[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 212338
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
705 PM EST WED JAN 21 2009

TROPICAL WEATHER DISCUSSION FOR NORTH AMERICA...CENTRAL
AMERICA...GULF OF MEXICO...CARIBBEAN SEA...NORTHERN SECTIONS
OF SOUTH AMERICA...AND ATLANTIC OCEAN TO THE AFRICAN COAST
FROM THE EQUATOR TO 32N. THE FOLLOWING INFORMATION IS BASED
ON SATELLITE IMAGERY...METEOROLOGICAL ANALYSIS...WEATHER
OBSERVATIONS...AND RADAR.

BASED ON 1800 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
2315 UTC.

...THE ITCZ...
THE ITCZ IS PRETTY ACTIVE THIS EVENING. ITS AXIS IS CENTERED
ALONG 5N3W 2N15W CROSSING THE EQUATOR AT 19W THEN EXTENDING TO
2S30W INTO NORTHEASTERN BRAZIL NEAR 4S40W. A CLUSTER OF MODERATE
TO ISOLATED STRONG CONVECTION IS WITHIN 150 NM N OF AXIS BETWEEN
15W-18W. SCATTERED MODERATE/ISOLATED STRONG CONVECTION IS WITHIN
125 NM N OF AXIS BETWEEN 22W-33W...AND FROM THE EQUATOR TO 3N
BETWEEN 34W-40W. SIMILAR CONVECTION IS NEAR 3N47W.

...DISCUSSION...

GULF OF MEXICO...
A STRONG COLD AIR OUTBREAK IS CURRENTLY OCCURRING ACROSS THE
GULF AND THE FLORIDA PENINSULA. AT 2100 UTC...A 1025 MB HIGH
LOCATED OVER SE LOUISIANA COVERS THE ENTIRE AREA. COLD AIR
STRATOCUMULUS CLOUDS DUE TO THE COLD ADVECTION OVER RELATIVELY
WARM WATERS ARE NOTED MAINLY OVER THE EASTERN HALF OF THE GULF
REGION. SURFACE WINDS ARE GENERALLY NORTHERLY AT 20 KT. WINDS
SHOULD RELAX BY TOMORROW AS SURFACE HIGH MOVES EWD TO NORTHERN
FLORIDA. TEMPERATURES WILL CONTINUE ON THE COLD SIDE TONIGHT
OVER FLORIDA UNDER CLEAR SKIES AND RELAXING WINDS. A WARMING
TREND WILL BEGIN ACROSS THE AREA TOMORROW. NO DEEP CONVECTION
IS OBSERVED IN THE REGION BECAUSE OF THE STABLE AND DRY AIR MASS
THAT IS PREVAILING. IN THE UPPER LEVELS...A SHARP SHORT-WAVE
TROUGH IS OBSERVED JUST OFF THE SOUTHEASTERN U.S...WHICH IS
SUPPORTING A COLD FRONT OVER THE W ATLC/CARIBBEAN SEA AND THE
COLD AIR ADVECTION. W TO NW UPPER LEVEL WINDS DOMINATE THE
ENTIRE GULF OF MEXICO.

CARIBBEAN SEA...
THE AFOREMENTIONED COLD FRONT ENTERS THE CARIBBEAN SEA THROUGH
THE WINDWARD PASSAGE THEN CONTINUES SW TO NEAR LIMON COSTA RICA.
LOW LEVEL CONVERGENCE NEAR THE TAIL END OF THE FRONT IS
SUPPORTING A PATCH OF MOISTURE WITH EMBEDDED LIGHT SHOWERS OVER
WESTERN PANAMA AND COSTA RICA. FRAGMENTS OF LOW/MID CLOUDS ARE
NOTED OVER CUBA AND THE NW CARIBBEAN. NORTHERLY SURFACE WINDS OF
UP TO 25 KT ARE OCCURRING WEST OF THE FRONTAL BOUNDARY WITH
SIGNIFICANT COOL AND DRY AIR ADVECTION. A COLD NIGHT IS IN STORE
FOR WEST-CENTRAL CUBA PARTICULARLY ACROSS THE INTERIOR SECTIONS
OF THE PROVINCES OF HAVANA AND MATANZAS AS A TONGUE OF COLD AIR
PUSHES SWD ACROSS THE STRAITS OF FLORIDA. TEMPERATURES BELOW 10
DEGREES CELSIUS OR 50 DEGREES FAHRENHEIT ARE POSSIBLE IN SOME
LOCALES. THE FRONT WILL SHIFT FURTHER SE OVER HISPANIOLA TONIGHT
BEFORE DISSIPATING ON THU. EAST OF THE FRONT...SURFACE WINDS ARE
GENERALLY EASTERLY 15 KT OR LESS AND ARE EXPECTED TO REMAIN THIS
WAY THROUGH THURSDAY. AN ELONGATED AREA OF MOISTURE MOVING
AROUND THE PERIPHERY OF THE ATLANTIC RIDGE IS PRODUCING
SCATTERED TO NUMEROUS PASSING SHOWERS ACROSS EASTERN PUERTO RICO
AND THE VIRGIN ISLANDS. THESE WEATHER CONDITIONS ARE EXPECTED TO
CONTINUE TONIGHT THROUGH TOMORROW MORNING. IN THE UPPER
LEVELS...THE BASE OF THE ABOVE MENTIONED VIGOROUS SHORT-WAVE
TROUGH REACHES THE NW CARIBBEAN. SOUTHWESTERLIES OF UP TO 80 KT
ON THE SOUTHEAST SIDE OF THIS TROUGH DOMINATES MOST OF THE WEST
AND CENTRAL CARIBBEAN. A WEAK HIGH IS CENTERED JUST WEST OF ISLA
DE MARGARITA VENEZUELA. SUBSIDENCE AND THE ASSOCIATED DRY AIR
COVERS MOST OF THE BASIN AND NORTHERN VENEZUELA.

ATLANTIC OCEAN...
A COLD FRONT EXTENDS FROM BERMUDA TO THE TURKS AND CAICOS
ISLANDS ENTERING THE CARIBBEAN SEA THROUGH THE WINDWARD PASSAGE.
SCATTERED SHOWERS ARE WITHIN 60 NM EITHER SIDE OF THE FRONTAL
BOUNDARY. NW WINDS OF 20 TO 25 KT ARE BLOWING BEHIND THE FRONT
WHERE BROKEN COLD AIR STRATOCUMULUS CLOUDS ARE ALSO OBSERVED. A
LARGE SURFACE 1030 MB HIGH NEAR 30N36W DOMINATES THE REMAINDER
OF THE FORECAST AREA. ALOFT...UPPER LEVEL RIDGING PREVAILS ALONG
30N WITH GENERAL SUBSIDENCE ALONG AND SOUTH OF THE RIDGE. AN
UPPER LOW IS LOCATED NEAR 14N50W GENERATING SOME SHOWER ACTIVITY
ON ITS NORTHEASTERN SEMICIRCLE. NUMEROUS CIRRUS CLOUDS ARE ALSO
OBSERVED EQUATORWARD OF 15N BEING ADVECTED FROM THE ITCZ
CONVECTION.

$$
GR


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