"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".

Tuesday, September 18, 2012

Pattern Shift Has Begun - Showers and Thunder More Widespread Today Statewide

Sunrise on Monday, Cape Canaveral, Florida
TODAY: Long-awaited (for some) pattern shift has arrived. What is meant by 'pattern shift'? We have been under the influence, intoxicated by easterly flow (onshore east coast winds) for quite some time.  Today herald's a shift in gears to SW flow at the surface and aloft as a frontal boundary draped up and down the entire U.S. East Coast presses eastward across the far Northeast states southward well into the Gulf of Mexico. This could mean a warmer afternoon toward the east coast south of I-4, in particular, and far South Florida with delayed onset of rainfall chances. Rain and thunder is already occurring under the cloud cover shown in the satellite image (below).

Quite a bit of lightning is occurring over North Florida early this Tuesday morning. This area is under the best 'upper level wind dynamics' which weaken the further south one proceeds, especially south of Dead Central Florida toward the Big Lake of Okeechobee. Outflows from activity further north look plausible to move in over the region north of I-4, so that area might be a bit stabilized by "that 'air' " before full heating of the day (which is now earlier due to earlier sunset and later sunrise) can be 'realized', or come to fruition/occurrence. Therefore, watching further south.
TODAY: Some storms could be strong, but brief due to fast motion, toward the East Coast south of I-4. The only reasoning being is that outflow from earlier activity and increasing cloud cover further north might cut off destabilization (as noted in the above caption); whereas, further southward, better heating accompanied by a bit of divergence aloft (not really significant) under SW flow aloft which is quite moist could pile up some heavy rainfall in short periods accompanied by lightning strikes 'afrequent' (under the assumption thunder storms can develop there alongn the 'red zone' shown).  

The off setting 'proverbial fly in the ointment' is that the east coast sea breeze today does not look likely to develop except maybe briefly before the frontal boundary gets further Southeast ward (and slows down significantly tonight presumably) south of Fort Pierce.  Meaning,  1) no chance of low level convergence; and 2) this will not be a summer time/like rain chance regime today where sea breezes or Lake Breezes are the biggest player (except far south).

Latest KSC sounding is showing 23 kts of wind around 2000 ft which will at least try to mix to the surface, so would expect no sea breeze today, possibly unusually breezy along waters and lakes for this time of year from a SW direction. 

The 700mb temperatures are not cold at all, although 500mb temperatures are cool enough that water over-loading aloft could translate in cooler temperatures in to the mid-levels regardless, for gusty winds in and near heavier showers and/or thunderstorms. 

Either way, guidance is split on activity today with the NAM going extremely low key as it has been for three days now in regard to storms and even showers, with the GFS showing a good chance to likely  along the east coast from Melbourne or so, southward..toward Fort Lauderdale. The best chance of an east coast sea breeze is well south of the Lake, so it may be that area will end up with a big storm.

Overall though, the air mass over much of the peninsula south of I-4 is fairly uniform early today, so the driving factors for this afternoon into early - mid evening might be from outflows resulting for earlier activity further north working southward into areas where heating has built up. 

The down fall of this is that outflows without a conflicting sea breeze can act purely to stabilize the atmosphere. Unless a vorticity max comes through, today could be a big bust, but not willing to hedge bets on that one this early in the day. In short, today's post is a 'play it safe just in case post", and speak of the worst case scenario, which is good rainfall and thunder coverage working south after 1pm through early evening. And this stabilizing factor seems more likely near and north of I-4 and less likely along the east coast south of Ponce Inlet.

BEYOND: The frontal boundary is expected to wash out in the next 2-3 days across all of Central Florida in a wide swath, with the upper level trough never clearing the area (nor the true front)...rather, it gradually gets replaced after frontalysis by high pressure from the north without any drying of the atmosphere, followed by a light onshore flow re-asserting itself by later on Thursday or Friday. Either way, showers will remain with temperatures running about where they have been lately, either coming in off the Atlantic or inland showers and thunder.

The earliest autumn since 1896 arrives this Saturday, September 22, at 10:49 A.M. (EDT). At this time, the Sun appears to cross the celestial equator from north to south.

 Coupling Up For  the Cape Canaveral Sunrise

No comments: