Low Confidence (Location/Chances) Of Late Afternoon/Early Evening Storms In Florida Today

ALL CONDITIONAL STORM CHANCE AREAS: Chance of rain showers or thunderstorms within the green bounds, most likely area is within the light blue and lavender, with the peak conditional chance along the east coast in the yellow highlight/dark green areas (see below). Another area not shown is along the West Coast from near Brooksville and south toward Naples. Also not seen here is an area extending toward Miami in SE Florida.

OBLIGATORY DISCLAIMER: As is always the case and as printed on the web page at 
http://www.highspeeddirt-steve.blogspot.com  all thoughts are of the author's own. Please refer to local official outlets (my most preferred is the National Weather Service until an 'event' (storm) develops), then your local televised news channel,  for the latest officially released information for where storms are located and expected to move toward.


TODAY: First of most importance there are three items to consider: 


(1) Nearly every forecast model is in disagreement with where rain/thunderstorms will develop today. It does appear that there will be an isolated  very strong storm or two or 3 today within the 'green' today, which is almost the entire state. The most likely area appears to be in the center of the state.  Even timing is an issue. One chain of thought calls for early afternoon activity which I had dismissed since sunrise, yet they are still showing the possibility. As of now it is supposed to be raining where I sit (for example) based on the short term local WRF model. Yet there is not a storm building anywhere in the state, with some cumulus along/over SE Florida and some that tried around the Big Bend but were snuffed out by high cirrus clouds.


 Note the two areas along the east coast: Those are outliers, but important. Important because if storms do develop and/or move into those locations, they could be severe, along I-95 toward US-1 late today after 6pm if conditions exist for such at that time. How/why? Temperatures aloft at 700mb are expected by one model to drop by several degrees after 4 or 5pm. Will that happen? Time will tell. But at least we have been forewarned of this possibility.


(2) Will there be many storms at all today in fact?  The atmosphere looked very unstable since sunrise, observed by the cloud types (did not need a model to see that).  However, the approaching disturbance to affect the state tomorrow is shielding cirrus clouds across the state, limiting  the atmosphere's instability, and in some model portrayals, by a big margin..significantly so.  I do believe that even still,at least sea breeze storms will form in the interior after 5pm.


The reason for the bigger threat along the East Side is caused by coastal low level helicity (sort of like little whirl pools or eddies that form along the sea breeze, which is closely paralleling the coast today. It is the near parallel motion that sets the eddies going. When a storm approaches them..they tend to 'jack up'..especially just east of I-95. If this situation does develop, it would not be until after 5:30 or even 6:30pm...and in full force east of I-95 around 6-7pm.   


(3) Lastly, there is a chance that mid-evening post thunderstorms could develop (or continue) in the favored inland location  as well as closer to the coast in South Central Florida (toward South Brevard/Indian River Counties). This is very remote but still possible. This storm would for after the sea breeze has relaxed.


(4) There is a big change to occur sometime after 4pm with wind fields as well as some lowering in mid-level temperatures. This might be throwing a lot of models of, and will affect (if this is real)..where the heaviest activity will occur).  It may also be why the weather is so benign this early afternoon. Nothing to happen until that time it occurs (if it does).  Since that time has not arrived yet...it's a waiting game. Waiting to see how long the high clouds stick around (which looks almost certain)....and if those mid-level wind fields indeed to change so quickly.


LASTLY: In Looking at the latest hourly information availabe which included (the mental analysis/picture) a vast variety of parameters, the most likely area as of 1pm for activity today is toward the center of the state, with a slight lean toward the east coast in  Volusia/North Brevard (South Florida is a different story altogether, and beyond the scope for one post). It is down there though that the first signs of an approaching rain chance are manifesting this hour.  Should the high clouds persist or thicken with time, the chance of rain diminishes significantly everywhere, other than perhaps toward South Florida, with maybe just some showers and a thunderstorm or two inland of non-strong character. Note though. No model shows a 'dead late day'...yet.


SATURDAY: The Storm Prediction Center already has the Panhandle and North Florida in a "Slight Risk" for severe weather tomorrow. In Florida, that would be mainly for hail. There is uncertainty though even there since persistent cloud cover would limit instability if it is there from early morning toward noon. It may be that Central and South Florida will end up with the stronger weather when all is said and done. I'm inclined to lean in that direction.


SUNDAY-TUESDAY: More chances for showers and some strong to severe storms will exist on 1, 2, or all days, depending where in the state one is located. After tomorrow, the Panhandle is 'out' since that area will be behind a cold front in more stable air.  The most favored area on Sunday appears to be for a portion of South Central to South Florida. But that too may change. Earlier guidance indicated the showers would begin over night into Sunday morning, and could be 'in the area' all day. Along and South of the BeachLine to Miami. 


That, plus we might not have a sea-breeze. If this indeed is the case, Sunday could just be mostly cloudy with showers ...and some thunderstorms from early afternoon to evening possible (perhaps). A lot of what occurs Sunday - Early Tuesday is contingent upon a combination of the surface winds and timing/passage of embedded disturbances aloft. All wet chances abate by late Tuesday in South Florida.

Rains Chances Slowly Increase For Florida...But When?

The BIGGEST Player for much of North America Today through Friday seems to be that big Double Whammy System in the Atlantic Off New England. It is barely moving if at all this morning. We can see in this image the third of three small MCS (Mesoscale Convective Complexes) that moved off the Coast of South Carolina since this morning. These are narrowly missing Florida, and the storms associated with them can be seen on The Weather Channel here in East Central Florida.

CLOSE UP OF THE SYSTEM OFF NEW ENGLAND.
THESE TWO AREAS ARE STAYING IN PLACE...ROTATING
IN PLACE DISCRETELY, WITH THE SOUTHERN ONE ROTATING NORTHWARD AROUND THE LARGER, NORTHERN ONE. NO MODEL SHOWS THESE AS SEPARATE ENTITIES!!

