[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 290551
TWDAT

TROPICAL WEATHER DISCUSSION...
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
205 AM EDT FRI AUG 29 2008

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
0345 UTC.

...SPECIAL FEATURES...
TROPICAL STORM GUSTAV IS CENTERED NEAR 17.9N 77.7W AT 29/0600
UTC OR ABOUT 52 NM WEST OF KINGSTON JAMAICA AND ABOUT 195 NM
EAST-SOUTHEAST OF GRAND CAYMAN MOVING W AT 7 KT. ESTIMATED
MINIMUM CENTRAL PRESSURE IS 993 MB. MAXIMUM SUSTAINED WIND SPEED
IS 55 KT WITH GUSTS TO 65 KT. PLEASE SEE THE LATEST NHC
FORECAST/ADVISORY UNDER AWIPS/WMO HEADERS MIATCMAT2/WTNT22 KNHC
AND/OR THE PUBLIC ADVISORY MIATCPAT2/WTNT32 KNHC FOR MORE
DETAILS. OUTFLOW FROM GUSTAV REMAINS GOOD IN ALL QUADRANTS. A
TURN TOWARD THE WNW AND NW IS FORECAST DURING THE NEXT COUPLE OF
DAYS WITH GUSTAV PASSING NEAR OR OVER W JAMAICA DURING THE NIGHT
WHILE STRENGTHENING AND MOVE NEAR OR OVER THE CAYMAN ISLANDS FRI
OR FRI NIGHT POSSIBLY AS A HURRICANE WHILE APPROACHING W CUBA ON
SAT. SCATTERED/NUMEROUS STRONG CONVECTION IS FROM 17N-20N
BETWEEN 75W-78W INCLUDING MOST OF JAMAICA. SCATTERED MODERATE/
STRONG CONVECTION IS WITHIN 60 NM OF LINE FROM S OF HAITI NEAR
17N72W TO 16N79W WITH SCATTERED SHOWERS/ISOLATED THUNDERSTORMS
COVERING A BROADER AREA FROM 14N-22N BETWEEN 70W-82W. GUSTAV IS
EXPECTED TO PRODUCE TOTAL RAINFALL ACCUMULATIONS OF 6 TO 12
INCHES ACROSS JAMAICA AND THE CAYMAN ISLANDS...WITH ISOLATED
MAXIMUM AMOUNTS OF UP TO 25 INCHES POSSIBLE. THESE RAINS WILL
LIKELY PRODUCE LIFE-THREATENING FLASH FLOODS AND MUD SLIDES.
RAINFALL ACCUMULATIONS OF 2 TO 4 INCHES ARE POSSIBLE OVER
SOUTHERN CUBA. RAINFALL WILL BE DIMINISHING OVER HAITI
TONIGHT...WITH AN ADDITIONAL 1 TO 2 INCHES OF RAINFALL POSSIBLE.

TROPICAL STORM HANNA IS CENTERED NEAR 21.1N 60.6W AT 29/0300 UTC
OR ABOUT 225 NM NORTHEAST OF THE NORTHERN LEEWARD ISLANDS MOVING
WEST-NORTHWEST AT 6 KT. ESTIMATED MINIMUM CENTRAL PRESSURE IS
1000 MB. MAXIMUM SUSTAINED WIND SPEED IS 45 KT WITH GUSTS TO 55
KT. PLEASE SEE THE LATEST NHC FORECAST/ADVISORY UNDER AWIPS/WMO
HEADERS MIATCMAT3/WTNT23 KNHC AND/OR THE PUBLIC ADVISORY
MIATCPAT3/WTNT33 KNHC FOR MORE DETAILS. OUTFLOW FROM HANNA IS
MAINLY TO THE E AND S MOSTLY DUE TO AN UPPER LOW JUST TO THE W.
HANNA IS FORECAST TO GRADUALLY MOVE AWAY FROM THE NORTHERN
LEEWARD ISLANDS AND BE LOCATED WELL TO THE NORTHEAST OF THE
BAHAMAS DURING THE NEXT COUPLE OF DAYS. GRADUAL STRENGTHENING IS
FORECAST DURING THE NEXT COUPLE OF DAYS AND HANNA COULD BECOME A
HURRICANE BY SATURDAY. SCATTERED/NUMEROUS STRONG CONVECTION
WITHIN 45/60 NM OF LINE FROM 17N61W 19N59W TO 21N60W WITH
SCATTERED MODERATE/STRONG CONVECTION COVERING THE REMAINDER OF
THE AREA FROM WITHIN 120 NM OF LINE FROM THE N LEEWARD ISLANDS
NEAR 17N62W 20N58W TO 23N61W.

...TROPICAL WAVES...
TROPICAL WAVE IS ALONG THE COAST OF W AFRICA ALONG 17W/18W S OF
17N MOVING W NEAR 10 KT. WAVE IS EMBEDDED WITHIN AN AREA OF DEEP
LAYERED MOISTURE AS DEPICTED ON THE MIMIC-TPW ANIMATION WITH A
BROAD MID LEVEL CYCLONIC ROTATION OBSERVED ON SATELLITE IMAGERY.
SCATTERED MODERATE/STRONG CONVECTION IS FROM 12N-18N BETWEEN THE
COAST OF W AFRICA TO 20W.

