000
AXNT20 KNHC 092345
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
805 PM EDT SAT MAY 09 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...

THE ITCZ AXIS IS CENTERED ALONG 6N9W 4N17W 2N32W CROSSING THE
EQUATOR NEAR 42W EXTENDING TO NE BRAZIL NEAR 1S47W. SCATTERED
MODERATE AND ISOLATED STRONG CONVECTION IS FROM 2N-7N BETWEEN
8W-18W. SIMILAR CONVECTION IS FROM THE EQUATOR TO 2N BETWEEN
47W-52W

...DISCUSSION...

GULF OF MEXICO...
SUBSIDENCE IN NORTHERLY FLOW ALOFT AND DEEP LAYER DRY AIR ARE
PRESENT ACROSS MUCH OF THE REGION. THIS SUBSIDENCE IS BEING
SUPPORTED BY A SURFACE RIDGE OVER THE N GULF. THE SUBSIDENCE AND
STABLE ATMOSPHERIC CONDITIONS ARE RESULTING IN GENERALLY FAIR
WEATHER ACROSS MUCH OF THE AREA. RETURN FLOW ON THE WRN
PERIPHERY OF THE AFOREMENTIONED SURFACE RIDGE IS RESULTING IN SE
WINDS ACROSS THE GULF...WITH WIND SPEEDS UP TO 20 KT ACROSS
PORTIONS OF THE W AND MIDDLE GULF...AS REVEALED IN BUOY OBS AND
RECENT SCATTEROMETER DATA. CONTINUED MAINLY FAIR WEATHER IS
EXPECTED THROUGH THE REMAINDER OF THE WEEKEND AS THE DISCUSSED
WEATHER PATTERN PERSISTS.

CARIBBEAN SEA...
STRONG SURFACE HIGH PRESSURE OVER THE CENTRAL ATLC IS RESULTING
IN FRESH TRADE WINDS ACROSS THE CARIBBEAN SEA. THESE FRESH TRADE
WINDS ARE FORECAST TO PERSIST ACROSS THE REGION INTO THE MIDDLE
OF NEXT WEEK AS THE ATLC RIDGE REMAINS NEARLY STATIONARY. THE
STRONGEST WINDS...NE-E 20-25 KT...ARE FOUND NEAR THE COAST OF
COLOMBIA. THE TRADE WINDS ARE ADVECTING POCKETS OF LOW LEVEL
MOISTURE WITH ISOLATED SHOWERS WESTWARD ACROSS THE CARIBBEAN.
THE GREATEST CONCENTRATION OF THESE SHOWERS IS N OF 15N E OF
71W...INCLUDING PORTIONS OF HISPANIOLA AND PUERTO RICO.
ATMOSPHERIC STABILITY ASSOCIATED WITH A BROAD UPPER RIDGE OVER
THE REGION IS ENHANCING FAIR WEATHER CONDITIONS ACROSS MUCH OF
THE CARIBBEAN. UPPER LEVEL DIVERGENCE BETWEEN THE RIDGE AND A
SHORTWAVE TROUGH OVER THE YUCATAN PENINSULA IS PRODUCING
SCATTERED SHOWERS AND ISOLATED TSTMS OVER THE SW CARIBBEAN S OF
11N W OF 78W. MORE WIDESPREAD TSTM ACTIVITY IS OCCURRING OVER
PORTIONS OF CENTRAL AMERICA GREATLY ENHANCED BY LOCAL EFFECTS.

ATLANTIC OCEAN...
A SURFACE RIDGE ASSOCIATED WITH A 1027 MB HIGH OVER THE CENTRAL
ATLC NEAR 32N48W IS DOMINATING MUCH OF THE ATLC PORTION OF THE
DISCUSSION AREA. THE SURFACE HIGH IS FORECAST TO MOVE SLOWLY
SOUTHWARD DURING THE NEXT DAY TO NEAR 30N49W AT 1025 MB.
SUBSIDENCE ASSOCIATED WITH THE RIDGE IS RESULTING IN GENERALLY
FAIR WEATHER CONDITIONS ACROSS MUCH OF THE ATLC PORTION OF THE
DISCUSSION AREA. HOWEVER...POCKETS OF LOW LEVEL MOISTURE WITH
ISOLATED SHOWERS ARE MOVING WESTWARD ACROSS PORTIONS OF THE SW
NORTH ATLC...WITH THE GREATEST OF THESE SHOWERS S OF 24N BETWEEN
60W-72W INCLUDING PORTIONS OF HISPANIOLA AND PUERTO RICO. ACROSS
THE TROPICAL ATLC...AN UPPER LEVEL RIDGE IS PRESENT S OF 12N E
OF 60W...WITH AN UPPER LEVEL HIGH NEAR 7N43W. DIVERGENCE ALOFT
ASSOCIATED WITH THE UPPER LEVEL RIDGE IS ENHANCING THE ITCZ
CONVECTION. THIS UPPER LEVEL DIVERGENCE ALSO SUPPORTED THE
RECENT CONVECTION AND ASSOCIATED MAJOR FLOODING ACROSS PORTIONS
OF NE BRAZIL. THE GREATEST CONCENTRATION OF CONVECTION OVER
BRAZIL IS NOW LOCATED OVER WESTERN PORTIONS OF BRAZIL...THOUGH
SCATTERED MODERATE CONVECTION ASSOCIATED WITH THE ITCZ IS
AFFECTING THE COAST OF NE BRAZIL.

$$
CANGIALOSI/COHEN