000
AXNT20 KNHC 081051
TWDAT 

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
805 AM EDT FRI MAY 08 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.

...THE ITCZ...

THE ITCZ AXIS IS CENTERED ALONG 5N8W 1N20W CROSSING THE EQUATOR 
NEAR 32W TO NE BRAZIL NEAR 3S41W. CLUSTERS OF SCATTERED MODERATE 
CONVECTION ARE FROM 1N-6N BETWEEN 11W-22W AND FROM THE EQUATOR 
TO 3N BETWEEN 23W-30W.

...DISCUSSION...

GULF OF MEXICO...
THE GULF IS DOMINATED BY FAIR WEATHER SUPPORTED BY N-NW FLOW 
ALOFT AND DRY STABLE AIR ON THE ERN PERIPHERY OF AN UPPER RIDGE 
CENTERED OVER NW MEXICO. AT THE SURFACE...S TO SE WINDS ARE 
FAIRLY UNIFORM ACROSS THE REGION DUE TO A QUASI-STATIONARY RIDGE 
AXIS EXTENDING FROM THE W ATLC TO THE N GULF COAST. WINDS ARE 
STRONGEST...15-20 KT...OVER THE WRN WATERS ACCORDING TO BUOY 
OBSERVATIONS AND A RECENT ASCAT PASS IN RESPONSE TO LOW PRESSURE 
OVER THE SRN PLAINS. LITTLE SIGNIFICANT CHANGE IN THE PATTERN IS 
EXPECTED THROUGH THE WEEKEND UNTIL THE NEXT FRONT SLIDES SWD 
ACROSS THE SE CONUS AND REMAINS INLAND ALONG THE NRN GULF COAST 
BY SUNDAY. 

CARIBBEAN SEA...
SCATTERED SHOWERS AND ISOLATED TSTMS CONTINUE ACROSS THE VIRGIN 
ISLANDS...PUERTO RICO...HISPANIOLA AND NEARBY WATERS N OF 17N 
BETWEEN 63W-77W. THIS UNSETTLED WEATHER IS BEING FUELED BY 
STRONG SW FLOW ALOFT AND AN OVERALL DIFFLUENT PATTERN TO THE E 
OF A SHORTWAVE TROUGH ACROSS THE BAHAMAS AND ERN CUBA. STRONG 
ELY TRADES AND ASSOCIATED LOW-LEVEL WIND SPEED CONVERGENCE IN 
THIS AREA ARE PROVIDING ENHANCED LIFT. LOCALLY HEAVY RAINS ARE 
FORECAST TO CONTINUE THROUGH LATE SATURDAY OVER HISPANIOLA AS 
THE MIDDLE TO UPPER LEVEL TROUGH GRADUALLY WEAKENS AND SHIFTS 
E-NE INTO THE CENTRAL ATLC. ELSEWHERE...CONDITIONS ARE 
GENERALLY TRANQUIL THOUGH ISOLATED SHOWERS ARE POSSIBLE ACROSS 
THE ENTIRE BASIN...ESPECIALLY OVER THE LESSER ANTILLES WHERE 
SHALLOW MOISTURE FETCH IS OBSERVED STREAMING IN FROM THE ATLC. 

ATLANTIC OCEAN...
THERE ARE ONLY A COUPLE AREAS OF ACTIVE WEATHER ACROSS THE ATLC 
DISCUSSION AREA. ONE OF THESE IS OVER THE NW BAHAMAS AND CENTRAL 
CUBA IN ASSOCIATION WITH A SURFACE TROUGH ALONG 78W AND UPPER 
DIFFLUENCE E OF A MIDDLE TO UPPER LEVEL SHORTWAVE TROUGH OVER 
THE STRAITS OF FLORIDA AND THE BAHAMAS. SCATTERED SHOWERS AND 
ISOLATED TSTMS ARE FROM 24N-29N BETWEEN 72W-76W. THE LOW-LEVEL 
BOUNDARY WILL LIKELY BECOME DIFFUSE OVER THE NEXT 24 HOURS AS 
UPPER LEVEL WINDS SHIFT AND AN UPPER RIDGE BUILDS OVER THE W 
ATLC WATERS. THE OTHER AREA OF INTEREST IS S OF 23N BETWEEN 
57W-70W...N OF THE ERN GREATER ANTILLES ISLANDS. INSTABILITY AND 
DIFFLUENCE ALONG AND TO THE E OF ANOTHER SHORTWAVE TROUGH IS 
ENHANCING SCATTERED SHOWERS ACROSS HISPANIOLA...PUERTO RICO... 
THE US/UK VIRGIN ISLANDS AND NEARBY WATERS TO THE N. REFER TO 
THE CARIBBEAN SECTION FOR MORE DETAILS. THE REMAINDER OF THE 
ATLC IS VOID OF ORGANIZED DEEP LAYERED CLOUDINESS SUPPRESSED BY 
A STABLE ATMOSPHERE...ESPECIALLY OVER THE SUBTROPICAL E ATLC 
WHERE THE FLOW IS HIGHLY CONFLUENT. OVER THE TROPICAL E ATLC... 
CLUSTERS OF MODERATE CONVECTION ARE LOCATED WITHIN THE ITCZ E OF 
22W AND OVER AFRICA ENHANCED BY BROAD SURFACE LOW PRESSURE AND 
AN UPPER RIDGE CENTERED NEAR 16N5W. A CONSIDERABLE AMOUNT OF 
SAHARAN DUST HAS SPREAD TO ABOUT 50W...ACCORDING TO THE CIMSS 
SAL PRODUCT.

$$
HUFFMAN