000
AXNT20 KNHC 181038
TWDAT 

TROPICAL WEATHER DISCUSSION 
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
805 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 0600 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 
1015 UTC.

...ITCZ...
THE ITCZ IS CENTERED ALONG 5N9W...CROSSING THE EQUATOR NEAR 20W 
TO 1S25W 2S25W AND INTO NE BRAZIL NEAR 3S40W. 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 IS OVER THE SE CONUS WITH AXIS ALONG 88W 
IN THE ERN GULF. BETWEEN THESE TWO UPPER FEATURES...A LARGE AREA 
OF MIDDLE TO UPPER LEVEL DIFFLUENCE EXISTS ACROSS THE NW GULF... 
TO INLAND OVER LOUISIANA AND MISSISSIPPI. THIS AREA OF UPPER 
DIFFLUENCE IS GENERATING SCATTERED SHOWERS AND ISOLATED TSTMS 
ACROSS THE NW GULF WITHIN 90 NM OF THE COAST BETWEEN CORPUS 
CHRISTI TEXAS AND MORGAN CITY LOUISIANA. EXPECT CONTINUED SE 
SURFACE FLOW OF UP TO 25 KTS 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 AND FLORIDA PENINSULA...A 
1026 MB SURFACE HIGH PRESSURE CENTERED OVER SOUTH CAROLINA 
EXTENDS A RIDGE SWD ACROSS THE FLORIDA PENINSULA AND CUBA. NE TO 
ELY FLOW AROUND THE SRN PERIPHERY OF THE RIDGE IS USHERING IN 
ISOLATED SHOWERS ACROSS THE FLORIDA KEYS AND STRAITS OF FLORIDA 
THIS MORNING.

CARIBBEAN SEA... 
THE CARIBBEAN SEA REMAINS FAIRLY TRANQUIL WITH FRESH EASTERLY 
TRADEWINDS OBSERVED ACROSS THE REGION. THE STRONGEST WINDS...AS 
USUAL...ARE ALONG THE IMMEDIATE COAST OF NRN COLOMBIA. ISOLATED 
SHOWERS ARE NOTED ACROSS ERN CUBA...HISPANIOLA AND PUERTO RICO 
AS A WEAK COLD FRONT IS LOCATED TO THE NORTH IN THE W ATLC ALONG 
21N. ALOFT...ZONAL UPPER FLOW DOMINATES WITH OVERALL MODERATE TO 
STRONG SUBSIDENCE 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 20N. THIS TROUGH SUPPORTS A 
COLD FRONT THAT ENTERS THE REGION NEAR 32N51W AND EXTENDS SW 
ALONG 30N55W 27N60W TO OVER THE TURKS AND CAICOS ISLANDS. 
SCATTERED SHOWERS ARE WITHIN 120 NM EITHER SIDE OF THE FRONT. TO 
THE W OF THE FRONT...A SURFACE TROUGH IS ANALYZED FROM 30N60W TO 
27N67W AS A SECONDARY TROUGH OF LOW PRESSURE AND IS FORECAST TO 
BE ABSORBED INTO THE MAIN FRONTAL BOUNDARY OVER THE NEXT 24 
HOURS. THE REMAINDER OF THE W ATLC IS IMPACTED BY A 1026 MB 
SURFACE HIGH CENTERED OVER SOUTH CAROLINA WITH A SURFACE RIDGE 
EXTENDING ACROSS THE FLORIDA PENINSULA AND BAHAMAS. SCATTERED 
STRATOCUMULUS CLOUDS ARE OBSERVED UNDER NE SURFACE FLOW AND ARE 
USHERING IN ISOLATED SHOWERS ACROSS THE BAHAMAS AND THE FLORIDA 
KEYS. ELSEWHERE ACROSS THE CENTRAL AND ERN ATLC...BROAD UPPER 
LEVEL RIDGING COUPLED WITH A 1025 MB SURFACE HIGH CENTERED NEAR 
30N29W IS PROVIDING THE ATLC WITH NE TO ELY SURFACE FLOW OF UP 
TO 20 KTS FROM THE W AFRICA COAST TO 60W.

$$
HUFFMAN