[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 231144
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
805 AM EDT SAT MAY 23 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.

...SPECIAL FEATURE...
A 1004 MB SURFACE LOW IS LOCATED NEAR 30N89W...OR ABOUT 75 NM
SOUTH OF MOBILE ALABAMA. A SURFACE TROUGH EXTENDS FROM THE
SURFACE LOW TO THE NW YUCATAN PENINSULA NEAR 21N90W. LOW LEVEL
CONVERGENCE NEAR THE SURFACE LOW...ALONG WITH DIFFLUENCE
ASSOCIATED WITH A MIDDLE TO UPPER LEVEL TROUGH AXIS ACROSS THE
CENTRAL GULF ARE SUPPORTING NUMEROUS SHOWERS AND SCATTERED TSTMS
ACROSS THE GULF N OF 26N E OF 90W....INCLUDING THE NE GULF
COAST. THE SURFACE LOW IS FORECAST TO MOVE N-NW DURING THE NEXT
24 HOURS AND LOCATE INLAND OVER SWRN MISSISSIPPI. HOWEVER...
ADDITIONAL DEVELOPMENT OF THIS SYSTEM IS POSSIBLE...AND A
TROPICAL DEPRESSION COULD FORM BEFORE THE LOW MOVES INLAND OVER
THE NRN GULF COAST LATER TODAY. REGARDLESS OF DEVELOPMENT...
HEAVY RAINS AND OCCASIONALLY GUSTY WINDS ARE EXPECTED ALONG
PORTIONS OF THE NRN GULF COAST THROUGH THE REMAINDER OF
SATURDAY. INTERESTS IN THIS AREA SHOULD MONITOR THE PROGRESS OF
THE SYSTEM.

...TROPICAL WAVES...
A TROPICAL WAVE IS ALONG 42W S OF 7N MOVING W NEAR 15 KT. THIS
WAVE IS ASSOCIATED WITH A MAXIMUM IN DEEP LAYER MOISTURE BASED
ON THE TOTAL PRECIPITABLE WATER PRODUCT FROM CIMSS WITH
SATELLITE IMAGERY INDICATING INVERTED-V SIGNATURE AND WEAK
CYCLONIC CURVATURE NEAR THE WAVE AXIS IN THE LOW LEVEL CLOUDS.
DEEP CONVECTION REMAINS EMBEDDED WITHIN PROXIMITY OF THE ITCZ
NEAR THE SRN EXTENT OF THE WAVE. SCATTERED MODERATE TO STRONG
CONVECTION IS S OF 3N BETWEEN 40W-50W.

A TROPICAL WAVE IS ALONG 85W S OF 12N MOVING W NEAR 15 KT. THIS
WAVE HAS LARGELY ENTERED THE E PACIFIC REGION AND MORE
INFORMATION CAN BE FOUND IN THE E PACIFIC TROPICAL WEATHER
DISCUSSION...TWDEP...OR WMO HEADER AXPZ20 KNHC.

...THE ITCZ...
THE ITCZ AXIS IS CENTERED ALONG 8N12W 3N22W CROSSING THE EQUATOR
NEAR 32W AND EXTENDING INTO NE BRAZIL NEAR 2S45W. CLUSTERS OF
SCATTERED MODERATE CONVECTION ARE S OF 5N BETWEEN 7W-20W.
SCATTERED MODERATE TO STRONG CONVECTION IS S OF 3N BETWEEN
40W-50W.

...DISCUSSION...

GULF OF MEXICO...
A DEEP LAYER TROUGH IS PRESENT ACROSS THE GULF WITH THE UPPER
LEVEL TROUGH AXIS EXTENDING FROM TEXAS TO THE FLORIDA KEYS. THE
ASSOCIATED SURFACE FEATURE...A 1004 MB LOW NEAR 29N89W IS
GENERATING NUMEROUS SHOWERS AND TSTMS...AS WELL AS STRONGER
WINDS...AS THIS LOW PRESSURE AREA PUSHES UP AGAINST A HIGH
PRESSURE RIDGE ACROSS THE SE CONUS. FOR MORE DETAILS ON THIS
SYSTEM SEE THE SPECIAL FEATURE SECTION ABOVE. ACROSS THE W
GULF...SUBSIDENCE ASSOCIATED WITH W-NW FLOW ALOFT IS SUPPORTING
GENERALLY FAIR WEATHER CONDITIONS...WITH UPPER LEVEL MOISTURE
AND HIGH LEVEL DEBRIS CLOUDS FROM SCATTERED SHOWERS ACROSS
CENTRAL MEXICO STREAMING EWD. GENERALLY LIGHT NLY WINDS ARE
OBSERVED ACROSS PORTIONS OF THE WRN GULF W OF 90W.

