000
AXNT20 KNHC 200602
TWDAT 

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL  
105 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 0000 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY
THROUGH 0515 UTC.

...THE ITCZ...

FROM COASTAL GAMBIA NEAR 10N14W TO 9N20W 4N30W 2N38W 2N46W...
INTO EXTREME NORTHEASTERN BRAZIL NEAR 1N51W. STRONG SHOWERS ARE 
IN A LINE FROM 4N TO 5N BETWEEN 44W AND 46W. DISORGANIZED 
ISOLATED MODERATE SHOWERS ARE ELSEWHERE FROM 2N TO 10N BETWEEN 
25W AND 30W...TO THE SOUTH OF 5N BETWEEN 30W 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. IT APPEARS THAT A CYCLONIC 
CENTER MAY BE TRYING TO FORM NEAR 25N103W IN MEXICO. WEAK SURFACE
HIGH PRESSURE AND A WEAK GRADIENT COVER THE AREA. THE COLD FRONT
HAS EXITED THE AREA COMPLETELY AND NOW SPANS THE ATLANTIC 
OCEAN...THE BAHAMAS...AND CUBA. ANY UPPER LEVEL CYCLONIC FLOW
COVERS THE U.S.A. GULF COAST STATES TO THE NORTH OF 30N.

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 PASSES THROUGH THE GULF OF MEXICO DURING THE 
LAST DAY OR SO NOW PASSES THROUGH 31N67W TO 26N70W TO THE 
SOUTHERN BAHAMAS NEAR 21N75W...AND THEN AS A DISSIPATING 
STATIONARY FRONT FROM 21N75W TO EASTERN CUBA...WESTERN JAMAICA
AND 16N80W. A SECONDARY SURGE OF COMPARATIVELY COLDER AIR WITH
COMPARATIVELY LOWER DEWPOINT TEMPERATURES IS TO THE NORTH OF 22N 
WITHIN 240 NM TO 360 NM TO THE WEST OF THE ORIGINAL COLD FRONT.
ISOLATED MODERATE SHOWERS ARE WITHIN 30 NM ON EITHER SIDE OF
20N75W 23N71W 25N67W 27N64W. AN EASTERN ATLANTIC OCEAN DEEP
LAYER TROUGH PASSES THROUGH 32N22W TO 25N28W. THIS TROUGH 
SUPPORTS THE COLD FRONT THAT PASSES THROUGH 32N26W TO 25N30W
TO 21N38W. A STATIONARY FRONT CONTINUES FROM 21N38W TO 22N47W
TO 25N56W. A WARM FRONT CONTINUES FROM 25N56W TO 27N58W BEYOND
32N59W. STRONG SHOWERS AND POSSIBLE THUNDERSTORMS ARE FROM
29N TO 31N BETWEEN 20W AND 22W. THE SHOWERS ARE ISOLATED FROM
27N TO 28N BETWEEN 24W AND 25W...AND FROM 23N TO 24N BETWEEN
29W AND 30W.

$$
MT