such, the low pressure field surrounding the storm does not expand as deeply northward into the Central Gulf of Mexico but remains more compact Toward South Florida and the Caribbean. This in turn permits a clean frontal passage by mid-afternoon across Central.

On the other hand the NAM/ECMWF opens up the pressure field more which results in a discrepancy on how well the actua surface boundary through the bottom 3000 ft of the atmosphere can work down the peninsula on Saturday. The GFS takes the boundary clear through past the tip of the state, whereas the NAM hangs it up across Central for 18 hours, and continues to hang up the trough across South Central in the mid-levels even after passage of the front.

Otherwise, they are in close agreement. This disparity mainly only affects residents along Coastal Brevard/Indian River/St. Lucie and perhaps Martin in terms of whether it will rain late Saturday through Sunday. If the GFS is correct, no rain in those locations...on the other hand...say no more. 

MORNING Rapid Update Cycle (RUC) Model shows the Jet Stream. The southern branch jet is lifting north for the first time in over two weeks, in fact, it hasn't been this far north for I can't remember when by tonight. The northern branch is strongly across the NE States. Another slug of high wind speeds aloft await in Canada and are not shown. The upper level trough is shown across Texas. This configuration will slow down the southern end of the front from digging into the Gulf into Friday.

AREAS TO WATCH for what might directly or indirectly instigate rainfall through Saturday and possibly into Monday for parts of Central and South . Satellite derived imagery is showing the vorticity (wind energy in simplest terms) across the SW Gulf. The GFS did not pick this up very well. There is another area over the Bahamas that should eventually work north tomorrow once the ridge across Central Florida moves out to sea and drops further south. The ECMWF and FIM were really latching on to not only this vorticity, but also that associated with the frontal boundary last night. Note the big red area over SW Texas.
Some of this energy is expected to cross North and North Central on Saturday. ..and possibly again on Monday or maybe even Sunday (South Florida). But don't forget about that area over the Bahamas, with more entering the Eastern Caribbean  and working west to the Central Caribbean.

TODAY: Sunny to partly cloudy with more clouds over South Florida as deeper atmospheric moisture builds north. The deeper (but not ultimately the most moist air) will reach the Beachline corridor to Tampa by Sunset or sooner and stall there for the overnight, gradually working toward I-4 and perhaps I-10 by later Friday.  Best chance of rain today from West Palm and South, mainly showers but perhaps thunder over the Everglades to extreme SW Florida. Highs in the low 80Fs with pockets of mid 80Fs. Light wind.

FRIDAY: Showers remain over the South as frontal boundary approaches. Remember most of the moisture with the front is located behind it as shown in the first image (satellite), but moisture will have worked well far north from the Tropics as well by this time late Friday into Saturday. Rainfall limited by lack of dynamics as mid level ridge hangs on. Light wind.

OVERNIGHT FRIDAY/SATURDAY: Frontal boundary works down the state, possibly getting south of Dead Central by early -mid afternoon Saturday, Good chance of rain and possibly some isolated elevated thunder both ahead of the front and immediately behind it. Rain ending north Florida by noon. Chances of elevated thunder near the east coast. No severe weather expected as of yet but not quite 100% guaranteed. 

BEYOND: Stopping here for the forecast, but a discussion concerning 'why' seems warranted.

GFS MODEL: Front clears the state by late Saturday with strong NNE-NE winds beyind the boundary along the east coast. Winds 22G32 by Sunday morning throughout the day NE-East Central Florida, but dry Saturday night through the first half of Sunday north of Ft. Pierce.

NAM/EURO: Front gets hung up across Central  with rain chances AND wind near the coast. Likely induced by instability over the Gulf Stream waters and strong surface winds blowing across the low level instability. Front gets to far South Florida with the mid-level trough hanging up near Lake Okeechobee leaving Central (mainly SOUTH of Route 50) in a deformation zone. Showers right at the coast die off after reaching the coast (beyond I-95). Winds will be blowing down the east coast from off the coast of New England after frontal passage. This should allow ocean temperatures to cool to the north side of the Cape, but should be blocked from cooling on the south side of the CAPE this go around. If so, the NAM might have something going for it for rain chances from Port Canaveral and South along the Coast on Sunday...but such fine details at this point? Not so sure about that. I've noticed that The Weather Channel seems to be favoring the NAM/ECMWF solution of continued wet. Thinking that the more conservative and better bet for now is to run with the GFS.

