Watching Weather Conditions For This Afternoon Central/North Central Florida

 

 

 

There is a large 'blob' of convection off the East Coast of South Central Florida at noon. It appears to be located/resultant from upper level divergence and low level convergence at the negative tilted base of the 200mb (40,000 ft) jet stream flow. Other convection along the SW Coast of Florida seems to be associated with a 500mb low within this trough.

 

There lies the 'potential' for the branch flow in yellow to weaken and/or cut off, at which point convection along the Florida east coast could stream inland. Mainly after 2pm. The latest 18 hour RUC simulated radar animation is showing showers with embedded thunder to stream in mainly near the north end of the CAPE, well inland to the west coast from that point as the flow around the low off the SW coast takes over the steering currents.

 

The latest HRRR model (which runs several hours slow unfortunately) is bringing 'some' activity on shore, to lesser extent, but stronger from Indian River County and north, with ONE strong storm moving across Central to North Central Brevard late in the afternoon.

 

Thus, although little to no rain is occurring at this time..or is mostly moving out, this could be because the low off the SW coast is wrapping up (closing).

Heating is occurring in cloud breaks for the time being, but some high clouds are working toward the East coast near Brevard.

 

Latest water vapor animated loops show much of the state is being 'dry slotted', however, SPC Mesoscale analysis shows that there is ample moisture in the convective layers between the Lifted condensation level and the level of free convection.  A pseudo warm front is moving slowly up the state from far south Florida at noon, and winds at the surface are responding to the tightening pressure gradient...as well as backing a bit more toward the NE in Northern Brevard (for example). Winds aloft below that level are more from the East to ESE.

 

Any severe weather to occur will likely happen in a very restricted area (if it does at all) right ahead to right behind the surface boundary.

 

This is just a 'precautionary' post. The situation would be much more clear if we were dealing with a strictly tropical or strictly non-tropical situation, but this one is neither. Models did not handle the precipitation fields well in regard to where the heaviest rains would occur for this event, but did handle the latitude at which they would. Osceola County likely owns the highest rainfall totals. For this reason, even today's events if they occur at all are highly questionable.

 

Another area to watch is interior SW Florida.

 

 

 

Windy With A Small Chance of Severe Category Storms By Noon

Current conditions as of 5AM. The trough still appears to be more of a 'warm front'. The image annotations are described below in the over view / explanation portion.  Note how TIGHT the isobars are compared to previous days.

TODAY: Very windy, mainly at the beaches through noon, but spreading well inland by noon. Winds should increase with sunrise and spread west toward the interior, especially north of Lake Okeechobee to the Beachline by mid afternoon. Generally, winds within one block of the beach and along the west banks of the Banana and Indian Rivers in exposed areas will be in the 24mph range with gusts toward 40 -42mph. ALTHOUGH, I saw an observation last night out of Virginia Key east of Miami reporting gusts to 52mph. Something to be advised of. This was likely related to heavy rainstorm activity in the area.


As I type, I can actually see stars?! While showers are inland and some strong rainstorms  are further south not far away.


Very little change in the line of thinking from yesterday's post. This post includes agreement with comments relayed by the National Weather Service Offices in MIA and MLB, which surprisingly were what was written here yesterday. They also are in line with those from the Storm Prediction Center (SPC) based in Norman, Oklahoma, which also match yesterday. Those being:


1) The SPC refers to the boundary near South Florida as a 'warm front'. This boundary will lift north from its eastern flank while moving little on the western flank which is embedded more toward a supporting upper level trough. Thus, this boundary will 'pivot' from the western flank while the eastern side will lift north and west during the day. As it does so, the pressure gradient between high pressure to the north and low pressure associated with the boundary will increase, thus the high wind threat. This will occur during the late morning through sunset.  In doing so, helicity along the northern lead of the boundary will increase, but mainly in the levels of the atmosphere above 2000 ft to 12,000 ft, whereas at ground level winds will be quite unidirectional (from the same direction). However, with any minor ripple or glitch in the current line of thinking there could be a threat of an isolated tornado. 


The purple area in the image above is where it appears that threat will exist between 2pm - 7:30pm, although it could be earlier than this for the region along the south end of the outlined area. 


The second reason to downplay a tornado threat as noted yesterday is that thermodynamics (instability/buoyancy) will be lacking due to lack of heating with cloud cover that is expected. The biggest threat areas though should be within 20 miles of the coast (east coast) where any long lasting and better breaks in clouds might occur. More appropriately, up to 10 miles DOWNSTREAM of where those breaks occur.  Any storm that might contain thunder should be a red flag today, but that too is questionable (thunder).

This is SPCs thinking  , as noted :  EXPECT NUMEROUS SHOWERS WITH 
WIDELY SCATTERED TO SCATTERED/EMBEDDED TSTMS IN 
CLUSTERS NEAR AND N OF WARM FRONT. BUOYANCY SHOULD 
DECREASE NORTH OF WARM FRONT WHILE LOW-LEVEL SHEAR/
SRH (Storm Relative Helicity) INCREASES.


This is their threat area in the image below. I threw in my own 'slant' for a 'threat area' 
of possible tornadoes as well in blue, but realize the SPC outlook is official.


Outside of the conditional tornado threat, any storm today with thunder could be severe thunderstorm warned if conditions warrant for 'winds' in excess of 58mph, since this
activity would not be related to fully tropical activity. This very well may be the case, 
but again, the question becomes, "can we even get thunderstorms in here today with 
warmer air aloft/less instability? The GFS implies there will be some instability, whereas the RUC which has been doing plain awful since yesterday, says 'no'.

THE OFFICIAL SPC OUTLOOK From Early Morning is in Green. This might be removed by 8AM though, but I doubt it. One can never be too careful in these instances.

2) The NWS Melbourne is also mentioning this threat in their early morning discussion, 
possibly because SPC had. They have mentioned it in the past though, but for a different reason.This treat looked real enough yesterday for the reasons cited this morning though for it to be mentioned in yesterday's post.


OTHERWISE:
SOUTH FLORIDA: Winds here from Palm Beach and South will decrease significantly 
with the passage of the warm front 'like' boundary. It appears this should occur by noon 
time. In fact, it will not be windy at all once it clears. Rain chances also diminish greatly, but some stray showers or even a thunderstorm 'might' occur. Temperatures aloft have 
warmed as noted yesterday , hence the lack of thunderstorms this morning and the other reason why the tornado threat is conditional.


