[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 132352
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
705 PM EST TUE JAN 13 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
1715 UTC.

...THE ITCZ...

THE ITCZ IS CENTERED ALONG 7N12W 4N20W 2N30W 3N40W...CROSSING
THE EQUATOR ALONG 45W...INTO NORTHEASTERN BRAZIL NEAR 1S48W.
SCATTERED MODERATE/ISOLATED STRONG CONVECTION IS WITHIN 90 NM
SOUTH OF AXIS BETWEEN 22W-27W...AND WITHIN 100 NM N OF AXIS
BETWEEN 27W-33W. SCATTERED MODERATE CONVECTION IS NEAR 5N15W.

...DISCUSSION...

THE GULF OF MEXICO...
AS OF 2100 UTC...A COLD FRONT EXTENDS FROM CENTRAL FLORIDA TO
THE YUCATAN PENINSULA ALONG 28N81W 23N86W 19N90W. A WELL DEFINED
BAND OF MULTILAYERED CLOUDS WITH EMBEDDED SHOWERS AND ISOLATED
TSTMS...SOME WITH HEAVIER RAIN AND GUSTY WINDS...IS ASSOCIATED
WITH THE FRONT. MOSAIC DOPPLER RADAR FROM THE SE U.S. REVEALS
THAT THE STRONGEST CONVECTIVE ACTIVITY IS CURRENTLY OVER CENTRAL
FLORIDA. SCATTERED SHOWERS AND ISOLATED TSTMS ARE ALSO AFFECTING
THE FLORIDA KEYS. THIS FRONT WAS REINFORCED THIS AFTERNOON BY A
DRY COLD FRONT SWEEPING QUICKLY INTO THE CENTRAL AND SE GULF.
THESE MERGED FRONTS WILL CONTINUE TO MOVE QUICKLY INTO THE
EXTREME SE GULF AND THE NW CARIBBEAN THIS EVENING...FOLLOWED BY
STRONG NORTHERLY FLOW...WITH GALE FORCE WINDS BRIEFLY TO OCCUR
ACROSS THE FAR SW BAY OF CAMPECHE. ADDITIONALLY...STRONG N TO NE
SURFACE WINDS ARE BLOWING THROUGH THE ISTHMUS OF TEHUANTEPEC
RESULTING IN GALE FORCE WINDS IN THE E PACIFIC REGION.
TEMPERATURES ARE IN THE 40'S AND 50'S OVER THE N GULF STATES
UNDER CLEAR SKIES WHILE TEMPERATURES S OF THE COLD FRONT REMAIN
IN THE 70'S. IN THE UPPER LEVELS...A BROAD MID/UPPER LEVEL
TROUGH WHICH SUPPORTS THE AFOREMENTIONED COLD FRONT EXTENDS FROM
THE GREAT LAKES REGION TO LOUISIANA CLIPPING THE NW CORNER OF
THE GULF INTO NORTHERN MEXICO. SOUTHWESTERLY WINDS AHEAD OF THE
TROUGH ARE ADVECTING ABUNDANT MID TO UPPER LEVEL MOISTURE FROM
THE EPAC ACROSS SOUTH-CENTRAL MEXICO AND THE YUCATAN PENINSULA
INTO THE GULF OF MEXICO AND THE FLORIDA PENINSULA. MID/UPPER
LEVEL SUBSIDENCE AND ASSOCIATED DRY AIR IS OVER THE REMAINDER OF
THE GULF WATERS.

THE CARIBBEAN SEA...
A TIGHT SURFACE PRESSURE GRADIENT BETWEEN HIGH PRES N OF AREA
AND THE SEMI-PERMANENT SFC LOW OVER COLOMBIA/PANAMA IS STILL
PRODUCING MODERATE TO STRONG TRADEWINDS ACROSS THE BASIN. AS
USUAL...THE STRONGEST WINDS ARE NEAR THE COAST OF COLOMBIA WHERE
AN EARLIER QSCAT PASS SHOWED ELY WINDS OF 20 TO 30 KT. CLOUDS
ARE ON INCREASE ACROSS THE NW CARIBBEAN AHEAD OF THE COLD FRONT
CURRENTLY MOVING OVER THE SE GULF OF MEXICO. THIS FRONT IS
FORECAST TO ENTER THE NW CARIBBEAN EARLY WEDNESDAY. UPPER
DIFFLUENCE BETWEEN A RIDGE OVER THE CARIBBEAN...WITH AXIS FROM
WESTERN VENEZUELA TO HISPANIOLA AND THE ABOVE MENTIONED BROAD
MID/UPPER LEVEL TROUGH IS HELPING TO INDUCE SOME CLOUDINESS OVER
THE WESTERN CARIBBEAN AND CUBA. MODERATE TO STRONG UPPER-LEVEL
SUBSIDENCE AND IMPLIED DRY AIR MASS DOMINATES THE E CARIBBEAN
AND VENEZUELA COURTESY OF THIS RIDGE.

THE ATLANTIC OCEAN...
A COLD FRONT ENTERS THE FORECAST AREA NEAR 31N77W THEN CONTINUES
SW CROSSING CENTRAL FLORIDA AND THE SE GULF OF MEXICO INTO THE
YUCATAN PENINSULA. SCATTERED SHOWERS AND ISOLATED TSTMS ARE
ASSOCIATED WITH THE FRONTAL BOUNDARY. MAINLY HIGH CLOUDS ARE
NOTED OVER THE BAHAMAS. JUST AHEAD OF THE FRONT...SW TO S WINDS
OF 20 TO 30 KT PREVAIL WHILE NW WINDS OF 15 TO 20 KT ARE SEEN
BEHIND THE FRONT. THE REMAINDER OF THE FORECAST REGION REMAINS
UNDER THE INFLUENCE OF A SFC RIDGE ANCHORED BY A 1029 MB HIGH
SITUATED NEAR 34N23W. ANOTHER 1027 MB SFC HIGH IS NEAR 28N54W.
MOSTLY FAIR WEATHER IS NOTED N OF 20N BETWEEN 30W-65W. ALOFT...A
RIDGE/TROUGH/RIDGE PATTERN DOMINATES THE AREA. THE UPPER-LEVEL
TROUGH STRETCHES ACROSS THE CENTRAL ATLC INTO THE DEEP TROPICS
WITH THE BASE OF THIS TROUGH ALMOST REACHING THE COAST OF
NORTHERN SOUTH AMERICA. UPPER DIFFLUENCE BETWEEN THIS TROUGH AND
AN UPPER-LEVEL RIDGE OVER THE E ATLC IS HELPING TO INDUCE A
LARGE AREA OF CLOUDINESS WITH EMBEDDED SHOWERS WHICH IS
AFFECTING MUCH OF THE TROPICS PARTICULARLY BETWEEN THE CAPE
VERDE ISLANDS AND 45W. THE GFS MODEL SUGGESTS THAT THIS AREA OF
MOISTURE WILL MOVE EWD UNDER THE TRADE WIND FLOW AFFECTING THE
LESSER ANTILLES AND THEN THE US/UK VIRGIN ISLANDS AND PUERTO
RICO LATE THURSDAY INTO FRIDAY.

$$
GR






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