"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, November 10, 2011

Cold Front Tonight as Sean Peaks in Strength

Morning Visible Satellite Image Shows Cold Front Across The Panhandle and stretching NNE to a large low near James Bay. Tropical Storm Sean as shown relative to Bermuda and generally forecast direction of motion.
RECAP: Cold front cleared the western Panhandle this morning and is nearing Tallahassee. Drainage flow everywhere last night with temperatures ranging through all of the 50Fs to mid-60Fs, warmest SE Florida coastal and Keys, and within 1 block of the beach from Canaveral and south. 

By an odd twist of fate JAX was colder prior to sunrise than Pensacola behind the front at 45F with a calm wind, albeit Pensacola was one degree warmer at 46F but with winds from the north at 20 gusting to 33mph making for a wind chill of 37F under cloudy skies. 

Elsewhere, Tropical Storm Sean has been on a NNE track and is forecast to miss Bermuda to the west. There was a big flare up of convection around 6AM (Bermuda Time) but that has since waned. Sean is now over cooler ocean waters in the mid-lower 70Fs with no Heat Content. Ocean Buoys in this area are scarce, and none of those closer to the storm were showing sustained tropical storm force winds but one. Sean is officially forecast to become a hurricane by tonight, but not so sure about that due to increasing shear and no ocean heat content. A plane is flying into the area as I write, and they might be able to whip up a (convoluted to some degree) ' technically a hurricane' status, but it will likely be very brief if ever and never be measured on the surface from what I can tell.

Sean will start to become absorbed tonight and more so by mid-day Friday by a much larger trough of low pressure now located near James Bay. High Pressure to the N through NE of Sean could push abundant moisture NW ward in strong SE Flow ahead of the cold front away from Sean. Pressure gradient winds along the coast of Nova Scotia to Greenland could generate surface winds stronger in those locations than what will be experienced in Bermuda . The latest GFS has Sean nearly gone around the same time the NHC has Sean a time will tell. Either way, no impacts to land other than indirectly due to high seas and pressure gradient winds between the cold front/Sean/and High Pressure.

Latest Analysis. The yellow area shows the surface low SE of James Bay and then Sean. The broad area indicates how these two features will eventually wed off the coast of New England with  very dynamic results upon NE Coastal Maine and through Nova Scotia. Other rains along the coast of New England will be related to the front combined with some of the moisture from Sean as the umbilical cord is made with the Mother Low near James Bay. In a sense, Sean will cocoon from the state of which it originated, a mere non-tropical or even subtropical entity.
OTHERWISE: Cold front approaching Central and South Florida today. Winds today will be NW with highs in the upper 70Fs to lower 80Fs, mainly South of I-4. Increasing cloud cover precedes the front, and this cloud cover could reach a portion of the region north or near I-4 during peak heating. Otherwise, nothing to speak of other than some light sprinkles possible along and just behind the immediate frontal boundary.

I conjured up a first grab stab   time phased image of the cold frontal position from its current position through the time it will be clearing the state by early Friday. Positions for Central might be delayed an hour or so if the front slows down during the afternoon during heating of the day, but either goes through well after dark:

TONIGHT/EARLY FRIDAY: The cold frontal passage tonight will be easily diagnosed by a surge of NNW winds of 20mph possibly gusting toward 30mph for about a 6 hour window of time from North Florida through most of South Central during which time the temperature will drop 10-15F degrees.. This surge never reaches South Florida to such extent but the cooler air does. Skies could be partly to mostly cloudy all areas for a few hours prior to and after passage.

Morning lows Friday  should range from the mid-upper 50Fs east coast from Canaveral South (warmer toward the lower 60Fs coastal SE Florida), decreasing west of the Intracoastals and down into the mid-upper 40Fs interior and west as far south as Lake Okeechobee. Friday will be the ODD (one day deal) for the east coast from Canaveral and South as far as the coldest temperatures are concerned. Winds relax late morning, but will likely pick up again with daytime heating under clear skies, and with mixing during peak heating range in the 15-23mph range across the state as winds slowly veering toward due north by Sunset. 

Big downfall to all of this. Very cool afternoon Friday, with highs barely getting above 60F toward Ocala and north, and just eking out a low 60F near DAB with breezy N-NNE winds around 18-23mph with mixing during peak heating. The main period of cold air advection will occur coincident with peak heating on Friday well behind the front, which will be a saving grace from what could otherwise be a very cold morning had timing been different.  The NAM is showing a near classic JAX Cold Wedge working into the north side of the Cape approaching the Port, but thinking for now it's too early in the season for those shenanigans, so discarding...highs other areas all of Central (except Tampa Bay) in the mid-upper 60Fs nearing lowers 70Fs coastal South Florida/Keys.

SATURDAY: High pressure will be building across the Deep South and northern Gulf and be center near Southern GA Saturday Morning. Very light winds and drainage flow could send temperatures near I-10 in select areas like Crestview, Marianna, and Tallahassee into the mid-upper 20Fs with widespread 30Fs (frost looks possible as well in these areas). Elsewhere, winds along the east coast of Florida will start to become more NE (and light) overnight, so that overnight lows from the Cape and South might occur well before midnight, level off, and possible rise a few degrees before sunrise into the low 60Fs ...mainly within only a few blocks of the ocean. Otherwise, with sunrise ENE winds develop as the high pressure center continues to build NE ward into the Western Atlantic. By day's end a broad and stacked elongated oval of  high pressure will extend well out into the NW Atlantic (close to where Sean demises) SW ward into the SW Gulf of Mexico. The cold event is all but over already for the South half of the state after sunrise Saturday.

SUNDAY/MONDAY: Mildly cool overnight coastal lows but no big deal, cooler inland with possible patchy inland fog. Winds become more east to eventually ESE-SE on Monday as high pressure continues to work offshore in stacked fashion.. It appears some vorticity (energy) from the old frontal boundary by now south of Cuba might get recirculated along the back/western extent of the surface to 850mb high (now well out at sea) late Sunday through early Tuesday. In doing do, showers could work up the east coast from the Keys and far Southeast Florida Sunday night through Monday, reaching dead central toward Indian River/Brevard/Southern Volusia from mid-morning through sunset after clearing South Florida.

Very warm Tuesday/Wednesday. Looks like the East Coast from Ft. Pierce and North will see the warmest days it has experienced in quite a while as winds will no longer be predominantly onshore and across the cooling ocean waters. Thought those easterlies would never end.

Another potentially potent Southern Plains to Ohio Valley frontal boundary which might result in a Quasi Linear Convective System type Squall Line from Eastern Oklahoma/NE Texas into Louisiana and through the Ozarks toward Ohio (as well as Indiana and Illinois) will be on the approach by Wednesday. 

Latest GFS indicates there might be a prefrontal trough ahead of the boundary which might result in some showers ...and who knows..maybe even a thundershower or two..across Dead Central moving offshore the east coast Wednesday afternoon and evening. 

This approaching front never clears Florida as thought (at least so far) but becomes absorbed in the ridge of High pressure which, as it might be, will dominate the states weather into at least early Thanksgiving. The GFS is up and down on rainshowers moving onshore beyond Wednesday with the next washing out front. For some reason, it has backed off on them as of the 2AM model run, which is a new twist. I'm hedging more on showers though given the wind fields it shows.          

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