CENTRAL FLORIDA: Front pivots from the western flank, with the eastern flank lifting 
north and west. Pressure gradient increases further across South Central/Central Florida. Rain showers and possibly thunder could form/increase after sunrise, although some areas might not see rain at all until at least noon if ever.


Pressure gradient. At this time, the barometric pressure near Tallahassee is 30.10". In Ft Lauderdale it is 29.80". The gradient is the degree of difference between those to 
numbers. On a normal summer day, they run close to identical. 




The warm front is expected to lift north of the Beachline around sunset or shortly
thereafter, at which point winds quickly wane , followed by waning rain chances as well


Further north, rain chances toward the east coast from Volusia County and north could 
continue past midnight but end by sunrise.


MONDAY: During the day , the boundary will have swept into the Gulf and become 
aligned NE to SW in the Gulf close to the upper level low. A weak but broad surface low will form from the mid-levels down to the surface of non-tropical nature, although this is debatable. Another low could exist near the Florida Panhandle along I-10 east of 
Tallahassee. Monday will be quite pleasant with standard fare land breezes in the morning with a South to SSE wind nearly paralleling the coast in the afternoon. Some 
thunderstorms could form under the conditions, but rainfall should not add up since storms will move from the SW at 15-20mph. Most likely, late in the afternoon , and could last 
until after dark, around 9pm.


TUESDAY/WEDNESDAY: Similar to Monday in the wind department as the low in the Gulf lifts NNE toward the Big Bend. This low will have a surface trough with it, a bit like a 
'pseudo cold front'. My line of thinking now is that thunder will be more likely Tuesday 
with this boundary and moisture still at play. On one or both days some of these storms 
could be strong along and east of I-95. The low will lift north through Georgia and along 
or just east of the Appalachians, with a secondary low running up the eastern sea board 
eventually toward the Statue of Liberty/New York early in the week.


THURSDAY: Remember , there is still our cold front from the Rockies that created
the early season snow. It is expected to be preceded by a prefrontal trough on Thursday with the front to follow sometime Friday. As of the last run of the GFS, that would be 
near noon on Friday. Rain shower/storm activity is expected to be quite low, or at least 
limited in strength and expected to be isolated showers mainly. The front should clear 
the state by Saturday morning and enter well south into the Caribbean during that day...making for a very pleasant weekend.


TEMPERATURES WITH FRONT: Don't even bat an eyelash. They are not expected to fall 
quite to the levels of the previous front, but it will be coolest in the same areas as was 
the case with the last front. Thus, the immediate east coast from Port Canaveral and 
South will be warmest, with mainly 50Fs expected across the peninsula in other areas. Afternoons could remain in the 80Fs. Winds will be much quicker to shift onshore as well.


SIDE NOTE: The NAM and NoGaPs models are showing for quick tropical development in 
the Northern Caribbean, with a weak low pressure area to form and race north and close to the east coast as the front moves in. For now, disregarding namely because even if so
it would have little impact beyond what has already been stated above.


BEYOND: The boundary will align across the Central Caribbean. As has been the case in 
the long range with the GFS, a bonafide' tropical system is expected to form and impact 
(this time) Jamaica. We shall see.

Storm Focus Shifts to South Half of Florida - No Tropical Development Expected

"LARGE TREE DOWN" - Cape Canaveral from Friday Evening Winds estimated to gust to near or over 60mph, and likely stronger (considering the above)

TODAY: Evolution is under way with sunrise of  overall future features as models come to agreement.


No real surprises. It does not appear that a truly tropical or even sub-tropical system will form, but if one were to be named it would likely be 'fictional' as was Hurricane Irene for which land based surface observations never verified sustained hurricane force winds, only in gusts. Any low to form will have strong winds not due to a tight circulation and low central surface pressure but rather from a tight pressure gradient in the mid-levels translated to the surface in wind gusts near and in stronger rain showers and thunderstorms...far removed from the center of lowest pressure.


OVERNIGHT: Heavy rainstorms with lightning occurred almost all night, mainly across Central and Northeast Florida. Rainfall totals so far have been between 2 -7", with somewhere around 1.5" being the overall overage across the East Half of the state north of West Palm Beach. By the time I'm done writing, they could go up another 1" in some places though. 


There were some chosen locations in Flagler, Volusia, Brevard, and south to Martin County that have run above 4" though. Winds in the stronger storms were reported generally in the 40-50mph range, but the storm we had here last night definitely had wind stronger than that..as attested to the image above of a tree that stood up to the 2004 hurricanes.


Quickly, the graphic below was saved to show how varied conditions are close to the coast overnight compared to well inland. A coastal/marine trough forms near the coast which is along where the heaviest rain fell.

NOTE winds of 6mph inland and a steady 20mph at the coast outside of rain showers. I labeled the purple line as " the nocturnal coastal trough". Formed by wind convergence along the beaches along sinking/subsiding air inland overnight where it cools...and between where the air remains unstable closer to the coast and the warmer ocean waters (aided by the Gulf Stream)

And Aloft, as the Easterly winds blow along the ground,   is the jet stream and divergence creating lift for the air mass below it...like a flower opening its petals.

It is within this upper level trough area the main 'feature low' will form, perhaps closer to the west coast, but two or three smaller surface lows could form between today and late Sunday along the surface boundary further south.

TODAY: At time, all factors are now in place for a more organized low pressure to evolve, and more factors are on the way through Sunday. It appears this will occur along the old frontal boundary of last weekend which ended up in the southern Florida Straits. High pressure is centered over the Mid-Atlantic with the cold front out west not expected to enter Florida until Thursday through Friday. Up until that time, showers and thunderstorms could occur. 


However, the days of strong onshore easterlies along the coast will end from South Florida To North from late early Sunday working north toward Monday afternoon with time, as will the onshore moving rain-shower regime.

Old front could return as a pseudo warm front. Strongest storm activity, and thus the focus of weather activity, will be along and north of this boundary with time going through today into Monday. Low pressures seems to be located both WSW of Naples as well as in the Southern Bahamas...both sides of Southern Florida

As noted, the focus should shift from onshore moving rain storms solely to those along and just ahead of the boundary to move north from the Straits. Already, there is a tornado warning out toward Southern Dade county based on radar. 


