000
AXNT20 KNHC 211143
TWDAT 

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL  
705 AM EST MON DEC 21 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 LIBERIA NEAR 6N10W TO 7N25W 3N40..INTO EXTREME 
NORTHEASTERN BRAZIL TO 1N52W. SHOWERS AND POSSIBLE THUNDERSTORMS
ARE FROM 3N TO 4N BETWEEN 47W AND 48W. POSSIBLE SHOWERS ARE 
ELSEWHERE TO THE SOUTH OF 7N.

...DISCUSSION...

THE GULF OF MEXICO...
UPPER LEVEL SOUTHWESTERLY WIND FLOW ORIGINATES IN THE EASTERN 
PACIFIC OCEAN...BETWEEN 80W AND 22N97W 16N93W 13N92W. THIS FLOW
IS PUSHING MOISTURE FROM THAT AREA ACROSS GUATEMALA AND MEXICO
INTO THE SOUTHWESTERN CORNER OF THE GULF OF MEXICO NORTHWARD
AND NORTHEASTWARD. THIS FLOW CROSSES FLORIDA BOUND FOR THE 
ATLANTIC OCEAN...AS PART OF LARGER SCALE UPPER LEVEL 
ANTICYCLONIC FLOW. UPPER LEVEL MOISTURE COVERS THE ENTIRE GULF 
OF MEXICO...EXCEPT FOR THE AREA FROM SOUTHEASTERN MEXICO
TO COASTAL MEXICO NEAR 20N.

THE CARIBBEAN SEA...
UPPER LEVEL ANTICYCLONIC FLOW ORIGINATES IN THE EASTERN PACIFIC 
OCEAN...BETWEEN 80W AND 20N98W 12N96W 8N96W. 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 HAITI TO THE NORTHEASTERN COAST OF COLOMBIA.
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 30N50W. A STATIONARY FRONT PASSES THROUGH THE 
WINDWARD PASSAGE TO JAMAICA...TO 17N80W AND CURVING TO THE 
NORTHERN BORDER OF COSTA RICA AND PANAMA. A SURFACE TROUGH
IS WITHIN 120 NM TO 240 NM TO THE SOUTHEAST OF THE FRONT FROM
10N TO 20N. LOW CLOUDS AND POSSIBLE PRECIPITATION ARE TO THE
WEST OF THE SURFACE TROUGH.
  
THE ATLANTIC OCEAN...
ALL THE MIDDLE LEVEL TO UPPER LEVEL CYCLONIC FLOW THAT SUPPORTS 
THE CURRENT ATLANTIC OCEAN FRONTAL BOUNDARIES 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 BEYOND 30N50W...TO THE AREA TO THE 
WEST OF THE EASTERN ATLANTIC OCEAN 32N26W 18N27W TROUGH. THE 
ORIGINAL COLD FRONT THAT PASSED THROUGH THE GULF OF MEXICO TWO 
DAYS AGO NOW PASSES THROUGH 32N50W TO 30N53W. A STATIONARY FRONT 
CONTINUES FROM 30N53W TO 25N60W...THROUGH THE WINDWARD PASSAGE
INTO THE WESTERN CARIBBEAN SEA. TO JAMAICA...TO 17N80W AND 
CURVING TO THE NORTHERN BORDER OF COSTA RICA AND PANAMA.
A SURFACE TROUGH IS WITHIN 120 NM TO 240 NM TO THE SOUTHEAST OF 
THE FRONT FROM 10N TO 20N. A SURGE OF COMPARATIVELY COLDER AIR 
IS ABOUT 400 NM TO THE NORTHWEST OF THE ORIGINAL COLD FRONT TO 
THE NORTH OF 28N. LITTLE TO NO PRECIPITATION IS DETECTED WITH 
THE FRONTS AT THIS TIME. AN EASTERN ATLANTIC OCEAN DEEP LAYER 
TROUGH PASSES THROUGH 32N26W TO 24N25W TO 18N27W. THIS TROUGH 
SUPPORTS A COLD FRONT THAT PASSES THROUGH 32N13W...ACROSS THE 
CANARY ISLANDS TO 24N20W TO 19N36W. LITTLE TO NO PRECIPITATION 
ACCOMPANIES THIS FRONT AT THIS TIME. SURFACE HIGH PRESSURE IS IN 
BETWEEN THE ORIGINAL COLD FRONT AND THE EASTERN ATLANTIC COLD 
FRONT...AROUND A 1017 MB HIGH PRESSURE CENTER THAT IS NEAR 
19N47W.

FOR ADDITIONAL INFORMATION PLEASE VISIT 
HTTP://WWW.HURRICANES.GOV/MARINE.

$$
MT