THE THREE MCS COMPLEXES EARLY THIS MORNING. THE MOST SOUTHERN ONE WAS VERY ACTIVE SHORTLY BEFORE I SAVED THIS IMAGE. HIGH PRESSURE JUST TO THE WEST AND OVER WEST FLORIDA IS BLOCKING THESE FROM REACHING THE STATE

TODAY'S VERY SMALL CHANCE OF AN ISOLATED RAIN SHOWER OR MAYBE THUNDER. EAST CENTRAL WOULD BE AFTER 6PM. THE ZIG ZAG LINE IS SUBSIDENCE TO THE WEST OF THE DISTURBANCE THAT IS OFF TO THE EAST, WHICH CAN BE SEEN IN THE FIRST  IMAGE ABOVE BUT NOT IN THIS ONE. LOW PRESSURE NEAR ORLANDO IS THERMALLY INDUCED (FROM HEAT)

SYNOPSIS: Big blocking low pressure system (s) off the New England/Mid-Atlantic Coast and high pressure over the NE Gulf at time, as has been the case the past 48 hours. Little has changed other than that the low pressure area is enlarging. This system is proving to be quite the forecaster's quandary for not only Florida but the Central Plains states today. This will continue to be the case until it moves..somewhere..which should be a bit more south..then east to northeast beginning later Friday as a system in the Central Plains today  finally gives it the boot.  The Central Plains states system will be forced to 'dig' toward the ESE-SE in days ahead, and in turn force the high pressure area near Florida that is creating all of the hot, dry afternoons to move south and east with time. At time, it appears fairly safe to say this process will begin on Friday but that to could change given the now unforecast/unanalyzed strength of the Atlantic System by the models. This system is indirectly affecting forecasts in the Plains as well, making what looked initially to be a very active severe weather day there not 'quite so bad'...but still 'bad'.


TODAY/THURSDAY: Until that time, the best chance of any showers or thunder will be in the areas drawn above, with an outlier on the South Side of Lake Okeechobee.


It is interesting that a lot of the reason we have not had rain is due to warm air in the mid -levels. Per the latest short term model, in disagreement with the other models run this morning, this warm 'cap' is to disappear this afternoon; however, moisture is too meager in general (PWAT too  low) to produce rain. I can tell by looking outside that the warm air aloft hasn't broken down yet over Brevard due to the haze. Perhaps even the short term model was a bit too hasty in removing this 'cap' of warm air.


Would like to add at this point, the for several days now the high pressure was supposed to break down, with some models (all of them) showing increased rain chances starting yesterday or Tuesday. But that low of the NE U.S. Coast is stronger and more stubborn than any model or person for that matter could foresee. Remember in the post two days ago, this possibility was alluded to? It was mentioned in could even end up drifting right over the state. That too, can still happen going into Friday, thus..the chance of no rain is always there until proven otherwise.


How much of glitch in any forecast going into the weekend will this have? Not too much, but the timing will be an issue. Timing, that is, of when the Atlantic System makes a move.


Two boundaries today. 1) a bit of a trough axis will lay across far N. Brevard County today until mid-late afternoon. We'll know when it breaks over East Central at the coast when we gain an on-shore wind component. In the upper levels moisture is slowly working south from far NE Florida and will build up behind this boundary. Another spoke, or boundary, lies further north toward JAX which will move little. Both of these boundaries could act as focal points for a small precipitation  'chance' later today...but the southern one near Brevard will rely on the wind shift..and that would have to happen at just the right time. If it happens too soon the area will be scoured out by subsidence behind the boundary with the land/sea breeze meeting each other over an area further to the NW where the air is too dry after day time heating removes the low level moisture in that area...caveat..with that boundary in place near North Brevard..just enough moisture could accumulate near it. Thus, the rain chance. Anything to form, if the timing is just right, would probably only be a rain shower though unless something very magical occurs beyond the scope of the laws of physics.


The same scenario will likely play out tomorrow as well, but a change will be in progress.


FRIDAY: Based on guidance, Saturday would be a transition time when the Plains system works far enough east to dislodge the high pressure over the NE Gulf. This would allow more moisture to work in, and with cold air aloft and late afternoon seabreeze / land breeze collision to occur along the east coast of the state late in the day. Better chance of thunderstorms on Friday...but isolated. However, forward motion...and more importantly to Florida, the direction of that forward motion owing to whatever the Atlantic System does..will make a big difference for the state down the road to 'recovery'.


SATURDAY/SUNDAY: Given the blocking pattern and it's evil history (for forecasters), the weekend will be interesting to see how it unfolds. COULD be that there will be rounds of rain/thunder chances at just about anytime, favoring the east side but not always. It gets more difficult when it is forecast that the sea breeze on the east coast will no longer develop. There will be cold air aloft and no capping, but lack of a trigger and any low level boundary collisions as well, in the presence of no forecast upper level disturbance could result in just lots of clouds and some showers. On the other hand, any unforeseen disturbance embedded in this "yet to develop pattern' could contain all kinds of little disturbances to generate very strong thunderstorms. At this time, it appears either Saturday or Sunday would be that day. ...keeping in mind that often any kind of blocking pattern is often hastened foreword too quickly by models..so that time frame could very well end up being Monday/Tuesday...or anywhere in between.

Isolated Shower and Remote Thunder Chances Begin Wednesday -Increase Sunday

Water Vapor Imagery This Morning: We have a large low pressure gyro off the  Mid-Atlantic Coast slowly dropping SSE this morning. Noted is where strong storms could occur today over South Carolina, Eastern Tennessee, and western North Carolina this afternoon into the Evening. Those storms could be important for NE Florida and perhaps a portion of the East Coast Wednesday as they push into the Atlantic tonight.

TODAY: Just looked at the morning sample taken by a weather balloon (in essence) of the atmosphere from the Kennedy Space Center. It is showing an increase in atmospheric moisture, but most of this is either at the lowest levels or highest. A dry layer remains above cumulus cloud level as has been the case for a while now,  and little change is expected from that through today into tonight. The most instability is just near and off both coasts which developed relative to the cooler air above the land mass over night. There was much more there this morning then in the past, and even more is expected to be there tomorrow morning. Daytime heating will dry out the interior, whereas afternoon sea breezes will create sinking motion near the coast to clear out any remaining cumulus clouds near the coast before noon...although they might linger longer toward coastal SE Florida. Highs will be in the low 90s inland and closer to the mid-80s at the beach. Not expecting any showers today, although a shower could pop up on the western portion of Tampa Bay late this afternoon into the early evening. Maybe they will eke out thunder due to low level forcing of local bay boundaries, but at this time it does not look like the moisture will be deep enough, nor will any 'forcing' be strong enough, in the absence of any upper level energy, to generate thunder there later today as of this hour.


