[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 041751
TWDAT

TROPICAL WEATHER DISCUSSION
NWS NATIONAL HURRICANE CENTER MIAMI FL
205 PM EDT TUE SEP 04 2012

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...WEATHER OBSERVATIONS...RADAR...AND
METEOROLOGICAL ANALYSIS.

BASED ON 1200 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
1745 UTC.

...SPECIAL FEATURES...

TROPICAL STORM LESLIE WAS CENTERED NEAR 25.0N 62.5W AT 04/1500
UTC. THIS LOCATION WAS ABOUT 525 MI...840 KM SSE OF BERMUDA.
LESLIE IS MOVING N AT 3 KT WITH AN ESTIMATED MINIMUM CENTRAL
PRESSURE IS 994 MB...AND MAXIMUM SUSTAINED WIND SPEEDS OF 55 KT
GUSTING TO 65 KT. NUMEROUS MODERATE TO STRONG CONVECTION IS FROM
20N-29N BETWEEN 56W-63W. SEE LATEST NHC FORECAST/ADVISORY UNDER
AWIPS/WMO HEADERS MIATCMAT2 /WTNT22 KNHC FOR MORE DETAILS.

TROPICAL DEPRESSION THIRTEEN WAS UPGRADED TO TROPICAL STORM
MICHAEL AT 04/1500 UTC...LOCATED NEAR 27.0N 43.5W...ABOUT 1220
MI...1965 KM SW OF THE AZORES. MICHAEL IS MOVING NNW AT 4 KT.
THE ESTIMATED MINIMUM CENTRAL PRESSURE IS 1006 MB WITH MAXIMUM
SUSTAINED WIND SPEEDS OF 35 KT GUSTING TO 45 KT. PUBLIC
ADVISORIES ON TROPICAL STORM MICHAEL ARE ISSUED UNDER WMO HEADER
WTNT33 KNHC AND UNDER AWIPS HEADER MIATCPAT3. THE FORECAST/
ADVISORIES ARE ISSUED UNDER WMO HEADER WTNT23 KNHC AND UNDER
AWIPS HEADER MIATCMAT3. MICHAEL IS GENERATING SCATTERED MODERATE
TO ISOLATED STRONG CONVECTION FROM 26N-29N BETWEEN 41W-45W.

...TROPICAL WAVES...

THE TROPICAL WAVE MOVING ACROSS THE CENTRAL TROPICAL ATLC
CONTINUES TO BE DIFFICULT TO PIN DOWN. AS OF 04/1200 UTC...THE
WAVE AXIS IS ANALYZED FROM 20N38W TO 12N39W. HOWEVER...MODEL
GUIDANCE AND LIMITED OBSERVATIONS NEAR THIS SYSTEM INDICATED NO
CYCLONIC CURVATURE NEAR THE WAVE AXIS...NOR AT 700 MB LEVEL...
WHERE CYCLONIC CURVATURE SHOULD BE BEST PRONOUNCED. THERE IS
MORE CYCLONIC CURVATURE AROUND THE MONSOON TROUGH IT IS LIKELY
THAT THIS WAVE BECAME EMBEDDED IN THE MONSOONAL GYRE SEVERAL
DAYS AGO.

...ITCZ/MONSOON TROUGH...

THE MONSOON TROUGH EXTENDS FROM THE WEST AFRICAN COAST OF
SENEGAL NEAR 16N16W CONTINUING WSW ALONG 16N23W 12N33W TO
11N43W...WHERE THE ITCZ AXIS CONTINUES TO NEAR 11N66W. SCATTERED
MODERATE TO ISOLATED STRONG CONVECTION IS WITHIN 150-170 NM ON
EITHER SIDE OF THE MONSOON TROUGH E OF 45W.

...DISCUSSION...

