000
AXNT20 KNHC 182337
TWDAT 

TROPICAL WEATHER DISCUSSION 
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
805 PM EDT SAT APR 18 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 SOUTHERN LIBERIA NEAR 5N8W...CROSSING THE EQUATOR ALONG 
20W...TO 3S30W 3S38W INTO NORTHEASTERN BRAZIL NEAR 4S44W.
NO SIGNIFICANT ORGANIZED PRECIPITATION IS RELATED TO THE ITCZ.

...DISCUSSION...

THE GULF OF MEXICO...
DEEP LAYER CYCLONIC FLOW FROM A CENTRAL U.S.A. TROUGH COVERS
THE AREA FROM COLORADO TO KANSAS...NEW MEXICO...OKLAHOMA AND 
TEXAS. THIS TROUGH SUPPORTS A DEVELOPING COLD FRONT THAT 
STRETCHES FROM NORTH TEXAS TO WEST TEXAS. UPPER LEVEL 
ANTICYCLONIC FLOW COVERS THE GULF WATERS THANKS TO A RIDGE
ALONG 93W. SHOWERS AND THUNDERSTORMS HAVE FORMED IN THE LOWER 
RIO GRANDE VALLEY OF TEXAS/EXTREME NORTHEASTERN MEXICO AND
FROM THE UPPER TEXAS GULF COAST TO THE WESTERN HALF OF THE 
LOUISIANA GULF COAST...IN AN AREA OF UPPER LEVEL DIFFLUENT
WIND FLOW ACCOMPANIED BY UPPER LEVEL MOISTURE AND LOW LEVEL
MOIST SOUTHEASTERLY WINDS. A SURFACE TROUGH ALSO IS IN THE
AREA FROM NORTHEASTERN MEXICO TO RIO GRANDE CITY IN TEXAS...
TO BEEVILLE BEYOND SOMERVILLE LAKE.

THE CARIBBEAN SEA... 
A WESTERN ATLANTIC OCEAN DEEP LAYER TROUGH SUPPORTS A COLD
FRONT THAT REACHES 20N70W JUST TO THE NORTH OF THE DOMINICAN
REPUBLIC...TO 19N77W JUST OFF THE COAST OF JAMAICA. THE FRONT 
BECOMES DISSIPATING FROM JAMAICA TO 19N80W AND 21N85W. SHOWERS 
ARE POSSIBLE WITHIN 30 NM OR LESS ON EITHER SIDE OF 22N63W
19N68W. A DISTINCT LINE OF CLOUDS MARKS THE DISSIPATING COLD 
FRONT IN THE CARIBBEAN SEA FROM JAMAICA WESTWARD.
THE UPPER LEVEL FLOW IS ANTICYCLONIC FROM THE SOUTHWESTERN 
CORNER OF THE GULF OF MEXICO...ACROSS THE YUCATAN PENINSULA TO 
CUBA...JAMAICA...AND HISPANIOLA. SEPARATE UPPER LEVEL 
SOUTHWESTERLY WIND FLOW EVENTUALLY MIXES WITH THE UPPER LEVEL 
ANTICYCLONIC FLOW SOMEWHERE NEAR 14N80W. THE FLOW BECOMES 
DEFINITELY CYCLONIC TO THE EAST OF 80W ALL THE WAY TO 60W.
UPPER LEVEL SOUTHWESTERLY WIND FLOW CONTINUES TO MOVE FROM 
NORTHERN SOUTH AMERICA...AND THIS FLOW ALSO APPEARS TO BLEND 
INTO THE SOUTHWESTERLY FLOW ON THE EASTERN SIDE OF THE TROUGH 
THAT HAS BUILT INTO THE AREA TO THE EAST OF 80W FROM THE
ATLANTIC OCEAN DEEP LAYER TROUGH.

THE ATLANTIC OCEAN...
A WESTERN ATLANTIC OCEAN DEEP LAYER TROUGH SUPPORTS A COLD FRONT 
THAT PASSES THROUGH 32N49W TO 25N60W TO 20N70W JUST TO THE NORTH 
OF THE DOMINICAN REPUBLIC...TO 19N77W JUST OFF THE COAST OF 
JAMAICA. THE FRONT BECOMES DISSIPATING FROM JAMAICA TO 19N80W 
AND 21N85W. SCATTERED MODERATE SHOWERS AND POSSIBLE 
THUNDERSTORMS ARE WITHIN 30 NM ON EITHER SIDE OF 25N59W BEYOND 
32N50W. SHOWERS ARE POSSIBLE WITHIN 30 NM OR LESS ON EITHER SIDE 
OF 25N59W 22N63W 19N68W. A DISTINCT LINE OF CLOUDS MARKS THE 
DISSIPATING COLD FRONT IN THE CARIBBEAN SEA FROM JAMAICA 
WESTWARD. A SECONDARY COLD FRONT IS WITHIN 180 NM TO THE 
NORTHWEST OF THE FIRST FRONT...TO THE NORTH OF 24N. THE SECOND 
FRONT IS EXPECTED TO OVERTAKE THE FIRST FRONT DURING THE NEXT
24 HOURS. SURFACE ANTICYCLONIC FLOW IS TO THE NORTH AND 
NORTHWEST OF THE FRONTS...AROUND A 1024 MB HIGH PRESSURE CENTER 
NEAR 33N77W. A SURFACE RIDGE IS TO THE EAST OF THE FRONTS ALONG
THE LINE FROM 35N18W TO A 1026 MB HIGH PRESSURE CENTER NEAR 
32N26W TO 28N36W 24N46W TO 19N60W.

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