FURTHER NORTH: A disturbance will drop SE and across the area above noted in RED  much later today (in general)...and create strong to marginally severe thunder later this afternoon into early evening. Another impulse may very well  make a repeat performance in the same area early Wednesday morning. Those could lay the frame work for some stronger storms over the Jacksonville area later on Wednesday if they manifest. However, it does look likely that they will.


WEDNESDAY: Chance of storms toward Jacksonville and over the St. John River Valley Basin in general. These, if they can form in the still somewhat questionable situation at hand, could end up being rather strong as a result of the cold air aloft combined with boundaries created by that activity moving off the South Carolina Coast.  There was some unstable air near the coasts of Central Florida this morning, and there is expected to be even more of it there tomorrow morning. Additional atmospheric moisture combined with strong winds aloft  should work in tomorrow to support a chance of an isolated shower early in the morning near the Cape and further south toward Ft. Pierce, with redevelopment of a possible thunderstorm from near Sebastian to just south of Vero Beach/Ft Pierce  in the afternoon, to possible into a portion of Osceola County later in the afternoon . An additional storm or two could form later in the afternoon around convergence of the sea breeze/lake breeze frontal boundaries off the Gulf/East Coast, and and Lake O '. Most likely on the NW-W side of the lake.
Any showers to form will be very isolated, with the best chance near Lake O.


THURSDAY: Isolated late afternoon sea -breeze front convergence thunder storms are possible down the spine of the state. See image below for these two days (Wednesday/Thursday). This is a first order 'best guess' based on what was available early this morning and will very likely have changed by later this afternoon or tonight. Just to serve as a heads up that there could be some thunder around the state Wednesday/Thursday. The GFS and now NAM are supporting the activity for Wednesday in a various forms though. The GFS for 36 hours now. Last night, in fact, the NAM was showing the potential for bombastic storms from JAX-N. Brevard late afternoon to mid-evening, but completely dismissed this chance only 6 hours later. Just to make a point how things can change fairly rapidly when using a model as a basis for where rain will occur.

IF YOU LOOK CLOSELY YOU CAN SEE A THIN VEIL DOWN THE SPINE OF THE STATE THIS MORNING. THAT IS SMOKE FROM A FIRE IN GEORGIA ,  ENTRAPPED IN THE MID LEVEL INVERSION, BEING FORCED TOWARD THE SSW-SW THIS MORNING. CIRCLED AREAS ARE "GREEN: WEDNESDAY, and BLUE: THURSDAY" PRELIMINARY RAIN CHANCES

BEYOND: The chance for isolated showers and thunderstorms will continue into Friday and Saturday, with a possible up tick toward Sunday or Monday. Models are varying in timing and strength of what could be one or two afternoons of strong thunderstorms from Jacksonville to Miami beginning Friday or Saturday...isolated. The bigger increase in coverage arrives on Sunday or Monday. Theres days favor the East Side of the state. There has been indications this activity will be quite potent; however, given the time of day (earlier than normal), and lack of a weak cap indicated, it could end up that these days will end up with general, wide spread thunder rather than stronger and more isolated activity.


Chances of afternoon thunderstorms outside of an inherent pre-noon time coastal shower activity could continue off and on for another week if the current longer range forecasts verify. However, I have very little faith in them at this point. But a pretty big change for most of North America is in the works heading toward next Monday and beyond once that low off the Mid-Atlantic Coast is out of the picture.


AND FINALLY: Way out in time the GFS is showing the first signs of a Summer Like Wet Season Pattern Developing going into the last week of May with much higher moisture content air in the tropics and a low level ridge axis across the state.  This will change though, and more than likely be pushed further out in time rather than sooner. The GFS seems to have a built in clock, perhaps 'climatology' as a part of its inheritance from the model developers/scientists/climatologists/meteorologists. Interesting to see this appear though. 

See the deep moisture down in the Caribbean approaching the Gulf by the lavender and deep red heading toward the last week in May? This would lay the foundation for more typical South/Central Plains Severe Weather, and eventually that for the Florida Wet /Thunderstorm Season. Also note all of the moisture over much of the Eastern and Southeastern States. This would be the indicator of continued thunderstorm chances in the Southeast and Deep South even as far out as May 25th. However, both of these depictions cannot be relied upon truth as much as in theory.

Showers Far SE-S Florida Today, Showers/Thunderstorms Possible Further North Beginning Monday

OLD BOUNDARY FROM DECAYED FRONT STILL OVER SOUTH FLORIDA FOR THE 3RD STRAIGHT DAY. IT IS ON IT'S LAST LEG TODAY, BUT SHOWERS ARE POSSIBLE IN THE AREAS IN GREEN, INTO THE KEYS.
NOTE THE HIGH PRESSURE OVER THE EASTERN GULF. THIS WILL BE ONE OF THE MAIN FACTORS IN DETERMINING PENINSULAR FLORIDA WEATHER DURING THE UPCOMING WEEK. AREAS IN PURPLE AND ORANGE INDICATE SHOWER./THUNDER CHANCES ON MONDAY AND/OR TUESDAY

TODAY: Old frontal boundary is about done with South Florida today. Whatever moisture remains will begin to lift north along the immediate east coast to Central Brevard Today with little to no notice. High pressure is over the Eastern Gulf at the surface and the mid-levels. Dry northerly flow today and a weak surface pressure gradient will allow the coasts to have a cool breeze while inland temperatures from either coast rise into the upper 80Fs to near 90F in a few spots.


MONDAY-FRIDAY: The majority of the upcoming week is highlighted by a near blocking pattern. For Florida concerns, the contributor to the block is low pressure off the Mid-Atlantic and NE U.S. Coast which will move little. Storm systems are forecast to roll out of the North Plains and the Great Lakes and dive toward South Carolina beginning tonight, as 'faux backdoor cold fronts from the north". However, they will mostly wash out after reaching Central Florida. Won't be surprised to see some major storms move through South Carolina in a day to two though, for starters. Other areas to watch through Wednesday will be Nebraska (today) into Kansas/Oklahoma/and North Central Texas by Wednesday. The system on Wednesday will more directly (and most likely) be one that will affect most of the state going into Friday and the weekend.


