"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".

Thursday, May 17, 2012

Chance of Strong/Severe Storms Today

Fairly Close model consensus so far this mid-morning with surface 'now' data indicating that a weak surface low could form for reasons described below. East coast sea breeze convergence along or even east of I-95 could, if current thinking
holds fast, result in rotation in a few storms from Saint Augustine
to Central Brevard  
TODAY: Tricky forecast, but waste not want not. So wasting no time to get this post out as a precautionary measure.  Some "scrappy Cu" (cumulus clouds) already forming in thinning early day mid-level clouds over Central and North Florida as sun beams in.  Jet stream level winds across the South Half of the state with agreement that Central Florida will be under the right entrance region  of those winds. Additionally, latest guidance in two models shows a  streak of 20,000 ft. winds at 500 mb (millibars)   streaking right across Central Florida later this afternoon right under the divergent winds aloft . Highest convective instability is forecast to exist from Lake Okeechobee and North, due the result of late night through early morning  rain activity further south where jet stream cirrus clouds continue to run over that Southward Area now and as it looks, the remainder of the day. Meanwhile, surface boundary to sink into North Central today, with latest surface and low level streamline analysis indicating convergence along that boundary increasing during the day, especially along any sea breeze front resulting in stronger upward vertical velocities.

With those factors in mind 1) Divergence aloft 2) strong 500mb wind core 3) instability and finally, the big question mark, 4) an east coast sea breeze which seems most likely north of St. Lucie County, and 5) coldest temperatures aloft from 10000 ft up are from Brevard and North. South Florida might be contending with outflow backlash from early day activity, but things could change down there quickly, as often seems to be the case. Regardless, without a doubt the region further north, as it stands now at least, holds the better chance of severe weather today . So with those factors in mind:

Questionable activity South Florida. More than likely, this region will see some storms today, but all things considered further north those factors seem to pale in comparison until after 7pm tonight. By that time certainly it could all be a different story. Otherwise, North bound we go where from this image alone one can see the skies have cleared with no high clouds coming in from the west off the Gulf of Mexico. 
ADDITIVE FACTOR: Low to mid level helicity values along the coast, especially from Brevard and North are shown to be the most consistent in guidance, with a concerning higher value running from near Southern Volusia toward Cocoa Beach, and again further north toward Ormond Beach give or take 50 miles north/south. Another factor is that latest guidance is showing stronger downdraft CAPE values encroaching in on the entire west side of the state from the Gulf. Downdraft CAPE tends to limit overall coverage, but that which can form , that is to say, can work against the downdraft cape into updrafts, can result in storms that rapidly build vertically, resulting in hail and/or strong downburst winds. Thus the area in red as well. Such downdraft CAPE would also, if it is true to form as a mere 'mortal model' can show, would INHIBIT activity over South Florida already covered in High Clouds.However, guidance is showing rainfall down that way, the type for lightning production. Best best at this point down there would be from Port Charlotte and South inland toward Lake Okeechobee and the Everglades for any potential strong storms,. 

THUS: The purple area would be considered for this post to be a zone to watch for rotating thunderstorms and maybe even a brief waterspout or tornado, especially South of St. Augustine and North of Vero Beach, with a possible highlight north 1/2 of Brevard County east of I-95 closest to the boundary, convergence, instability, divergence, and 500mb wind core (IF IT IN FACT WILL EXIST). Any activity especially after 4:30Pm near the coast (if it manifests) is worth monitoring today, especially for deviant right or left moving activity. Storms or showers could continue in isolated fashion after 9pm. toward midnight.

FRIDAY: With today's "Potential Soap Opera Drama" on the line, tomorrow per the latest NAM model shows yet more, thus today / tonight could fold with... "...To Be Continued".  Today's boundary gets 'locked up' in the quick upper level winds and has a hard time dropping, at least permanently, much further south than Southern Brevard, if even that. Net result is the same sort of set up on Friday only this time from Brevard County and South toward Palm Beach County. See no reason why high clouds again might not be a factor further south, toward Dade County at least. Otherwise, might need to watch mostly inland toward West Central and SW Florida, as winds gain more of an east ward yet light component in higher levels of the atmosphere. 

Beyond Friday is a big TBD, but based on what I'm seeing the previous post looks valid yet still, namely early day activity east side translating toward the interior mid-late afternoon, with activity attempting to migrate back east yet again toward or after sunset through Tuesday. 

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