The image above is from the RUC model and closely matches that of other models. Note the strong winds to the north of the boundary (the blues and purples with stronger winds indicated by the wind barbs within those colors) . 


That stronger wind appears to be headed toward South Central Florida today through Overnight Sunday. Otherwise, the main feature outside of this boundary will be low pressure aloft in the East Central Gulf. It would be far too extensive to describe how the models vary, because they all do. But there does seem to be some sort of agreement that there will be weak surface lows along BOTH coasts embedded within a large mid level circulation, which as it would be, will be located near the base of an even larger trough created by a merger of the southern and north branch jet streams. As that low /trough lifts north so will to the surface boundary 6-7 miles below it. More storms could occur along SE Florida, with some heavier rain showers as far north as the Cape.


As the main upper low wraps up and gets organized, it will draw warmer air into its upper circulation, thus the air mass will become less thermodynamically unstable; however, as these lows organize,  wind shear/bulk shear through levels of the atmosphere, and in turn helicity will increase especially on Sunday through overnight Monday as the warm front (or so I've called it here) lifts north and meets the stronger baroclinic zone across South Central Florida. Again, according to the NAM model, not a given.


The Storm Prediction Center has Southeast Florida in a Slight Risk for Tornadoes Today and into  tonight for these features, but a smaller risk area extends toward the Cape area. Any tornado will be isolated if  at all, but the wind risk will become, from how I see it, quite real in any storms that can form especially tomorrow into early Monday morning post-midnight across South Central Florida, especially near the coast and inland as far as I-95. There is quite a show going on right now near Homestead with a big storm.


Elsewhere, another wind surge looks to be in the cards as I write to approach South Central Florida by 2-3 pm. Winds will be strongest where they have been all along, namely within 1 block of the beach and along the west banks of the Banana and Indian Rivers in exposed areas. Winds in heavier rainstorms could gust to 40-50mph, although with the upper levels warming more, I'm not seeing as much lightning any more except with the storm that was tornado warned over South Florida and a small bit off shore. There was much more lightning last night and early this morning before the upper low started to ingest warmer/tropical air. Already, winds at the beaches such as Patrick are gusting to 39mph last hour without the help of a rain storm...while away from the beaches winds dropped off gradually further from the coast. Winds are also stronger near the West Coast. 


SUNDAY Weather should improve over South Florida, but could go down hill from near Ft. Pierce after sunrise and north to Port Canaveral later in the afternoon as the boundary is lifted north and up the peninsula. As a heads up:


BASED ON THE NAM ONLY, which tends to go over board and has not been too reliable lately, this is the worst possible case scenario on Sunday:


A slight risk for tornadoes could be at hand by mid-morning north of West Palm Beach, with that risk extending as far north as Port Canaveral by Midnight if not sooner. If South Florida is in a risk area now, that is 'nothing' compared to what the NAM shows to evolve between now and tomorrow. 


The only thing NOT going for a more assured RISK is that instability will be greatly limited, but not completely. However, low and mid-level helicity,  increased moisture in the low-mid levels, BULK shear from the surface to 700mb, and even some angular momentum indicated by the 850-700mb wind barbs and timing of night along the nocturnal, coastal marine trough which develops at night would all add up to some pretty darned vicious storms. Again, this is based only on this model. With the 'tools' I have availbe, it is the only one that shows all of the parameters needed to be known to make such a determination. It may very well be though this period will be just like all the past two days, but I'm having my doubts about that. The NWS in Melbourne is making no mention of it, much to our relief. At least, not yet.


The worst weather appears could occur from Ft. Pierce and working north to Port Canaveral between 11AM through 4AM Monday morning, and extending as far west as a few miles west of I-95 toward the county lines. After that point , the threat diminishes as portrayed by the NAM as the low level boundary gets further removed from the upper level low over the Gulf of Mexico. But, there is still much to be learned, and plenty of time to learn of 'it'.


BEYOND: Outside of this ongoing saga, it appears a shift in the overall hum-drum will occur overnight Sunday through Monday ...as winds die and shift to a southerly component of only a light wind compared to these past few days. In other words, normal wind and even normal to warm daytime highs on Monday outside of the JAX area.  The cold front will be on the approach, but the entire peninsula could be good for afternoon and evening thunderstorms, favoring the east side from mid-afternoon through late night each day through Wednesday.


The GFS has a prefrontal trough to go through Central on Thursday, with the actual front on Friday. The weather on both of these days across Central will depend on the time of day each one is to pass. So far, two consecutive runs of the GFS show the prefrontal trough which could be weather active to cross Central near sunset Thursday with the actual cold front to cross before noon Friday. South Florida will likely get the benefit of getting better rains from both features, but not exclusively.


NEXT WEEKEND: Looks to be everything this weekend is not, and what last weekend was.

Thunderstorms and squally rains rotate into the coast before sunrise this morning. They seemed to take a slight cyclonic like curve as the approached the coast (and the nocturnal coastal trough) which was pushed west toward the banks of US1. Heavier rains fell on the lee of that trough in Rockledge toward Sebastian Inlet.

"Utter and Total Devastation " (as far as the fence is concerned) . It just recently collapsed to the ground while typing the post today.

Increasing Wind and Rain Threat "Sometime" Over The Weekend

"The Beginning"  - Sunset on Wednesday Evening As The First Rains Move In From the East 

SYNOPSIS-CAST :


Out of respect for the events of late and low confidence level of future ones, today's post is an  attempt to explain in generalities  the current conditions and complexity involved with the weekend weather forecast leading into 'potentially' the first half of next week. 


