[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 041147
TWDAT

TROPICAL WEATHER DISCUSSION
NWS NATIONAL HURRICANE CENTER MIAMI FL
805 AM EDT SUN SEP 04 2011

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 0600 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
1015 UTC.

...SPECIAL FEATURES...

TROPICAL STORM LEE IS CENTERED NEAR 29.7N 92.W AT 04/1200 UTC
OR 45 NM W OF MORGAN CITY LOUISIANA AND ABOUT 30 NM SW OF
LAFAYETTE LOUISIANA MOVING NE AT 3 KT. ESTIMATED MINIMUM
CENTRAL PRESSURE IS 986 MB. MAXIMUM SUSTAINED WIND SPEED IS 40
KT WITH GUSTS TO 50 KT. MOSAIC DOPPLER RADAR AND LIGHTNING DATA
INDICATES INCREASED SCATTERED MODERATE CONVECTION WITHIN 180 NM
OF THE SOUTHERN SEMICIRCLE OVER THE PAST 6 HOURS MOSTLY LOCATED
SOUTH OF THE LOUISIANA COASTLINE. EAST OF THE CENTER...THREE
MAIN CONVECTIVE BANDS ARE ACTIVE OVER THE MIDDLE AND NE GULF
WATERS...WHICH CONTINUE TO STREAM HEAVY PRECIPITATION INLAND
OVER SE ARKANSAS...MOST OF LOUISIANA AND MISSISSIPPI...CENTRAL
AND SOUTHERN ALABAMA...AND THE FLORIDA PANHANDLE. THE NUMEROUS
MODERATE AND ISOLATED STRONG CONVECTION OVER THE GULF WATERS IS
LOCATED FROM 26N TO 31N BETWEEN 83W AND 89W. SEE LATEST NHC
INTERMEDIATE PUBLIC ADVISORY UNDER AWIPS/WMO HEADERS MIATCPAT3/
WTNT33 KNHC AND THE FULL FORECAST/ADVISORY UNDER AWIPS/WMO
HEADER MIATCMAT3/WTNT23 KNHC FOR MORE DETAILS.

HURRICANE KATIA IS CENTERED NEAR 21.4N 58.6W AT 04/1100 UTC OR
320 NM NE OF THE NORTHERN LEEWARD ISLANDS MOVING NW AT 10 KT.
ESTIMATED MINIMUM CENTRAL PRESSURE IS 987 MB. MAXIMUM SUSTAINED
WIND SPEED IS 65 KT WITH GUSTS TO 80 KT. NUMEROUS MODERATE AND
ISOLATED STRONG CONVECTION REMAINS TIGHTLY CLUSTERED NEAR THE
CENTER FROM 19N TO 24N BETWEEN 56W AND 61W. SEE LATEST NHC
FORECAST/ADVISORY UNDER AWIPS/WMO HEADER MIATCMAT2/WTNT22 KNHC
FOR MORE DETAILS.

...TROPICAL WAVES...

TROPICAL WAVE IS ANALYZED FROM 09N22W TO 17N23W MOVING W AT
10-15 KT. EXAMINING RECENT UPPER AIR TIME SECTION ANALYSES FROM
DAKAR SENEGAL AND HOVMOLLER DIAGRAMS OF SATELLITE IMAGERY OVER
WESTERN AFRICA AND THE EASTERN TROPICAL ATLC FROM THE PAST FEW
DAYS...IT APPEARS THIS WAVE PASSED DAKAR BETWEEN 03/0600 UTC AND
03/1200 UTC ALOFT IN THE 800-900 MB RANGE. GLOBAL MODEL GUIDANCE
ALSO INDICATES THE CYCLONIC ATTRIBUTES ASSOCIATED WITH THE WAVE
ARE EXPECTED TO CONTINUE A WESTWARD MOTION AT LOW LATITUDE THE
NEXT FEW DAYS. SCATTERED MODERATE CONVECTION IS FROM 05N-10N
BETWEEN 22W-29W.

TROPICAL WAVE IS ANALYZED FROM 21N39W TO A 1012 MB LOW ON THE
SOUTHERN EXTENT OF THE WAVE AND EMBEDDED WITHIN THE MONSOON
TROUGH NEAR 13N37W MOVING W-NW AT 15-20 KT. TOTAL PRECIPITABLE
WATER IMAGERY INDICATES MAXIMUM VALUES ALIGN ALONG THE WAVE AXIS
WITH WIDELY SCATTERED MODERATE CONVECTION OCCURRING FROM 14N-17N
BETWEEN 33W-39W.

...ITCZ/MONSOON TROUGH...