CARIBBEAN SEA...
SCATTERED SHOWERS AND ISOLATED TSTMS PERSIST ACROSS THE ERN
CARIBBEAN N OF 13N E OF 71W. THIS ACTIVITY IS BEING DRIVEN BY
UPPER LEVEL DIVERGENCE IN MOIST SWLY FLOW ALOFT BETWEEN AN UPPER
LEVEL TROUGH OVER THE WRN CARIBBEAN...AND AN UPPER LEVEL RIDGE
ACROSS THE SE CARIBBEAN. THIS ACTIVITY IS EXPECTED TO CONTINUE
OVER THE NEXT COUPLE OF DAYS ACROSS THE NRN CARIBBEAN AS THE
UPPER SHORTWAVE TROUGH SHIFTS EWD ACROSS THE GREATER ANTILLES
BRINGING INCREASED CHANCES FOR SCATTERED SHOWERS. CLOSER TO THE
UPPER LEVEL TROUGH AXIS ACROSS THE WRN CARIBBEAN...ISOLATED
SHOWERS ARE OBSERVED OVER ERN CUBA...JAMAICA...HISPANIOLA AND
NEARBY N/CENTRAL CARIBBEAN WATERS FROM 15N-21N BETWEEN 72W-81W.
MEANWHILE...THE SURFACE PRESSURE GRADIENT SW OF A SURFACE RIDGE
OVER THE CENTRAL ATLC IS MAINTAINING ELY WINDS UP TO 20 KT
ACROSS PORTIONS OF THE ERN CARIBBEAN.

ATLANTIC OCEAN...
SCATTERED SHOWERS AND ISOLATED TSTMS ARE OCCURRING S OF 32N W OF
73W INCLUDING THE BAHAMAS AND THE NEARBY W ATLC WATERS ALONG THE
COAST OF FLORIDA. THIS ACTIVITY IS BEING SUPPORTED BY UPPER
LEVEL DIFFLUENCE IN MOIST SWLY FLOW ALOFT BETWEEN AN UPPER LEVEL
TROUGH OVER THE GULF OF MEXICO AND WRN CARIBBEAN...AND AN UPPER
LEVEL RIDGE ACROSS THE SW NORTH ATLC. THE MOST CONCENTRATED AREA
OF CONVECTION IS LOCATED OVER THE ERN STRAITS OF FLORIDA AND
ANDROS ISLAND IN THE BAHAMAS FROM 22N-25N BETWEEN 76W-79W.
FARTHER TO THE E...AN UPPER LEVEL TROUGH IS PRESENT WITH AN AXIS
EXTENDING FROM AN UPPER LEVEL LOW NEAR 30N54W TO 27N60W TO
26N70W. ATMOSPHERIC INSTABILITY NEAR THE UPPER LEVEL LOW AND
TROUGH...AS WELL AS UPPER LEVEL DIFFLUENCE IN MOIST SWLY FLOW
ALOFT...ARE SUPPORTING SCATTERED SHOWERS AND ISOLATED TSTMS
WITHIN 200 NM EITHER SIDE OF A LINE FROM 32N44W 26N46W 22N62W
SWD TO OVER THE NE CARIBBEAN SEA. THIS ACTIVITY IS ALSO BEING
SUPPORTED BY LOW LEVEL CONVERGENCE NEAR A SURFACE TROUGH
EXTENDING FROM 32N51W TO 20N62W. ACROSS THE E ATLC...A SURFACE
RIDGE IS PRESENT WHERE MAINLY ZONAL FLOW ALOFT IS OCCURRING AND
FAIR WEATHER CONDITIONS PERSIST UNDER N TO NE SURFACE FLOW.
ACROSS THE TROPICAL ATLC...AN UPPER LEVEL RIDGE IS S OF 14N E OF
40W WITH AN UPPER LEVEL HIGH NEAR 7N29W. UPPER LEVEL DIVERGENCE
ASSOCIATED WITH THE UPPER LEVEL HIGH AND UPPER LEVEL RIDGE IS
ENHANCING THE CONVECTION ASSOCIATED WITH THE ITCZ.

$$
HUFFMAN





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