CURRENT: First of two parts is the surface or near ground level weather (that which we experience first hand). High pressure has indeed  settled into the Mid-Atlantic as expected.A  Deep trough is over the Rockies making for some very early season snow fall in all locations  expected (per the photos relayed to me from my good friend who lives in Cortez, Colorado in that state's southwest corner.)  This can be seen by extracting the latest surface depiction put out by the Rapid Update Cycle (RUC) model below:

RUC of 12PM: Onshore flow along the Florida east coast with blue arrows (and shading) showing the wind is rotating around the HIGH pressure (H) center near Pennsylvania. The flow is clockwise around the high and heads north ahead of  LOW (L) pressure centered over NE Montana, which has a trough extending Southward from it. The zig zag blue is the ridge of High Pressure  axis extending from Eastern Canada to the Texas Gulf Coast.  The question marks in orange are for where or even IF a low will form during the weekend ...and whether that low, if it forms, will be a surface low or one in the mid-levels of the atmosphere....for now...the 5,000 ft level which is near the lowest of what would be considered "mid-level"  

Just to be sure, I've extracted the latest 10M (meter) plot from the LDIS (Local Data Integration System) from the MLB (Melbourne) NWS (National Weather Service) website of Florida...below:

LDIS for 10M: If you recall yesterday's plot, the color coding was all blue. Now some light greens are getting into the picture of sustained 20-25knts winds near the ground (over the waters). The purple areas are little bubble 'troughs' that are formed as the winds suddenly drop off when hitting the shore line. When joined, they form a marine/coastal trough up and down the east coast. So far as of sunrise, all or most of the rains have occurred at and west of the trough (as well as offshore). Some lightning and thunder was observed last night to early morning from JAX toward Ft. Pierce, with the heaviest and most persistent area near Ft. Pierce in St Lucie County toward Vero Beach...where rains persisted and kept reforming in the same area.

Rainfall in St. Lucie county per radar estimates and an actual COCORAHS observer were close to 5 Inches here. This could be considered a localized 'rain event'. Pointing this out, because this will be how the weather will materialize through Saturday and into Sunday. Some areas will see little to no rain, whereas other areas will or could get excessive amounts mainly at or near the coast.  Interestingly this morning, the rain in St. Lucie did not progress to the west, but stayed in the same area as it was refueled by the heat and moisture source, i.e. The Atlantic.

last night was a good example of how the weekend could unfold. The difference will be that surface winds will be stronger everywhere and there should be more pockets of rainfall, especially on late Saturday into Sunday. Just where those areas will be is very difficult to determine until a low pressure area at the surface or just above the surface materializes. At that point, we can count places out and hone in on 'target areas'.

But, now look well overhead at the jet stream level, remembering how breezy it is today from the east-northeast at ground level:

25,000 feet overhead. There is a big zig zag ridge axis in blue and the trough out west even at this level, but note the trough over Florida and the WSW winds over head (oppostive direction than the surface wind shown in the previous images). There is even a bit of a low circulation where the red "L" is drawn along the trough axis in red.

THE PATTERN TODAY INTO TONIGHT:
Winds will increase in 'surges' as has been the case since the pattern first began to evolve. Another surge is expected toward dusk tonight. Surges are often accompanied by increased cloud coverage and rainfall in some locations for a brief time. We could see another 'event' overnight tonight of rain as well, but just where is impossible to know.

Winds toward sunset will decrease significantly away from the coast overnight, but remain a bit elevated at the beaches tonight although not as strong as during the daylight / early evening. Another surge of diurnal nature could occur with sunrise with more showers just about anywhere as it approaches lasting through late morning. These could work across at least the spine of the state before weakening beyond that point. 


SATURDAY: Increasing winds once again as the pressure gradient kicks it up a notch, beyond even any diurnally driven 'surge' due to the increasing pressure gradient between high and low pressure . Winds at the beaches could increase to SUSTAINED 22 -28mph with gusts to 35mph. Wind in and near any rainshower or perhaps thunderstorms will be noticeably higher with  approaching activity, but could quickly wane immediately as and after a storm has passed, before coming back up to 'status quo' during the following hour.  It is possible that surface winds will barely wane, if not pick up even further along the coast from Miami toward Brevard Saturday night as rain storms continue this common theme almost anywhere along the east coast at night and less so 30 miles or more inland.

HINT: If one is outside at night and you detect the wind starting to increase but cannot see the sky, that can mean a rainstorm is either near by or about to pass over head.

SUNDAY/BEYOND: This time frame continues to remain the "Great Beyond" at this point, leaving this space to briefly recap and surmise.


MODEL GUIDANCE TRENDS: 

ISSUE #1:  The first observation is that the ECMWF and Canadian Model, and now even the NAM of 'old unreliable fame' are coming into closer agreement to what the GFS had portrayed last Saturday when it was first mentioned here that there could be an upcoming rain event along the Florida east coast. It is now the GFS that is no longer sticking to those guns. Only the NoGAPS comes close, but it is forming a low much further to the east of the state than any others, having no impact whatsoever to the state.

ISSUE #2: The NAM is now in close agreement with the ECMWF in location of a low pressure trough and eventual 5000 ft or 850mb low toward SW Florida. Only a very weak low pressure circulation at the surface is noted, but they are quite close. And, for a change, it is the GFS that is much faster to form a low..even faster than previously thought, which runs eventually up the east coast. That is, on Saturday evening. All of the windy and wet weather in any case with a low will be north -northeast of the low. Thus, even though the GFS forms one near Miami, they remain dry..whereas further up the coast rain chances increase. But even so, the GFS has very little rain with the system over land...in fact, even any wind. PROBLEMATIC FOR SUNDAY'S FORECAST if one is to consider this model.

ISSUE #3: Line of thinking. For now, it is probably best to run with model agreement/concurrence which would be a blend of the ECMWF (Euro for short) and the NAM (even though it has been very unreliable lately). There is another reason though. The NAM is much slower in the low pressure center evolution, and is depicting the areas of rainfall much better than the GFS. The GFS is too general, making it appear as if it will rain everywhere up and down the coast at almost the same time, whereas the NAM has a better handle on capture convergence bands and vorticity banding, and thus not showing 'rain everywhere' simultaneously. 

ISSUE 3: For consideration. If the GFS verifies, rain is pretty much over on Sunday as the low moves up the east coast (except toward Jacksonville). This is a big change from previous runs. If the line of thinking with the NAM/Euro is correct, rain chances remain elevated through Monday at least.

FINAL THOUGHTS: Watch for a mid-level low as opposed to surface low to form either right over the state or in the eastern Gulf over the weekend. This could be the dominant feature. If so, then we'll have to watch for it to 'cut off'. As noted several posts ago, cut off lows are seldom forecast with much accuracy beyond 48 hours, and none is yet shown to occur. But if so, they move slowly. 