GULF OF MEXICO...
DRY AIR ALOFT IS NOTED ACROSS THE UPPER LEVELS OF THE GULF
BASIN. THIS UPPER LEVEL ENVIRONMENT IS SUPPORTIVE OF FAIR
WEATHER CONDITIONS ACROSS MOST OF THE GULF BASIN AND A SURFACE
RIDGE ANCHORED BY A 1017 MB HIGH CENTERED OVER THE NE GULF NEAR
27N87W PROVIDING LIGHT TO GENTLE ANTICYCLONIC FLOW ACROSS THE
AREA. DESPITE THE LOCATION OF THE SURFACE HIGH CENTER...
SCATTERED SHOWERS AND THUNDERSTORMS ARE DEPICTED ON DOPPLER
RADAR IMAGERY...IMPACTING THE COASTAL WATERS NEAR THE FLORIDA
PANHANDLE AND ALABAMA N OF 28N E OF 89W. THE ACTIVITY IS
ASSOCIATED TO AN UPPER LEVEL SHORTWAVE TRACKING S ACROSS THE SE
CONUS. MODEL GUIDANCE SUGGEST THIS UPPER FEATURE WILL GENERATE A
SURFACE LOW PRESSURE SYSTEM WITHIN THE CONVECTIVE REGION...
KEEPING THE RAIN SHOWERS ACTIVITY OVER THE NE AND N-CENTRAL
WATERS OF THE GULF OVER THE NEXT 24 HOURS. OTHERWISE...AN UPPER
LOW LOCATED IN THE WRN ATLC SPINNING JUST SEVERAL MILES OFF THE
SE FLORIDA PENINSULA WILL DRIFT WEST BRING A SLIGHT CHANCE FOR
SCATTERED SHOWERS AND ISOLATED THUNDERSTORMS ACROSS THE STRAITS
OF FLORIDA AND FAR ERN GULF DURING THE NEXT 24 HOURS. FAIR
WEATHER WILL REMAIN ELSEWHERE ACROSS THE REMAINDER OF THE BASIN
DURING THE FORECAST PERIOD.

CARIBBEAN SEA...
WATER VAPOR IMAGERY CONTINUES TO SHOW DRY AIR ALOFT ACROSS MOST
OF THE CARIBBEAN BASIN THIS AFTERNOON...ASSOCIATED TO AN UPPER
LEVEL RIDGE OF HIGH PRESSURE CENTERED OVER HISPANIOLA. MIDDLE TO
UPPER LEVEL MOISTURE INCREASES OVER THE FAR SW BASIN...S OF 14N
W OF 76W. SCATTERED SHOWERS AND TSTMS ARE OCCURRING WITHIN THIS
REGION...IN CLOSE PROXIMITY WITH THE ERN PACIFIC MONSOON TROUGH
ANALYZED ACROSS SRN NICARAGUA TO TO NRN COLOMBIA. THE SURFACE
FLOW OVER THE FAR ENE CARIBBEAN CONTINUES UNDER THE INFLUENCE OF
THE LARGE CYCLONIC WIND FIELD ASSOCIATED TO TROPICAL STORM
LESLIE...LOCATED NNE OF THE NORTHERN LEEWARD ISLANDS. OTHERWISE
...GENTLE TO MODERATE EASTERLY TRADE WIND FLOW IS ELSEWHERE
ACROSS THE DISCUSSION AREA...INCREASING TO 25 KT OVER THE
COASTAL WATERS OF NRN COLOMBIA. GLOBAL MODELS SUGGEST THE
CONVECTION OVER THE SW BASIN CONTINUING DURING THE NEXT 24-36
HOURS...WITH NO OTHER CHANGES ELSEWHERE ACROSS THE DISCUSSION
AREA.

ATLANTIC OCEAN...
WATER VAPOR IMAGERY CONTINUES TO SHOW AN UPPER LOW WOBBLING IN
THE WRN ATLC BETWEEN THE NW BAHAMAS AND THE SE FLORIDA PENINSULA
AROUND 26N79W. SURFACE CONVERGENCE AND MIDDLE TO UPPER LIFTING
GENERATED BY THE UPPER LOW IS PRODUCING AN AREA OF SCATTERED
SHOWERS AND ISOLATED THUNDERSTORMS FROM 24N-28N BETWEEN 77W-81W
INCLUDING INLAND PORTIONS OF THE NW BAHAMAS AND THE FLORIDA
PENINSULA. THIS AREA OF SHOWERS IS EXPECTED TO LINGER DURING THE
NEXT 24 HOURS...BEFORE THE UPPER LOW BEGINS TO LIFT N LATER THIS
EVENING. FARTHER EAST... THE LOW LEVEL CENTER OF TROPICAL STORM
LESLIE BECAME EXPOSED TRACKING NORTHWARD. SEE SPECIAL FEATURES
SECTION ABOVE FOR MORE DETAILS. THE NEXT SYSTEM IS NEWLY
UPGRADED TROPICAL STORM MICHAEL TO THE WELL TO THE E OF LESLIE
...ALSO DESCRIBED IN THE SAME SECTION ABOVE. THIS LEAVES THE
REMAINDER OF THE ATLC BASIN UNDER FAIR WEATHER CONDITIONS...
PROVIDED BY A BROAD UPPER LEVEL RIDGE OF HIGH PRESSURE CENTERED
NEAR 22N25W..COMBINED WITH DRY SAHARAN DUST ALOFT NOTED ON
METEOSAT-9 IMAGERY.

FOR ADDITIONAL INFORMATION PLEASE VISIT
HTTP://WWW.HURRICANES.GOV/MARINE

$$

GARCIA




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