MONDAY: First off, I want to point out the source of moisture next week for any rain chance will not come from the south, but rather from the North. Days will be characterized by very little surface gradient flow, and groudn level winds will nearly solely be dictated by coastal sea breezes. Inland temperatures could approach record levels or if not, just be plain old hot approaching the low-mid 90Fs on various days, with the coast in the mid-upper 80Fs before onset of the sea breeze. Perhaps by Friday the  east coast will see 90F degrees readings as well.


The first storm system to dive south from interior positions of the mid-Atlantic Coast states  is forecast to bring moisture into all of North Central Florida tomorrow from north to south, reaching the Beachline by sunset or shortly thereafter, mainly on the east side. Afternoon sea breeze should keep the moisture convergence, and hence showers and possible thunderstorms along and west of I-95...but this bears watching. Storm motions would be from the NNW, which will struggle with the sea breeze and likely avoid the cooling subsidence behind the sea breeze front.


TUESDAY/FRIDAY: Pretty much the same scenario everyday. Whether or not rain/thunder will be realized, and if it is , where..is contingent upon the strength and breadth of the oscillating area of high pressure to our West. If it is weaker, each impulse from the north (carrying moisture with it)...will affect more of the north half of the state than on days when it is stronger or when the impulses are too weak or are not transporting enough moisture with them.  Everyday will not be carbon copy of the day before. Some days could favor further to the west..whereas other days could favor the immediate  east coast.


Temperatures will be quite warm in this regime. It is possible both from this synoptic scale regime  as well as from a climatologically perspective, that Central and North Florida will encounter some of the highest temperatures of 2011 during the next week if not beyond into next week, with highs in the mid-90Fs. Far to soon to say for sure, especially since these 'warm to hot events' are seldom foreseen and not well handled by guidance. The chance of abnormally warm temperatures can also occur as late as early-mid June to keep things in check.


It does not look like far South Florida will get into the 'rain game' initially, but should the pattern shift to even a stronger blocking pattern as indicated by the GFS by Friday..they too will be pawn for the rainstorms.


SIDE NOTE: Long range guidance has been implying that a big blocking weather pattern (one that changes little for over a week at least) could be in the making. This has been implied to occur for several days now, and this morning's model run of the GFS is no different. Most favored has been a classic "Omega Block"..I wrote about that type of pattern several months ago, and will re-introduce that type of pattern should it emerge. The other blocking pattern shown last night was a strong "REX BLOCK" on the East Coast of the U.S. In either case though, the pattern over Florida is nearly the same as an end results (and as described in the earlier paragraphs).


FINAL NOTE: Should thunderstorms be able to develop in the next week, they will be isolated to possibly scattered, but also restricted to a particular 'favored zone' for that particular day . They could also be quite strong to marginally severe at times with both modes of strong storm characters involved (small hail/strong wind gusts).  Would not be surprised to see some sort of 'mesoscale accidents' on a day or two, with a storm somewhere between Jacksonville to Orlando being especially feisty, especially if a storm can impinge through the East Coast sea breeze front...in which case a coastal community could get a good rain.


Should high pressure over the Gulf shove just a bit further east toward the state, all rain chances most everywhere will go to zero..and the heat would be "On" with little relief.

IN The Mood For Clouds, A Shower, A Storm? Let's go PWAT CHASING!!!

WHAT WAS THE "TOTAL" PWAT THIS DAY? HOW WAS IT DISTRIBUTED VERTICALLY AND HORIZONTALLY ACROSS CENTRAL FLORIDA THIS DAY? WHAT WERE THE WINDS AND TEMPERATURES ALOFT?~
IMAGE: LEADING EDGE OF A SHELF CLOUDY ABOUT TO TURN "OUT FLOW GUST FRONT", CAPE CANAVERAL

Throughout previous posts, and in the current Convective/Wet Season in Florida in progress, I've used this term, PWAT. But what is that, and why is precipitable water value expressed in these discussions?  


Namely, because it is important in a variety of ways. It can define days that will have clouds (or none) and at what level(s) of the atmosphere they will be for starters. It also determines if there will be showers or storms. But it does not stand alone. Other parameters include the vertical thermal profile of the atmosphere (temperatures near the ground and aloft), the amount of instability in the lower levels and conversely, the amount of stability above the lower levels.


Technical precipitable water (PWAT)—(Or precipitable water vapor.) The total atmospheric water vapor contained in a vertical column of unit cross-sectional area extending between any two specified levels, commonly expressed in terms of the height to which that water substance would stand if completely condensed and collected in a vessel of the same unit cross section.

The total precipitable water is that contained in a column of unit cross section extending all of the way from the earth's surface to the “top” of the atmosphere. Mathematically, if x(p) is the mixing ratio at the pressure level, p, then the precipitable water vapor, W, contained in a layer bounded by pressures p₁ and p₂is given by

where g is the acceleration of gravity. In actual rainstorms, particularly thunderstorms, amounts of rain very often exceed the total precipitable water vapor of the overlying atmosphere. This results from the action of convergencethat brings into the rainstorm the water vapor from a surrounding area that is often quite large. Nevertheless, there is general correlation between precipitation amounts in given storms and the precipitable water vapor of the air massesinvolved in those storms.

AUTHOR'S NOTE: So what if you're not so hot at, or are even familiar with, the mathematical principles of "Integration" as shown in the example above by that vertical squirrelly line running up and down with p1 and p2 shown?  All that means in the equation, is that they are using the moisture content from one pressure level (p1) to the next higher level in the atmosphere (p2)..of whatever chosen levels desired. For instance, to even have rain  in Florida I'd look at the surface to 700mb (10000 ft, the standard height/level) for starters, and to simplify it. There has to be 'some' moisture at 700mb, but it doesn't have to be a lot...in fact, lower moisture at or near that level will ENHANCE storm strength because the more moist (and more buoyant) air below that level will rise faster into the drier and colder air above the warm/moist air below, inducing rising air currents/lift/convective type clouds/showers/thunderstorms. The 'w= 1/g' portion of the equation is the upward component (g being gravity)...so 1/g is the inverse of the downward pull of gravity.  In sum, we are looking at the mixing ratio (which involves moisture( integrated from one level of the atmosphere to another.

1.  A little easier now (I never say, "simply" because nothing is ever THAT simple). 

What is PW?

PW stands for Precipitable Water. It is a parameter which gives the amount of moisture in the troposphere (which is the part of the atmosphere that contains weather as we know it).

2. How is PW determined?

PW is determined by taking all the mass of water vapor in the troposphere and depositing it on the earth's surface (or as shown in that equation up to, 'integrating' the moisture content through two chosen levels of the atmoshere).