Both models then bring another surge of moisture northward  from across the South Half of the state on Monday as the boundary buckles  with more rain chances mainly along and south of Route 46 toward Southern Volusia. Strong or breezy ENE winds Continue..perhaps veering to the ESE on Monday and weakening. Low pressure forms off East Central (somewhere) in the Atlantic downwind of the Gulf Stream and dragging the front back south and through the state Monday night.

BEYOND MONDAY: Will run with the majority that rain chances will end Monday night, although the FIM Experimental suggests a quick return to windy sprinkles along the East Coast by Tuesday. The GFS hedges more toward Wednesday and Beyond for this to occur.

TEMPERATURES: No cold air is expected. With N-NE  winds blowing across the Ocean South of the Cape with the coolest air in the 50Fs (at least) limited to NW Florida south toward Gainesville and the interior toward West Central north of Tampa. Highs and lows in the 70Fs, with 60Fs inland.

IN short, the big question is rainfall chances late Saturday through the first half of Sunday East Central. The other question is how quickly rain shower chances (likely only trace amounts) re-emerge early to mid week next week.

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Wednesday, October 26, 2011

Chances of Rain Increase This Weekend

HURRICANE RINA: Rina is in the center of this image. Note that one any northward track it will encounter more and more shear . Additionally, it will begin to interact with land on a continue Westward course of any fashion, and likely begin to entrain the dry air shown in orange over the Yucatan. The storm is best off it were to stay but, it is moving away from the best Ocean Heat Content waters, so expect it to be downgraded today.

TODAY: High pressure has built rapidly eastward since yesterday over the Deep South and into the Atlantic. It is also sinking southward a bit as well as anticipated. Early morning inverted coastal trough set up with the deeper easterly winds, with lows at the coast in the mid-70Fs where as inland temperatures were in the lower to mid 60Fs in north winds on the front side of the inverted trough. With daybreak, the inverted trough washed out and winds subsided as the north half of the state is more entrenched within the high pressure rather than being in gradient flow with low pressure over the Caribbean.  

There is an impressive inversion at all the locations resulting in broad but flat topped stratocumulus clouds resulting in some sprinkles, but heating of the day in an other wise cloud free sky is eroding those away. It appears per satellite imagery that small cumulus clouds are replacing these clouds in many locations. Guidance up until this morning indicated that some showers could occur near coastal Brevard after dark and north into Volusia which looks 'possible', but other wise another mild night in store.

THURSDAY: Much warmer all areas with highs in the low-mid 80Fs and a more southerly surface flow while high pressure persists across the state in the Mid-Levels. Deeper atmospheric moisture from far South Florida should work as far as Dead Central by sunset, but very poor lapse rates seems to inhibit a broad coverage of showers/storms despite ample moisture. Looks more like clouds once again over showers until later in the day working from Southern Portions toward Central Thursday night into Friday.

FRIDAY-SATURDAY Frontal boundary that has emerged from the Rockies is really dragging its "Southern End Heals" as the ridge that has moved into the Atlantic continuously rebuilds back toward the west across Florida and the Gulf. The front gets stretched thin buat manages to slide into North Florida and slowly south to Central where it remains until late Saturday. Best chance of rain for the peninsula on this day, but any Thunder appears to be restricted to far south Florida where low level winds converge more and instability will be the greatest. For good precautionary measure, could through in thunder as far north as Southern Osceola over toward Vero. Otherwise, heading into Saturday it appears the best chance of rain will be on and behind the front due to isentropic lift over Central, with the boundary and moisture from South Florida working South Through the day.

SUNDAY: Boundary appears will get to the frontal graveyard close the Florida Straits, but a secondary (and stronger system and associated jet stream streak now near the Aleutians (Bay of Alaska) will be dropping into the NW U.S. In response, the front buckles and lifts back north toward Dead Central to just south of I-4 by Monday increasing rain chances once again.

HERE is where the first predicament (of several) comes. The 00z ECMWF (European Model) has the developing low (cyclogenesis) from this newer impulse to occur over the Northern Gulf of Mexico south of Pensacola, whereas the 12Z (8am EDT) GFS run reads, "No Dice, the low will from in the Ohio Valley". Big difference as far as Florida is concerned in terms of any potential 'active weather' vs. the continued " status quo benign" pattern over the state per the past week.  For now, I'm hedging more toward the GFS trend since it also is no longer bringing Rita into the state (amongst other reasons such as continuity from the past 8 days, this model's trends in the past 96 hours, and La Nina climatology).  How strong/deep this secondary trough will eventually get is another matter, so Monday has two strikes against it now in regard to how well the weather for this time frame can be predicted.

