[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 202343
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
705 PM EST THU DEC 20 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 1800 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
2315 UTC

...THE ITCZ...
ITCZ AXIS IS CENTERED ALONG 6N10W 4N25W 5N35W 4N45W AND INTO
SOUTH AMERICA NEAR 2N52W. CLUSTERS OF MODERATE TO ISOLATED
STRONG CONVECTION ARE WITHIN 180 NM EITHER SIDE WEST OF 27W.
SIMILAR CONVECTION IS NEAR 6N14W AND INLAND OVER LIBERIA.
A DIFFLUENT PATTERN ALOFT IS ENHANCING THIS CONVECTIVE ACTIVITY.

DISCUSSION...
GULF OF MEXICO...
A COLD FRONT HAS ENTERED THE NW CORNER OF THE GULF. AS OF 2100
UTC THE FRONTAL SYSTEM EXTENDS FROM CENTRAL LOUISIANA TO NE
MEXICO NEAR 25N98W. AN AREA OF SHOWERS AND TSTMS IS AHEAD OF THE
FRONT AFFECTING THE N-CENTRAL GULF WATERS...PARTICULARLY N OF
27N BETWEEN 87W AND 93W. THIS CONVECTIVE ACTIVITY IS ALSO
AFFECTING THE FLORIDA PANHANDLE AND PARTS OF ALABAMA AND
MISSISSIPPI. MODERATE TO STRONG S TO SW WINDS ARE BLOWING AHEAD
OF THE FRONT. AN EARLIER ASCAT PASS REVELED 20 TO 25 KT MAINLY
OVER THE MIDDLE GULF N OF 26N. THIS WINDS WILL GRADUALLY SPREAD
EWD OVER THE NE QUADRANT OF THE GULF LATE TONIGHT AS LOW PRES
FORMS OVER SE LOUISIANA AND QUICKLY SLIDES E TO ACROSS N FLORIDA
THROUGH FRI. WINDS WILL SHIFT TO THE NW IN THE WAKE OF THE
FRONT. A RIDGE OF HIGH PRESSURE CONTINUES TO DOMINATE THE
REMAINDER OF THE GULF. ALOFT...A SHORT-WAVE TROUGH MOVING EWD
ACROSS THE LOWER MISSISSIPPI VALLEY SUPPORTS THE COLD FRONT. A
SUBTROPICAL JET WITH CORE WINDS OF NEAR 110 KT IS CENTERED OVER
THE N GULF WATERS/N FLORIDA DRAWING UPPER-LEVEL MOISTURE ACROSS
THE GULF FROM THE E PACIFIC. NEAR ZONAL FLOW SOUTH OF THE JET
CONTINUES TO MAINTAIN DRY AND STABLE CONDITIONS. THE NEXT COLD
FRONT IS EXPECTED TO MOVE INTO THE NW GULF SAT AFTERNOON...
AND EXTEND FROM THE WRN FLORIDA TO E BAY OF CAMPECHE BY SUN
AFTERNOON. MODERATE TO STRONG NLY WINDS AND BUILDING SEAS CAN BE
EXPECTED BEHIND FRONT.

CARIBBEAN SEA...
WEATHER CONDITIONS ACROSS THE CARIBBEAN SEA ARE PRETTY QUIET
THIS EVENING UNDER THE INFLUENCE OF A MID/UPPER-LEVEL RIDGE
WHICH IS PRODUCING STRONG SUBSIDENCE AND IMPLIED DRY/STABLE
AIRMASS. THE SURFACE TROUGH THAT WAS AFFECTING THE NW CARIBBEAN
DURING THE PREVIOUS DAYS HAS WEAKENED. ONLY A FEW PATCHES OF LOW
LEVEL CLOUDS WITH ISOLATED SHOWERS REMAINS OVER THE AREA.
TYPICAL FRAGMENTS OF MOISTURE ARE BRINGING ISOLATED PASSING
SHOWERS TO THE NE CARIBBEAN... INCLUDING PUERTO RICO AND THE
SURROUNDING ISLANDS...AND TO THE ABC ISLANDS. ADDITIONAL POCKETS
OF MOISTURE ARE ALSO STREAMING ACROSS NICARAGUA AND COSTA RICA
UNDER A NELY WIND FLOW. LIGHT TO MODERATE TRADES WILL PREVAIL
OVER MUCH OF THE AREA THROUGH MONDAY.

ATLANTIC OCEAN...
A WEAK PRES GRADIENT CHARACTERIZED BY A COLD FRONT CLIPPING THE
REGION ALONG 31N AND A WEAK SFC TROUGH ALONG 66W/67W DOMINATES
THE W ATLC. A STATIONARY FRONT EXTENDS FROM 28N59W TO 31N40W
THEN CONTINUES NE AS A COLD FRONT CROSSING E OF THE AZORES. A
LOW IS EXPECTED TO DEVELOP ALONG THIS FRONTAL BOUNDARY NEAR
28N56W DURING THE NEXT 24 HOURS OR SO. SATELLITE IMAGERY SHOWS
ALREADY A LARGE AREA OF SHOWERS WITH ISOLATED TSTMS NEAR THE
TAIL END OF THE STATIONARY FRONT. FAIR WEATHER STRATOCUMULUS
CLOUDS ARE BEING TRANSPORTED AROUND A 1022 MB SFC HIGH CENTERED
NEAR 28N39W. A FRONTAL BOUNDARY ASSOCIATED WITH A DEEP-LAYERED
TROUGH OVER THE E ATLC TRAILS ACROSS THE AFRICAN COAST AND
EXTENDS TO 22N16W. A NARROW BAND OF MAINLY LOW CLOUDS IS
RELATED TO THE FRONT. IN THE TROPICAL ATLC...DIFFLUENCE
ASSOCIATED WITH AN UPPER-LEVEL HIGH LOCATED OVER NE BRAZIL
IS SUPPORTING CONVECTION ALONG THE ITCZ AND NEAR ZONAL FLOW
CONTINUES TO TRANSPORT UPPER-LEVEL MOISTURE EASTWARD ACROSS THE
REGION S OF 14N. A SFC TROUGH WAS ANALYZED ON THE 1800 UTC MAP
ALONG 59W SOUTH OF 14N. AN ASCAT PASS FROM THIS MORNING SHOWED
SOME WIND SHIFT ASSOCIATED WITH THIS TROUGH. THERE IS ALSO
SCATTERED MODERATE CONVECTION IS THIS AREA ENHANCED BY UPPER
DIFFLUENCE. THIS SHOWER ACTIVITY IS AFFECTING THE WINDWARD
ISLANDS AND NE VENEZUELA.

$$
GR






This weather bulletin was brought to you by:
www.nashvilleweather.net