(Images: Latest RUC depiction (and surface observations) reveal a weak surface low over land, with a stronger one developing in the Gulf south of Louisiana; Water vapor shows the supporting upper level system over Southeast Texas; and, forecast for 2pm Thursday shows pre-frontal trough and cold front affecting Florida).
SYNOPSIS: Low pressure is developing over the North/Central Gulf early this Wednesday morning, while a much stronger low prevails way North in Canada. These two systems will phase during the course of the next 24-36 hours as they both move east. Over Florida, the Rapid Update Cycle (RUC) forecast and surface observations reveal a weak inverted trough along the Florida East Coast this morning, under/near which winds are essentially calm with muggy air conditions. The warmest temperatures are along the A1A corridor where temperatures in the low 70s are found. In deed, Cocoa was 62F/Melbourne 64F degrees last hour whereas my porch reads 71F. To put things in perspective, we haven't seen a temperature as low as 62F yet this season along A1A, but such readings have already been common place west of US1.
TODAY: Winds in the mid-upper levels will begin to respond to the presence of the low pressure complex over the Deep South as it approaches from the west and as such, winds aloft will begin to strengthen from the SW at all levels except near ground level where they will remain from the SE to eventually S late in the day toward evening. The depth of moisture availability through the atmospheric column will increase today providing the potential for rainshowers at any time with increased cloud coverage, especially with heating of the day. There is no triggering mechanism in place to pass overhead, so afternoon showers will be generated due to convergence boundaries along the sea breeze. Best chance for any showers along the immediate coast will likely be very late morning to early afternoon today - - shifting inland by afternoon much like yesterday.
TONIGHT: Warm evening in store with increasing clouds and showers remaining a possibility.
THURSDAY: The once again delayed launch of the Shuttle will likely be delayed further, if not definitely.
As has been depicted for 36 hours now, the cold front will be preceded by a pre-frontal trough. The trough will cross the peninsula during the afternoon Thursday between 12pm - 7pm from west to east. Due to the lack of instability along/ahead of this feature, a unidirectional wind profile aloft, and lack of low level forcing without the presence of strong surface winds than otherwise could occur in other similar set ups, the possibility of severe weather appears to be remote. Therefore, would not expect to see a Severe Thunderstorm Watch box being issued for the state; however, due to strong winds aloft during Thursday afternoon and along and behind the pre-frontal trough, there could be some locally near severe level wind gusts in any strong thunderstorm that can develop. Should these occur, the most likely location would be from North Central to South Central Florida from coast to coast between the hours of 12pm (on the west coast first) to 6pm (on the east coast) along the pre-frontal surface trough in the 'whited-out' area of the included image above.
The actual cold front lags a good 6 hours behind this boundary. Once any potential threat of thunderstorms passes, the potential continues for rain until shortly after the actual cold front passes. So one all is said and done, the best chance for rain on Thursday appears to begin after 1pm on the east side of the state with the strongest storms from 2pm -7pm, followed by areas of light to moderate rain through the overnight hours.
FRIDAY: The cold front proper will be overhead if not already having cleared all of North and Central Florida at sunrise. Cloudy skies, light rain, and an abrupt wind shift to the NW-NNW will accompany the front. Temperatures will drop noticeably within an hour or two after passage but level off for the remainder of the day somewhere in the mid-70s. Skies could remain mostly cloudy for several hours after FROPA (frontal passage), if not for most of the day. Refinement on the timing of persistent cloud cover will need to be made contingent upon how well things come together over night tonight and early Thursday.
SATURDAY: "Brisk Winds and Fair" (as our old barometer used to read after a cold front). And quite cool to downright cold to boot. Looking for morning lows inland to be in the mid-upper 40s over all but extreme East Central (namely the intracoastal communities) where lows should be in the low-mid 50s. Skies to be near clear with an afternoon high in the low 70s. This will be like a normal January day. Winds to begin to relax a bit over the late night. As one would expect, the coldest of air will be located over the Panhandle where some temperatures in the 30s might be found.
SUNDAY: Winds becoming more northerly and decreasing with another relatively cold morning accompanied by clear skies. Nice morning to wear your Sunday Best that's been stored away for 7 months. Winds to gradually shift to NNE by late in the day.
MONDAY-WEDNESDAY: Moderating overnight/early morning temperatures east of US1 as an onshore component wind direction becomes established. However, as we work toward Tuesday or Wednesday especially, the remaining cold air now having pushed east will be riding over warm ocean Atlantic water and generate stratocumulus clouds which will be advected on shore up and down the entire Florida East coast. These cloud should remain east of the spine of the state and more likely thin considerably once one works west of I-95 over Central and North Florida, but approach the Big Lake along and south of its eastern shores. Maybe a spit of light rain will accompany the clouds periodically of non-significant nature. Afternoon high temperatures, should these cloud indeed develop to the level I fear, will be held at bay in the mid-upper 70s due to lack of full, mid-fall sunshine.
TROPICS: Tropical Storm Tomas has been downgraded to depression status as it moves slowly west through the Southern Caribbean. It is somewhat perplexing as to why the system has been weakening since shear is not all that strong and water temperatures are still warm in that region. The same storm system that will clear Florida overnight Thursday and Friday will pick up what will either once again be Tropical Storm or Hurricane Tomas and lift it off to the NNE-NE by late in the weekend into early next week. Regardless of the storms wind strength, it is the rainfall this system will be remembered by for the folks in Haiti, The Dominican Republic, and perhaps Eastern Cuba.
Of greatest concern is over Haiti where over the past ten years they have been heavily directly affected by 4 tropical systems and of course this year's Earthquake in January. The mountainous terrain over Haiti peaks at over 8000 ft upon de-forested soils, leaving water runoff a major issue should heavy and persistent rainfall occur there. And, as it now appears, that rainfall potential looks to be looming as a coming reality by late in the weekend. The eventual track of this tropical system is problemmatic as well. Seeing as how the system is already so far south, the trough passing to the north may have a hard time carrying the storm away entirely, so even if the central circulation passes to the north, moisture/rains could lag behind over the land areas already outlined for an extended period. Therefore, flooding will be the big issue for the tent metropolis.