The depth of moisture that would be on the earth's surface is the PW value. The mass of water vapor is determined by the dewpoint (saturation mixing ratio) of the air integrated over the troposphere. Higher dewpoints lead to higher PW values, especially if the relatively high dewpoints extend through a significant vertical depth. The scale below gives an indication of the moisture content of the troposphere via PW. Note, these are TOTAL precipiciptable water values in the 'weather region' which can be quite high up there. 

*****Author's Note: THIS is where I think some folks mistake a lower PWAT value as meaning it will not rain. It is NOT the total PWAT that matters nearly so much as how and where that moisture is distributed vertically, as well as how much square footage on the ground it encompasses, as well as what type of conditions surround the area of concern!!! 

Conversely, a very HIGH PWAT does not guarantee rain if the entire atmosphere is a big soupy mess. It just means it will be very cloudy and in the case of a Florida summer, very humid and sticky. I've seen this over and over again when frontal boundaries go stationary over the Central Peninsula. Almost a guaranteed Forecast Bust if one is calling for big rain chances area wide. Often on these days, the forecast calls for a good chance of rain that never materializes (not always though). These days can be very 'conditional' though, since we can never know all the time what is going on in the atmosphere aloft in regards to the atmospheric profile. THAT is a problem.

0.50 inches or less = very low moisture content
0.50 to 1.25 inches = low moisture content
1.25 to 1.75 inches = moderate moisture content
1.75 to 2.00 inches = high moisture content
2.00 inches or above = very high moisture content

3. (Operational) significance of PW:

Flooding potential: A forecast area has a climatological normal PW for a certain time of year. In cases where the PW value is 2 to 3 or greater times more than the climatological value, flooding becomes more likely when (I'll add, "IF") a heavy precipitation event occurs.

!*****Lightning: In a high CAPE environment, high PW will lead to storms that produce an abundant amount of lightning.

PERSONAL NOTE: In Florida, not necessarily true. Our highest lightning days can be when PW is 'moderate'. But again, it depends on how the moisture is distributed. We need an area in the mid-levels that is NOT saturated, odd as it may sound. Additionally, when air aloft is colder then 'normal' (that is another discussion FOR SURE)...this produces more ice particles (hail) aloft which, in theory, when they clash well aloft, generate more lightning whether or not the hail reaches the ground does not matter. NOTE: In the full bore summer time, the most prolific lightning makers will produce  small pea or smaller hail mixed in with the rain. Originally, that hail was likely much larger before reaching your noggin.  The statement about the 'clashing hail...causing friction' is also very much in question in my mind. There is a lot more to it than that). Also, I think the hail does not only go up and down until falling, but also moves horizontally in and out of swirling currents. Still a lot to be researched.

Updraft velocity: PW is the most significant contribution to water loading. ****Water loading reduces updraft strength since gravity tries to push the precipitation mass downwards-- against the momentum of the updraft. High PW also produces a heavier downdraft. The updraft being reduced is especially evident in a weak shear environment where the downdraft locates very near the updraft, thus destroying the updraft.*****

***This was my point previously. Water loading, TOO MUCH PWAT kills updrafts and makes it cloudy and clammy, with some showers storms around which are of short duration and do not lend will for active lightning as well.****

Hail: High PW tends to reduce hail size since the updraft velocity is reduced. Again, we need a drier level to induce the moist, buoyant air below to RISE through the dry layer.  Moisture content even higher does not have to be very much, in fact..but 'some' is needed. Bone dry won't work in other words.  The most active storms will have several thin drier layers distributed throughout the vertical column (the troposphere/boundary layer)...to promote more rising, the moistening, then more rising again into cold cold cold air way up there.

Hail is another story altogether. It is fairly common knowledge that hail rises and falls in the updrafts, gaining more and more layers of ice until it is too heavy for the storm's supporting updraft. This is SO over simplified.  Hail can fall far from the updraft in supercell thunderstorms where no rain exists...namely and mostly in the Plains. In Florida, when it starts to hail in the summer it is usually in the last stages of the storm. Lightning will be most prevalent just before we know it to be over our heads and through the falling of it..but shortly thereafter the storm will collapse under its own weight.

Convective wind gusts: A high PW often occurs when the troposphere is fairly saturated. This can reduce convective wind gusts since convective wind gusts require dry mid-level air to add to their significance. 

Get it? Big wet blobs (preferably very cold ones, colder than what one would expect based on morning sounding data) will accelerate DOWN ward through dry air, just as they will upward during storm formation. Convective wind gusts can be microbursts, wet microburts, and downdrafts. Extensive study has been made concerning these terms...I originally included a link to a study (of many) that was made and published, but not so sure the individual would like the paper mentioned in this post. If you would like the URL (web link)...flash and email or Facebook message this way.

FORECAST: No issues today. Sunny, but guess what..some riches low level PWAT air might move into Eastern Portions of North Central late today bringing in some late afternoon/early evening clouds. Let the PWAT FUN BEGIN!

Caveat Change of Strong Thunderstorms Late Afternoon-Evening South Half of Florida

CONDITIONAL-CAST TODAY: EXPLANATION OF IMAGE BELOW

SOUTH OF BLUE LINES IS WHERE STRONG STORMS COULD OCCUR AFTER 4pm  unitl just after dark
RED ARROW SHOWS DIRECTION OF ANVIL BLOWOFF
PURPLE: SUSPECT SATELLITE IMAGE. Not sure what those clouds are yet
NOTE THE STORM NEAR TAMPA BAY RELATED TO TROUGH NUMBER 1

LASTLY: YELLOW ARROW: STRONG WINDS ALOFT OF 100-120kts AFTER  3PM to DARK

TODAY: Interesting day today that could amount to a whole lot of nothing. Model guidance continues to be very inconsistent in the precipitation fields. Then again, I used to NEVER use them, other than to see if they broke any out. Sometimes they are almost right on the mark, whereas other times you wonder if the model has the right day. Today, none of the models agree much on where or even IF rain will fall today. And when it does, it is at different times. Per once model, it should be raining right on my roof as I type. Not even remotely close.

