000
AXNT20 KNHC 201159
TWDAT 

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL  
705 AM EST SUN DEC 20 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 0600 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY
THROUGH 1115 UTC.

...THE ITCZ...

FROM COASTAL GUINEA NEAR 10N14W TO 8N20W 4N30W 2N40W 
2N46W...INTO EXTREME NORTHEASTERN BRAZIL TO THE EQUATOR
ALONG 52W. STRONG SHOWERS ARE FROM 2N TO 3N BETWEEN 34W AND 
35W...AND FROM 3N TO 4N BETWEEN 50W AND 51W. DISORGANIZED 
ISOLATED MODERATE SHOWERS ARE ELSEWHERE FROM 4N TO 6N BETWEEN 
12W AND 15W...AND TO THE SOUTH OF 5N BETWEEN 27W AND 52W 
INCLUDING IN NORTHEASTERN BRAZIL.

...DISCUSSION...

THE GULF OF MEXICO...
UPPER LEVEL SOUTHWESTERLY FLOW IS PUSHING MOISTURE FROM THE AREA 
OF 10N BETWEEN 97W AND 107W IN THE EASTERN PACIFIC OCEAN TOWARD 
THE NORTHEAST. THE UPPER LEVEL MOISTURE CROSSES MEXICO AND 
COVERS THE ENTIRE GULF OF MEXICO. AN UPPER LEVEL TROUGH IS 
FORMING ALONG 25N102W IN MEXICO TO 13N104W IN THE EASTERN 
PACIFIC OCEAN. WEAK SURFACE HIGH PRESSURE AND A WEAK PRESSURE 
GRADIENT COVER THE AREA. THE COLD FRONT HAS EXITED THE AREA 
COMPLETELY AND NOW SPANS THE ATLANTIC OCEAN...THE BAHAMAS... 
CUBA...AND JAMAICA. ANY UPPER LEVEL CYCLONIC FLOW COVERS THE 
U.S.A. GULF COAST STATES TO THE NORTH OF 30N TO THE EAST OF 90W.

THE CARIBBEAN SEA...
UPPER LEVEL ANTICYCLONIC FLOW ORIGINATES IN THE EASTERN PACIFIC 
OCEAN NEAR 5N BETWEEN NORTHERN COLOMBIA AND 90W. THIS FLOW 
CONTINUES INTO THE WESTERN CARIBBEAN SEA...CURVING ACROSS CUBA 
AND BEYOND. THE HIGH LEVEL MOISTURE WITH THIS FLOW COVERS THE 
AREA TO THE WEST OF A LINE FROM THE WINDWARD PASSAGE TO THE 
NORTHERN COAST OF COLOMBIA NEAR 11N75W. DRY AIR IN SUBSIDENCE
COVERS THE REST OF THE CARIBBEAN SEA TO THE EAST OF THE HIGH 
LEVEL MOISTURE. THE ANTICYCLONIC FLOW THAT IS IN THE WESTERN 
CARIBBEAN SEA ULTIMATELY IS PART OF BROADER LARGE SCALE 
ANTICYCLONIC FLOW THAT EXTENDS INTO THE ATLANTIC OCEAN BEYOND 
20N60W. THE SURFACE PRESSURE GRADIENT IS WEAK.
  
THE ATLANTIC OCEAN TO THE EAST OF 65W...
ALL THE MIDDLE LEVEL TO UPPER LEVEL CYCLONIC FLOW THAT SUPPORTS
THE CURRENT WESTERN ATLANTIC OCEAN COLD FRONT IS WELL TO THE 
NORTH OF THE AREA. UPPER LEVEL ANTICYCLONIC FLOW THAT STARTS
IN THE WESTERN CARIBBEAN SEA MOVES ACROSS CUBA AND THE BAHAMAS
INTO THE CENTRAL ATLANTIC OCEAN AND BEYOND TO 30W. THE ORIGINAL
COLD FRONT THAT PASSED THROUGH THE GULF OF MEXICO DURING THE 
LAST DAY OR SO NOW PASSES THROUGH 31N64W TO 24N70W TO THE 
SOUTHERN BAHAMAS TO EXTREME EASTERN CUBA TO JAMAICA NEAR 18N77W.
THE SECONDARY SURGE OF COMPARATIVELY COLDER AIR WITH 
COMPARATIVELY LOWER DEWPOINT TEMPERATURES HAS CAUGHT UP TO THE
ORIGINAL COLD FRONT. SHOWERS ARE POSSIBLE IN THE CARIBBEAN SEA 
TO THE SOUTH OF JAMAICA BETWEEN 76W AND 83W...AND WITHIN 30 NM 
AND 60 NM ON EITHER SIDE OF 28N59W 25N66W 21N75W. AN EASTERN 
ATLANTIC OCEAN DEEP LAYER TROUGH PASSES THROUGH 32N22W TO 24N30W
TO 21N40W. A STATIONARY FRONT CONTINUES FROM 21N40W TO 21N50W.
A WARM FRONT CONTINUES FROM 27N57W BEYOND 32N55W. STRONG SHOWERS 
AND POSSIBLE THUNDERSTORMS ARE WITHIN 30 NM ON EITHER SIDE OF
23N28W 26N24W 28N20W.

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MT