[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 291045
TWDAT

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

...SPECIAL FEATURES...
TROPICAL STORM GUSTAV IS CENTERED NEAR 18.1N 78.1W AT 29/0900
UTC OR ABOUT 74 NM WEST OF KINGSTON JAMAICA AND ABOUT 190 NM
EAST-SOUTHEAST OF GRAND CAYMAN MOVING WNW AT 7 KT. ESTIMATED
MINIMUM CENTRAL PRESSURE IS 991 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.
SCATTERED STRONG CONVECTION IS WITHIN 120 NM OF THE CENTER IN
THE NW SEMICIRCLE. SIMILAR CONVECTION IS WITHIN 60/75 NM OF LINE
FROM SW HAITI NEAR 18N74W TO 14N80W.

TROPICAL STORM HANNA IS CENTERED NEAR 21.7N 62.3W AT 29/0900 UTC
OR ABOUT 215 NM NORTH-NORTHEAST OF THE NORTHERN LEEWARD ISLANDS
MOVING NORTHWEST AT 12 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. HANNA IS EXPERIENCING
WESTERLY SHEAR PARTIALLY EXPOSING THE LOW LEVEL CENTER THUS
OUTFLOW FROM HANNA IS TO THE E AND S. SCATTERED MODERATE/STRONG
CONVECTION COVERS THE AREA FROM 16N-20N BETWEEN 57W-64W
INCLUDING THE LEEWARD ISLANDS AND MOVING TOWARD THE VIRGIN
ISLANDS AND FROM 20N-22N BETWEEN 58W-61W.

...TROPICAL WAVES...
TROPICAL WAVE IS OFF THE COAST OF W AFRICA ALONG 18W/19W S OF
17N WITH A BROAD LOW LEVEL 1006 MB CENTER ALONG THE WAVE NEAR
13N MOVING W NEAR 10 KT. THE LOW IS BASED ON SURFACE
OBSERVATIONS AS WELL AS THE BROADS CYCLONIC ROTATION OBSERVED ON
SATELLITE IMAGERY. SCATTERED MODERATE WITH EMBEDDED CLUSTERS OF
ISOLATED STRONG CONVECTION COVERS THE AREA FROM 11N-18N BETWEEN
18W-22.

TROPICAL WAVE IS ALONG 39W/40W FROM 14N TO 24N WITH A 1010 MB
LOW ALONG THE WAVE AXIS NEAR 18N MOVING WNW NEAR 10 KT. HIGH
AMPLITUDE WAVE WITH A BROAD INVERTED-V CURVATURE OBSERVED ON
SATELLITE IMAGERY. SCATTERED MODERATE/STRONG CONVECTION IS FROM
18N-21N BETWEEN 38W-42W.

TROPICAL WAVE IS ALONG 56W S OF 13N MOVING W NEAR 10 KT. THIS
WAVE NO LONGER HAS THE TYPICAL INVERTED-V CURVATURE AND LACKS
ANY SHOWERS/DEEP CONVECTION.

...THE ITCZ...
THE ITCZ AXIS IS ANALYZED ALONG 10N20W 12N32W 18N39W 11N53W. THE
ITCZ HAS BEEN DISRUPTED BY THE TROPICAL WAVES AND T.S. HANNA.
CLUSTERS OF SCATTERED MODERATE CONVECTION ARE FROM 6N-14N
BETWEEN 20W-27W AND FROM 7N-12N BETWEEN 31W-37W.

...DISCUSSION...

GULF OF MEXICO...
BROAD UPPER TROUGH DOMINATES MOST OF THE GULF EXTENDING FROM AN
UPPER LOW OVER SW NORTH CAROLINA ACROSS THE FLORIDA PANHANDLE
NEAR PANAMA CITY TO OVER THE N YUCATAN PENINSULA. UPPER RIDGE
OVER MEXICO IS PROVIDING UPPER LEVEL DIFFLUENCE TO GENERATE
CLUSTERS OF SCATTERED SHOWERS/ISOLATED THUNDERSTORMS S OF 27N W
OF 91W AND THE UPPER RIDGE ASSOCIATED WITH T.S. GUSTAV IS
PROVIDING SIMILAR UPPER LEVEL DIFFLUENCE TO GENERATE SIMILAR
ACTIVITY S OF 25N E OF 90W TO OVER S FLORIDA AND AND IN THE
FLORIDA STRAITS. VERY WEAK SURFACE RIDGE ENCOMPASSES THE N GULF.
MODERATE SUBSIDENCE AND DRY AIR ARE NOTED N OF 26N E OF 93W TO
OVER FLORIDA SUPPRESSING ANY SHOWER ACTIVITY KEEPING THE
REMAINDER OF THE GULF TRANQUIL THIS MORNING.

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 THIS MORNING...SEE SPECIAL FEATURES
ABOVE. THE BROAD UPPER HIGH ASSOCIATED WITH GUSTAV IS ALSO
DOMINATING MOST OF THE CARIBBEAN AS WELL. SCATTERED SHOWERS/
ISOLATED THUNDERSTORMS HAVE ARE OVER THE W CARIBBEAN WITHIN 150
NM OF LINE FROM 16N80W 17N84W TO THE YUCATAN CHANNEL NEAR
22N85W. THE ITCZ CROSSES THE N PORTION OF SOUTH AMERICA
GENERATING SCATTERED SHOWERS/ISOLATED THUNDERSTORMS S OF 13N TO
INLAND OVER COLOMBIA AND NW VENEZUELA BETWEEN 71W-76W.

ATLANTIC OCEAN...
THE CONCERN FOR THE ATLC IS IN THE VICINITY OF THE LEEWARD AND
VIRGIN ISLANDS THIS MORNING AS T.S. HANNA APPROACHES...SEE
SPECIAL FEATURES ABOVE. AN UPPER HIGH IS CENTERED NEAR 30N67W
WITH AN UPPER LOW TO THE S...N OF THE MONA PASSAGE NEAR 23N67W
WITH BOTH ENCOMPASSING THE W ATLC. THE UPPER LOW IS GENERATING
SCATTERED SHOWERS/ISOLATED THUNDERSTORMS WITHIN 90/120 NM OF
LINE FROM 23N68W TO 27N61W. A SURFACE TROUGH IS NE OF THE
BAHAMAS EXTENDING FROM 28N70W TO 23N75W GENERATING ISOLATED
SHOWERS  WITHIN 90 NM OF THE TROUGH AXIS. A SHARP UPPER TROUGH
IS IN THE CENTRAL ATLC EXTENDING ALONG 47W TO NEAR 21N INDUCING
AN UPPER RIDGE TO THE W FROM NEAR T.S. HANNA NNE TO BEYOND
32N55W. 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 50W ANCHORED BY A 1026 MB HIGH W OF THE AZORES.

$$
WALLACE






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