"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 4, 2010

Windy, Cold Blast Is On the Heels of Clouds/Showers

Images: Enhanced infrared satellite imagery shows the upper level low over the Northern Gulf and moisture plume from the SSW across Florida generating low/mid level clouds and showers. Tropical Storm Tomas is located just off to the bottom right of this image. Other image depicts a forecast for systems at 4pm this afternoon.

SYNOPSIS: Mid-Upper level low in the Northern Gulf is beginning to open up as it phases with a larger low pressure system located near Hudson Bay within the larger trough extending down the U.S. Eastern seaboard, mid-Atlantic, and NE states. Warm front extends across N. Florida where it had its passage through Central Florida Tuesday. Humongous region of high pressure embraces the western 2/3 of the country with strong northerly flow enhanced along its leading edge and behind the low pressure trough to its east. Cold front out-lines the leading edge of the cold air invasion approaching Florida as noted in the included image and as annotated currently. Front and trough postions are annotated for the generally speaking outllook at 4pm this Thursday afternoon.

TODAY: Shuttle Launch for today cancelled. No surprise there. Extensive cloudiness will be the rule of the day. The shield of overall largest rain coverage passed across the peninsula during the wee morning hours toward sunrise, and now seems to have shifted east as the low pressure areas aloft begin to merge NNE of Florida. However, as you can see, there is still at least one and maybe two pre-frontal troughs on the approach preceding the actual cold front. Deep layer moisture being advected north from near the Yucatan (SW Caribbean) will continue to stream across the state today, and as such, clouds will be the rule with some embedded light to moderate showers. With the cloud coverage, afternoon high temperatures will be held at bay in the upper 70s with SSW-SW winds.

Just exactly how much interaction between the pre-frontal troughs and heating of the day with the Florida peninsula is yet to be seen considering this early morning hour at time of writing as well as the expected cloud coverage limiting thermal instability, but don't expect a tremendous amount of regeneration until mid-late in the afternoon at which time both 500mb and 850mb energy (vorticity) is forecast by the 06Z GFS model run to pass over head preceding and during cold frontal passage (which will be over night).

All things considered, believe that clouds will be the rule with embedded areas of light to moderate rainfall patches which can occur anywhere/anytime across the state. Winds aloft will become quite strong throughout the day but remain light in comparison at the surface and will be unidirectional (from the same direction) with altitude. As such, although lack of directional shear will preclude development of rotation within any given storm structure, speed sheer will provide the ascent within the very moist envelope to enable continued cloud and shower recycling. Additional low level convergence in advance of pre-frontal trough(s) will give the added boost required for great precipitation coverage as well as intensity but timing of such features is highly questionnable if indeed they even manifest as forecast by some of the models. The time for the greatest chances of both heavier rains and coverage appears to be between 3-8pm this afternoon and evening.

TONIGHT: Cold front now appears as though it will clear all of Central Florida by 2-3AM and the entire state shortly after sunrise Friday. Skies will clear noticeably within the first 3 hours after FROPA (frontal passage) as temperatures being to drop. It is possible that the warmest time of the day Friday will be whenever you get out of bed in the morning, thus a sweater or jacket is highly recommended to be in arm on the way out the door and on the way to work, because by late in the afternoon the sky will have cleared and gusty, very cool/cold NW winds will be 'a-blowin' in full cold air advection mode straight out of Canada. It's a little early for the snow birds, but keep your eyes open as we might spot a flock pass over head.

FRIDAY: Day will break clear, crisp, windy, and cold by all standard for this time of year. We won't have felt temperatures like this state wide since early spring. Cold air advection from the broad expanse of high pressure passing across the country's Plain states will penetrate south of the Florida Keys with no problem whatsoever. High temperatures could top out in the upper 60s to low 70s but the winds will make it feel cooler, particularly in shady spots.

Shuttle launch? It's going to be another touch-n-go situation. My fears are that given the time it is supposed to go that the winds will be at their worst due to the fact that mid afternoon will be the peak time for the cold air aloft to mix down to the surface under sunny skies (and full insolation), thus transporting the stronger winds downward from their point of origin which will be aloft. Winds will die down by late evening several hours after sunset but not become calm.

FRIDAY NIGHT-SATURDAY: Pretty darned cold. Not extreme by any means, but we'll definitely know it. Saturday will be the best day for the afternoon launch if it won't have gone on Friday. Winds will die down some although not entirely but temperatures (although not a launch criteria factor for this event) will be very cool all day. Additionally, the clear skies will be optimal.

SUNDAY: Rebound! Mostly for the immediate east coast initially east of I-95 up and down the entire Florida East Coast. Surface and mid-level winds to veer more toward the NNE-NE as the core of high pressure approaches the mid-Atlantic coast.

Problem. Being as this is the first cold air invasion of the season the ocean temperatures in the Western Atlantic are still very warm in comparison. The core of the coldest air, having now passed east of the state, will pass over the warm waters and generate low level clouds which could be advected onshore up and down the coast by mid-late afternoon by the veering winds. Contingent upon the depth and extent of cloud coverage, we might start to feel a barely detectable sprinkle hither and yon, but for the most part this won't be a problem late Sunday.

MONDAY: Large temperature gradient from the coast east of US1 to the more inland locales. A much warmer morning in store for the coast with lows in the low-mid 60s, whereas the inland portions as well as the Florida west coast will be in the 40s and 50s from Naples to Tallahassee. Additionally, and assuming the clouds move in along the east coast as feared, the overnight low temperature along the east coast will be moderated by both the wind blowing off the warm Atlantic waters as well as the thermal blanket provided by the cloud coverage reducing the impact from any potential radiational cooling. Sprinkles do appear a possibility as well, east of I-95.

TUESDAY-NEXT THURSDAY: Not much change through the week other than temperatures state wide from coast to coast will be moderating. We'll still have to see what happens with the stratocumulus cloud decks which if they haven't developed by now, probably never will.

TROPICS: Tropical Storm Tomas is beginning to curve more northerly and has its eyes somewhere between extreme Eastern Cuba and Haiti. I do not believe this storm will regain hurricane status, but if it does it will be a low end Category 1. The main concern is that it appears likely the central circulation will pass just west of, or right over, the west side of Haiti. This is a bad thing, seeing as how the greatest moisture influx will be on the right side of the storm. Rains will fall over Haiti well before the storm center makes its closest pass, and persist well after the circulation has moved on as deep layer moisture continues to be drawn northward and across the mountainous, rugged terrain which peaks around 8700 ft. Deep moisture loves steep rugged terrain , as such features act as a lifting mechanism , let alone the lifting mechanism provided by the storm itself. In other words, big rains spell out "landslides and flash flooding" for the tent metropolis for a region already plagued by the devastating January earthquake as well as four other tropical systems during the past ten years of high consequence. Enough is enough!

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