BEYOND: Latest GFS is running with a very La Nina like pattern with perhaps a bit of a NAO (Negative Atlantic Oscillation) along the  NE U.S. Coast, so this region will be host to a variety of forecast conundrums all their own through the weekend and into next week if the NAO does appear to be developing. Locally, whatever comes out of the next few days and early next week, it appears that the October climatology that I'm most familiar with along coastal East Florida of NNE-ENE winds will prevail other than in the presence of a frontal boundary. This means that cooler ocean temperatures will be drawn down the seaboard, with near shore waters already in the lower 70Fs.  This helps set the stage for inverted coastal troughs with a more direct easterly flow that is at least 8,000 ft deep and not too strong. Thus, coastal cloudiness from time to time and perhaps some very light rainfall with round the clock 70Fs heading to later next week.

HURRICANE RITA: As of noon when I started writing this post, Rita was in a good position to hold its own strength, but was moving toward water of less Heat Energy as well as getting closer to land. Thus, believe the storm will start to weaken. If it weakens too much, it could get steered into the NE Yucatan and be 'gone', at least for a while. It is a very small storm, so it could weaken quickly. Any distance further from the coast could keep Rita alive and well though. Rita is also heading toward drier air to  its north and could start to entrain some of that drier air. Shear lurks just to the storms north as well, and the further north it progresses the stronger it gets. The GFDL run is now the only model taking it to Florida. With plenty of time to spare, and with the chance of Rita being nothing more than a tropical storm if that were to occur..this should not be a 'major' issue, but is worth watching just in case. 

IN SUMMARY: Much of what the weather will be like Friday through at Least Tuesday remains a difficult reading to make...the Crystal Ball remains foggy. Perhaps it's time to resort to a Snow Globe to shake things up a bit, but the Southern Branch Jet  across the Southern Gulf and Florida is not budging, which has been the biggest thorn in the 'forecast' side. Most of the active weather should be under and south of this feature, which means better rain chances for the Keys from time to time in the next few days. So far, the Friday/Saturday/and Sunday look to be the best days for chances of rain..but decreasing from north to south during this time frame.

*** Per The Weather Channel, Rina had been downgraded as I was getting ready to hit the "send" button.

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Tuesday, October 25, 2011

Whether Which Witches Weather Wrist Watch is W-right?

IMAGE (11AM/TUESDAY): Old frontal boundary that provided the big cool down over Florida finally moving out into the Atlantic on its north end while the southern end lags well behind into the Caribbean. Storm system taking shape over the Rockies to move east today in the Plains with return, low level easterly upslope flow under cold, SW Flow aloft creating snow in portions of Colorado. High pressure building rapidly east northeast from Texas and into the mid-Atlantic at all levels today with return clockwise flow in the mid-levels eventually out of the east over Florida  but emanating (per streamline analysis) off Virginia by this evening, whereas longer fetch low level  flow across Florida will become more easterly across the state toward sunset and beyond. This shallow moisture return will  make for mostly sunny skies today with onshore moving stratocumulus clouds.  Hurricane Rina in the SW Caribbean moving little if at all last hour in a favorable area for strengthening, as long as it stays there. An eye was clearly visible last hour but then was obscured by the CDO (central dense overcast).  Ocean Heat Energy (the depth of warm water) is totally ample for the storm to sustain itself in this area of near zero wind shear, low level convergence, and upper level divergence.

TODAY: NE-ENE winds of 12-22mph this afternoon with a high  of 80-84F. Winds later today become more easterly and decrease a bit. Outflow cirrus clouds in the upper levels from Rina are being caught up in the Subtropical jet which has been in place 'for ages' across South Florida are  being advected to that area as a result. This should continue over this area through the day, but could come to an end tonight as a portion of the jet pulls away briefly from the state as the next trough/system approaches the Southern Plains. Overnight lows at the beaches tonight in the low 70Fs, and a good 5-10 degrees cooler further inland.

