Slow Transition to Moisture Laden Southeast Flow Emerging Through Wednesday

A slightly better chance of thunderstorms today toward Ocala and interior Volusia/Flagler and in the Gainesville area. Also along the SW Coast. Coast showers could re-appear within 1 hour of sunset (very isolated) along the Central to Southeast Coast...more numerous the NE Coast toward JAX and SE Georgia.

TODAY: Not much change in the line of thinking from yesterday's post. An inverted trough has appeared, temporarily as almost a very weak close surface low over Brevard County. This feature will move inland with the sea breeze and daytime heating as a weakly defined, inverted thermal trough to act as a focal point for more thunderstorms than the past few days over the interior (which isn't saying much). Lightning was observed near noon time in North Brevard as the showers, moving generally toward the NNW moved inland from Central Brevard.  There is a small chance of an isolated shower or two re-appearing within one hour of sunset along the beaches most anywhere while the activity over the interior should dwindle rapidly after sunset. Northeast Florida seems the most likely candidate for that early evening activity, although one or two is possible Central.


TUESDAY: Another slice and dice day of where/when the renegade showers will occur. Most likely before 11AM along the east coast, progressing into the interior by shortly after noontime and re-emerging as thunderstorms from early afternoon, and peaking in strength between 4:30-7pm. in other words, much like today.


WEDNESDAY and Beyond: The NAM has been consistent (for a change) at showing a region of higher moisture (PWAT) air over the SW Atlantic to progress WNW toward Florida during the course of the next 48 hours. For two consecutive runs one can actually trace the rain field areas it depicts approaching systematically toward the east coast of Florida for arrival by late Wednesday afternoon. The GFS is far less as obvious, but both do show a broader coverage of atmospheric moisture for a greater coverage of showers and some thunderstorms, but by no means will every one be seeing rain. All in all, it might seem more like a typical summer day albeit just a tad cooler by a few degrees. Favoring the west side late in the day for the heavier storm activity. Thursday looks similar.


Elsewhere, during the next few days a frontal boundary will be inching eastward toward the State. It is moving at such a snail's pace as it rams into the ridge running down the Appalachians as noted in the image above (with yet more in the Atlantic)..that it can barely reach Central Florida before being stretched thin (Saturday/Sunday time frame).  For comparison's sake, were this a 'normal' frontal boundary in mid-winter it would be through the state by Tuesday night from its current location, which is  down the Mississippi River Valley area.  It still appears the boundary will make it to Central Florida or thereabouts, and be able not to progress much further. That is at the surface. Just above the surface the upper level supporting trough lags well behind..as if to emphasize this is not a 'big temperature dropper', but rather a focal point for showers/thunder.


Beyond Saturday we are already into the time frame of greater unreliability and tremendous variations from run to run, although the GFS has been fairly consistent in having this boundary merge with a broad area of low pressure over the Caribbean.  In fact, the morning run now cuts the remaining frontal boundary off into a close surface to upper level low pressure area encompassing most all of Florida by the middle portions of next week. This is highly unlikely as well as any other extended outlook has and ever will be. But the implications, or rather, the tendency for this model to want to evolve into some sort of transformation of low pressure areas off and on again for over a week near or over Florida in the extended can't be completely ignored. There is a brief drying period during the transformation, but the gist has been that no big temperature dropping frontal systems appears yet to be fully in the making for a big cool off for anywhere beyond the Panhandle and Northern portions of the state into October. That too, could change. But not within the next week when fall begins on September 22nd at 5:05AM. Last year, our first fall like day arrived almost simultaneously with the passage of Tropical Storm Nicole (September 31st). From October 1st and beyond, summer or any semblance of summer ceased to exist.

Persistent Current Patter Remains In Place Through Tuesday

Sunday morning rain-shower near the Coast of North Brevard County. This shower seemed to form along the leading edge of wind surge, which never quite made it beyond the immediate coast...and after which retreated to offshore. This could be the chain of events that unfolds the next two or three mornings, which an enhanced area of more prolonged rainfall somewhere between Coastal North Brevard toward St. Augustine each day during that time frame.

General Area of Rain shower activity today (mostly isolated), except possibly along the coast from North Brevard, through Volusia, and into Flagler County where there is potential for some higher rainfall totals. Little change in the current pattern is expected through Tuesday.

TODAY-TUESDAY: Little change in the overall pattern appears to be in order for the next 48-72 hours. Weak low pressure that formed near the Carolina Coast slid NNE ward during the past 24 hours and has left a remnant mid-level boundary just off the SE U.S. coast. 


Yesterday, the end of that boundary reached into the JAX area, whereas this morning the boundary had pushed south toward Daytona as high pressure built down the Appalachians. It is that boundary which will be the prime instigator for potential more coastal rain events due to the fact that this thinly stretched out boundary cannot progress further east due to a vast high pressure area extending completely across the Atlantic to the coast of Africa and southern portions of Europe.  It is possible that heavy rain fall events could occur in the next 48 hours somewhere along coastal North Central to Northeast Florida from overnight to early morning and one or more of these days. Meanwhile, a frontal boundary will be inching in from the west (now across the Southern and Central Plains)...but the log jam will be hard to break. Thus, little change for a while until 'something gives'.


The weather today is a far cry from what occurred on this date in 1926 (85 years ago), the year of the Great Miami Hurricane. Even as little as 24 hours prior to that storm, hurricane warnings were not hoisted. 


I will add that there is also a secondary bubble of high pressure over the SE States center just NNW of Florida. This appears to have broken off from the fixture that was over Texas most of this year (since early mid-spring time) which generate the drought there. That high pressure is almost completely gone for now, but an even large high pressure dome could be in the making for much of the Western U.S. during the week ahead. It was the leading (and in sinking( side of that high pressure that was responsible for the string of dry days over Florida last week. That high pressure will gradually flatten out with time, with a portion eventually  ejecting eastward into the Atlantic with the other portion retrograding into the NW Gulf and back into Texas. This process will be a slow one though.

