"But seeing they could not See; hearing they could not Hear"
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"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".

Sunday, February 27, 2011

"Black Monday" Begins Later Today - Sunshine State Lives Up To Name

Image: Surface plot for 7AM (EST) Monday morning, shows the general placement of surface features at the time. By this time, a tri-modal "Black Monday" (see below) severe weather will be occurring.  The yellow area shows a generalized area of most intense activity/areal coverage with the aqua showing other severe type activity to occur through Monday, spreading east with time.  Not shown is additional flash flooding concerns in South East Ohio, parts of Kentucky, Indiana, and Pennsylvania (to name a few).

TODAY: High pressure will reign supreme today as the last of yesterday's surface features which layed dormant overnight are quickly eroding during the first hours of daylight. All upper level support for any feature other than the high pressure ridge axis shown in this image exited during the wee hours.

This afternoon will be warm and sunny. Coolest temperatures in the upper 70s will be found primarily within 1 mile of any coast due to light afternoon sea breezes, quickly warming as one heads toward the interior into the low-mid 80s. Warmest temperatures by mid-afternoon will be located in general within the bounds of the yellow area I've sketched in. Coastal temperatures south of North Central and Northwest Florida will not be as greatly effected as they were earlier this month  (in the cool sense) due to warming sea surface temperatures the past 10 days. For example, the temperature at the Cocoa Beach pier has warmed from the lower 60s to 70F. The temperatures off Daytona have warmed into the low to mid-60s from the mid-upper 50s as well. Last to warm will likely be those offshore the coast of St. Augustine to JAX and perhaps along the Panhandle Coast.  Inland lakes, including Okeechobee have also warmed notably since those of  early and mid-month readings.

Winds today over the South half of the state will be primarily from the SE once the diurnal heating/temperature cycle is fully in place. No rain today with less clouds, some locations may barely see a cloud at all.

TONIGHT/MONDAY: Winds become near calm overnight, with a few patches of shallow inland fog. Lows in the low-mid 60s many locations, with a few upper 50s well inland north of Lake Okeechobee and North Florida.  Afternoon temperatures will be warmer all locations on the east side of the state than today, reaching into the low 80Fs. Winds will be generally from the South at 10-18mph during the afternoon, but gain a bit of a more onshore component during the afternoon which could take coastal temperatures back down to the upper 70s with a few more cumulus expected inland as high pressure relaxes a bit to the east and south preceding the approach of the approaching storm system 'complex' towards the U.S. Coast, primarily from Eastern Georgia to New York.

Meanwhile, a  complex Tri-Modal  synoptic scale configuration of a variety of atmospheric conditions consisting of at least two or three low pressure systems, a warm front, cold front, and dry line (initially)  will create areas of combined directional/speed shearing wind profiles and thermal/moisture gradients, just to name a few to generate storm modes ranging from flat out long duration heavy rains to a QLCS type squall line (primarily the south portion originally) to more isolated, discrete rotating thunderstorm structures which will  spread east with time. The QLCS is essentially a 'mixed mode' line of embedded discrete cells with bowing line segments, rather than a flat out linear squall line. Backbuilding storm cells (that is to say, regeneration of newer storm activity following intial storms) after the first severe weather threat has passed, could re-initiate in the area just along and south of where the warm front is located particularily over NE Arksansas, West Tennesse, SW Kentucky, and Southern Illinois. 

There is a moderate risk of severe weather associated with this said scenario as discussed by the Storm Prediction Center (SPC) embedded within a very large area of slight risk which will expand with time toward the U.S. East Coast.  Florida is not included in any of this activity though, at least not in the 'severe' weather sense at any time. Strong tornadoes are possible, most specifically from South Central Arkansas  northeastward to Western Tennessee and extreme SW Kentucky, not to discount other areas where this region will be potentially impacted first by discrete cells and then, after a lull in activity, by the quasi-linear convective system. Other outside areas to watch will be SE Kansas toward Southern Oklahoma (east of I-35).

 And we've only discussed the forecast synoptic scale features. Within those features will be the mesoscale boundaries/nuances that will evolve/activate beyond the scope of any forecast other than  short short or real-time releases.

Local weather offices and media services are all handling their area of interest and will be issuing the proper watches/warnings/alerts as the activity unfolds.  This severe weather event will likely be much more significant than the event which occurred  just a few days ago as was expected would be the case in the post written a few days ago.  Recall, there was over 200 severe weather reports with the last system. Believe this go around we might be able to double that number, namely in the wind damage report category.  Outside of the risk of tornadoes (some could be strong, long tracking) and winds, flash flooding will be a big concern in those areas that already have estuaries nearly full from last week.  The only  fatalities from last weeks severe weather event were caused  indirectly by drowning (Arkansas).

TUESDAY: Last of "Black Monday" will be offshore or nearly so in regards to severe thunderstorms by afternoon, although the areas of flood potential will remain in part of the Ohio Valley and South half of Pennsyslvania.  The cold front  will extend across North Central Florida and will cross Central proper between 11am - 2pm.  During/after this time the surface features will start to decouple from the upper level support.  By sunset the front should be as far south as somewhere between Vero Beach-Ft Pierce on the east side.  After dark through sunrise Wednesday the remnants will sneak through South Florida to be located along or even south of the Florida Straits by mid-afternoon.

Best chance of rain with the front will over North Central Florida and eastern portions of South Central from 10AM - sunset, working south with time.  Still giving us a 30/40% chance of rain during this time as was posted two days ago, but some places already have a 100% chance of rain (at any one given location), we just don't know exactly where those location will be.  

Hedging at looking at all of South half Volusia, Brevard, Seminole, Indian River, and St. Lucie County continuing south to the north half of Palm Beach county when all is said and done overnight Tuesday night.  Only difference in thinking is to take out thunder chances altogether, although will leave in a 10% chance of a rumble from 11AM - 3PM from Sanford south to Sebastian and inland toward eastern Orange County and Osceola County.  Only because of the timing of the boundary passing during peak heating.  But even that appears is a stretch (for thunder) given there will be close to nil instability due to lack of insolation (preceding cloud cover) and weak wind profiles as the system decouples.

WEDNESDAY-FRIDAY: Winds will be NE-ENE almost immediately following frontal passage. Long term ENE-ESE winds will follow during this time frame, with a long fetch off the Atlantic. Prolonged onshore flow could generate coastal showers first over SE Florida then working to Central and North Central Coasts on Thursday/Friday. High in the 70s, lows in the 60s and a rip current threat for the entire East Florida coastline.

BEYOND: Next system will approach 'sometime' next weekend or beyond. There is large disagreement with model guidance regarding the next storm system. The trend of the GFS has been showing a much more dynamic system though (at least in the past 24 hours worth of model runs), so it bears watching.

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