WEDNESDAY: Deeper on shore flow uniformly easterly could set up a coastal inverted trough, with moisture convergence along the coast for possible showers as soon as pre-dawn and through the day once moisture wraps from behind that frontal boundary well out in the Atlantic and manages to be advected westward around/ahead of the clockwise circulation of High Pressure building eastward into the Carolinas/Virginia and eventually centered offshore tomorrow.  Split flow over the Gulf from the departing Southern Branch tropics and the approaching Polar System (jet) in the Plains over the Gulf could induce formation of a mid-level trough into Thursday from the Central Gulf and across the Peninsula by nightfall. Once this happens, if it does, that would cut off the moisture feed by disrupting the deep easterly flow and end the chance of rain, but could  ALSO act as an elevated warm front from the tropics going into Friday (whole new story for a later time).

BEYOND: No point in going further at this point. There's as many model variations as there is hours in the 24 hour day going into Thursday through early next week. But a general observation of strictly personal note is that models are having an importunate time deciphering whatever the inevitable will be because we have 'officially' entered fall.  The general rule of thumb is that it takes one month from the time the sun is at whatever position it is at for the atmosphere to respond in the mid-latitudes through a DEEP layer of the atmosphere. The sun crossed the equator on Sept 22nd (astronomical fall). It is now just over one month later and now we have snow in the Rockies and a hurricane in the Caribbean. The mid-latitudes through a deep column are responding in earnest (granted, it has snowed already in the Rockes), while the lower latitudes are in the 80Fs with a hurricane.

The  problem the models are having is which pattern will be more dominant: 1) A polar jet stream and progressive pattern over all of the U.S.; or a 2) more progressive northerly jet stream pattern combined with a retrograding pattern in the low latitudes? Actually, both seem to be happening this morning ..and as a result the final outcome per each model varies vastly depending on which each side of the coin each one favors. To site a few examples relevant only to overnight and some early morning model runs. Or better put, these scenarios will change by later today:

GFS/FIM favored for Rina to work toward the Yucatan, getting sheared in the process, and passing toward the lower and middle Keys as a Tropical Storm going Depression. The GFS then weakens the storm further and drops it back south, whereas the FIM takes the storm toward Miami and up the east coast (after confronting high pressure in the SW Atlantic) toward Ft. Pierce then rapidly out to sea as the frontal boundary by that time is across Central Florida. Such a scenario could spell out the strongest winds across the Keys and then East Central due to pressure gradient winds in that area.

The other option is for the storm to never make it out of the Caribbean since that is where the most favorable environment for it will remain, with more shearing winds  on the approach in 48 hours to its north beyond the strong shear already in place. In fact, the latest NAM is now changing the focus of attention from Rina to Central Florida with another weak low to form along the inverted trough from the central Gulf to Central noted above. It takes this weak circulation to Central on Friday with very high PWAT air and a chance of thunder, whereas Rina is left almost in the some location it currently is placed, but closer to the Yucatan and being weakened due to its proximity to land.  

In all cases, the other thing to consider as far as detectable weather impacts is, "How far South will the front now passing through the Rockies and Plains actually proceed across Florida?". Model consensus seems to be leaning toward the actual front never clearing Central and South Florida, but rather merging with the area of low pressure Rina is within, while the actual front proceeds off to the east across the NE States. This is what is occurring now with the front out in the Atlantic and seems feasible.
Do note these forecast tracks:

IMAGE shows that the single level statistical models take Rina to Central Florida whereas the dynamical models and consensus/Ensembles leave it much further south or getting just so far north and shearing out/dying as impacts far South Florida.

It may be that those more northern tracks toward Central are actually from these models sensing development of a completely different low as advertised by the latest NAM run at 12z (8AM EDT), and to some degree the overnight ECMWF.

The  pink/red tracks across the Keys closely resemble the FIM/GFS tracks.  We also have Invest 97L not shown in the above graphic, well off toward the East Southeast of Rina. This system looks like its moving at the speed of light toward the West compared to Rina, and eventually will start to interact with the storm. Will it force Rina toward the east coast of the Yucatan or push it more toward the north? Will 97L even hold together? 

CONSEQUENTLY: A plethora of scenarios is coming into play varying from a tropical storm or depression to cross the Keys toward SE Florida to a possible severe thunderstorm threat across Central in the Friday/Saturday time frame depending on one's model preference as of early today. Too many factors are at play in the interim before late week to even supposition a confident gander. 