TROPICAL WAVE IS ALONG 38W/39W FROM 12N TO 21N WITH A 1009 MB
LOW ALONG THE WAVE AXIS NEAR 18N MOVING WNW NEAR 10 KT. HIGH
AMPLITUDE WAVE IS EMBEDDED WITHIN AN AREA OF DEEP LAYERED
MOISTURE AS DEPICTED ON THE MIMIC-TPW ANIMATION BUT WATER VAPOR
IMAGERY SHOWERS MODERATE SUBSIDENCE OVER THE AREA S OF THE LOW.
CLUSTERS OF SCATTERED MODERATE/ISOLATED STRONG CONVECTION ARE
FROM 18N-21N BETWEEN 37W-43W.

TROPICAL WAVE IS ALONG 54W/55W S OF 13N MOVING W NEAR 10 KT.
THIS WAVE HAS LOST ITS INVERTED-V CURVATURE AND LACK DEEP
LAYERED MOISTURE AND CONVECTION.

...THE ITCZ...
THE ITCZ AXIS IS ANALYZED ALONG 10N19W 16N33W 10N52W. THE ITCZ
HAS BEEN DISRUPTED BY THE TROPICAL WAVES AND T.S. HANNA.
SCATTERED MODERATE CONVECTION IS FROM 9N-13N BETWEEN 30W-36W
WITH CLUSTERS OF SIMILAR CONVECTION FROM 7N-12N BETWEEN 19W-30W.

...DISCUSSION...

GULF OF MEXICO...
BROAD UPPER TROUGH DOMINATES MOST OF THE GULF EXTENDING FROM AN
UPPER LOW OVER WRN NORTH CAROLINA ACROSS THE FLORIDA PANHANDLE
NEAR PANAMA CITY TO THE NW YUCATAN PENINSULA. UPPER RIDGE OVER
MEXICO ARE PROVIDING UPPER LEVEL DIFFLUENCE TO GENERATE CLUSTERS
OF SCATTERED SHOWERS/ISOLATED THUNDERSTORMS S OF 27N W OF 90W.
VERY WEAK SURFACE RIDGE ENCOMPASSES THE N GULF. MODERATE
SUBSIDENCE AND DRY AIR IS NOTED N OF 26N BETWEEN 85W-93W
SUPPRESSING ANY SHOWER ACTIVITY KEEPING THE REMAINDER OF THE
GULF TRANQUIL TONIGHT.

CARIBBEAN SEA...
THE MAIN CONCERN CONTINUES TO BE T.S. GUSTAV FOR THE N/CENTRAL
CARIBBEAN AND ACTIVITY ASSOCIATED WITH T.S. HANNA FOR THE
LEEWARD/VIRGIN ISLANDS TONIGHT...SEE SPECIAL FEATURES ABOVE. THE
BROAD UPPER HIGH ASSOCIATED WITH GUSTAV IS ALSO DOMINATING MOST
OF THE CARIBBEAN AS WELL. SCATTERED SHOWERS/THUNDERSTORMS HAVE
DEVELOPED INLAND OVER NICARAGUA MOVING INTO THE CARIBBEAN WATERS
FROM THE BORDER OF COSTA RICA TO 13N W OF 82W. THE ITCZ CROSSES
THE N PORTION OF SOUTH AMERICA GENERATING SCATTERED SHOWERS/
ISOLATED THUNDERSTORMS WITHIN 45 NM ALONG THE COAST OF COLOMBIA
TO PANAMA. THE ENTIRE CARIBBEAN IS EMBEDDED WITHIN DEEP LAYERED
MOISTURE AS DEPICTED ON THE MIMIC-TPW ANIMATION...SO ISOLATED
SHOWERS/THUNDERSTORMS ARE POSSIBLE OVER THE REMAINDER OF THE
CARIBBEAN.

ATLANTIC OCEAN...
A CONCERN FOR THE THE ATLC NE OF THE LEEWARD/VIRGIN ISLANDS IS
T.S. HANNA TONIGHT...SEE SPECIAL FEATURES ABOVE. AN UPPER HIGH
IS CENTERED NEAR 30N69W WITH AN UPPER LOW TO THE S...N OF PUERTO
RICO NEAR 23N66W ENCOMPASSING THE W ATLC. THE UPPER LOW IS
PROVIDING UPPER LEVEL SHEAR FOR T.S. HANNA AND GENERATING
SCATTERED SHOWERS/THUNDERSTORMS FROM 21N-25N BETWEEN 63W-68W. A
SURFACE TROUGH IS NE OF THE BAHAMAS EXTENDING FROM 28N70W TO
23N73W GENERATING ISOLATED SHOWERS/THUNDERSTORMS WITHIN 75 NM OF
THE TROUGH AXIS. A SHARP UPPER TROUGH IS IN THE CENTRAL ATLC
EXTENDING ALONG 47W TO NEAR 22N INDUCING AN UPPER RIDGE TO THE W
FROM NEAR T.S. HANNA NNE TO 32N54W. AN E/W UPPER RIDGE COVERS
THE E ATLC ALONG 21N TO 40W. AT THE SURFACE...A BROAD SURFACE
RIDGE REMAINS OVER THE ATLC N OF 25N E OF 55W ANCHORED BY A 1027
MB HIGH W OF THE AZORES.

$$
WALLACE





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