[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 301203
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
805 AM EDT SAT AUG 30 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...
HURRICANE GUSTAV IS CENTERED NEAR 20.8N 81.6W AT 30/1200 UTC OR
OR ABOUT 75 NM SOUTHEAST OF THE ISLE OF YOUTH CUBA MOVING N-NW
AT 10 KT. THE CENTRAL PRESSURE IS DOWN TO 965 MB...A DROP OF
ABOUT 24 MB IN 24 HOURS. MAXIMUM SUSTAINED WIND SPEED IS 100 KT
WITH HIGHER GUSTS. 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. DATA FROM AN
AIR FORCE RECONNAISSANCE AIRCRAFT INDICATE THAT GUSTAV CONTINUES
TO RAPIDLY STRENGTHEN AND NOW IS A DANGEROUS CATEGORY THREE
HURRICANE ON THE SAFFIR-SIMPSON HURRICANE SCALE...THE SECOND
MAJOR HURRICANE OF THE 2008 ATLANTIC HURRICANE SEASON. FURTHER
STRENGTHENING IS POSSIBLE IN THE SOUTHERN GULF OF MEXICO.
OUTFLOW REMAINS GOOD IN ALL QUADRANTS. SCATTERED/NUMEROUS STRONG
CONVECTION IS WITHIN 60 NM IN THE NE QUADRANT AND WITHIN 90 NM
OF THE CENTER ELSEWHERE. SCATTERED MODERATE/STRONG CONVECTION
COVERS THE REMAINDER OF THE AREA FROM 18N-22N BETWEEN
78.5N-83.5W. OUTER RAINBANDS OF SCATTERED SHOWERS/ISOLATED
THUNDERSTORMS COVER THE AREA FROM 17N-23N BETWEEN 77W-84W
INCLUDING W JAMAICA AND PORTIONS OF CUBA.

TROPICAL STORM HANNA IS CENTERED NEAR 21.9N 66.3W AT 30/0900 UTC
OR ABOUT 210 NM NORTH OF SAN JUAN PUERTO RICO AND ABOUT 270 NM
EAST OF GRAND TURK ISLAND MOVING W AT 10 KT. ESTIMATED MINIMUM
CENTRAL PRESSURE IS 1001 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 CONTINUES TO EXPERIENCE SW SHEAR RESULTING IN A PARTIALLY
EXPOSED LOW LEVEL CENTER AND THE OUTFLOW TO THE N AND E OF THE
CENTER. SCATTERED/NUMEROUS STRONG CONVECTION IS WITHIN 45 NM OF
LINE FROM 20N63W TO 23N64W WITH SCATTERED MODERATE/ISOLATED
STRONG CONVECTION COVERING THE REMAINDER OF THE AREA FROM
18N-25N BETWEEN 60W-66W.

TROPICAL WAVE IS ALONG 23W S OF 20N WITH A 1005 MB SURFACE LOW
ALONG THE WAVE NEAR 14.5N MOVING W 10-15 KT. A BROAD MID LEVEL
CYCLONIC ROTATION IS OBSERVED ON SATELLITE IMAGERY ASSOCIATED
CONVECTION MOSTLY REMOVED FROM THE LOW. SCATTERED STRONG
CONVECTION IS WITHIN 30 NM EITHER SIDE OF THE N PORTION OF THE
WAVE BETWEEN 17N-19N. CLUSTERS OF SCATTERED MODERATE/ISOLATED
STRONG CONVECTION COVER THE REMAINDER OF THE AREA WITHIN 90 NM
OF LINE FROM 18N21W TO 14N27W AND SMALL CLUSTERS WITHIN45 NM OF
THE LOW CENTER. CONDITIONS APPEAR CONDUCIVE FOR DEVELOPMENT AND
THIS SYSTEM COULD BECOME A TROPICAL DEPRESSION DURING THE NEXT
COUPLE OF DAYS.

...TROPICAL WAVES...
TROPICAL WAVE IS FROM 25N43W THROUGH A 1009 MB LOW NEAR 19N44.5W
TO 16N45W MOVING WNW NEAR 10 KT. BROAD INVERTED-V SATELLITE
IMAGERY CURVATURE IS OBSERVED WELL N OF THE ITCZ. CLUSTERS OF
SCATTERED MODERATE/ISOLATED STRONG CONVECTION ARE FROM 18N-25N
BETWEEN 42W-45W.

TROPICAL WAVE THAT WAS ALONG 62W HAS BEEN DROPPED FROM THE
ANALYSIS. IT MAY BE NECESSARY TO RE-INTRODUCED THE WAVE WHEN IT
REACHES THE E PACIFIC REGION.

...THE ITCZ...
THE ITCZ AXIS IS ANALYZED ALONG 16N16W 11N25W 9N32W 11N45W
10N51W 11N61W. THE ITCZ CONTINUES TO BE DISRUPTED BY THE
TROPICAL WAVE IN THE SPECIAL FEATURES. CLUSTERS OF SCATTERED
MODERATE/ISOLATED STRONG CONVECTION ARE FROM 6N-12N BETWEEN
20W-40W WITH CLUSTERS OF SCATTERED MODERATE CONVECTION WITHIN
150 NM OF THE SW COAST OF AFRICA BETWEEN 5N-10N.