This forecast discussion addresses the best case scenario for rain over much of the areas that really need it due to on going drought. However, if this does occur after 4-5pm, the storms could be very strong with 1/4-3/4" inch hail in the very strongest of storms (1 or 2 storms some where), with 'hefty, 'hefty' gusty winds.  I would not expect storms before 4pm to be very strong. Storms are not expected to be officially bonafide severe though due to lack of instability and stronger winds in the mid-levels even though higher up they are about as stronng as we ever see here, even in the winter! .NOW: What I'm calling 850mb trough number 1 moved  in on the west coast during the early morning ..and is now starting to lift off to the NNE. In its wake of showers and a decaying thunderstorm over South Tampa Bay.. is a lot of anvil debris  which is being caught up in the strong jet stream winds  overhead  and spreading to the east coast.

 However, these should thin out during the next few hours heading toward latter portions of the afternoon. Additionally, toward the west side of the state clearing is already in progress, and as such, so is increasing instability.  Meanwhile, on the east side of the state near the coast is where coastal helicities will continue until late afternoon as long as the wind remains from the SE-SSE. These winds penetrate about as far inland as I-95 (at most) with any strength.

IN TROUGH ONE THUNDER STORMS HAVE OCCURRED. ONE IS NEAR TAMPA BAY. THIS TROUGH IS FORECAST TO LIFT NNE QUICKLY AND BEGIN TO BE REPLACED BY TROUGH 2.

MEANWHILE, EAST OF THE TROUGH THE ENVIRONMENT IS CAPPED AT 700MB. THIS IS FOR NOON TIME. AS YOU CAN SEE, NO RAIN ON THE EAST SIDE OF THE STATE. See the placement of TROUGH 2 in the second image after 6pm. TROUGH 2 is way up there in Virgina, and will generate some strong storms there.

Here on the left is 6pm. Trough 1 is well to the north and Trough 2 has moved in. In thinking of the best chance for rain or storms, by this time the high clouds will be cleared, and more important, height falls at the 850 and 700mb levels will break the cap which would permit storms to form rapidly toward 5pm on the east half of the state where the clouds might have begun to clear. At this time is when winds aloft will be the strongest as it so happens..up to nearly 120 kts at 200 mb. 

Additionally, temperatures will begin to fall to meet the dew points and precipitable water values will rise and lift north a bit in response to height falls. Temperatures aloft are quite cold at 700mb and 500mb...cold enough to support hail and strong wind gusts of 40-50mph. If the mid level winds were any stronger we would be dealing with big time severe storms today. 

Strongest storms, if they form will be within 6 miles of the East Coast where the strongest onshore component wind is found and as such, low level coastal helicities that feed into the storm along the storm relative wind fields . Any storm that does form ,and strongly, is likely to move right on offshore to the east and into the Atlantic.

NOW FOR THE CAVEAT: The high clouds have to clear for the atmosphere to destabilize. At least on the west half of the state.  And that is just the beginning. All in all, confidence is low today of anything to materialize of note worthy record keeping, but the above is something to keep in mind. Wouldn't hurt to watch the 3pm  onward time frame...just to see what might be brewing in your neck of the woods. Could be that activity will start before that time if it does. Also expecting some frequent lightning with any strong storm.

BEYOND: Weekend is looking nice, with only a marginal chance of thunderstorms sometime well into next week. Become warm by Sunday or Monday.

Chance of Showers/ Isolated Strong/Marginal Severe Storm East Coast Friday??

GFS Just Stream Forecast For Early Friday Afternoon. Area in Green Shows where the best chance of there being  a few isolated strong/marginally severe storm during the morning or  mid-afternoon hours

TODAY: No question at this time as to where the richest atmospheric resides this afternoon; that being over South Florida. It is rounding the ridge over NE Florida and trying to work up the west coast, as well as lifting slowly north everywhere as the high starts to move out late this afternoon.  In viewing the latest visible satellite image, we can see the more extensive cloudiness over South Florida with the expanding cloud field to the north as moisture tries to work north but can't with the ridge continue to be in place, but pulling off to the east this afternoon. As such, circulation around the high is creating some easterly winds this afternoon.   


Lower Clouds are interesting this afternoon if you happened to catch them just right. The low clouds are trying to form at the that level but are capping off with their tops making little curly tufts breaking off to the east...as if catching stronger mid level west winds at that level, yet models are showing little in the way of winds up there. Could be they are simply hitting dryer air.  In the satellite image we see what looks a bit like a 'mackerel sky' pattern from the top down, with little north/south stretched bands of clouds such as in the red circle and over West Central Florida. This would indicate wind shear.

In close inspection the red circled area (for instance) is showing scalloped cloud patterns. Also, but hard to tell unless in animation, thin cirrus clouds are pushing quickly across from west to east in the increasing winds from 20,000 to 35,000 '

TODAY: Winds will continue from the ENE-NE this afternoon becoming more easterly and decreasing some tonight as the veer toward the SE overnight into the early morning hours. Shower activity should start to let up and shift more toward the West Coast up toward Tampa toward sunset and there after until around 8-9pm. Skies will remain partly cloudy over Central and South Florida, with a occasional mostly cloudy periods under either the cirrus clouds or increasing low - mid level clouds, especially heading toward sunset.  There is a slight chance of a few isolated coastal rain showers well after dark through early morning, but only worth a hint of mention.


EARLY FRIDAY: Virtually every model is painting a different picture just to set the record straight right from the get go. Therefore, confidence level is low.  With that said, I'll paint the two extremes of possibilities first.


1) Chance of showers and coastal thunderstorms as moisture returns north up the east coast, namely after 5-6am Friday. Best chance of showers is from Brevard County and south. One model is indicating a prelude to a prefrontal boundary to approach in the early afternoon to generate this activity, which would include thunder near South Brevard to Vero Beach - my take? I think the model is over done, and would leave it as a chance of showers along and east of I-95 during this transitional period, mainly from Volusia County and South.  Otherwise, day should break under partly cloudy to most cloudy skies, perhaps clearing a bit after mid-morning with heating of the day.


2) Noon time. Meanwhile, a weak low pressure circulation is expected to form roughly 150 miles west of West Central Florida in the Gulf underneath the lift provided by approaching very strong jet stream level winds of nearly 110 kts.  This circulation could be briefly closed, but not expecting the strength of the circulation as it stands now to make too great an impact in the overall scheme of things.  This circulation will cross Central Florida during the early - mid afternoon and likely lose its characteristics as it interacts with daytime heating over the land mass, of which I don't expect to be much (in the heating category).


