[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 292353
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
805 PM 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 1800 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
2315 UTC.

...SPECIAL FEATURES...
HURRICANE GUSTAV IS CENTERED NEAR 19.3N 80.0W AT 30/0000 UTC OR
ABOUT 20 NM SOUTH OF THE ISLANDS OF LITTLE CAYMAN AND CAYMAN
BRAC. THIS IS ALSO ABOUT 80 NM EAST OF GRAND CAYMAN AND ABOUT
315 NM EAST-SOUTHEAST OF THE WESTERN TIP OF CUBA MOVING NW AT 10
KT. ESTIMATED MINIMUM CENTRAL PRESSURE IS 975 MB. MAXIMUM
SUSTAINED WIND SPEED IS 70 KT WITH GUSTS TO 85 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. CONVECTIVE BANDS AND OUTFLOW FROM
GUSTAV REMAIN WELL-DEVELOPED IN ALL QUADRANTS AS THE STORM MOVES
UNDER AN UPPER RIDGE LOCATED OVER THE NW CARIBBEAN. SCATTERED
MODERATE TO STRONG CONVECTION IS WITHIN 175 NM OF THE CENTER
WITH AN OUTER BAND OF SCATTERED MODERATE/ISOLATED STRONG
CONVECTION MOVING ACROSS WRN CUBA.

TROPICAL STORM HANNA IS CENTERED NEAR 21.8N 63.8W AT 29/2100 UTC
OR ABOUT 240 NM NORTH-NORTHEAST OF SAN JUAN PUERTO RICO AND
ABOUT 405 NM EAST OF GRAND TURK ISLAND MOVING WNW AT 9 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 WEST-SOUTHWESTERLY SHEAR THUS
OUTFLOW FROM HANNA IS MAINLY LIMITED TO THE E AND S OF THE
CYCLONE. SCATTERED STRONG CONVECTION COVERS THE AREA FROM
17N-25N BETWEEN 60W-64W...INCLUDING THE NRN LEEWARD ISLANDS N OF
GUADELOUPE.

TROPICAL WAVE IS ALONG 21W/22W S OF 19N WITH A 1006 MB LOW
CENTER ALONG THE WAVE NEAR 14N MOVING W NEAR 10 KT. A BROAD
CYCLONIC ROTATION IS OBSERVED ON SATELLITE IMAGERY WITH
SCATTERED MODERATE/ISOLATED STRONG CONVECTION FROM 14N-18N
BETWEEN 18W-24W. SIMILAR CONVECTION...LIKELY EMBEDDED WITHIN THE
ITCZ IS FROM 9N-12N BETWEEN 21W-30W. CONDITIONS APPEAR FAVORABLE
FOR POSSIBLE DEVELOPMENT OF THIS SYSTEM DURING THE NEXT COUPLE
OF DAYS AS IT TRACKS WESTWARD.

...TROPICAL WAVES...
TROPICAL WAVE IS ALONG 44W FROM 14N TO 23N WITH A 1010 MB LOW
ALONG THE WAVE AXIS NEAR 19N MOVING WNW NEAR 15 KT. HIGH
AMPLITUDE WAVE WITH A BROAD INVERTED-V SATELLITE IMAGERY
SIGNATURE OBSERVED. SCATTERED MODERATE CONVECTION IS FROM
19N-25N BETWEEN 38W-43W.

TROPICAL WAVE IS ALONG 60W S OF 13N MOVING W NEAR 15-20 KT. THIS
ILL-DEFINED WAVE LACKS ANY SHOWERS OR DEEP CONVECTION.

...THE ITCZ...
THE ITCZ AXIS IS ANALYZED ALONG 11N23W 10N30W 13N41W 13N47W
10N58W. THE ITCZ HAS BEEN DISRUPTED BY THE TROPICAL WAVES WITH
CLUSTERS OF SCATTERED MODERATE CONVECTION FROM 6N-12N BETWEEN
19W-31W.

...DISCUSSION...