...DISCUSSION...

GULF OF MEXICO...
HURRICANE GUSTAV IS BECOMING A CONCERN FOR THE SE GULF AND THE
FLORIDA STRAITS AS IT CONTINUES ON ITS NW TRACK ACROSS THE NW
CARIBBEAN...SEE SPECIAL FEATURES ABOVE. BROAD UPPER TROUGH
DOMINATES MOST OF THE GULF EXTENDING S INTO THE GULF NEAR MOBILE
ALABAMA TO THE NE YUCATAN PENINSULA. UPPER RIDGE OVER MEXICO
EXTENDS ACROSS THE FAR W GULF W OF 90W AND IS PROVIDING UPPER
LEVEL DIFFLUENCE TO GENERATE CLUSTERS OF SCATTERED SHOWERS/
ISOLATED THUNDERSTORMS OVER THE W GULF W OF 90W. THE UPPER RIDGE
ASSOCIATED WITH HURRICANE GUSTAV IS PROVIDING UPPER LEVEL
DIFFLUENCE E OF THE UPPER TROUGH TO GENERATE SCATTERED SHOWERS/
ISOLATED THUNDERSTORMS S OF 28N E OF 87W TO OVER THE FLORIDA
PENINSULA AND THROUGH THE FLORIDA STRAITS. MODERATE SUBSIDENCE
AND DRY AIR ARE NOTED WITHIN 90 NM OF THE UPPER TROUGH AXIS N OF
24N.

CARIBBEAN SEA...
THE MAIN CONCERN CONTINUES TO BE HURRICANE GUSTAV FOR THE NW
CARIBBEAN...SEE SPECIAL FEATURES ABOVE. ISOLATED SHOWERS AND
POSSIBLE ISOLATED THUNDERSTORMS REMAIN OVER THE N LEEWARD
ISLANDS AND THE VIRGIN ISLANDS ASSOCIATED WITH OUTER RAINBANDS
OF T.S. HANNA. BROAD UPPER HIGH ASSOCIATED WITH GUSTAV IS
DOMINATING THE CARIBBEAN W OF 70W. SCATTERED SHOWERS/ISOLATED
THUNDERSTORMS ARE OVER THE W CARIBBEAN N OF 13N W OF 77W. AN
UPPER HIGH IS CENTERED JUST E OF GUADELOUPE IN THE LEEWARD
ISLANDS EXTENDING A RIDGE OVER THE E CARIBBEAN TO 70W. MODERATE
SUBSIDENCE AND DRY AIR ARE OVER THE E CARIBBEAN LIMITING SHOWERS
OVER THE AREA INCLUDING THE WINDWARD ISLANDS WITH THE EXCEPTION
OF THE ACTIVITY ASSOCIATED T.S. HANNA OVER THE LEEWARD/VIRGIN
ISLANDS.

ATLANTIC OCEAN...
MAIN FOCUS FOR THE ATLC IS OVER THE SW ATLC IN ASSOCIATION WITH
HURRICANE GUSTAV AND IN THE VICINITY NE OF THE LEEWARD/VIRGIN
ISLANDS WITH T.S. HANNA...SEE SPECIAL FEATURES ABOVE. THE UPPER
HIGH ASSOCIATED WITH HURRICANE GUSTAV IN THE CARIBBEAN EXTENDS
ACROSS CUBA AND THE BAHAMAS OVER THE FAR W ATLC PROVIDING UPPER
LEVEL DIFFLUENCE TO GENERATE SCATTERED SHOWERS/ISOLATED
THUNDERSTORMS S OF 29N W OF 76W ACROSS THE N BAHAMA ISLANDS AND
CUBA TO OVER THE FLORIDA PENINSULA AND THROUGH THE FLORIDA
STRAITS. AN UPPER LOW REMAINS N OF THE MONA PASSAGE NEAR 23N68W
AND IS RESPONSIBLE FOR THE UPPER LEVEL SHEAR ASSOCIATED WITH
T.S. HANNA. A SHARP UPPER TROUGH IS IN THE CENTRAL ATLC
EXTENDING THROUGH 32N49W SSE TO 19N45W. ANOTHER UPPER TROUGH
CONTINUES TO DIG S OVER THE NE ATLC N OF 26N FROM 19W-32W
INDUCING AND AMPLIFYING AN UPPER RIDGE TO THE W WHICH IS
ENHANCING THE ACTIVITY ASSOCIATED WITH THE TROPICAL WAVE IN THE
CENTRAL ATLC. THE E/W UPPER RIDGE IS BEGINNING TO BREAKDOWN OVER
THE E ATLC AND APPEARS TO BECOMING ASSOCIATED WITH THE TROPICAL
WAVE IN THE SPECIAL FEATURES. ALSO AT THE SURFACE...A SURFACE
RIDGE OF HIGH PRESSURE REMAINS OVER MUCH OF THE ATLC N OF 26N E
OF 58W AND N OF 28N E OF 75W ANCHORED BY A SERIES OF HIGHS N OF
THE REGION.

$$
WALLACE






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