By noon this area is expected to approach West Florida with showers and some isolated thunder perhaps and then enter and cross the spine of the state around noon-1pm, accompanied by showers and thunderstorms. Some of which could be strong. Over the past 36 hours the favored areas for a strong storm have been near Daytona,  Cocoa Beach/Cape Canaveral, and Vero/Ft. Pierce areas.


**However: If one looks at the Topsy-turvy NAM model, which for two days has showed variables such as favorable wind fields for tornadogenesis near St. Augustine (last night), to a strong storm at Cape Canaveral (in two previous runs)..it has now gone to the opposite extreme and shows barely any rain at all over the state tomorrow other than a few showers THE ENTIRE DAY.  This might be because of two reasons : 1) too much cloud cover in the upper levels associated with the jet streak cutting off instability potential below combined with a near uniform vertical  moisture profile throughout the boundary layer with no dry slots in an otherwise favorable one with  the cold temperatures aloft department for strong storms. In short, not enough heating to get anything going in the absence of a trigger (earlier, it showed numerous triggers) such as liitle vorticity maxima and vertical velocity pockets at various levels.


On the other hand, the GFS is the same with the timing of rain from west to east after noon time..but more generous with more showery type rains.  Even with cold air aloft which would favor strong/severe storms, accompanied by the strong upper level winds..the mid-level winds (in both cases) do not change much in strength with height and are fairly uniform in direction as well.  This leaves us with just cloudy skies and some rain showers with lack of instability at the low levels.


And on the third hand (should you have one), we have the local WRF model which, like the SPC one, is showing early morning (even before sunrise) thunderstorms/showers near the East coast between Daytona to Vero Beach. This is what I'm thinking might just be some showers if anything.


Both models then bring in the second wave in the afternoon associated with the weak surface low and the main 850-700mb short wave trough axis which actually is mainly to the north of the state  when again, there could be some thunderstorms.


To add to the post, numerical guidance is showing anything from  a 20% chance of rain to as much as 50% percent (The Weather Channel for my location reads 40%). Most of what we are hearing, I think, is just a best guest' ruf-estimate mish-mash' of all the available information, none of which will be close to reality in all likelihood.


  I do have a problem with believing there will be ample moisture for storms in the low-mid level state wid..and like an older version of the GFS which had the best moisture return limited to Central and South Florida, namely from Brevard County -Tampa and South, then favoring up the east side of the state toward at least Ormond Beach if not St. Augustine for an isolated storm, which could be strong if it holds of until mid-afternoon. Guidance hints at moisture north of Brevard but varies on when it will be there, and as such, whether it will just be showers or a strong/severe storm.  On model shows something very strong up there in fact...that is in the afternoon associated with the mid-level trough axis.


SPC is NOT making any mention of strong or severe storms. In fact, they don't even MENTION the state at all in their discussion (but do mention the mid-Atlantic region and somewhere else that i don't even recall where now though..but it wasn't Florida) despite the near favorable credentials for as said storms.


  In the world of weather though, the sum total of 'near favorable conditions and parameters' ...now mater how many variables are 'close', does not add up to a sum total of 'severe' or 'strong". Often, everything  being "almost good enought' ends up with nothing other than clouds...that is, the NAM solution.  BTW: The RUC model today has been out to lunch. It did not even initialize the rains over Southeast this morning, and is not initializing them yet in successive runs since early in the morning. This means neither here nor there though in regard to tomorrow, since it does not run out that far in time.


I'll add just as an observation which is likely only 'in my mind' since I'm looking for answers;  that all of the NWS offices and SPC seem to be strangely 'mute' about tomorrow..sounding a bit in-definitive. But the point is, despite the strong winds aloft tomorrow (limited to the upper most levels and not the mid levels) and cold air aloft, weak instability seems to be the factor that would limit to some extent if not entirely an active weather day. Perhaps the NAM has it correct with almost nothing at all?  Only later model runs and closer scrutiny of satellite imagery will reveal what is to come.


In closure, as written in the prelude of today's post, should thunderstorms develop tomorrow, they could be strong to severe..most likely on the East Side of the state. Best chance of said will be from 1:30pm - 5pm from near Ormond Beach to Ft. Pierce. Other thunder storms could form just about anywhere, but would most favor the east coast. It will be interesting though to see what moves in on the West Coast earlier in the day. That, and how it trends as it pushes east (assuming something does move in)..will dictate how the end result of the day on the east side of the state.


Expect most if not all activity everywhere to end by sunset or shortly thereafter with a few stragglers, if there is anything to 'straggle'.


BEYOND: Quiet through the weekend as NW flow moves in. This might actually be a warm, dry NW flow..but it is way to sketchy to say for sure until after tomorrow is through. It does look to be dry though. Only exception would be continued shower chances far South Florida, possibly another shot at thunder close to Miami Metro area on Saturday, perhaps on Sunday if they play their cards right.

Isolated Showers and Some Thunder Possible, A Storm or Two Strong Interior/West Late

Greens: Showers possible (thunder audible mainly west of I-95) Red: Better chance of mid-afternoon to early evening thunder-one might be strong, Blue: beast chance of one or two strong storms

TODAY: As of 1pm I think a  much weakened surface front which is becoming close to non-existent is almost right over my head as I type.  Winds are near calm and it feels warm out there. Some puffy cumulus are visible just to the N-NW along the leading edge of the boundary.  Otherwise, a surface high building in  from the WSW-SW is cutting right thru the constructs in the vertical profile of the approaching front, leaving the mid-upper level portions well over head, but separated from just a surface boundary moving into Central Florida at the surface. The wind shift is due more from high pressure building in across the Panhandle rather than down from the North.  Be that as it may..


Instability this hour is building near the Sarasota even this hour..with the axis running from near that location to Central Brevard County. Additional instability will mount through the mid afternoon, mostly toward West Central and West Florida.  Behind the boundary, winds become ENE up to 3500 feet, then near calm in the ridge axis, with  westerly wind (and quite brisk) in the upper levels. Precipitable water values per the SPC latest analysis are only running about 1.3" inches..just barely enough to sustain a thing. In fact, there is little to be found on radar. Not much more to say about the surface boundary, as today's weather will be more of a function of sea breeze convergence coupled with the steering flow and ample moisture to generate some convective activity beginning pretty soon now, but mostly after 3-4pm.