Did you hear about the big rainfall totals overnight Friday night into early Saturday near Jacksonville? Here is a Storm Total (of rainfall) obtained via weathertap.com compiled from the JAX radar yesterday morning, followed by a preliminary informational statement release by that office. This was Day 1 evidence of that boundary at play. 

"A FRONT STALLED OUT OVER THE AREA COUPLED
WITH A MID LEVEL DISTURBANCE HELPED PRODUCE STRONG STORMS WITH
HEAVY RAIN ACROSS A PORTION OF THE JAX METRO AREA. 3.35 INCHES OF
RAIN WAS REPORTED AT CRAIG FIELD OVERNITE. HOWEVER...THERE HAVE
BEEN DOPPLER ESTIMATES OF NEARLY 10 INCHES NEAR JAX AND PONTE VEDRA
BEACH. MAJOR FLOODING WITH UP TO 3 FEET OF STANDING WATER AT JAX BCH
AND 6 INCHES OF STANDING WATER IN A CLUB NEAR ARLINGTON.
DOPPLER RADAR CONTINUES TO INDICATE CONVERGENT BANDS OF SHOWERS...
SOME HEAVY...ALONG THE COAST" - JAX (Jacksonville NWS Office)

Meanwhile, this morning the same sort of event occurred in Volusia County, although not nearly to such a degree. It appears it might not be over quite yet, even though as of this time the rain there has ended, more lurks very close to the coast if not already back on shore as I type. I've noted an area of interest in lavender where more convergent rain-bands could set up today or tonight in the first image.


Elsewhere, despite model guidance and actual 'near current' data portraying dry conditions over South Florida, rain showers moved into Palm Beach County..much to everyone's surprise. These are low topped showers, but nonetheless persistent. These showers appeared yesterday morning and once again this morning despite lack of rock hard evidence that would call for them to be placed in a forecast due to lack of any sufficient surface features other than some moisture.  There appears to be a small cyclonic circulation approaching far SE Florida as of noon time, so more showers could move into Dade/Broward Counties, and after a break toward the Keys, they might be in for more later today and tonight as well.


Otherwise, when looking at parameters to support thunderstorms, the most unstable atmosphere has been along the east coast of Central Florida mainly from Central Volusia to Central Indian River Counties. Despite these parameters that are based on low level factors, the mid-levels are too dry to support anything other than low topped showers in the absence of a triggering mechanism other than convergence which happens rather sporadically and haphazardly. Only closer to the near 'phantom boundary' near Volusia/Flagler where moisture is deeper through a greater extent of the atmosphere does it appear more certain that rain chances should  be higher, as well as some thunder. Even an offshore waterspout should not be counted out. A YouTube friend of mine shared that he saw a waterspout offshore South Brevard Saturday morning, but this was not noted in official documentation released from MLB.


MONDAY/TUESDAY: As it appears now, little will change in the given on again/off again pattern until a deeper, stronger  trough can approach from the west   toward the state to nudge high pressure out of the way.  I will write that this was originally portrayed to occur (several days ago) in full by Saturday, then Sunday..but it keeps being pushed further out in time. Thus, although a BIG change is expected to transition through on Wednesday and be in full affect by Thursday..we'll just have to keep monitoring. It is the time of year for the first cold front to reach Central Florida, so this train of reasoning is not out of the question.


BEYOND: With the above already stated, one can make the assumption (and if 'reading' the models, it would be a fact)..that by Thursday the mean moisture advection will commence from the SouthWestern Atlantic and even the northern Caribbean. This would bring forth even deeper atmospheric moisture and a return to thunderstorms, especially by late Wednesday and more so on Thursday through Saturday. That is the course of thought as of this morning, but it will take two more model runs (or by tomorrow morning) for this to be more assured.  In the great beyond, a combination of the front (trough) from the continent is depicted to merge with moist/cyclonic (low pressure) circulation from the Caribbean over Florida, at which point the GFS looses credibility completely. The over all trend though, is increased rain chances on Wednesday as thunder storms become more likely (or in other terms, beyond occurring in only random/isolated fashion).

Sunday Morning, September 18, 2011 

A Few Isolated, Strong Storms Possible Mid- Afternoon Until 9pm

Sunrise Thunderstorms East of Florida This Morning

TODAY: A state divided with further complications. A tropical wave over South Florida with abundant moisture and a high energy vort max from the Continent at the base of a large upper level trough approaches, so far, unseen due to lack of moisture further north. But, it will run into ample moisture toward mid-late afternoon across South Central Florida.


SOUTH FLORIDA: A dampening out tropical wave containing abundant moisture is washing across South Florida south of Lake Okeechobee. Showers and some thunder began fairly early there as a result. Little is happening further north.  Storms might let up for a short time early afternoon, but pick up again as a disturbance approaches from the NW-WNW aloft most directly entering Central Florida.


CENTRAL FLORIDA: Isolated Storms, but they could be strong as a large disturbance begins to move in closer to the peninsula this afternoon. Moisture in the atmosphere is very low north of the Beach line, but there is just enough to maybe squeeze out a storm toward DAB or JAX if the timing is right, but it will be late.


Further South toward the Beach Line, what remains of the old boundary of the past 5 Days has pushed south and is aligning very close to the jet stream flow aloft to move in as the day progresses. Moisture is just enough to squeeze out some storms, and with the winds aloft forecast to be in the 40-60 kts range, combined with the upper level vort max (shown below) this might not be enough yet to trigger storms alone. It does look however, like a storm or two could get going on the NE side of Lake Okeechobee, which like yesterday, would send an outflow boundary northward to meet up with that old mid-level boundary referenced above. That boundary has been the cause of storms for several days now..and this might be its last shot.