So far, the only thing coming to light appears to be that no cold air is on the way for Florida. The other flailing to consider is the old pre-conceived notion from the GFS of a 5-7 duration of onshore flow and coastal showers for the East Coast that has come and gone and then re-appeared since last week in its extended. In short, the forecast for late Thursday on Through Halloween weekend and into the beginning of next week is all as well as  perplexing, befuddling, and of course....frighteningly bewitching. 

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Monday, October 24, 2011

Mostly Benign Fall Like Weather To Continue Through Wednesday


Been a few days since I've posted, as the forecast at that time has remained on track. ..although it has been entertaining to watch each and every model flip flop and disagree between and within themselves in even only the mid-range for a number of days concerning how this week will unfold. The long range has been a comedy, and this will likely continue during the change of seasons.  After tiring of watching the flip flops from one extreme to another, decided to post and run with La Nina climatology even though the presentation for today's post could certainly change, will run with the following for the short term with post- and re- flection  on past and future trends:

TODAY: Mid Level trough that was in place since our last cold front never cleared the state. That much was correct. A short wave trough that produced severe weather in Oklahoma over the weekend progressed east yesterday and dropped a portion into the mid-level trough over Florida that was already in place overnight completely moisture starved. Although mostly transparent, it did bring the dewpoints up a bit and reflected at the surface with a NW -WNW wind which should continue today toward sunset.  The old frontal boundary that was east of the state backed a bit on the southern end toward far SE Florida, whereas the more northern portion has moved on out into the Atlantic. Weak low pressure formed off the SE coast bringing some showers there yesterday, but that too should kick out by afternoon. At time, only clouds are over this area with showers mostly offshore. The clouds could remain a problem for most of the day until the 850mb trough moves out tonight. Otherwise, some high cirrus clouds thinly dispersed could pass over head Central and South Florida today with highs in the mid-70Fs, a bit warmer South Florida, although if the clouds remain near the SE Coast it's debatable.

Latest water vapor image shows the annotated dry air in orange, mid and upper level troughs, and minimal Tropical Storm Rina well to the south. Believe the NW motion at 6mph this morning is due to the passage of the first trough pulling it north. Once that trough moves further east tonight the northward motion should cease. In fact, per loops, it looks like it already has although the latest NHC does not state that to be so.

TONIGHT: Winds become more northerly to NNE overnight as the mid-level troughs finally start to move east of the state and high pressure builds across the Deep South in their wake. Coastal lows might occur within the first two hours of sunset, then level off toward the lower 70Fs if not rise after 3AM as winds blow across sea surface temperatures in the upper 70Fs...inland lows a good 8-12 degrees cooler from US1 and westward.  Hey, if one lives along and east of A1A, US1 is inland. 

TUESDAY: Shallow NNE-NE wind with a trajectory coming off the Carolina Coast will be moist only in the lowest levels making for another rain free day with perhaps some low topped / flat bottomed stratocumulus clouds with highs again in the 70Fs. Looks like another round of 24 hour 70Fs for the coast, with slightly cooler inland and west coast morning lows.

WEDNESDAY: High pressure at the surface builds further east into the Atlantic and mid-level high pressure finally starts to follow suit with deeper easterly flow although still coming off the Mid-Atlantic coast as opposed to a long easterly trajectory from well out in the Atlantic which otherwise would advect deep moisture across the state, or at least have the potential to. Could be a pocket of moisture convergence that will move across South Central Florida on this day resulting in light low topped showers there, but otherwise continued round the clock 70Fs for the coast, with daybreak and sunset stratocumulus clouds during the diurnal temperature change cycle (as the sun rises and sets). 

THURSDAY/SATURDAY: Gets messy. The latest GFS and now the NAM (since it extends toward this time frame) imply that the next frontal boundary which has been delayed a full 48 hours since first portrayed last week will stretch ENE-WSW along the southern branch subtropical jet, leading to passage of a pre-frontal trough with no temperature change associated with it toward Thursday afternoon. This boundary is to eventually align very close to the Florida Straits (the north side of them) by Saturday as the main front skims the North half of the state with a return to 70Fs and increased clouds after a warm Thursday. Timing will remain an issue probably for the next day or so, and impacts of the pre-frontal trough will depend on the time of day it moves through each area. So far, it appears that Thursday will be much warmer with highs in the low-mid 80Fs..with the better chance of rain over South Florida, showers possible almost anywhere until better ironing out of the finer details can be made. But do note, at one time this front has been portrayed to being everything from a squall line with 40Fs to follow, to being completely benign and dry with zero impacts other than a cool down. The morning run is favoring the later, but as a reminder, it could change on the next run.

