[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 300557
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
205 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 0000 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
0345 UTC.

...SPECIAL FEATURES...
HURRICANE GUSTAV IS CENTERED NEAR 19.7N 80.7W AT 30/0600 UTC OR
OR ABOUT 43 NM NORTHEAST OF GRAND CAYMAN AND ABOUT 275 NM
EAST-SOUTHEAST OF THE WESTERN TIP OF CUBA MOVING NW AT 10 KT. AN
AIR FORCE RESERVE HURRICANE HUNTER PLANE RECENTLY REPORTED A
MINIMUM CENTRAL PRESSURE OF 971 MB. MAXIMUM SUSTAINED WIND SPEED
IS 75 KT WITH GUSTS TO 90 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.
GUSTAV REMAINS A CATEGORY ONE HURRICANE ON THE SAFFIR-SIMPSON
SCALE. GUSTAV RECENTLY HAS DEVELOPED A 25 NM WIDE EYE AS
REPORTED BY AIR FORCE RESERVE AND NOAA HURRICANE HUNTER
AIRCRAFT. WHILE GUSTAV HAS GOOD OUTFLOW IN ALL QUADRANTS...WATER
VAPOR IMAGERY SUGGESTS WESTERLY FLOW ASSOCIATED WITH THE GULF OF
MEXICO TROUGH UNDERCUTTING THE OUTFLOW. SCATTERED/NUMEROUS
STRONG CONVECTION IS WITHIN 75 NM IN THE NW QUADRANT WITH
SCATTERED MODERATE/STRONG CONVECTION COVERING THE REMAINDER OF
THE AREA FROM 18N-21N BETWEEN 77W-82W. OUTER RAINBANDS OF
SCATTERED SHOWERS/ISOLATED THUNDERSTORMS COVER THE AREA FROM
16N-22N BETWEEN 75W-85W INCLUDING JAMAICA AND PORTIONS OF CUBA.

TROPICAL STORM HANNA IS CENTERED NEAR 22.1N 65.3W AT 30/0300 UTC
OR ABOUT 226 NM NORTH OF SAN JUAN PUERTO RICO AND ABOUT 326 NM
EAST OF GRAND TURK ISLAND MOVING WNW AT 12 KT. ESTIMATED MINIMUM
CENTRAL PRESSURE IS 1002 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 WESTERLY SHEAR RESULTING IN A
PARTIALLY EXPOSED LOW LEVEL CENTER AND THE OUTFLOW TO THE E OF
THE CENTER. LARGE AREA OF SCATTERED/NUMEROUS STRONG CONVECTION
IS FROM 21N-23N BETWEEN 61W-64W WITH SCATTERED MODERATE/STRONG
CONVECTION COVERING THE REMAINDER OF THE AREA FROM 19N-24N
BETWEEN 60W-65W WHICH IS JUST NE OF THE LEEWARD ISLANDS.

TROPICAL WAVE IS ALONG 22W/23W S OF 19N WITH A 1008 MB SURFACE
LOW ALONG THE WAVE NEAR 14N MOVING W NEAR 15 KT. A BROAD MID
LEVEL CYCLONIC ROTATION IS OBSERVED ON SATELLITE IMAGERY
ASSOCIATED CONVECTION REMOVED FROM THE LOW. CLUSTERS OF
SCATTERED MODERATE/ISOLATED STRONG CONVECTION ARE WITHIN 90/120
NM OF LINE FROM 18N20W TO 14N26W. CONDITIONS APPEAR CONDUCIVE
FOR DEVELOPMENT AND THIS SYSTEM COULD BECOME A TROPICAL
DEPRESSION DURING THE NEXT COUPLE OF DAYS.

...TROPICAL WAVES...
TROPICAL WAVE IS ALONG 44W FROM 13N TO 22N WITH A 1011 MB LOW
ALONG THE WAVE AXIS NEAR 19N MOVING WNW NEAR 10 KT. HIGH
AMPLITUDE WAVE WITH A BROAD INVERTED-V SATELLITE IMAGERY
SIGNATURE OBSERVED WELL N OF THE ITCZ. CLUSTERS OF SCATTERED
MODERATE/ISOLATED STRONG CONVECTION ARE FROM 17N-24N BETWEEN
39W-47W.