Surface winds north of the lake are forecast to be quite light and variable in the lower levels of the atmosphere after good heating has set in and breaks down the light NW flow now in place as I type, so a light sea breeze should initiate by 2pm  ...coming off of warm and moist ocean water temperatures above them. There has been some drying in the atmosphere mostly north of Ft Pierce/Vero...so this area north of Vero will have to wait until late as the sea breeze is in place for a few hours to get things going -  timed with the upper level disturbance..as well as some colder air aloft in the mid-levels that comes with it.

 If things play out just right in the timing of the disturbance, late time of day after sea breezes have come in to play and the Lake Breeze, and any outflow from the south...any storm or three to go up toward the Beach line and south in Osceola County and north of the lake  could be strong and hold itself together to the coast. At one point storms might become almost scattered in nature right along the boundary after 6pm . Again, it could end up being later. Guidance portrays rains in those areas as soon as 4pm..but I'm hedging toward later, as has been the case the past 4 days...other than an earlier storm toward Ft. Pierce and maybe working toward Sebastian Inlet. 

This was my line of thinking early this morning. This satellite water vapor image shows the storms that were ignited during the predawn hours along the boundary that seems to have shifted south. There is an apparent low pressure circulation east of JAX as well today..that area is forecast to drop south a bit during the day and maybe even back in toward the coast toward 6pm, thus, a storm could occur near JAX and DAB closer to that boundary along which some atmospheric moisture which would have to converge along it.  


TUESDAY: There might be an isolated storm once again east central, but if so..early. Otherwise, it looks more like far SW Florida will have the rain chances later on Tuesday and Wednesday.


THURSDAY/FRIDAY: Maria is supposed to have moved well north and east of the state, and will leave a weal mid level trough behind along the East coast from just of JAX to off the mid-Atlantic. High pressure building in across the east tier of states is forecast to recirculate moisture along the trough into JAX and eventually further south heading toward Saturday. However, at this hour the storm is nearly stationary and is being sheared apart. Will it maintain? So far the models have been saying 'yes' in some form or another.


SATURDAY/BEYOND: Winds become more easterly to southeasterly, and advect more tropical moisture into the state heading into next week. At which point, rain chances could be in place each and every day toward the end of the month. The Tropics from the eastern Gulf, all of the Caribbean, and toward the Bahamas will need to be watched during this time frame for development, especially heading toward the end of next week.

Questions Abound Today Concerning Where, When, and If

Storm Approaching Merritt Island toward Port St John on Saturday viewed near the South Gate Entrance of the Kennedy Space Center near Port Canaveral. It is evident from this image that this storm was 'feeding' on the mid-level boundary across Central Florida by the long line of clouds on the right portion of the image . Although not frequent, this storm ejected powerful lightning bolts and dropped very heavy rain. Another storm was further north, and outflow from that storm fed into this storm, further magnifying its very small but dutiful strength.

Zoomed in a bit. Lightning was coming out well to the left and right of the rain core noticeable in the center

TODAY: Very difficult forecast for today. And no surprise. Recall the model forecasts for today were 'dumped', and it was stated we'd figure it out today?...It is still hard to figure out even at this hour.  After looking through overnight guidance, that which came out so far this morning, as well as monitoring actual information using 3 hour animations of the changes since sunrise...today's post is again in lieu of any model. They all agree to disagree concerning where and when it will rain today...if anywhere.  Thus, here's the line of thought and how it transpired.


Initially, it looked like good rain coverage over most of the state along and south of I-4 with the most south of Lake Okeechobee oozing into toward East Central and perhaps toward Jacksonville. But....

IN looking at water vapor loops, it appeared that a weak circulation off of SE Florida which contains drier air might prevent the tropical wave forecast to move in from the East to have the effect thought in regard to increased rain chances over South Florida (which was to be high end coverage). In fact, it is now noon and there is not hint of rain to occur anytime soon. In fact, after reviewing time sequenced loops of the past several hours, this area is becoming more stable. There is moisture, but it is at the wrong levels to generate storms.  The other area is the old boundary across North Central Florida. It seems to have moved little, and actually a storm went up along it off shore earlier this morning that showed rotation and quite a bit of lightning. This boundary remains in place today, but not nearly as clearly.

Rotating Thunderstorm Off Shore Along the Boundary Across Central Florida

See the colored text for important  finer details. With all factors considered and after some internal 'negotiating a reason for rain', the case for best rain chances was  created. Storms were thought to form west of the coast of SE Florida and move toward the West Coast as well as over the Keys. Across Central in the white lines is south of that boundary that has been in place for 4-5 days. Out in the Northern Gulf though appears to be a disturbance moving east to move over the state..or approach after 5pm. This could add lift but add nothing for an atmosphere too dry over NW Florida but toward JAX is a different story.  The SPC analysis page also shows a circulation over NE Florida and it now shows up on the satellite image last hour (below). I was also watching for an outflow boundary to move west from the Atlantic to maybe start off some showers around 1pm ..but that seems to be fizzling well off to the east...although one model managed to pick up on it, to generate rain by 1pm. Not going to happen though

The circulation near JAX is evident, and another along the East Central Coast which was on analysis is not evident but drawn in with a question mark. Note how at noon nothing is happening  anywhere. 

Finally, the last factor that just became evident is that unlike any model forecast has shown and which explains why nothing is happening, most of the state has become capped in the mid-levels with convective inhibition. Thus, it looks to be another late day to evening rain chance, if any. One model showed close to no rain most anywhere today which might have ended up being right on...


The other 'finally' is that the next trough approaching from the WNW-NW forecast to up the rain chances on Monday might be moving in faster than thought. This could mean less rainfall coverage tomorrow due to the bad timing of its arrival for late day storms (except toward the South Half of the State). Thus, the forecast for Monday is in limbo. 


And one more thing while on a roll, so too may be the forecast for Tuesday out to lunch (per TV). Much depends on how strong, big, and in which direction Maria takes in the next 48 hours.


 If it stays further to the east than thought, the state might not get into the sinking air surrounding the storm..so there could be some rain chances as shown by the very conservative and unreliable NAM model.  The next boundary moving in tomorrow could get hung up across South Central Florida on Monday (in that case) and be a rain player for 'somewhere' for Tuesday, of isolated fashion.  Beyond Tuesday, the rain chances dwindle either way with an up tick on the weekend coming up.