SATURDAY/SUNDAY: High pressure quickly builds eastward across the Deep South into the SW Atlantic with return onshore flow. Very breezy with more 70Fs round the clock in shallow on shore flow. Any rains to remain south of Florida initially but should retrograde toward the Keys and far South Florida late weekend .

 TROPICS/RINA/PATTERN: All in all, the general pattern has been for quick moving systems to skirt across the northern U.S. very progressively with a near neutral to retrograding pattern over the South Florida and the Caribbean . Other than an occasional mid-level trough across the southern tier of states this area has been neutral. Southern Branch Jet Stream across Florida with an impulses being sheared out before dropping into the state as a result, and no impulses on the approach from off the Southern California coast leads to quick and moisture starved Northern Stream impulses since they cannot tap into deep moisture from the south and surface high pressure continuously re-establishing across Texas, the Northern Gulf, and North Florida means quick and ineffective cold frontal passages other than a wind shifts and a shot of showers. Very La Nina like .

Thus, the future of Rina remains problematic. For now, if one assumes the above paragraph, this storm will never pose a problem for Florida...and we'll have 
" 'Rinal' Failure". Models that are bringing it to Florida have it doing so by the weekend. For that to occur, they also show it strengthening , significantly at that, and being drawn further north, then being pulled ENE-NE ward ahead of the next front later this week. 

Never say never in these cases, so it is worth watching. But, given the trends of the past few days during 'down time', the GFS has not once brought it northward nor strengthened it to the level portrayed by those models that have brought it north. Shear should increase again north of the system tonight, so I'm favoring the idea it will be lingering in the same general area as late as Halloween.  We'll know soon enough ...but South Florida residents should at least keep an ear open for any rapid changes in strength and motion through Thursday.

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Thursday, October 20, 2011

Breezy and Cool, No Measurable Rain For 5 Days (At Least)

COLD FRONT now in the Atlantic South across Cuba will eventually go stationary as it confronts High Pressure further east. Low pressure at all levels wraps up over the Great Lakes. High Pressure building across all Southern Tier states and the Northern Gulf. Area of unsettled weather from the South Central Caribbean toward Central America to persist for at least another week...any development should be slow, but has potential for greater organization during the coming weekend. 

TODAY: Cool start to the day. Coolest in a long time. Tallahassee reached 37F this morning, coldest in the state and equal to that of Laramie , Wyoming. Other areas have been colder though from the north central Plains toward Minnesota where temperatures were in the 20Fs in many locales. Tornado in South Florida rated EF-2 on the Dr. Ted Fujito Enhanced Tornado Scale.

STRONG JET STREAM nearly over head. Florida is in the left exit region, so that combined with high clouds streaming northward from the Southern Caribbean off of an area of 'disturbed weather' could create some of the wisps of cloud overhead periodically. Circled are the speeds of those winds well aloft in knots (miles per hour is faster than those numbers reflected). In the summer months, for comparison, these values are closer to 5-15 knts.

Cold air stratocumulus clouds should continue to impact the west side of the state from Tampa and South on brisk WNW-NW winds off the warm Gulf waters. These could advect (push toward) South Florida and the lower Keys. A few streaks of high cirrus clouds could pass over head from time to time as well almost anywhere , but will be very thin.  Highs today along and north of the "Magic Dividing Line" in the upper 60Fs and in the lower to mid-70Fs south of the line, although temperatures along the immediate west coast could be a bit cooler due to the clouds. WNW-NW winds during early-late afternoon of 15G22mph, a bit stronger on the west coast side. No rain. Lows tonight in the lower 50Fs to upper 40Fs as far south as the north banks of Okeechobee. Immediate East Coast from Cocoa Beach South close to 56F.

FRIDAY: Cooler start to the day than this morning, with similar daytime highs, although it should warm up a bit more in the afternoon as winds decrease and become more northerly. No longer coming off of the Gulf, clouds should not be an issue tomorrow toward the west coast. Pristine afternoon.

SATURDAY: Very cool once again, but not quite as cool as Friday morning, A1A lows similar to Friday morning. Afternoon highs in the mid-70Fs most everywhere and almost clear.

