000
AXNT20 KNHC 180546
TWDAT 

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

...ITCZ...
THE ITCZ IS CENTERED ALONG 5N9W...CROSSING THE EQUATOR NEAR 18W 
TO 1S20W AND ALONG 1S TO THE NE BRAZIL COAST NEAR 46W. NO 
SIGNIFICANT CONVECTION IS NOTED IN THE DISCUSSION AREA.

...DISCUSSION...

GULF OF MEXICO...
A DEEP LAYERED TROUGH IS ACROSS THE CENTRAL CONUS WHILE AN 
AMPLIFIED UPPER RIDGE AXIS IS ALONG 90W IN THE CENTRAL GULF. 
BETWEEN THESE TWO UPPER FEATURES...A LARGE AREA OF MIDDLE TO 
UPPER LEVEL DIFFLUENCE EXISTS ACROSS THE NW GULF...TO INLAND 
OVER TEXAS AND LOUISIANA. THIS AREA OF UPPER DIFFLUENCE IS 
GENERATING SCATTERED SHOWERS AND TSTMS ACROSS THE NW GULF N OF 
27N W OF 91W. EXPECT CONTINUED SE SURFACE FLOW OF UP TO 25 KT W 
OF 85W TO PROVIDE AMPLE LOW-LEVEL MOISTURE AND INSTABILITY 
ACROSS THE NRN GULF AHEAD OF A DEVELOPING LOW PRESSURE AREA OVER 
ERN TEXAS/WRN LOUISIANA BY LATE SATURDAY. THE NEXT COLD FRONT IS 
FORECAST TO ENTER THE NW GULF WATERS EARLY SUNDAY. ELSEWHERE 
ACROSS THE ERN GULF...A 1026 MB SURFACE HIGH PRESSURE IS 
CENTERED OVER SOUTH CAROLINA AND EXTENDS A RIDGE SWD ACROSS THE 
FLORIDA PENINSULA AND CUBA PROVIDING MOSTLY FAIR SKIES AND 10-15 
KT ELY SURFACE FLOW.

CARIBBEAN SEA...
A WEAKENING COLD FRONT EXTENDS INTO THE N/CENTRAL CARIBBEAN 
THROUGH THE WINDWARD PASSAGE TO NEAR 19N77W. SCATTERED SHOWERS 
ARE WITHIN 50 NM EITHER SIDE OF THE FRONT. OTHER SCATTERED 
SHOWERS ARE NOTED E OF THE FRONT INLAND AND OVER THE ADJACENT 
COASTAL WATERS OF HISPANIOLA AND PUERTO RICO. ELSEWHERE THE 
CARIBBEAN REMAINS FAIRLY TRANQUIL WITH FRESH EASTERLY TRADEWINDS 
OBSERVED S OF 18N. THE STRONGEST WINDS...AS USUAL...ARE ALONG 
THE IMMEDIATE COAST OF NRN COLOMBIA. ALOFT...ZONAL UPPER FLOW 
DOMINATES AND IS NOTED ACROSS THE ENTIRE BASIN.

ATLANTIC OCEAN...
A BROAD UPPER LEVEL TROUGH ACROSS THE WRN ATLC DIPS S INTO THE 
DISCUSSION AREA AND REMAINS N OF 25N. THIS TROUGH SUPPORTS A 
COLD FRONT THAT ENTERS THE REGION NEAR 32N52W AND EXTENDS SW 
ALONG 30N55W 26N60W 21N70W AND INTO THE N/CENTRAL CARIBBEAN 
THROUGH THE WINDWARD PASSAGE. SCATTERED SHOWERS ARE WITHIN 90 NM 
EITHER SIDE OF THE FRONT. TO THE W OF THE FRONT...A 1026 MB 
SURFACE HIGH IS CENTERED OVER SOUTH CAROLINA AND COVERS THE W 
ATLC WITH SURFACE RIDGING AND SCATTERED STRATOCUMULUS CLOUDS. 
THESE SCATTERED CLOUDS UNDER NE SURFACE FLOW ARE USHERING IN 
ISOLATED SHOWERS ACROSS THE NRN BAHAMAS AND EXTREME SRN FLORIDA 
PENINSULA. ELSEWHERE ACROSS THE CENTRAL AND ERN ATLC...UPPER 
LEVEL RIDGING COUPLED WITH A 1027 MB SURFACE HIGH CENTERED NEAR 
28N34W IS PROVIDING THE ATLC WITH NE TO ELY SURFACE FLOW OF UP 
TO 20 KTS FROM THE W AFRICA COAST TO 60W.

$$
HUFFMAN