FINAL CONCLUSION: This might be way over generous on the rain fall today but watching these areas when push comes to shove. The red is most concentrated rainstorms, and the areas near those red L's need
to be monitored. South Central is where the most unstable air is evolving as of noon time with the greatest moisture in the mid levels right along that old boundary shown in purple. With stronger upper level winds pushing in from the WNW late today and increasing mid level winds late as well, storms appear to be late in coming (after 5pm) once again north of Okeechobee County/St Lucie County. If a storm forms along that boundary and rolls off to the southeast (or even northeast toward Volusia), it could become quite potent toward Seminole County and into NE Orange and North to North Central Brevard County or into Volusia as it meets the east coast sea breeze from the SE - SSE which will form later in the day to any degree of 'strength'.  If it can rain...unlike some models show nearly none, we'll find out later today. But , if so, it could linger over interior South Central toward the east coast of Brevard/Indian River/St. Lucie County until mid-evening.

Summer's Last Gasps Through Monday, Cape Verde Season Shut Down (?)

Launch of a Delta II Rocket this morning from Cape Canaveral as captured by this blogger

“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”

TODAY'S SYNOPSIS (ANALYSIS): Not sure if there is a lot to talk about today or if there is very little. In general, the surface boundary has moved very little since yesterday and has become much less defined. Today seems to be a sort of 'transition' day with the mid-level trough having shifted much further north. Although moisture is now much further north nicely aligned with the best wind fields, instability further north is very insufficient for surface based storms, but sufficient to carry a storm based in the mid-levels. Exactly how the transition will have evolved further prior to sunset is unknown. None of the models have seemed to once again captured reality. In review of radar/satellite animations and trends, it is apparent that a weak disturbance is again crossing the state, but of much weaker origin than that of yesterday. It also appears to be based in the mid-levels but does have lightning associated with it regardless. This area of interest is  to cross just north of  Dead Central along the Beach Line and south of I-4, but favoring more toward the North.


Further South, dry air in the mid-levels is attempting to impinge across Southwest Florida but might make little more progress. This could actually enhance thunderstorms along the Southern  portions toward the Everglades/Lake Okeechobee/ and near the coast from Ft. Lauderdale north to  Ft. Pierce, especially along the east coast sea breeze.


Further North toward Central. Very light east coast sea breeze circulation close to the decaying surface boundary should prevail. Skies are quite sunny and heating is strong, but there is a very persistent area of sinking air over Brevard County in the wake of yesterday's system. Another disturbance (weak) is approaching, but will take until nearly 3-4pm to reach beyond the Orlando area, during which time the far east might be able to fully 'recover' and uncap. Thus, Brevard in particular is highly uncertain.

In this image from the Storm Prediction Center's webpage it can be seen that precipitable water is lower over the SE Gulf and trying to move into SW Florida. This is attributed solely to lower moisture in the mid-levels and could eventually enhance storm strength across South Florida especially along the East Coast sea breeze and around Lake Okeechobee breezes as far north as Ft. Pierce. The area near Brevard is circled mainly because nothing could happen in this area today. BUT, on the other-hand, conditions could change quite rapidly between 5-6pm as the area of weak rain-showers with some lighting approaches from the West, especially along and east of the east coast sea breeze .  

 The area in red is noted as being a bit capped this afternoon which currently completely precludes the area from receiving rain today. However, if it suddenly becomes uncapped late today, it would be right as the weak disturbance approaches from the west. To add, spiraling low level currents associated with the east coast seabreeze could build up around Canaveral Bight toward Port St. John and south toward Sebastian/Vero.  Southern Brevard/Indian River/St. Lucie Counties might contend as well with outflows from storms around the Big Lake to add to the mix. Under the assumption of course that anything can get going. Might be a late rain or storm show far east coast again tonight with rains lingering toward 10pm...and storms could get feisty if they can manifest along coastal Brevard and Indian River Counties.


Final note that again models are useless today. For example, according to the GFS it should be raining over much of East Central as I type, yet the sky is blue. Perhaps it is just fast. If it is correct but wrong on the timing, then east central could get a prolonged rain (light) in places through 10pm tonight. Looking out there now though, nothing suggests it will even rain at all.

**NOTE Best bet is keep an eye to the sky for those in this purple area heading toward 5pm and beyond in Brevard.. The surface boundary is still around there regardless and you never know when someone will slide one under the table to the waiter.

SUNDAY: Another random day of either very low rain chances or good ones. Thus, we'll play it by ear . I can see what guidance states but I again do not trust it mainly because it looks like something might be waiting in the wings well out in the Gulf which could head toward the state. The only thing that does not change is that the areas for rain look best roughly as in the same spots it has already occurred during the past 3 days.


MONDAY: Perhaps the last gasp of summer in the rain department. Not that we won't have more rain chances coming down the pipe. Simply, it looks like the end of the diurnal cycle, which actually ended with the passage of Irene. After Monday rain chances go to near zero through Friday when a small chance will be introduced somewhere, probably over South Florida. There where be some small chances somewhere, but it would be fleeting and small.


TROPICS: The Climate Prediction Center formally announced that as of August we are in a La Nina pattern. Much more will be posted in that regard in a follow up post in a day or so concerning what impact that has on Florida weather later in the year and into the winter. In regard to the tropics, it often means a continued late Tropical Season. Already, and as noted the other day, the Caribbean 's Pot Has yet to really be stirred...and is prime and ready for activity. It is that time of year that the Cape Verdes Season ends..and  it is definitely looking like there is little more to come down the pipe from there from off of Africa. Thus, we shift toward the Caribbean/ Eastern Gulf and western Atlantic closer to Florida and the Bahamas.  