THE MONSOON TROUGH EXTENDS FROM THE AFRICAN COAST NEAR 14N17W
ALONG 11N27W TO 13N37W TO 05N48W. THE INTERTROPICAL CONVERGENCE
ZONE AXIS EXTENDS FROM 05N48W TO 03N51W. ISOLATED MODERATE
CONVECTION IS FROM 05N-07N BETWEEN 11W-14W...AND FROM 05N-10N
BETWEEN 49W-53W.

...DISCUSSION...

GULF OF MEXICO...
THE MAIN AREA OF INTEREST IN THE GULF IS TROPICAL STORM LEE AS
IT IS FORECAST TO MOVE ONSHORE OF THE LOUISIANA COAST DURING THE
DAY SUNDAY AND CONTINUE ON A SLOW NORTHEASTWARD TRACK BY SUNDAY
EVENING. MOSAIC DOPPLER RADAR ACROSS THE NORTHERN GULF INDICATES
A BROAD AREA OF NUMEROUS SHOWERS AND SCATTERED TSTMS REMAINING
MAINLY N OF 26N. PLENTY OF LOW TO MID-LEVEL MOISTURE IS BEING
ADVECTED NORTHWARD ON THE EASTERN PERIPHERY OF LEE WHERE UPPER
LEVEL DIFFLUENCE IS MAXIMIZED. THIS PRECIPITATION SPREADS INLAND
THIS MORNING ACROSS SE ARKANSAS...MUCH OF LOUISIANA AND
MISSISSIPPI...CENTRAL AND SOUTHERN ALABAMA...AND THE FLORIDA
PANHANDLE. THE LATEST RAINFALL FORECAST IS FOR 10 TO 15 INCHES
FROM THE CENTRAL GULF NORTHWARD INTO THE TENNESSEE RIVER VALLEY
THROUGH LATE MONDAY WITH POSSIBLE ISOLATED MAXIMUM AMOUNTS OF 20
INCHES. THESE RAINS ARE EXPECTED TO CAUSE EXTENSIVE FLOODING AND
FLASH FLOODING. REFER TO FLOOD PRODUCTS AND HURRICANE LOCAL
STATEMENTS ISSUED BY LOCAL NWS FORECAST OFFICES FOR MORE
DETAILED INFORMATION ON THESE THREATS.

CARIBBEAN SEA...
MOSTLY NORTHERLY UPPER LEVEL FLOW IS IMPACTING THE WESTERN
CARIBBEAN AS AN UPPER LEVEL RIDGE AXIS IS POSITIONED OVER THE
EASTERN GULF OF MEXICO ALONG 84W. UPPER LEVEL DIVERGENCE IS
AIDING IN SUSTAINING CONVECTION ASSOCIATED WITH TROPICAL STORM
LEE OVER THE EASTERN GULF...HOWEVER THE NORTHERLY FLOW IS
PROVIDING FOR RATHER SUBDUED CONDITIONS OVER MUCH OF THE
CARIBBEAN. MIDDLE TO UPPER LEVEL CONVECTIVE DEBRIS MOISTURE W OF
76W AND A FEW ISOLATED SHOWERS AND TSTMS N OF 14N BETWEEN 75W
AND 84W ARE NOTED ON SATELLITE IMAGERY. OTHERWISE LIGHT E-SE
TRADES WERE NOTED ON AN EARLIER ASCAT PASS AROUND 04/0202 UTC
WHICH ARE EXPECTED TO PERSIST ACROSS MUCH OF THE BASIN THROUGH
THE REMAINDER OF THE WEEKEND.

ATLANTIC OCEAN...
THE MAIN IMPACT IN THE ATLANTIC OCEAN IS HURRICANE KATIA AS
DESCRIBED IN THE SPECIAL FEATURES SECTION ABOVE. WATER VAPOR
IMAGERY INDICATES A FAIRLY ELONGATED MIDDLE TO UPPER LEVEL LOW
CENTERED NEAR 34N71W WITH AXIS DIPPING SOUTHWARD TO 23N ALONG
72W. THIS TROUGHING IS SUPPORTING A WEAK SURFACE TROUGH
EXTENDING S-SW INTO THE DISCUSSION AREA ALONG 32N70W TO THE NW
BAHAMAS NEAR 26N78W. ISOLATED SHOWERS AND TSTMS ARE OCCURRING
WITHIN 180 NM EITHER SIDE OF A LINE FROM 32N66W TO 22N77W. THE
REMAINDER OF THE CENTRAL AND EASTERN ATLC IS UNDER THE INFLUENCE
OF A SURFACE RIDGE ANCHORED BY A 1024 MB HIGH CENTERED NEAR
33N45W.

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

$$
HUFFMAN



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