GULF OF MEXICO...
BROAD UPPER TROUGH DOMINATES MOST OF THE GULF EXTENDING FROM AN
UPPER LOW CENTERED NEAR 28N86W EXTENDING SOUTH TO OVER THE NRN
YUCATAN PENINSULA. UPPER RIDGE OVER MEXICO EXTENDS ACROSS THE
WRN GULF W OF 92W AND IS PROVIDING UPPER LEVEL DIFFLUENCE TO
GENERATE SCATTERED SHOWERS/ISOLATED TSTMS SW OF A LINE FROM
GALVESTON TEXAS TO CAMPECHE MEXICO. SIMILARLY SCATTERED SHOWERS
/TSTMS ARE WITHIN 60 NM OFFSHORE OF THE LOUISIANA AND EAST TEXAS
COAST. AN AREA OF UPPER DIFFLUENCE E OF THE TROUGH IS LOCATED
ACROSS THE SE GULF AND STRAITS OF FLORIDA GENERATING SCATTERED
SHOWERS/TSTMS E OF A LINE FROM THE YUCATAN CHANNEL TO THE BIG
BEND REGION OF FLORIDA. A VERY WEAK SURFACE RIDGE ENCOMPASSES
THE N GULF. MODERATE SUBSIDENCE/DRY AIR IS NOTED N OF 24N E OF
90W TO OVER THE FLORIDA PENINSULA SUPPRESSING ANY SHOWER ACTIVITY
ACROSS THE CENTRAL AND NE GULF.

CARIBBEAN SEA...
THE MAIN CONCERN CONTINUES TO BE HURRICANE GUSTAV FOR THE NW AND
NORTH CENTRAL CARIBBEAN ALONG WITH SCATTERED SHOWERS/TSTMS
ASSOCIATED WITH T.S. HANNA ACROSS THE LEEWARD ISLANDS...SEE
SPECIAL FEATURES ABOVE. THE BROAD UPPER HIGH ASSOCIATED WITH
GUSTAV IS DOMINATING MOST OF THE WRN CARIBBEAN. SCATTERED
SHOWERS/ISOLATED TSTMS ARE OVER THE GULF OF HONDURAS FROM
15N-17N BETWEEN 83W-89W. AN UPPER HIGH IS CENTERED OVER THE
LEEWARD ISLANDS EXTENDING A RIDGE ACROSS THE NE AND CENTRAL
CARIBBEAN TO 75W. MODERATE SUBSIDENCE AND DRY AIR IS NOTED E OF
75W WITH THE EXCEPTION OF THE CONVECTIVE ACTIVITY ASSOCIATED
WITH T.S. HANNA ACROSS THE LEEWARD ISLANDS.

ATLANTIC OCEAN...
MAIN FOCUS FOR THE ATLC IS IN THE VICINITY OF THE LEEWARD
ISLANDS AND NE OF PUERTO RICO AS T.S. HANNA CONTINUES TRACKING
WNW...SEE SPECIAL FEATURES ABOVE. AN UPPER HIGH IS CENTERED NEAR
30N63W WITH AN UPPER LOW TO THE S...N OF THE MONA PASSAGE NEAR
22N68W WITH BOTH ENCOMPASSING THE W ATLC. THE UPPER LOW IS
GENERATING SCATTERED SHOWERS/ISOLATED TSTMS FROM 24N-28N BETWEEN
67W-71W. AN AREA OF UPPER DIFFLUENCE ASSOCIATED WITH THE TROUGH
OVER THE ERN GULF OF MEXICO IS ACROSS THE BAHAMAS GENERATING
AN AREA OF SCATTERED SHOWERS/TSTMS FROM 25N-27N BETWEEN 75W-80W.
A SHARP UPPER TROUGH IS IN THE CENTRAL ATLC EXTENDING ALONG 45W
S TO NEAR 20N 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 22N TO 40W. AT THE SURFACE...A SURFACE RIDGE OF HIGH
PRESSURE REMAINS OVER THE ATLC N OF 25N E OF 50W ANCHORED BY A
PAIR 1025 MB HIGHS CENTERED NORTH OF THE REGION NEAR 35N35W AND
36N46W.

$$
HUFFMAN




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