Indeed, the morning GFS has a very large cyclonic circulation developing over the entire Caribbean all of next week including the Bahamas, all of the Great Antilles..and portions of the Lesser Antilles after Maria has made its final goodbyes (more on that storm tomorrow).


In closing, it was during the La Nina of 1999 that two storms came out of the Caribbean..one of them being..ironically...IRENE, in October.

Harvey and Irene , September and October 1999, La Nina 

Potential Exists For More Active Rain/Thunder Central/South

Image shows a departing disturbance east of Florida and a much larger and organized disturbance (up to this point in time at least) approaching the West Coast of Florida  from the WSW-W. Nate is shown in the Bay of Campeche (BOC)

  Rather interesting and a bit complex day in store. As has been the case, a stationary frontal boundary remains across Dead Central. This boundary has oscillated a bit off and on, sometimes acting more like a warm front as it moves north a bit (Wednesday) and then south a bit as a cold front (Thursday). It looks as if today the boundary will act again as a warm front...which means better chances for thunder as opposed to predominant rain with only isolated thunder that stays more toward South Florida.  Today's post, being what it is, almost completely disregards the model forecasts for today since none of them seemed to have picked up on this system. The main fall back or 'concern' is how well put together this area will remain during the course of the afternoon. Since  early this morning it has not faltered, and lightning activity associated with it has increased. It is even showing up on a Tropical Web site , appearing almost more impressive than Nate to the untrained eye. (see the figure further below). The clincher today will be whether this 'complex of storms' holds together or simply fizzles before reach Florida. This post trusts it will hold together, but either way there is still a rain chance over the South half of Florida.


Timing of the actual disturbance shown in the image west of Tampa Bay puts it toward the East Side around 9-11pm tonight, but it is the lifting in the atmosphere ahead of it that might actually generate (and potentially enhance) rainfall coverage and strength of thunderstorms particularly south of the surface boundary. The air so far today, like the past three days, is most unstable over South Florida or roughly from Ft. Pierce and South. However, it is possible a good part of that instability will be lifted north later today closer to the stationary boundary into Central Florida as this disturbance presses closer to the west coast.

This is the latest radar as of 1:30pm out of Tampa's NWS WSR-88D radar. Drawn in is the stationary front's approximate location. The two red lines indicated the area within them to be effected by this disturbance through midnight tonight either by rain, thunder, or simply enhanced cloud coverage. South Florida will likely see rains well in advance of this system since that location is already most unstable and had no early morning clouds in place. It may be that South Florida will not be nearly as effected by this system as will Central Florida and Portions of North Central if not North Florida from near Gainesville - St. Augustine....that would be tonight.

This Gulf Disturbance does not have any vorticity analyzed with it, but it does have Low Level Convergence and Upper Level Divergence with it..which means that perhaps the vorticity is not being picked up and/or showing on analysis, which after all is extrapolated from a model (which I've tossed for today).

This images looks rather messy. I didn't think so until i look at it now.  Florida is in the upper right. Note the disturbance to the west of Tampa. The white arrows are the DLM, or Deep Layer Mean flow. The blue and yellow circles near it are convergence and divergence. Thus, it looks like this 'whatever'...or disturbance should make it across the state.  Otherwise, Nate can be seen in the BOC spiraling in place. The cloud coverage is not as 'impressive' with Nate it is west of Tampa  when not in animation. DRY AIR is noted north of both systems..which is located North of the Boundary lying  across Central Florida,. The driest air is restricted to the Panhandle currently.. 

TODAY:Having not seen any official forecast discussions regarding what is in the Gulf   remains an allusive mystery this hour of the day. Timing clearly showing it moving toward the East or ENE and approaching Tampa Bay..per their radar. Based on this timing, it will cross central Florida from late afternoon through and past midnight...in some form or another. Thus, it could cross as merely cloud cover, under the assumption it even makes it as far as the state. Models for two days showed something coming to Florida today, but for some reason as of this morning it was no longer portrayed. This sure looks like one to me though.


The best thunder/rain should occur system or not this afternoon over South Florida working north with time. Again, guidance has been a bit all over the place with where the best or strongest thunder will occur today, but the consensus would be from near Boynton Beach north to Vero Beach. Yet further north ...North Brevard to the Volusia Line could be a contender for thunder or heavy rain (or perhaps long lasting light to moderate rain) due to outflows from the south meeting up with the surface boundary combined with  increasing mid-level  lift ahead of the system to the west. Although in the image below is a caption reading 6pm and beyond for the northern areas, 5pm might be a better time frame for starters just to play it safe. Some stronger storms appear to be  most likely to occur, if any where, over Palm Beach, Martin, St Lucie, and Indian River Counties.

Storms could be enhanced near and north of Ft Pierce due to the lake shadow as well as toward West Palm. Further south, the east coast sea breeze combined with a SW steering flow that is weaker than further north could generate stronger almost summer like storms toward the Broward/Palm Beach County line.  To the north toward Brevard county a light sea breeze combined with lift ahead of the approaching system and its location closer to the main frontal boundary..as well as the outlying possibility of outflow from storms created earlier to the south could enhance a storm toward Ports Canaveral/St. John/Rockeldge/Cocoa Beach area. If So, that would be between 5pm -7pm. Elsewhere, rain is possible further north and just maybe thunder as far north as Daytona...from elevated type storms with what would probably be in - cloud lightning as opposed to cloud to ground lightning. This area has never stood out in guidance (yet) to be a thunder contender, but since I'm not using much guidance anyway we'll give further north the benefit of the doubt. Again, just for starters. rains could linger until midnight on the east side of Central Florida tonight.

  
TROPICS: As of now, Nate is not expected to get beyond his little Watering Hole in the Bay, as opposed to the sudden shift in models that occurred yesterday. This bears with the initial line of thinking and forecast reasoning, as well as with what history has told us over the past 120 years..so why change now?  Likewise, Maria's fate is uncertain if there is to be one. The official forecast has the storm heading right through the Lee ward Islands and toward the Bahamas which at that point uncertainty becomes quite large. In fact, the storm's short term course toward the WNW for days ahead seems a bit flaky. 


