000
AXNT20 KNHC 212347
TWDAT 

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
705 PM EST SUN DEC 21 2008

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...
ITCZ IS CENTERED ALONG 6N8W 3N18W 7N33W 7N39W 5N53W. A SURFACE 
TROUGH IS EMBEDDED WITHIN THE ITCZ ALONG 35W/36W S OF 14N. 
CLUSTERS OF WIDELY SCATTERED MODERATE CONVECTION ARE FROM THE 
EQUATOR TO 9N BETWEEN 17W-34W. ELSEWHERE...SCATTERED MODERATE/ 
ISOLATED STRONG CONVECTION IS LOCATED WITHIN 90 NM OF THE SOUTH 
AMERICAN COAST BETWEEN 46W-60W.
  
...DISCUSSION...

GULF OF MEXICO...
A COLD FRONT EXTENDS FROM THE FAR W ATLC ACROSS NRN FLORIDA 
ENTERING THE GULF OF MEXICO THROUGH THE FLORIDA BIG BEND REGION 
CONTINUING SW TO 27N90W AND INLAND OVER NE MEXICO NEAR 25N97W. 
SCATTERED SHOWERS ARE WITHIN 60 NM OF THE FRONT. IN THE WAKE OF 
THE FRONT...COOLER AND DRIER CONDITIONS ARE OBSERVED WITH 
OVERCAST STRATOCUMULUS CLOUDS COVERING THE NRN GULF WATERS THIS 
EVENING. ALOFT...BROAD UPPER LEVEL TROUGHING IS SUPPORTING THE 
COLD FRONT DRAPED ACROSS THE GULF WITH A WEAK UPPER LOW OVER THE 
ISTHMUS OF TEHUANTEPEC NEAR 17N95W. SOUTH OF THE FRONTAL 
BOUNDARY SUBSIDENCE IN DRY AIR RESIDES OVER SRN FLORIDA AND THE 
SRN GULF.

CARIBBEAN SEA...
THE CARIBBEAN SEA IS UNDER THE INFLUENCE OF A BROAD UPPER RIDGE 
WHICH IS PRODUCING STRONG SUBSIDENCE IN DRY AIR ACROSS THE 
ENTIRE BASIN. THIS UPPER-LEVEL RIDGE ALSO ENVELOPS CENTRAL 
AMERICA AND THE NRN PORTION OF SOUTH AMERICA. AS A RESULT... 
AREAS OF LOW LEVEL CLOUDS WITH EMBEDDED LIGHT SHOWERS ARE NOTED 
ACROSS THE REGION USHERED IN ON E-NE WINDS. MOST NOTABLY 
ISOLATED SHOWERS ARE WITHIN 120 NM OF A LINE FROM 18N75W TO 
CENTRAL COSTA RICA NEAR 10N84W. SIMILAR CLOUDINESS WITH POSSIBLE 
ISOLATED SHOWERS ARE OBSERVED ACROSS HONDURAS AND BELIZE. 
 
ATLANTIC OCEAN...
A COLD FRONT EXTENDS ALONG THE ERN U.S. SEABOARD AND ENTERS THE 
DISCUSSION AREA NEAR 32N79W THROUGH JACKSONVILLE FLORIDA AND 
INTO THE GULF OF MEXICO. SCATTERED SHOWERS ARE WITHIN 60 NM OF 
THE FRONTAL BOUNDARY. TO THE SE ACROSS THE W ATLC...A WEAKENING 
1019 MB SURFACE HIGH IS CENTERED NEAR 27N61W AND CONTROLS THE 
ATLC BETWEEN 50W-77W. A LARGE AND BROAD UPPER LEVEL RIDGE IS 
ALOFT EXTENDING FROM THE CENTRAL CARIBBEAN WITH AXIS THROUGH 
PUERTO RICO TO BEYOND 32N58W AND ENCOMPASSES THE ATLC N OF 18N 
BETWEEN 50W-80W. A SURFACE TROUGH IS ACROSS THE CENTRAL ATLC 
ANALYZED FROM 27N44W TO 18N45W. THIS TROUGH IS SUPPORTED BY AN 
UPPER-LEVEL TROUGH ACROSS THE CENTRAL ATLC WITH AXIS ENTERING 
THE FORECAST AREA NEAR 32N32W SW TO 20N40W AND WSW TO NEAR 
15N55W. UPPER DIFFLUENCE E OF THIS UPPER TROUGH ALONG WITH AN 
UPPER RIDGE ANCHORED ON A HIGH SE OF THE CAPE VERDE ISLANDS NEAR 
7N7W IS HELPING TO INDUCE CONVECTION ALONG AND NEAR THE ITCZ 
AXIS. SURFACE HIGH PRESSURE CENTERED WELL N OF AREA COVERS THE 
NE ATLC AND NW AFRICA. NE TO E WINDS ARE EXPECTED TO INCREASE 
ACROSS THE TROPICAL ATLC LATE MONDAY TO AT LEAST MIDWEEK AS 
STRONG HIGH PRESSURE BUILDS N OF THE AREA. 

$$
HUFFMAN