Showers could be felt or be near by about anywhere within the 'green' above..and in some locations, most likely west of I-95, thunder might be heard from a distance if not directly overhead the close to the spine of the state one is located.  The best chance for a strong storm (if there is one) will be toward the West Side of state after 5-6pm when dewpoints begin to rise after peak heating.  A strong storm could put down some frequent lightning, strong winds gusts, and pea hail at its worst in one or two select locations if the timing is right. Not expecting severe storms today. The strongest activity looks to occur over an open, rural area.


THURSDAY: The moisture associated with the wind field boundary will settle toward Miami Metro and the Keys. Showers could be found throughout the night toward Palm Beach County into mid-morning as the moisture field sinks south, favoring Palm Beach to Boynton Beach into late morning.  Best chance of thunder tomorrow appears will be over Broward, Dade,and Collier Counties beginning early afternoon. By late in the date the high pressure responsible for the developing NE winds today further north will be crossing the state and into the Atlantic all evening. Winds will become ESE-SE over night with a return of atmospheric moisture to the more northern counterparts of the state.


FRIDAY: High pressure well to the east, and SE-SSE winds harvest moisture return to nearly all of the state. Another mid-upper level trough will be passing to the north of the state on Friday with the cold pool reaching into the north 1/2 half  of the state, but not forgetting the South as well.  On Friday, should the above materialize as forecast since yesterday but now more amplified, showers and thunderstorms could develop by early afternoon, some strong to marginally severe over the East Half of the state...any very isolated  severe category storm will most likely be along and east of I-95 from Ft Pierce Beach to St. Augustine or JAX...but this is a new evolution (for example, two previous model runs favored solely (and might add strongly so) the Brevard County area). It looks guaranteed that cold air (the forecast 850mb temperatures are almost obscene) under a nearly uncapped environment would get the show rolling early and would therefore put a significant damper on the potential strength of storms should they hold off until late in the day.  Winds aloft in the jet stream over Central are forecast to be in the 90-110 kt range...with Central in the right entrance region of the southern branch of the split-flow pattern that has been developing over the CONUS, adding in upper level divergence which is favorable for rising air currents in the mid-levels.


SATURDAY/SUNDAY: So far, looks like Friday will scour the atmosphere out. However, per my post 2 or 3 days ago...it was stated that thunder chances could exist Friday through Tuesday. The Weather Channel was showing this to be the case this morning (3 days later now)...but I'm not so sure about that now. Looks like it could be nearly a week before rain chances return beyond Friday as of this morning.

Partly to Mostly Cloudy Wednesday, Isolated Showers and Some Thunder Possible

Author's "Weather Station" recently installed. Not too excited yet.  It lacks one critical asset, namely accuracy.  But THANKS to the "Unpredictable WeatherGuys" on Facebook. This gem was won in a drawing which they conduct. It has a remote reader/sensor , wireless, to access observations from the comfort of my TV remote, snacks in hand while watching The Weather Channel.

TODAY: Relatively dry easterly breezes reign supreme today through tonight as a frontal boundary approaches the Western Florida Panhandle. Skies are mostly clear to partly cloudy across the state other than the panhandle where some showers are developing closer to the approaching front.


WEDNESDAY: The front will be located across NW Florida at sunrise.  This boundary will progress east-southeastward during the late morning into North Central Florida by mid-late morning. Meanwhile aloft, the supporting  mid-upper level trough will pass on east to ENE ward toward the mid-Atlantic coast (well North of Florida), leaving the sprawling surface front to enter all of North Central Florida between 9-11AM with the greatest moisture convergence right on and behind the boundary.  The front is expected to be roughly across Volusia County at 9AM and into North Brevard by 11AM.  Accompanying the boundary will be some light showers earlier in the day, transitioning to some moderate showers and isolated thunder after 11AM - noon time over North Brevard, Seminole, far Southern Volusia, and Northern Orange Counties.  Most of this activity it appears could be accompanied by more extensive cloud cover.


If we take the 'union' of GFS and NAM forecast precipitation subsets...the best chance of thunder tomorrow will occur near West Osceola and Polk Counties after 1pm- 5pm where greater surface heating/instability will be permitted to mount;however, the previous NAM and the latest GFS place the better chances of thunder over North Brevard from near Cape Canaveral to Mims into Seminole County after 1pm.  Given the wind fields portrayed by all models, severe weather is not likely.


The models do agree though that at the lowest levels the immediate surface front will reach into South Central Florida by early afternoon, but is nothing more than a wind shift, whereas just above the surface the mid-upper level troughs lag by a good 6-12 hours. Not sure what the net affect will be, but given that surface winds will be NE behind the front, rain chances on the East Side of the state beyond 1pm should be simply showers, with the better thermodynamics further south and west toward Western portions of South Central Florida. It does not appear that South Florida will receive any rain tomorrow from the front.  Rain chances could continue as late as sunset over the East Side of the state south of Daytona if the GFS verifies, but this will likely end up being simply cloud cover.


THURSDAY: The remaining surface boundary will skirt the east coast as high pressure over laps from the the west and north...all features...similar to the previous front, become non-entities over far South Florida. The best chance of Storms on Thursday and Friday look to be far SW Florida, Broward, Dade Counties, and the Keys, with mainly Dade and the Keys highlighted into Friday as moisture beings to return to the north overnight into Saturday.


SATURDAY: Model disagreement abounds per the author's observation and backed up by NWS forecast discussions. Saturday could end up being a bit like a modified summer day type pattern favoring inland showers and isolated thunder for South Central and South Florida as surface winds begin to swing around to the gradient SE-SSE  direction but with sea breezes generated from both coasts and moisture lifts back to the north.  Very typical for mid-Spring/pre-thunderstorm season (for Central/South), and more in line with the earlier onset of thunderstorms over South Florida, although it might be one or two more fronts before the full onset becomes even more evident.


In Summary, it's starting to look more and more since the previous system that the Thunderstorm season is starting right where it left off in 2010, over SW Florida at some point in time during the next two weeks. On the far far out there.  The GFS is starting to show very high Precipitable water values of 2"+ down in the Caribbean and trying to approach the southern Gulf going into mid portions of May.  This would be the missing ingredient needed to get the Florida Storm Season underway going into June...and potential act to ignite the Southern Plains State's Severe Weather activity from that perspective going later into May (outside of other moisture sources that region draws from).