If per chance the storm were to follow a path noted earlier of low level convergence it  would again  be steered a bit more toward the west..in which case then any projections further out in time are already out of sync/agreement with reality. Even the most southern track in the forecasts though have the system curving before reaching Florida. That seems quite realistic as of today ...namely because the Blocking Pattern Referred to the other day remains...and thus so does the surface boundary over Florida. 


*** Future Forecast no matter What I'm hearing on "TV" are being disregarded by this listener. The future of the forecasts is completely contingent upon when the blocking pattern breaks down..which can be anywhere from 4 -10 days (at least)...we are on Day 3-4 now..and the pattern so far looks to hold until AFTER Maria presses north of Florida to the east.  Models keep breaking it down (which is normal to have happend)..but the truth of the matter remains uncertain. It's a day by day deal. ..therefore, until the blocking pattern has clearly broke which could be as soon as Sunday or as late as  Wednesday...the best forecast rule to follow is "Run With Persistence"...and keep an eye on Maria.


For pre planning purposes though, late Sunday through Monday look to have much better chances for rain.

Nate's Fate (or Lack Thereof) Grows Uncertain By The Hour - And Maria?

Analysis From www.spc.noaa . gov   , The Storm Prediction Center. This nformation is extrapolated from trends, observations, and the RUC Model (without going into the finer details). This Image shows a 'disturbance' or vorticity maximum (max) crossing Central Florida. After which, things will be quite calm for a majority of the day, East Central. Another disturbance is shown to cross Central Florida During the afternoon (lower left). South Florida will remain the most unstable throughout the day, while north of the Purple area some recovery from passage of the first disturbance will take all of the afternoon to accomplish. In short, rain chances end up occurring in the same places and at the same time as yesterday for the day with some minor differences.

TODAY/FLORIDA: A disturbance is crossing Central Florida now but you'd never know it from looking outside. In its wake will be some minor drying in one atmospheric level and NVA (negative vorticity) and subsidence over Central Florida. South Florida will not contend with this settling of the atmosphere and will grow increasingly unstable during the afternoon, although the level of instability attained yesterday so far does not look to be as great as yesterday to start with.


Meanwhile, further north the passage of the boundary shown in orange above continues to impact North Florida. In fact, Tallahassee last hour was 56F degrees and Crestview was 59F. Many other readings hovered close to 60F this morning with much drier air. This influx of lower dewpoints (drier air) reaches to Flagler County  toward Brooksville if not closer toward North Tampa Bay. Temperatures this morning actually got into the low 70Fs in many locations, and last I looked Okeechobee was at 68F with light fog. It has been a LONG time since temperatures have gone this low..since late Spring.


Thus, it will take a while for the atmosphere to be in working order for storm generation today (Central)since the sun rises a bit later and is at a lower angle in the sky. Regardless, with enough destabilization at work   under sunny skies (clouds not a problem like earlier yesterday) and another disturbance approaching..thunderstorms are again a good bet across South Florida and portions of South Central Florida mainly along the east side from Vero Beach south to Ft. Lauderdale or just north of Miami beginning just away from the coast sometime after 2:30pm -3:oopm time frame. Not sure a sea breeze will come into play today, but I suspect a light one can sneak in there.Some of these storms could be rather strong with gusty winds and inherent lightning strikes.


There is a chance that if activity gets started earlier(South) than expected that outflow from these storms will work back away from the coast and generate another round well west of I-95. That same outflow could press north to St. Lucie/Indian River/and Southern Brevard Counties for activity after 4-5pm.


Further north the thunder chance looks a little less certain, but a storm might be able to get going near the Surface boundary in Northern Brevard due to outflow moving north from earlier storms to the SW and South and ramming into the prevalent synoptic scale frontal boundary.  Once again, rains could linger until around 8pm in light fashion along to just off the coast of Central Brevard south to St. Lucie Counties.


Even further north, do not believe that much beyond the Volusia county line the atmosphere will recover enough with ample moisture in depth coincident with the vort max passage to generate anything other than rain showers...but changes are in the works and this could change during the course of the late morning to early afternoon. So far though, not seeing through any guidance for storms to transpire beyond what has already been written above.


FRIDAY: Models again are showing a series of disturbances to cross the central peninsula..even more pronounced than today. Almost makes one wonder if they aren't 24 hours slow. Regardless, tomorrow looks again similar to today..however, as noted yesterday, moisture and the boundary will lift further north as Katia moves away and further North as well. That factor combined with the agreement that high pressure will press in from the east across South Florida in the wake of Maria. Dynamics should then also cross further north but not be as strong, so the fate of Friday is a bit uncertain, especially over South Florida where there will be near zero dynamics other than daytime heating, (which should be sufficient for thunder west of Miami Metro in the Glades).


BEYOND: Saturday and 'Beyond' depends on the pressure  and moisture pattern more closely related to tropical activity, which has been changing rapidly this morning now that overnight model data has become available and will still be filtering in through 3 pm this afternoon. Speaking of the Tropics:


TROPICS: In summary and to cut to the chase, models are trending to agree to disagree this morning. Last night almost all guidance was in near complete and total agreement that Tropical Storm Nate would be doomed for shelling pesos in Mexico; however, the 2AM GFS (which has been quite good all summer)...just shifted gears into reverse. It was first to show that NATE would now lift out of the BOC (Bay of Campeche) once Katia pulls further away...and other more frequently processed data is starting to follow suit.


 Although there is very dry air over the Northern Gulf behind the boundary that is over Central Florida..as noted previously, that boundary is to lift north as Katia moves further north and the ridge builds in across South Florida (Friday). This in turn lifts moisture north as well as merges it with some that has oozed south around the backside of the broad expanse of territory covered by old Lee which is now all in the mid-levels of the atmosphere. Until this can be fully ascertained to be of truth, the future forecast for Florida remains uncertain. We will know with much greater certainty though by 3pm this afternoon. But note that even the shorter term track models are trending the turn northward as opposed to only 3 hours ago prior to this writing.

