AXNT20 KNHC 012345
TWDAT 

TROPICAL WEATHER DISCUSSION  
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
705 PM EST MON DEC 01 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...
THE ITCZ AXIS IS ANALYZED ALONG 8N13W 6N25W 4N40W...AND INTO 
NORTHERN BRAZIL NEAR 2S52W. SCATTERED MODERATE CONVECTION IS 
FROM 2N-6N BETWEEN 30W-40W. SIMILAR CONVECTION IS NEAR 6N20W. 
SCATTERED MODERATE/ISOLATED STRONG CONVECTION IS OVER LIBERIA 
AND OVER THE GUYANAS.

...DISCUSSION...

GULF OF MEXICO...
A VIGOROUS DEEP LAYERED TROUGH EXTENDS FROM THE GREAT LAKES 
REGION ACROSS LOUISIANA INTO THE NW CORNER OF THE GULF PRODUCING 
VERY STRONG SWLY WINDS OVER THE EASTERN HALF OF THE AREA AND THE 
SE CONUS. THIS TROUGH SUPPORTS A PAIR OF COLD FRONTS. ONE IS 
OVER THE W ATLC AND CENTRAL CUBA WHILE A REINFORCING COLD FRONT 
RUNS FROM THE FLORIDA PANHANDLE ALONG 27N90W INTO THE DEEP 
SOUTH TEXAS. GALE FORCE WINDS ARE BLOWING BEHIND THE SECOND COLD 
FRONT OVER THE NE GULF WATERS. AS COOLER AIR BEHIND THE FRONT 
IS ADVECTED OVER RELATIVELY WARMER GULF WATERS...LOW LEVEL 
INSTABILITY IS GENERATING SCATTERED STRATOCUMULUS CLOUDS IN THE 
WAKE OF THE FRONT MAINLY N OF 24N. IN ADDITION...LOW LEVEL 
CLOUDS WITH EMBEDDED LIGHT RAIN ARE BANKING UP AGAINST THE 
SIERRA MADRE MOUNTAINS PARTICULARLY SOUTH OF TAMPICO. SIMILAR 
CLOUDS ARE ALSO NOTED OVER THE BAY OF CAMPECHE. ONCE AGAIN...A 
GAP WIND EVENT IS EXPECTED ACROSS THE ISTHMUS OF TEHUANTEPEC IN 
ABOUT 24 HOURS AS THIS NEW COLD SURGE MOVES SOUTHWARD ALONG THE 
EASTERN SLOPES OF THE SIERRA MADRE MOUNTAINS. SOUTHERLY RETURN 
FLOW WILL INCREASE OVER THE NW WATERS TUE NIGHT IN ADVANCE OF 
THE NEXT COLD FRONT MOVING OFFSHORE TEXAS WED NIGHT.

CARIBBEAN SEA...
MAIN FEATURE ACROSS THE BASIN IS THE STRONG COLD FRONT CURRENTLY 
AFFECTING CENTRAL CUBA WITH SHOWERS AND ISOLATED TSTMS. AS OF 
2100 UTC...THE FRONT EXTENDS OVER THE WESTERN ATLC AND THE NW 
BAHAMAS THEN CONTINUES SW ACROSS CENTRAL CUBA CROSSING OVER THE 
CAYMAN ISLANDS TO A 1011 MB LOW LOCATED NEAR 15N82W. THIS LOW IS 
FORECAST TO DISSIPATE IN ABOUT 24 HOURS. THE FRONT IS GENERATING 
SCATTERED MODERATE CONVECTION OVER THE CARIBBEAN SEA SOUTH OF 
CUBA. THIS ACTIVITY IS BEING ENHANCED BY UPPER LEVEL DIFFLUENCE 
BETWEEN THE UPPER-LEVEL TROUGH OVER THE GULF OF MEXICO AND A 
RIDGE ANCHORED ON A HIGH OVER HISPANIOLA. THE SURFACE LOW 
LOCATED NEAR CABO GRACIAS A DIOS NICARAGUA IS ALSO PRODUCING A 
PATCH OF MODERATE CONVECTION OVER NE NICARAGUA. THE FRONT IS 
FORECAST TO MOVE EWD AND EXTEND FROM EASTERN CUBA TO THE SW 
CARIBBEAN NEAR 12N83W ON TUE...WHERE IT WILL STALL AND WEAKEN 
THROUGH THU. OVER THE EASTERN CARIBBEAN...MOSTLY FAIR WEATHER 
PREVAILS DUE TO STRONG SUBSIDENCE AND IMPLIED DRY AIR MASS. ONLY 
TYPICAL PATCHES OF LOW-LEVEL MOISTURE WITH EMBEDDED LIGHT 
SHOWERS ARE SEEN ACROSS THE REGION...MORE CONCENTRATED OVER THE 
LESSER ANTILLES MAINLY SOUTH OF DOMINICA. A DIFFLUENT PATTERN 
ALOFT IS ALSO HELPING TO INDUCE THIS SHOWER ACTIVITY. FRESH 
EASTERLY TRADES ARE BLOWING ACROSS THE EASTERN CARIBBEAN. WINDS 
ARE EXPECTED TO INCREASE BEHIND THE COLD FRONT OVER THE NW 
CARIBBEAN TONIGHT REACHING 20 TO 30 KT. 

ATLANTIC OCEAN...
A VIGOROUS DEEP LAYERED TROUGH IS OVER THE ERN CONUS WITH STRONG 
UPPER LEVEL DIVERGENCE E OF THE TROUGH ACROSS THE W ATLC WATERS. 
THIS THOUGH SUPPORTS A COLD FRONT THAT ENTERS THE DISCUSSION 
AREA NEAR 31N73W AND EXTENDS SW ACROSS CENTRAL CUBA INTO THE 
CARIBBEAN SEA. SCATTERED SHOWERS AND TSTMS ARE WITHIN 70 NM 
EITHER SIDE OF THE FRONT. TO THE E...A 1030 MB SURFACE HIGH 
LOCATED N OF AREA EXTENDS A RIDGE OVER THE CENTRAL AND W ATLC 
ROUGHLY BETWEEN 40W-70W. ACROSS THE E ATLC...A SURFACE LOW IS 
CENTERED NEAR 27N31W WITH A SURFACE TROUGH EXTENDING SW FROM THE 
LOW CENTER ALONG 17N37W TO 12N46W. THIS SURFACE FEATURE IS 
SUPPORTED BY SHARP UPPER LEVEL TROUGHING THAT EXTENDS FROM AN 
UPPER LOW NORTH OF THE REGION NEAR 33N37W INTO THE DEEP TROPICS 
TO NEAR 12N58W. THE REMAINDER OF THE ATLANTIC OCEAN IS UNDER THE 
INFLUENCE OF A BROAD RIDGE CENTERED SE OF THE CAPE VERDE ISLANDS 
NEAR 12N18W. UPPER DIFFLUENCE BETWEEN THESE TWO UPPER-LEVEL 
FEATURES IS HELPING TO INDUCE SCATTERED SHOWERS ALONG AND AHEAD 
OF THE SFC ABOVE MENTIONED SFC TROUGH. 

$$
GR