TROPICAL WAVE IS ALONG 62W S OF 12N MOVING W NEAR 15-20 KT. THIS
WAVE IS INLAND OVER SOUTH AMERICA AND REMAINS ILL-DEFINED WHILE
LACKING ANY SHOWERS OR DEEP CONVECTION. THIS WAVE MAY BE DROPPED
FROM THE SURFACE ANALYSIS AT 0600 UTC BUT IT MAY BE NECESSARY TO
RE-INTRODUCED THE WAVE WHEN IT REACHES THE E PACIFIC REGION.

...THE ITCZ...
THE ITCZ AXIS IS ANALYZED ALONG 8N25W 12N40W 10N53W 11N60W. THE
ITCZ CONTINUES TO BE DISRUPTED BY THE TROPICAL WAVES. CLUSTERS
OF SCATTERED MODERATE/ISOLATED STRONG CONVECTION ARE FROM 5N-14N
BETWEEN 20W-39W.

...DISCUSSION...

GULF OF MEXICO...
BROAD UPPER TROUGH DOMINATES MOST OF THE GULF EXTENDING S ACROSS
THE FLORIDA NEAR PENSACOLA TO THE NE YUCATAN PENINSULA. UPPER
RIDGE OVER MEXICO EXTENDS ACROSS THE FAR W GULF W OF 94W 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 E OF 85W TO
OVER THE FLORIDA PENINSULA. MODERATE SUBSIDENCE/DRY AIR ARE
NOTED WITHIN 120 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. SCATTERED SHOWERS AND
POSSIBLE ISOLATED THUNDERSTORMS ARE OVER THE LEEWARD AND VIRGIN
ISLANDS ASSOCIATED WITH OUTER RAINBANDS OF T.S. HANNA. BROAD
UPPER HIGH ASSOCIATED WITH GUSTAV IS DOMINATING THE W CARIBBEAN.
SCATTERED SHOWERS/ISOLATED THUNDERSTORMS ARE OVER THE GULF OF
HONDURAS S OF 17N TO THE COAST OF HONDURAS BETWEEN 84W-87W AND
BETWEEN 10N-15N W OF 82W TO INLAND OVER N COSTA RICA AND
NICARAGUA. AN UPPER HIGH IS CENTERED OVER THE LEEWARD ISLANDS
EXTENDING A RIDGE OVER THE E CARIBBEAN TO 66W. MODERATE
SUBSIDENCE AND DRY AIR ARE OVER THE SE CARIBBEAN LIMITING
SHOWERS OVER THE AREA INCLUDING THE WINDWARD ISLANDS.

ATLANTIC OCEAN...
MAIN FOCUS FOR THE ATLC IS IN THE VICINITY NE OF THE LEEWARD/
VIRGIN ISLANDS AS T.S. HANNA CONTINUES TRACKING WNW...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 28N ACROSS THE
BAHAMAS AND CUBA W OF 74W TO OVER THE FLORIDA PENINSULA AND
THROUGH THE FLORIDA STRAITS. AN UPPER LOW IS N OF THE MONA
PASSAGE NEAR 23N68W WHICH IS GENERATING SCATTERED SHOWERS/
ISOLATED THUNDERSTORMS WITHIN 75/90 NM OF LINE FROM 30N65W TO
25N71W. THIS UPPER LOW IS RESPONSIBLE FOR THE UPPER LEVEL SHEAR
ASSOCIATED WITH T.S. HANNA. A SHARP UPPER TROUGH IS IN THE
CENTRAL ATLC EXTENDING THROUGH 32N47W SSE TO 19N44W INDUCING AN
UPPER RIDGE TO THE W FROM NEAR T.S. HANNA NNE TO BEYOND 32N55W.
ANOTHER UPPER TROUGH IS BEGINNING TO DIG S OVER THE NE ATLC N OF
27N FROM 20W-35W 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 THAT COVERS THE
REMAINDER OF THE E ATLC IS BEING SUPPRESSED TO S OF WITH THE
AXIS ALONG 20N TO 30W. AT THE SURFACE...A SURFACE RIDGE OF HIGH
PRESSURE REMAINS OVER MUCH OF THE ATLC N OF 25N E OF 60W
ANCHORED BY A PAIR 1025 MB HIGHS CENTERED N OF THE REGION AND N
OF 30N FROM 60W-75W WITH A 1018 MB HIGH N OF BERMUDA.

$$
WALLACE





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