SATURDAY LATE DAY: Possible light onshore flow from the NE, accompanied by a few stratocumulus clouds. ..especially toward sunset North Central. A minuscule few  raindrops could fall near the coast, but we'd have to be out side with palms raised upward to find them. Most likely if ever after dark.  

Watching the southern Caribbean. The NAM implies better organization or chance of tropical development toward Central America but will disregard at time due to zero impact anywhere either way. Precipitable water values should rise more over South Florida during this time and into next week, but believe any rain spits to occur Saturday or Sunday will be further north, when the mid-level trough (and cooler air aloft) finally puls east and lifts north, leaving a decaying mid-level boundary across South Central as has been depicted to occur by the GFS for several days now and which the NAM of this morning now implies will occur. Cooler air in the mid-levels NORTH of that boundary will improve mid-level lapse rates for potential rain spits, despite the more moist overall atmospheric profile further south where temperatures aloft will be warmer limiting lapse rates.

SUNDAY-WEDNESDAY : Similar to late Saturday, mostly sunny with a better chance of coastal clouds and a rain spit, mainly toward dusk and sunrise. Lows slowly warming from the east to west side into early next week, with afternoon highs in the mid-70Fs...warming to the upper 70Fs to near 80F plus or mins 2-3 degrees by Tuesday inland, but remaining near 78-79F along A1A. By Tuesday, the A1A corridor up and down the east coast could be in the 70Fs round the clock as winds blow  toward shore across water temperatures in the upper 70Fs. Inland highs several degrees warmer by Wednesday.

NEXT FRONT: The GFS is backing off with each and every run on the impacts the next front will have in the Thursday or Friday time frame. Due to slow moisture return, the latest run showed the front to go through dry with a resumption of one cool morning with a quick rebound to status quo to what we will experience by Monday. This seems a bit questionable though for South Florida, but even still is the consideration that the front never makes a clean passage at all. The GFS is very aggressive with that scenario though.

BEYOND: Latest GFS implies no rain until November 1 with very typical fall like weather. However, much  will depend on what happens well to the state's south. Given the latest trends of the Jet Stream though, believe any tropical development or system will never see the light of day on Florida, but showers will be on the increase across the middle and lower Keys heading toward mid to late week, or at least the chance of them will increase based on the latest information available.


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Wednesday, October 19, 2011

Windy, Mostly Cloudy to Cloudy, Rain Chances End Mid Afternoon

Cold front approaching the Peninsula, with two other troughs behind it today. These troughs will affect the weather over the state (the last one in particular) through Thursday night

FLORIDA DODGED A BULLET: Although there were 3 tornadoes (so far) yesterday, no more appear to be likely as winds become unidirectional with height and helicity and instability are moving out and away. The Tornado Watch which had been extended  shrank in size overnight has since been lifted entirely. Yet, the most lightning seen  with this event has occurred and continues over the Keys mainly this morning, where heavy rainfall of over 14" has fallen there in some locations. By far, this was a "Key's Event" for the duration, with coastal SW Florida toward Ft Myers having one of their own.  Wind was never as strong as with the event further north in these locations as what occurred over a week ago though, with a peak gust in a storm of 43mph.  Three  tornadoes have been logged though per the SPC Storm Reports from their website:

TORNADO and Wind Reports noted per the color code. Preliminary.

Even though these tornadoes were reported, Florida still dodged a bullet compared to the rain (reign) of cannonballs that could have occurred had a few factors been different. Already noted previously was the warm air aloft being a negating factor. Another two major factors are that even though the surface low in the Gulf got a bit more organized, it lifted much more north rather that east. As a result, the warm frontal like boundary associated with it,  and the very richly moist and warm air behind that boundary, was never able to make it north of St. Lucie County. The boundary was never able to work north, being trapped underneath a 500mb jet streak from the sub-tropics.  Warm air aloft without the more buoyant moist air present over Central simply could not mold storms despite the tremendous amounts of wind energy present. 

Like a potter molding a vase, Central  had the spin but no clay. 

Even so, despite the fact that the wind energy was not as tremendous over South Florida, there was still 3 tornadoes. Image if that quality of air mass had extended north into the twisting wind profiles over Central and North Central Florida. Results could have been MUCH different.  Florida dodged a bullet, but it looked pretty clear this would be the case by late afternoon toward sunset.  The urgency placed by the press on this one was not unwarranted though, all things considering.  As noted often here, the word 'potential' means just that.  I could potentially scream in the middle of a church service, but chances are, that will never happen. 