BUT LASTLY: Inevitably, either somewhere along the east coast will get inundated with more high rain totals, and not to be left out, if the Euro comes to fruition which has not been mentioned much, the SW Coast of Florida. Both the GFS (to give it credit) and NAM increase precipitable water significantly heading into Saturday, which means heavy rains somewhere, including the Metro Areas of SE Florida.

GREAT BEYOND: In any case, no matter which model verifies heading toward Monday, there is a chance that more rainfall could be in the forecast for quite sometime after a 1-3 day break...but then again, oddly, my Accurite Weather Station forecasts for the first time in days NO rain in it's automated weather icon of a cloud with rain falling out of it and now has sunshine. Have to watch that thing and see if it has something going for it.

Wednesday Evening After the Rainbow

Stronger Breezes and More Frequent/Heavier Showers To Increase This Weekend

Current Local Data Integration System (LDIS) Plot From 3pm, Thursday (today).
This surface plot shows the average 10 meter winds by the wind barbs and color coded scale to the right. Note that winds are weaker toward the interior and west side of the state. High pressure is to the north and low pressure to the south.

SHORT POST TODAY AS WINDIER AND WETTER TREND CONTINUES   INTO SATURDAY/SUNDAY:
Taking a little time today to show graphically what is going on in the next 48-72 hours. The above zoomed in image of Florida shows in general the isobars of constant barometric air pressure aligned across the state. Note how close together they are due to how close the low and high pressures are (as well as to the strengthening high pressure). The closer together the lines, the stronger the wind. They will get much 'closer' on Saturday or Sunday. 


As mentioned in previous posts, High pressure from Canada will be added to the mix on Friday...in fact, the process has just begun. But it is still building southward behind the big low that finally is departing Nova Scotia after spending nearly two weeks over the Great Lakes to the NE States. Now that the low is moving out, high pressure can move in and down the coast to replace it at all levels through the bottom 10 - 15,000 ft above (or up to 3 miles  overhead).  This can be seen by looking at the wind forecast for 20,000 feet by  Saturday morning.

High pressure arcs into Canada well aloft, and the GFS has an upper low forming West of the Fort Myers area in the SE Gulf. That trough to the west shown above will bring wintry, wet, stormy, and possibly flooding conditions to parts of the Plains states going into and through the weekend at times. Dry and pleasant weather will persist to the north of Florida where it had been unpleasant for so long last week. 

Note the potential for the upper low off the Florida West Coast. Underneath that low Southern Branch jet stream winds are  expected well overhead our state, while at the surface winds are expected to increase much more than than area today from the ENE-East. Convergence is noted along the east coast as the easterly winds collide with the coastline and converge or press/squeeze the air mass and the moisture in it. This process  induces rainfall at the coast, although most will already be coming toward the coast from well off shore. This can be seen by what is occurring today.

Convergence on the east side and divergence on the west side where the winds slacken and spread apart to a very small degree. Convergence is more suitable for heavier rain fall whereas divergence tears it apart.

The winds shown in the image above are expected to "surge" increase as more high pressure circulates out over the Atlantic from the building dome of high pressure to the north up in to Canada by Saturday morning, although they should increase more in small phases now and then at just about anytime before that time. The most notable times for diurnally driven surges are near sunrise and during peak heating, and sometimes late in the day toward sunset, with the weakest winds at night outside of rain showers.


This will be how winds will operate in coming days. Thus,during the late morning toward noon toward 6-7pm rain can cross the state but weaken beyond  20 miles inland in most cases, but as night falls instability over land decreases and showers cannot sustain themselves. On the other hand, the ocean remains a constant warm 80F+ degrees day and night, thus the most instability will be near the beaches so that off and on rain showers can continue. This is the main reason the big rainfall totals should occur near the beaches through Sunday...evening accumulations outside of external forces such as a well developed low pressure system.


Expect more weather like today on Friday, with slightly stronger winds and more rain showers. Not everyone is getting rain today, and most are not. This will be the case once again tomorrow, but some more areas should see rain at some point, with winds increasing a bit.


SATURDAY/SUNDAY: It is during this time frame that surface winds should increase even more as the opposing pressure patterns begin to butt heads most affirmatively. Neither system to the north or to the south wants to budge, and the result is a tightening pressure gradient and stronger wind, and thus more convergence at the coast and more rain with thunder possible. Winds in heavy rain showers or thunder could gust toward 40mph later on Saturday and Sunday. By Sunday the NAM and to some extent try to form a surface low near the SE Coast, but that is only one option. If it does occur, weather 'action' would increase first along the coast of SE Florida to eventually work up the east coast and worsen with time. But that is only one scenario.


BEYOND: Like before, models do not agree on IF, WHEN, HOW, WHERE, or WILL a surface low will form to further complicate matters.  'IF' one forms the weather over the state will be significantly affected. 


"WHERE" - "IF" f a low forms to far off the east coast and moves north, weather everywhere is significantly improved. The closer to the coast to on shore a low forms, the more downhill the east coast conditions will become as it moves up the coast.


IF it forms more toward the interior or off the west coast, conditions everywhere could be varied vastly but in a different way from what the weekend has to bring. 


"HOW" - Another scenario involves only a mid-level low forming over the state and stretching NE toward SW Across the state with time. This was depicted originally by the GFS a few days ago and is now what the Euro (ECMWF) model is showing today.  And as if in jest, the Canadian has two lows, one performing like the GFS but it goes into the Gulf and wraps around another one rather than moving all the way up the east coast. 


BUT IN ANY SCENARIO: WHEN? There seems to be agreement on this parameter. Later Sunday.


Thus, the future remains unknown.    If a system forms over or west of the state, rain chances continue well into next week, but the winds subside significantly. Any boundary left over in the Caribbean when all is said and done, whenever next week that might be..could induce a purely tropical system to form heading toward the last week of October.  So, more opportunities to watch the tropics still loom in the next two weeks at least. 