Most recent 8AM EDT information. Earlier, only 2 tracks took NATE northward. I have also drawn in YELLOW the latest forecast 2AM track of the GFS Model. The official forecast track is shown in WHITE.
Note that the GFS takes NATE as a tropical Storm/Depression into a loop around North and Central Florida as the system begins  to bump heads with high pressure building across the Mid-Atlantic Region. 

NATE is shown in the little white circle , center of image. In lavender is the error of margin in the official forecast track. Two things to notice is that there is abundant heat energy to the north of the system, partially under that dry air by those reds and oranges over the Northern Gulf Coast region. There is energy under that dry air though, as well as in the Caribbean. The CARIBBEAN has not been touched this hurricane season and could easily remain a hot bed for future activity. That area has been shown to get active from time to time now...but guidance has yet to figure how, when, or why.

Elsewhere, there is Maria. This storm is just ekeing out  tropical storm strength and is moving rapidly to the west around 23 mph. I've noted in this image the forecast margin cone of error the Hurricane Center has generated (yellow arrows). Included as well are notes that the greatest shear currently is toward the north side of that cone and the best heat energy is located to the south side of the cone. Forecast tracks of consensus models are very close to the official forecast track, but several other models are taking Maria further south toward the Central Leeward and maybe even northern portions of the Windward Islands. That is what the NAM model has been showing, but then again, the NAM has not been remotely reliable in months. 

Here we see the steering in the white arrowed lines. If Maria remains weak (which looks likely at this time)..the storm could continue west and into the greatest heat energy levels in the water. This heat energy extends into the Caribbean. Thus, this storm ALSO needs to be watched, although all models at this point are taking Maria well north of the windward islands, and then to curve out to sea even further east of the U.S. than Katia has. 

  
Lastly, some model guidance had indicated that a tropical wave would be pushed out ahead of Maria toward the Caribbean and South Florida during the next 72 hours. Whether or not this will even come to fruition is too soon to set in concrete, but if so, would affect the weather outlook for Florida going into latter parts of the weekend.  Also to note, the GFS has been showing every other run or so for another storm, perhaps Ophelia, to form or move into the Caribbean heading toward the last week of September. The last run no longer shows this. Perhaps it was actually picking up on Maria though but has yet to resolve the information as it filters in (?).  


To further complicate matters is that fall is trying very hard to take hold of Florida. Typically, the first cold frontal passage into Central Florida occurs during the mid-last portions of the month, although last year this did not happen in full until September 31st. It was with that event that summer ended immediately overnight with a flick of a switch as a tropical system cut past far South Florida.  That event ended summer for all but SW Florida for another 7 days as easterly flow took over. The GFS of 8pm showed that to occur as soon as next week, but as of 2AM that all abruptly changed. We will need another 2 runs to confirm  Which will it be..End of Summer or Beginning of Fall? 

Faith in Future Forecasts Fruitless - Synechdoche Required

RUC FORECAST FOR EARLY AFTERNOON: At the surface a stationary frontal boundary is aligned near Tampa Bay toward North Brevard County. Aloft, a mid and upper level trough is located in general where the lavender boundary is drawn. The deepest atmospheric moisture is focused along the surface boundary, but ample moisture resides in both directions for showers or thunderstorms today.   Note the large red circle. This is shown as such for a reason which is later discussed.

TODAY: Another day of sketchy forecasting at hand so synecdoche is the word of the day, but a few rules of thumb can likely be applied, so I'll try not to palliate.  As expected could occur, a vorticity max passed across Central Florida overnight producing thunderstorms on the west side into the interior which weakened the further east it progressed. It is possible at least one or two more will follow suite during the course of the next 36-48 hours, but timing is nearly impossible to determine. The latest RUC does forecast a fairly significant impulse to cross Central Florida after noon time through dark though today, so rain chances could elevate during this time frame, hence the good chance of rains in the official forecast per official outlets (I'm assuming). On the otherhand, that energy might go into manifesting as simply cloud cover, especially north of the Beach Line. 


Otherwise, the best instability and chances for thunderstorms will occur along and south of the stationary frontal boundary (wherever it happens to be this afternoon) and where skies are cleared enough for instability to build up. Those storms will move briskly toward the ENE so even locations upstream of their formation could get in on the act, even if mostly cloudy. Skies over South Florida are much more sunny this morning than they are closer to the frontal boundary, but bigger breaks are anticipated central by noon time..not so sure about that either if more energy moves in to early. The best instability is forecast to mount South of the surface front for storm initiation, but steering could transport this activity into the prevalent cloud covered skies just to the north of their initiation.  The surface front will waiver north/south by 50 miles today and tomorrow, but should lift north as Katia progresses north as well. 


In the image above is the mid-level depiction of Hurricane Katia to the east of Florida. As the storm lifts north of the latitude of Central Florida, this should also lift the surface boundary north a bit as well, especially because high pressure is expected to build in from the east across South Florida in Katia's wake. By Friday the boundary should be as far north as I-10.


In consideration of all the factors above, it appears showers or considerably cloudiness could be in store for  North Florida, with showers and a very small thunder chance from near the Flagler/Volusia County line south to North Brevard. Further South toward Central Brevard to Palm Beach County (especially if a sea breeze can form), thunderstorms are more likely. Indian River/St. Lucie/Martin/Palm Beach County toward the coast seem the most likely candidates for this activity after 3pm and beyond until dark at some point. The west coast also has a chance of thunderstorms.     


THURSDAY/SATURDAY: There is great uncertainty in the forecast for the follow up days, but given the expectation (and likelihood) that high pressure will build across South Florida from the Atlantic, this will place South Florida in very weak steering currents with an east coast sea breeze as far north as at least Sebastian Inlet. But, this high pressure will have drier air associated with. Hence, the greatest moisture reside across Central and North Central Florida..at least for a day or two. What happens in the Bay of Campeche in regard to a potentially strengthening tropical system is also a big player. If a storm can get wrapped up in this location, then the moisture source for Florida will be reduced and as such, the rain chances everywhere. So far, it looks like it will be a long time coming before that will occur though. Thus, thunder storm and rain shower chances prevail during this time frame..with that chance working northward toward JAX with time.