TODAY: Cold front to clear Central Florida and South Florida almost simultaneously today in the 3-6pm time frame. The front is followed by WSW winds becoming West ahead of the 925mb trough, then eventually west behind that one. Winds breezy to gusty in the 18-23mph range, but gusts to 32mph might be in the offing. It does not look like we will see a long period of significant cloud breaks today, although there will be a period when we could see the sun briefly off and on..not likely over South Florida though. But at least it will not be cold with highs in the upper 70s toward 80F,very muggy and wet feeling.

TONIGHT: The latter of two boundaries will cross the state, with the 850mb trough (the third) hanging up a bit across Central and lifting northward, never quite clearing as high pressure builds in rapidly behind it from the NW Gulf and South Central Plains.  The associated areas of low pressure are being lifted north just as much as progressing east, all into an area of low pressure in the upper Ohio Valley. Very windy near the Windy City of Chicago (named for folks who blew hot air, not the weather). Which thankfully, will prevent Florida from getting all that cold.

THURSDAY: Cool with winds letting up substantially by morning, but picking up in the 15-22mph range in the afternoon. Skies could start out partly cloudy, but become cloudy at times with the last boundary and associated moisture with it in the area. Highs in the low 70Fs, but warmer by a 3-5 degrees far south Florida.

FRIDAY: Winds subside shortly after sunset with better clearing. Friday morning lows mainly in the mid-50s although a few lows near 48-52F are possible inland and west and south toward Okeechobee. The A1A corridor will be teetering and teasing the 6-0 mark on "Ole' Mercury', at least for a brief time give or take 2 degrees.  Friday afternoon similar to Thursday, with lighter winds and less chance of clouds even still.

SATURDAY/SUNDAY: High pressure in the low to mid levels will cross the northern Gulf and SE States over the weekend. Despite moisture still alive and well (but very shallow and much less), Florida will be on the descending side of the clockwise circulation around this high, clouds might have a harder time being seen except toward the Gulf Coast side.  Atlantic Stratocumulus clouds should stay well offshore through Monday afternoon with a light north wind in the afternoons. Lows remaining in the 50Fs inland and mid-60s along A1A.with highs remaining in the mid-upper 70Fs and near 80F far south.  

MONDAY/TUESDAY: Winds gradually become light and onshore Monday afternoon, but the depth of onshore flow will be to shallow to generate anything more that stratocumulus clouds.

WEDNESDAY: Here is where the line in the sand is drawn....potentially BIG CHANGES in store with two regimes Wednesday/Thursday...and then beginning next Weekend through the first week of November.

REGIME 1: Cold front will develop and move toward the state once the 700mb high pressure center moves east and off the coast of the Carolinas. A chance of onshore showers, and maybe thunder  late Wednesday with a front to move through around Thursday. As mentioned yesterday, the pattern of highs and lows begins to look quite bizarre, which usually means it could be exceptionally beautiful or the contrary for an extended time. So far, it is looking like the 'contrary' from near Halloween and Beyond.
In fact, it looks very typical for mid-fall some years. A not pretty one. 

Front moves through, but with a very rapid switch in winds to the NE-ENE at all atmospheric depths as the high off the mid-Atlantic is re-enforced, with possible onshore moving showers beginning within 48 hours after fropa (frontal passage). This is number one on the check list of 'questionables'.

REGIME 2: Contingent Upon the net affect of Regime 1. Our old TWO frontal boundaries. Both lying eventually across the Northern Caribbean ..don't forget them. One being from today and tonight, the other from mid next week. It is possible that cyclogensis could occur along these boundaries underneath the sub tropical jet.

THE GFS is implying that a tropical storm could form in the Central Caribbean and move west toward the western Caribbean generally south of Cuba. Tropical or not...perhaps just a large area of low pressure will be in place. Either way, this is to combine with strong high pressure over where else, the Carolinas. Sound familiar?  WINDY is the result, with showers. In fact, if the low pressure area develops per this latest run, sustained winds of 'sub Tropical Storm Force' could occur or develop about 3-4 days after Halloween, with our without a tropical storm.

At this point though, given the recent implications, even the word 'potential' to 'cry wolf' on for such an event is stretching it . More appropriately, there seems to be some long-range model consensus that high pressure will be to the north, and low pressure to the south. But how they will align and what comes out of it is an entirely different matter.

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