[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 041744
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
105 PM EST TUE DEC 04 2007

TROPICAL WEATHER DISCUSSION FOR NORTH AMERICA...CENTRAL
AMERICA...THE GULF OF MEXICO...THE CARIBBEAN SEA...NORTHERN
SECTIONS OF SOUTH AMERICA...AND THE 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 1200 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
1715 UTC

...THE ITCZ...
ITCZ IS CENTERED ALONG 5N9W 4N20W 4N35W 3N45W AND INTO SOUTH
AMERICA NEAR 1S51W. CLUSTERS OF MODERATE TO STRONG CONVECTION
ARE ALONG THE SW COAST OF AFRICA BETWEEN THE PRIME MERIDIAN AND
10W. SCATTERED MODERATE/ISOLATED STRONG CONVECTION IS WITHIN 60
NM EITHER SIDE OF THE AXIS BETWEEN 22W-31W. SIMILAR CONVECTION
IS FOUND N OF AXIS FROM 6N-10N BETWEEN 35W-38W.

DISCUSSION...

THE GULF OF MEXICO...
AS OF 1500 UTC...A COLD FRONT ENTERS THE AREA THROUGH THE
STRAITS OF FLORIDA...JUST SOUTH OF THE FLORIDA KEYS TO VERACRUZ
MEXICO ALONG 23N90W 18N96W. A THIN BAND OF SCATTERED SHOWERS AND
ISOLATED TSTMS IS WITHIN 60 NM OF THE FRONT. THIS FEATURE IS
EXPECTED TO STALL OVER THE FLORIDA STRAITS TONIGHT AND GRADUALLY
DISSIPATE THROUGH WED. A QUIKSCAT PASS FROM AROUND 1200 UTC
SHOWED MODERATE TO STRONG WINDS OF 20-25 KT BEHIND THE FRONT
OVER THE SW PORTION OF THE GULF. THE REMAINDER OF THE AREA IS
EXPERIENCING LIGHT TO MODERATE WINDS AND FAIR WEATHER DUE TO
BUILDING HIGH PRESSURE BEHIND THE FRONT. A 1024 MB SFC HIGH IS
ANALYZED OVER THE DEEP SOUTH. ALOFT...AN UPPER-LEVEL TROUGH
EXTENDS MAINLY EAST TO WEST ACROSS THE CENTRAL GULF SUPPORTING
THE COLD FRONT. WV IMAGERY REVEALS STRONG SUBSIDENCE AND VERY
DRY AIR BEHIND THE TROUGH AXIS.

THE CARIBBEAN SEA...
WEAK SURFACE PRES GRADIENT DOMINATES THE AREA DUE TO THE
PRESENCE OF A COLD FRONT ACROSS THE STRAITS OF FLORIDA/GULF OF
MEXICO AND A COUPLE OF TROUGHS OVER THE TROPICAL N ATLANTIC.
THIS PATTERN IS PROVIDING LIGHT N TO NE WINDS ACROSS THE
CARIBBEAN. AN AREA OF SCATTERED SHOWERS IS OVER THE SW CARIBBEAN
ENHANCED BY UPPER DIFFLUENCE. ALOFT...WLY FLOW DOMINATES THE
BASIN N OF 16N...INCLUDING THE GREATER ANTILLES WITH A RIDGE
COVERING NORTHERN SOUTH AMERICA... CENTRAL AMERICA AND THE
REMAINDER OF THE CARIBBEAN SEA. TYPICAL PATCHES OF LOW LEVEL
MOISTURE ARE SEEN PARTICULARLY AROUND THE CAYMAN ISLANDS AND
JUST SOUTH OF PUERTO RICO.

THE ATLANTIC OCEAN...
A COLD FRONT ENTERS THE REGION NEAR 31N67W THEN CONTINUES SW
ACROSS THE W ATLC CROSSING THE BAHAMAS JUST NORTH OF NASSAU INTO
THE STRAITS OF FLORIDA AND THE GULF OF MEXICO. A BAND OF SHOWERS
AND ISOLATED THUNDERSTORMS IS WITHIN 60 NM OF THE FRONT. AN
EARLIER QUIKSCAT PASS SHOWED SW WINDS OF 20 TO 25 KT AHEAD OF
THE FRONT N OF 26N W OF 60W. ANOTHER COLD FRONT EXTENDS FROM
31N33W TO 23N48W. CLOSE TO THE TAIL END OF THIS FRONTAL
SYSTEM...A WEAK 1012 MB SFC LOW PERSISTS. IT IS CENTERED NEAR
22.5N51W. A TROUGH RUNS FROM THE LOW TO THE LEEWARD
ISLANDS...WHERE IS PRODUCING SOME CLOUDINESS AND LIGHT SHOWERS.
VIS SATELLITE IMAGERY SHOWS VERY WELL THE CYCLONIC CIRCULATION
ASSOCIATED WITH THIS LOW THAT IS GENERATING ISOLATED TO
SCATTERED SHOWERS. A 1020 MB HIGH IS CENTERED NEAR 31N43N
PRODUCING FAIR WEATHER STRATOCUMULUS OVER THE CENTRAL ATLC. THE
SURFACE HIGH IS EXPECTED TO MOVE RAPIDLY TO THE NE OVER THE NEXT
24 HOURS. IN THE TROPICAL ATLC...A WEAK SURFACE TROUGH IS ALONG
58W FROM 10N-17N. A RIDGE DOMINATES THE E ATLC ANCHORED ON A
HIGH LOCATED NE OF THE MADEIRA ISLANDS. THIS HIGH WILL MOVE SW
APPROACHING TO THE FORECAST AREA.  ALOFT... MOISTURE/HIGH CLOUDS
ARE BEING TRANSPORTED EASTWARD AROUND A BROAD E-W UPPER RIDGE
COVERING THE TROPICAL ATLC S OF 21N. A TROUGH/RIDGE/TROUGH
PATTERN IS OVER THE REMAINDER OF THE REGION.

$$
GR







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