000
AXNT20 KNHC 220003
TWDAT 

TROPICAL WEATHER DISCUSSION 
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
805 PM EDT TUE APR 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 1800 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY
THROUGH 2315 UTC.

...THE ITCZ...
FROM THE LIBERIA COAST NEAR 6N11W TO 3N20W TO THE EQUATOR
ALONG 27W TO 2S40W INTO NORTHEASTERN BRAZIL NEAR 2S44W.
DISORGANIZED ISOLATED MODERATE SHOWERS ARE TO THE SOUTH
OF 6N BETWEEN 10W AND 30W.

...DISCUSSION...

THE GULF OF MEXICO...
BROAD AND LARGE-SCALE MIDDLE LEVEL TO UPPER LEVEL CYCLONIC FLOW 
COVERS THE AREA...THANKS TO A TROUGH SHOWN CLEARLY ON WATER 
VAPOR IMAGERY. THIS TROUGH SUPPORTS THE FIRST COLD FRONT THAT
IS CLEARING THE FINAL PARTS OF SOUTH FLORIDA AND PASSING THROUGH 
THE STRAITS OF FLORIDA. A SECONDARY COLD FRONT IS MOVING INTO
THE FLORIDA PANHANDLE AND ALABAMA...MISSISSIPPI...AND LOUISIANA.
MIDDLE LEVEL TO UPPER LEVEL DRY AIR IN SUBSIDENCE IS 
EVERYWHERE...EXCEPT FOR THE MULTILAYERED MOISTURE THAT COVERS 
THE AREA FROM THE NORTHWESTERN CARIBBEAN SEA ACROSS CUBA INTO
THE STRAITS OF FLORIDA...ACROSS THE BAHAMAS TO THE NORTH OF 22N 
TO THE WEST OF 74W INTO THE ATLANTIC OCEAN. SURFACE ANTICYCLONIC 
FLOW COVERS THE GULF OF MEXICO TO THE WEST OF THE FIRST COLD 
FRONT...AROUND A 1022 MB HIGH PRESSURE CENTER NEAR 24N95W.

THE CARIBBEAN SEA... 
BROAD MIDDLE TO UPPER LEVEL SOUTHWESTERLY WIND FLOW COVERS THE 
AREA FROM NICARAGUA TO HISPANIOLA...AT THE EDGE OF THE CYCLONIC 
FLOW AROUND THE GULF OF MEXICO TROUGH ON WATER VAPOR IMAGERY.
UPPER LEVEL SOUTHWESTERLY WIND FLOW MOVES FROM NORTHERN COLOMBIA
ACROSS THE REST OF THE CARIBBEAN SEA...AND EXITS THE AREA AS IT 
PASSES ON TOP OF THE EASTERN CARIBBEAN SEA ISLANDS...FROM THE 
GUADELOUPE PASSAGE SOUTHWARD. 

THE ATLANTIC OCEAN...
THE EASTERN EDGE OF THE BROAD LARGE-SCALE TROUGH FROM THE GULF
OF MEXICO REACHES INTO THE WESTERN ATLANTIC OCEAN. CYCLONIC FLOW
FROM THE TROUGH IS TO THE WEST OF 75W. ISOLATED MODERATE SHOWERS
ARE TO THE NORTH OF 26N BETWEEN 71W AND 74W. LARGE-SCALE UPPER 
LEVEL ANTICYCLONIC WIND FLOW COVERS THE AREA BETWEEN 50W AND 
71W. A TROUGH EXTENDS FROM A 1022 MB LOW PRESSURE CENTER NEAR 
26N57W TO 29N52W TO 30N44W. A CENTRAL ATLANTIC OCEAN DEEP LAYER 
TROUGH TO THE NORTH OF THE AREA SUPPORTS A COLD FRONT THAT IS 
ALONG 31N/32W BETWEEN 40W AND 54W. A MIDDLE LEVEL TO UPPER LEVEL 
TROUGH GOES FROM 31N37W TO A CYCLONIC CIRCULATION CENTER NEAR 
26N38W TO 18N38W. AN UPPER LEVEL TROUGH EXTENDS FROM A BROAD 
CYCLONIC CIRCULATION CENTER NEAR 22N17W TO 13N21W.

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MT