Phase 3 (?) Has Begun, Gradual Increase in Wind and Coastal Rain Chances Through Friday Evening

Image from near sunrise this Wednesday morning. A weak, but evident, low level wind surge accompanied by some sprinkles to 0.01" of measurable rain occurred shortly after sunrise along the Central Florida Coast. These initials light spritz's were followed by a rainbow to the west ..just as the final rains last Friday evening ended at sunset with a rainbow to the East. Interesting. Perhaps Florida will soon be on the wet end of the rainbow (especially the east coast) in a few days. 

TODAY: What I've referred to as "Phase 3" of an upcoming and slowly evolving pattern began this morning as a 700mb trough (at 10,000 ft) clipped the east coast from the North, related to the old upper low which has moved off the NE U.S. Coast. Associated with that trough was a NNE-NE upper level wind component (very light) and slightly cooler air at 5000 ft.  (Phases 1 and 2 were a wind shift a ground level (the surface) and at 925mb (2000 ft above ground level, or AGL). This cooler air at 5000 ft is just enough to generate a thick enough stratocumulus (stratocu) deck of clouds to put out some rain. It is pretty obvious by looking outside that above those cloud tops it remains bone dry per the blue sky which is prevalent in most locations. Colder air per the RUC (Rapid Update Cycle) model is filtering in at the 5000 ft level from Volusia County and north with all else constant, but that is the necessary ingredient to continue some sprinkles and more clouds as can be seen in the image below. As anticipated, rains ended for the Keys yesterday..but on the early end of the window of opportunity (by noon for the most part). 


Note the enhanced cloudiness further out in the Atlantic (below). Those are associated with cooler air at 5000mb moving in toward North Brevard County, which appears will arrive around the 4:30pm time frame. Thus, increased cloudiness for the North half of the state initially on the east coast will spread to the west before and during, to after sunset.  Further south, there appears to be a fairly persistent convergence/vorticity band developing off the Western Bahamas and advecting into Palm Beach County. It's hard to tell if any sprinkles are associated with that feature, but the cooler air at the 5000 ft level is not present there yet.

Some enhanced cloudiness and showers/sprinkles could occur as far south as North Central Brevard prior to or near sunset. The convergent band near West Palm might very well continue, or suddenly halt. at any time.

Otherwise, outside of the areas noted above, the remainder of  today and tonight will be similar to yesterday other than the slightly stronger wind at the surface today, decreasing a bit about 1-2 hours after sunset. Skies to remain partly cloudy this evening with more sprinkles possible from time to time. No model shows any sig (significant) changes over night.

THURSDAY: The only real difference between today and tomorrow is that the 700mb trough around 10,000 feet will have continued south to meet up with the old frontal boundary south of the Florida Straits. .possibly pushing toward the North Coast of Cuba. As it presses south, winds aloft across Central and North Florida will become more easterly at that level will as opposed to the somewhat flaky and weak NNE-NE direction of today...cooler air just above the deck and slowly increased moisture will increase rain chances to more measurable amounts from West Palm Beach to JAX from near daybreak through the remainder of the day, but most places will see plenty of sun as well outside of the showers which will be mainly restricted to 15 miles of the east coast at most. Winds to remain status quo around 15-22mph at times at the beaches and spreading inland during heating of the day, then waning and backing off after sunset. Rain fall totals perhaps 1/4" in a few select coastal locations between sunrise and set, but wouldn't be surprised to see a little more between Oak Hill and JAX.

FRIDAY: High pressure will now build more affirmatively southward from SE Canada and merge with high pressure working NE from the Deep South states in response to a very vigorous Pacific West Coast Trough pushing through the Sierras, the Wasatch, and the Rocky Mountains. As these two high pressures merge, the pressure gradient across Florida will increase as low pressure continues from the Florida Straits through the entire Caribbean and Gulf of Mexico.   With increased winds comes better moisture convergence along the east coast, especially along what appears will be a coastal trough to set up due to frictional effects of the shallower shelf waters to the 2000 ft level. This trough and increasing speed shear at the 10,000 ft (700 millibar (mb)) level results in mass moisture convergence up and down the east coast, with the strongest gradient throughout all levels directly between high pressure to the north and low pressure to the south, which currently appears will be from West Palm Beach to Jax.  

The first heavier rainshower with perhaps some thunder could occur by mid-late afternoon at the beach from Port Canaveral to JAX, although the GFS continues to have an affinity for Port Canaveral for some reason. That could easily change.

SATURDAY: Yet another surface wind surge, likely caused by falling upper level temperatures with perfectly aligned isobars (lines of constant barometric pressure) from the surface to 10,000 ft as well as the strengthening high pressure to the north will kick up the surface winds once again to a steady state of 20-25mph, mainly within a few blocks of the coast. The GFS is honing in now on the region from West Palm Beach proper to JAX for the period from Friday through Sunday to receive the heaviest rainfall in the 2-4" inch range, and restricted solely to  25-30 miles of the east coast, with slightly lower amounts in Southern Palm Beach to Southern Dade and the Keys. Actually, much lower with less than an inch in this area.

<TIME OUT: At this point, it is worth noting that during the Florida transitions, the vigorous and powerful trough moving through the West will be digging deep with plenty of very cold air with it (cold by October standards). Snow has already fallen over the Sierras and more is on the way. This cold  and very unstable air will spread east  generating snow over all of the higher elevations of the mountain ranges out west, possibly as far south as Northern Arizona in one spot, NW New Mexico, the ranges of Utah and those of Colorado included. Severe weather could occur from the Western Texas Panhandle region to as far north as South Dakota. 


Totals in the highest elevations could exceed one foot. Some folks (okay, maybe just one person) were caught off guard in the Sierras this morning, and were out putting snow chains on their vehicles in the snow.) Testament to why it pays to remain attentive to the weather, as if not heeding tornado warnings weren't bad enough.


I have mentioned the blocking pattern that will be in place over the South East states in several blog posts now. To put it in a better perspective, despite how strong this approaching trough is and will be to create all of the chaotic weather out west, even that will not be enough to dislodge that block. The trough simply lifts up and over the block into Central Canada, with another to follow during the weekend.  TIME IN>

TEMPERATURES: I have a feeling that heading into Friday afternoon both high and low temperatures could remain in the 70s at the beaches unless there are better breaks in the clouds, which is always possible.  Ocean temps in Brevard are now running at 80F, so onshore flow of at least 20mph or stronger across those waters accompanied by clouds and cool rains with gusty winds should keep the temps down at the beaches from Central  Palm Beach County and North. Additionally broken to scattered clouds should hold down inland temps to the low 80Fs, although this scenario appears more likely in the temperature fields on Saturday if things materialize as they might.  