LATEST enhanced infrared satellite image and precipitation locations today with notes included on the right margin in orange. Note the cleared skies over South Florida south of the boundary across Central Florida. The blue dot on the east coast is what is left of thunderstorms that formed along a vort max (vorticity maximum, aka - 'disturbance') early this morning and moved across the state. Thunder 'seems' most likely today in the orange areas, but naturally can't possibly be all inclusive. Thunder will not occur in those entire areas either. NOTE the area in the Bay of Campeche and toward the SOUTHEAST SIDE of the Yucatan. This is referred to below in the "Tropical" headlines.    

  
TROPICS: "Much ado about nothing or reason for greater attention in the SW Gulf ?" is the question of the day. Models are split 50/50 on whether this area will become well organized and then threaten the northern Gulf toward the Pensacola/SE Louisiana area...or...never progress into the Gulf at all. Big Difference. So word of the wises, be prepared for surprises...but not anytime soon. This system has a long way to go before becoming 'well organized'..at least as of this morning. Once the area is investigated by the Hurricane Hunters more will be revealed.


For instance, the ECMWF model implies that as Katia moves north, that storm literally drags all of the dynamics and pressure systems associated with remnant Lee along with it. That includes a profound blocking pattern the United States has entered. Blocking patterns tend to hold fast for 4 to 10 days, thus, it is more then questionable that a hurricane in passing would have such an effect on a Northern Hemisphere blocking pattern. But, that is not to say that some variant of that model's hypothesis can't be reached. Either way, all models show that Katia will become one MONSTER of a extratropical storm heading into the North Atlantic ocean in the next 3-7 days. Extratropical Katia could be a major player in many locations in the Northern Hemisphere two weeks down the line.


In regard to the  ECMWF, haven drawn the blocking pattern out, the next assumption is that this willl open the gates for the system in the SW Gulf to emerge and work north and east toward the NE Gulf as a hurricane.


HISTORY OF THE BOC: Historically, the majority of storms that form in this location are pulled northward , but not all of them. In going back and looking at this history, I found that the storms that did so nearly ALL occurred early in the season and not later. This would be because cold frontal boundaries, such as what is now in place...penetrate further into the Deep South the later in the season one progresses with time preventing from working north. That is...all of them but 3 since 1900..and two of them occurred onlly 2 years apart around 1903. The only other one that was actually a hurricane at this time of year was Hurricane Opal...which incidentally followed a Gulf storm just a time prior to another one. Think Lee. The problem with such a due course of action in 2011 is the current location of the frontal boundary and the VERY dry air behind it. This will have to be greatly displaced..and for that to occur, so would the high pressure over Texas have to be displaced, which has been in place since Spring. 


Another observation made this morning is that the models might be giving this system more 'pre-organization' than is realistic. This determination was realized when looking at lightning data and satellite imagery. The most lightning is occurring on the Southeast side of the Yucatan and not in the Bay of Campeche. Thus, the area of low pressure might be much broader than the tight knit depiction of the models.


Below is a two fold image..the lightning as noted above..placed side by side with the track of Opal. Note that Opal FORMED SE of the Yucatan, then crossed it..then took its course toward the Southeast U.S. Other storms that were tracked from the BOC (Bay of Campeche)  toward the U.S.  did not originate there..but rather further east in the Caribbean.

To the left is lightning imagery. To the right is the track of Opal. Note where Opal Formed.

Opal crossed the Yucatán Peninsula while still a tropical depression from September 27 then strengthened northward in the Gulf, becoming the most powerful Category 4 Atlantic hurricane before making a second landfall, October 4, in the Florida Panhandle near Pensacola as a 115-mph (185-km/h) hurricane. Opal devastated the Pensacola/Panhandle area with a 15-ft (5-m) storm surge and travelled up the entire state of Alabama, becoming a tropical storm in Tennessee. Opal also caused heavy damage in the mid-Atlantic states before dissipating. This is the track implied by the ECMWF, except it is not generating in the BOC..and it has the storm taking this course of action in fairly rapid fashion. That means, Katia needs to pull out the blocking pattern in place in the next 96 hours. The ECMWF is not the only model to show this trend as a side note. So this is not to imply the ECMWF solution is not plausible.


The other side note to consider is that 'even if' this system develops in the BOC and lifts northward, it still must contend with upwelling created by Tropical Storm Lee as well as cooler rain waters that drained into the coastal areas off the Mississippi and other tributaries. Thus, to palliate the storm's future course (in this example) perhaps a 'big storm' would be greatly weakened before a true landfall.


The final note on this system...is that other than hurricanes..there was a   Tropical Storm that crossed the Big Bend area of Florida at this time of year ..this seems more likely if anything were to move north.


Outside of the BOC, there is yet another developing system approaching the Leeward Islands. This looks to be our next named storm system. Again, guidance is leading the reader in two directions. Will that system follow the course of Katia..or continue toward the Caribbean?  Again, we are back to square one with what Katia does or with..or what results from..the storms interaction with the remnant blocking pattern of "Lee".


Thus, Future Forecasts are Fruitless not only in regard with Florida's Local Weather, but with regard to the tropics as well.


In closing, the more interesting system if none of these systems impacts the Deep South will be the NEXT one toward the last week of September. By that time, and under the assumption the blocking pattern does not break down early (in which case none of these shorter term systems will directly strike the U.S)..the pattern will or should be in the process of breaking down, but not before the next Atlantic system will already be in the Caribbean. As always, all thoughts are of the writer's own..images provided are actual guidance or real-time information...and future projections, especially beyond 1-2 days are as good as a blind man relying on a blind seeing eye-dog.