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

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

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

Friday, April 20, 2012

An Isolated Strong Storm Not Out of The Question, Severe Weather Threat Remains Saturday

Rain fall (green) as showers to Thunder Orange To Purple Strong storms after 4:00pm today are possible as noted in the discussion below. Note in this 1:20pm image the 'Lake Shadow" NE of Lake Okeechobee; the clearing area due to SW winds blowing across the lake and stabilizing the atmosphere upstream of those winds along the NE side of the Lake
TODAY: A bit like yesterday, just more of it. Sea breezes both coasts will play in to today. Today looks like a summer day out there, and the air feels a bit like one. There is one big difference today from yesterday, that being higher Convective Available Potential Energy (CAPE). There is more of 'that' today than we have seen in quite some time and local data integration system from KSC backs up the model's claim, if not more so of the cast near Vero and South. That air will be transported into Central after the sea breezes set up and spread around. 

Temperatures aloft today are cold all things considering so there is an added storm potential bonus. The key factor for stronger storms toward the east side will be in the timing and cloud/shower extent prior to 4pm across Central Florida. For now, will gamble on hedging toward pretending it is summer in regard to timing, and throw in the cold air along with respectable vertical velocities shown on the questionable NAM model, although other models are showing 'values' as well. Would add some 'umpf' late day along the east coast near I-95 from DAB to Vero, with a focus toward Brevard/Volusia/Indian River, and St Lucie Counties...with the chance of stronger activity noted in the purple for a variety of reasons beyond the usual 'technical difficulties" that either could be stronger parameters than guidance shows or be non-existant. Rains could persist until after sunset but not much longer as it appears now as activity moves offshore and or loses the 'juice' .

SATURDAY: This is a big question mark day in regard to severe weather. Suffice it to say it is not a day for the beach, as cloud cover or a very big bad storm threat will loom. If cloud cover is less, all the greater the storm threat, so either way...a watchful eye will be necessary. I had made up a graphic earlier today before the 12z runs, so will use that one instead of recreating the wheel which will change on the next run anyway...due to ever changing model resolutions.

Consensus now as gone back to previous reasoning, in regard to where Severe Weather in the form of 'damaging hail could fall' as well as where/how/why there could be some tornadoes on Saturday. 

Instability (CAPE) is not all so impressive (not at all actually) , and the wind fields have been bouncing around a bit in regard to whether or not there will be anything beyond an isolated spin up VS. an actual full blown tornado or so...if not a few. Last nights hodographs which show the curvature and strength of the winds aloft portray a definite chance of tornadoes during brief windows of  so called "opportunity" from SW Florida up toward Ormond Beach, (if not outside those realms) with the conditions spreading north from mid-morning toward late afternoon as the day progresses. Otherwise, other showers could occur elsewhere. There has been some trepidation from official outlets against the chance of strong updrafts, as noted yesterday, due to weak instability.

However, I have noticed that low lifted condensation levels continue to be forecast by early afternoon (values we'd normally expect not to see until near dark, when summer storms get there strongest) to be unusually low, meaning LOW storm bases...and that factor compiled with Rich Theta-E air well up through the mid-levels and good helicity values could overcome any weakness in instability regardless.

One other factor to point out is that this does not appear to be an in and out of here situation by any means. With a threat of severe weather as far north as JAX toward Tallahassee and as far south as the Keys at various time frames due to what might be TWO warm fronts swiping from south to north..timing is literally impossible from my perspective at this point. The important thing to bring forth and stress is to STAY AWARE! This will not be your standard 'severe hum-drum fare" type of day, especially if a worst case scenario were to evolve. Do note, the low is forecast to form near the Loop Current, so unexpected intensification of that surface feature over those warm waters could make the difference between a slight risk of severe to a booster shot up toward a rare moderate risk, unless a high overcast and the theta-E air does not manifest as forecast. In which case, one will be left wondering what the fuss was all about for the get go. The above statement was not made by any office, but best to stress worst case than be  nonchalant and off guard to any sudden 'potential'.

This image as noted is based on the 06z NAM run valid for 3z tomorrow night (11pm). Later runs match closely in regard to the main features but change with the finer details as to where, when, or even IF severe weather  will occur. The image portrays  Helicity in the lower levels of the atmosphere. Since that time, the values have changed in the forecast, but who is to say they will not change right back again later on before tomorrow morning,? Thus, I posted this as an example showing a warm front location and surface low for Saturday night around 11pm. Values by this time have spread for South Florida northward during the day with a severe threat as that occurs in this 'Example". Those values are high for Florida and not messing around. Serious stuff in other words.
The good thing is, guidance does show that it might not be a good day AT ALL to plan outdoor activities, so there is literally NO EXCUSE not to have a TV on Channel 13 (Central local channel), or your favorite news channel, tuned in and ON otherwise. If things do get cranking, your news channels will be covering tomorrow Live and Real time, possibly commercial free during any high points. So far, tomorrow has had a greater potential for severe weather than we have seen since last spring in the hail and twisting winds category.

Here is another interesting observation, the  forecast sounding based hodograph. The big loop , or arc, shows how winds curve with height within a Theta-E rich atmosphere. In fact, one of the downfalls for severe tomorrow will be that the entire column of the atmosphere in any storm will be saturated beyond recognition..but low level forcing along northward moving boundaries with energy criss crossing from the west could set just about anything off, any time from late morning through early evening.
In the upper right is the winds with height. Note how quickly they turn, or shift in the low levels. Also note how close the vertical red and green lines are. That shows gobs of moisture without any dry slots to aid in lift, or buoyancy. The lower left is the main point I wanted to point on in thee wind fields...LOOP! To the right, we see this hypothetical 'sample' is for a location near Titusville.

BE AWARE point blank. Things can change in later forecasts, and I expect everyone on TV will be saying the same. Or they should be.

BEYOND: Activity could continue into early Sunday toward noon time with a lull in activity somewhere along the line, but it appears any tornado threat will be gone after the wee hours of the night. There is a chance the entire mess will be over with by noon most locations with rain and thunder North Central to North, but as noted already, there is simply too many timing issues to make even close to a believable or rather trustworthy forecast regarding Sunday's weather. Need to get past Saturday yet still.

Otherwise, no rain for many days seems to be in the cards with much cooler morning lows interior Central and North, and quite cool comparatively speaking elsewhere for several mornings. North Central could feel 'chilly' prior to 10A<. Afternoons will be quite pleasant though.

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