BEYOND: Here is where we stop for today's post. If you've watched The Weather Channel or local news stations, there is much to ponder and await for regarding potential sub tropical cyclone development toward the second half of the weekend and/or the beginning of next week. BUT NOTE....

THREE SCENARIOS HAVE COME OUT BY MONDAY:

1) The GFS has now shown on various runs from yesterday to the latest as of 8AM for a low to form along the Southwestern Bahamas , to off the coast of Naples, and lastly..for one to form over South Florida.  In all cases, it seems that a wave of energy breaks off from old storm Philippe and rides along the boundary lying across North Cuba, inducing a wave of low pressure that eventually closes up into a surface low near the South West Bahamas. But when that closure is to occur is up in the air (if ever). In every case, the low is then thought to form into a depression or tropical storm, albeit a bit of a hybrid one and not fully tropical.


With that factor to consider:


1. If it moves up the Gulf Stream on the east side of the state, weather will dramatically improve for the state other than along the immediate coastal locations from Palm Beach to JAX as it passes. 


2. If it forms toward Naples and moves North the weather across the state goes dramatically down hill, with double the rainfall along the east coast (up to 9" by the time all is said and done) with the potential for low topped , mini-supercell thunderstorms capable of producing a brief tornado over Central to North Central Florida.


3. And finally, as is shown in the 8AM of the morning run of the model, the low is forecast to quickly achieve tropical storm strength, with winds as strong as 40-50 mph moving up the spine of the state   to St Augustine as soon as Monday evening, with very high rainfalls totals up to 9" along coastal Brevard, as well as the potential for mini-supercell storms created by sharply veering wind profiles in the lower levels of the atmosphere. This 'storm' would have some tropical characteristics because it does have a tiny 'warm core' (as opposed to a cold core low, <I checked out the forecast upper level temperatures), but is closed off well up to 20,000 ft if not higher which looks very suspicious.


Other runs of other models vary from no low forming at all, to two lows forming ..one near Naples and another into the Central Gulf.  The latest European hedges on the "off the SW Coast" scenario which is the one I've personally favored for the past day or so..that is..if one is to form at all. If so, rains will become more state wide with that potential for a tornado threat even if it is a good 120 miles off the west coast (especially along and east of I95).


In all cases, the unsettled weather for Florida is over by Wednesday as a low lifts north and becomes extra-tropical, dragging a frontal boundary across the state by mid-week next week. And guess where it ends up, over the Southern Caribbean. High pressure to build in back behind it and a rapid shift to more onshore easterly flow returns, this time a dry flow for quite some time.

It's "10-4 Good Buddy" As Phase 2 of 3 Begins This Afternoon

IMAGE from the Local Data Integration System (LDIS) around the time of sunrise this morning, taken from the Melbourne, Florida National Weather Service (NWS) provider web links. This image shows, in general, the surface temperature at 7:15AM. The coldest temperatures are noted from the interior north along I-10 south to Gainesville and nearing Ocala toward The Villages. Although not as cool this morning (40Fs are still present), this is the same areas where it has been coolest the past 3 mornings as was thought would be in the post 3 days ago . Note it is the A1A corridor to far south Florida that is the warmest, as was the case all mornings.

TODAY: Continuing on track today with the gradual evolution of events leading up to the first bonafide chance of measurable rainfall sometime toward sunrise toward noon Thursday along the east coast. Most likely, any measurable rainfall will occur between St. Augustine to Vero Beach, with trace amounts possible just about anywhere. 


For today, similar weather to that which was experienced yesterday wherever one was. Another chance of skies becoming mostly cloudy at times south of Lake Okeechobee, initially near the coasts and working into the interior and west side later in the day. It appears the only chance of rain will be along the Keys, with a chance of thunder along the middle and lower Keys.


PHASE 2: Yesterday, very light NNE winds north of far SE Florida occurred as the winds at 2000 ft became NNE. Today, the low pressure area in the NE states is very close to the coast just south of Boston Harbor resulting in moderate to heavy rainfall across that area into the Southern 1/4 of New Hampshire and up along Coastal Maine. This low will move off to the ENE during the day very slowly. Meanwhile further south, the 850mb trough extending from this low (at 5000 ft) <associated with the large low pressure system> is working down the east coast. With its passage down the Florida east coast this afternoon, winds at that level will become NNE-NE as well, remaining very light. All in all, this means nothing to the observer, although surface winds this afternoon might become a tad stronger today making for a more notable light wind from the NNE-NE late in the day with a slightly better chance of stratocumulus clouds of greater vertical height, but still remaining widely dispersed/apart from each other. Toward South Florida overall moisture depth and extent is greater due to the circumstances surrounding the old frontal boundary over the Florida Straits.


As the mid-level trough works down the coast toward this evening associated with high pressure building toward the mid-Atlantic states, this boundary should be pushed south of the Keys even further and ending the chance of rain by nightfall.

Weak low pressure west of the Keys is shown in this graphic from the Storm Prediction Center (SPC) website. High pressure is seen in the Deep South. This high pressure extends well to the north , building into SE Canada. The strength and depth of it will be increased as the low near the NE U.S. Coast moves further offshore through Thursday., eventually ending any chance of rain for the keys.  

On the flip side, the more the chances of rainfall decreases for the keys, the better the chances of clouds and eventually rainfall along the Florida East Coast increases going into overnight Wednesday night/Thursday.


Below is an image from the RUC (Rapid Update Cycle) model for 7am this morning. Also noted on this image is what is to evolve going into late Thursday/Friday out West.

This image is for the 850mb standard level, or near 5000 feet Above Ground Level (AGL): Near Florida, we see by the dashed red line indicating the trough at 5000 ft (850 millibars MB) in this plot for that level. The old frontal boundary is in solid red along the Straits. High pressure building northward into Southern Canada at that level. The high pressure will strengthen and build east toward the Mid-Atlantic and Northeast states behind the departing low shown near Boston.  Out WEST, the developing low pressure trough is pushing across the Western States with a low center near the SE Bay of Alaska moving into British Columbia. Annotations are for the late Thursday time frame. Very cool/cold area within the large trough will make for cold temperatures over the mountains/higher elevations of the Rockies along the Wasatch and Rockies, with a cold pocket in the sinkhole of SW Colorado...due to drainage near Cortex.  Meanwhile, Southerly flow ahead of that trough and on the backside of the high pressure further east will up rain chances, with severe weather possible in the Texas Panhandle northward into Western Kansas. 

WEDNESDAY- PHASE 3: As the low pressure off the NE states moves further away, phase 3 - The 700mb trough will swing down and pass across Florida. High pressure behind that boundary during the day will shift winds at that level to ENE-NE eventually as well (as opposed to the WNW direction they are today). Surface winds will remain NNE-NE round the clock at this point at 10-15mph and moisture depth will gradually increase as well, as such will the chance of more cloud cover but remaining mostly partly cloudy state wide as South Florida conditions improve. The old frontal boundary will now be down across Cuba.


THURSDAY/FRIDAY: Low pressure all across the Caribbean and SW Gulf toward the SW Atlantic, combined with high pressure building into the Mid-Atlantic States through a deep layer will increase moisture further with time across Florida. The pressure gradient will eventually increase with steady state 15 -20mph winds by early Friday. The first chance of measurable rainfall somewhere along the Florida east coast appears to come with and just ahead of the first wind surge early Thursday. During the day this chance spreads up and down the entire coast, but remains fairly light, but measurable EAST of I-95.


FRIDAY/SATURDAY: Additional wind surges in the 2-5000 ft levels increases low level speed shear and lift. With these winds comes vorticity streamers embedded in a bit of a baroclinic zone , with thermal winds aided in lower level wind speed strength, with pressure gradient winds at ground level. Rain showers increase in frequency and number and become heavier as moisture levels in the atmosphere above increase. Some thunder could occur by late Friday into Saturday. The GFS run of 2AM has an affinity for Indian River County north to Central Volusia counties on Saturday for bigger rainfall totals with potentially thunderstorms. At this time, there might be a slight chance of waterspouts mainly offshore, with perhaps a land-falling waterspout, although that chance will be very low and remote.


Throughout the duration of higher rain chances along the east coast much of the state beyond the spine of the state will likely remain rain free. In fact, most areas beyond 20-30 miles from the coast will be rain free through Friday. 


The typical drive from further west, say for example from Orlando on Saturday, could consist of seeing increasing and lowering clouds as one approaches the coast, eventually running into some rain near I95 getting heavier crossing US1 and the rivers. Just an example, but the same general scenario about anywhere except perhaps South of Lake Okeechobee where there could be an 'Everglades Affect" along Alligator Alley heading toward Sunday. It will not be raining anywhere all the time, but an umbrella could become mandatory equipment when heading out; either that or simply wearing a bathing suit.


Late Saturday-Monday: The same old same old. Temperatures along the coast could possibly not vary more than 8 degrees if not less in areas of more consistent shower activity , remaining in the mid-upper 70Fs. Eventually almost every where along US1 and east will receive measurable rainfall by Friday Evening into Saturday.  So far as of 2AM, the GFS is honing in on Saturday being particularly 'active' along the east coast from Brevard toward Martin Counties with stronger winds and possibly storms with thunder (but that could easily change with the next model run which will become early this afternoon).


It does not look like any stronger activity will move faster than 6-10mph since steering currents will remain around that speed. The strongest winds will be found 'just above the deck' around 2-8000ft, which is below the steering level, but fast moving low clouds are likely to be observed. Thus, the bigger rainfall totals of possibly over 4" by Tuesday over a 96 hour period will occur where the slower moving and heavier rain/thunderstorms occur.


The GFS still indicates totals of 9", namely just off shore from Port Canaveral to Central Palm Beach County, with actual land based estimates up to 4.5". 


As suspected, the latest GFS is now extending the length of the REX blocking pattern to evolve as noted yesterday might be the case, from Monday to Wednesday, however surface winds will decrease in that case.  And talking about winds, it looks like the strongest winds will remain just offshore, with coastal winds perhaps quite noticeably breezy to near windy on Saturday. Otherwise, it does not look like they will be anything unusual. The shallower shelf waters will aid in lift, and local geography could end up in higher rainfall totals though on land if all of the above evolves, but I will point out that none of the official resources (those being the Weather offices of the NWS) are talking big rainfall totals. In fact, only Miami mentioned them, and they as of early morning played them DOWN (might have been a mistake on their part though in regard to Palm Beach County).


BEYOND the TUESDAY/WEDNESDAY TIME FRAME: Models are in excellent agreement (of the 6 different ones I looked at including the Canadian, the European ECMWF, and the Navy NOGAPs...that we will have high pressure to the north and low pressure to the south in a modified REX block (modified in that the low is not completely closed in the mid-levels). The latest GFS (Global Forecast System) Model however eventually closes the low near Cuba to South Florida by Wednesday...and works it down to the surface just off the SE Coast of Florida. A Subtropical or a hybrid type low pressure system could form almost anywhere from off the Florida East Coast to off the West Coast into the SE Gulf, through the Yucatan Channel over into the Caribbean toward the Bahamas anytime and anywhere by early next week. 


Models all seem to agree on such, but not on where or how.  For example, the 2AM GFS shows a low to form off of SE Florida that gets wrapped NW ward , strengthening into a sort of hybrid tropical storm (of name) that cross NE and North Florida, then wrapping around the parent upper low over the Caribbean and moving the named system into the East Central Gulf of Mexico.  I'm not buying it though. In any case though, the point is that although the prolonged wind/rain conditions of onshore winds developing Thursday will have by then been long gone, rain chances continue for a different reason. 


Models seem to agree as well that heading toward Monday/Tuesday, low pressure over the Southern Gulf to the SW Atlantic will build northward across Florida as the high pressure to the north relaxes/realigns. This will end the stronger onshore flow as well as rain chances along the coast, but would also induce more of a modified afternoon thunderstorm regime.


It should be clear to realize from all that has been written above, that there is great uncertainty throughout all time frames beginning Friday (considering that is 3 days away already). But some heavy rainfall totals, if only just offshore, seems to be in the cards. The devil's in the details.