[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 040553
TWDAT

TROPICAL WEATHER DISCUSSION
NWS NATIONAL HURRICANE CENTER MIAMI FL
205 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 0000 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
0515 UTC.

...SPECIAL FEATURES...

TROPICAL STORM LEE IS CENTERED NEAR 29.5N 92.6W AT 04/0600 UTC
OR 75 NM W OF MORGAN CITY LOUISIANA AND ABOUT 50 NM SW OF
LAFAYETTE LOUISIANA MOVING N AT 2 KT. ESTIMATED MINIMUM CENTRAL
PRESSURE IS 987 MB. MAXIMUM SUSTAINED WIND SPEED IS 40 KT WITH
GUSTS TO 50 KT. MOSAIC DOPPLER RADAR AND LIGHTNING DATA INDICATE
VERY LITTLE DEEP CONVECTION IS NEAR THE CENTER OF LEE WITH
NUMEROUS SHOWERS AND ISOLATED TSTMS FROM 29N TO 31N BETWEEN 92W
AND 95W. FARTHER EAST OF THE CENTER...TWO MAIN CONVECTIVE BANDS
ARE ACTIVE OVER THE NE GULF WATERS...WHICH CONTINUE TO STREAM
HEAVY PRECIPITATION INLAND OVER SOUTHERN MISSISSIPPI...SW
ALABAMA...AND THE WESTERN FLORIDA PANHANDLE. THE NUMEROUS
MODERATE AND ISOLATED STRONG CONVECTION OVER THE GULF WATERS IS
LOCATED FROM 25N TO 31N BETWEEN 84W 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.

TROPICAL STORM KATIA IS CENTERED NEAR 20.3N 57.4W AT 04/0300 UTC
OR 350 NM E-NE OF THE NORTHERN LEEWARD ISLANDS MOVING NW AT 9
KT. ESTIMATED MINIMUM CENTRAL PRESSURE IS 992 MB. MAXIMUM
SUSTAINED WIND SPEED IS 60 KT WITH GUSTS TO 75 KT. SCATTERED
MODERATE AND ISOLATED STRONG CONVECTION REMAINS TIGHTLY
CLUSTERED NEAR THE CENTER FROM 18N TO 24N BETWEEN 55W AND 60W.
SEE LATEST NHC FORECAST/ADVISORY UNDER AWIPS/WMO HEADER
MIATCMAT2/WTNT22 KNHC FOR MORE DETAILS.

...TROPICAL WAVES...

TROPICAL WAVE IS ANALYZED FROM 21N34W TO A 1012 MB LOW ON THE
SOUTHERN EXTENT OF THE WAVE AND EMBEDDED WITHIN THE MONSOON
TROUGH NEAR 12N36W MOVING W-NW AT 15 KT. TOTAL PRECIPITABLE
WATER IMAGERY INDICATES MAXIMUM VALUES ALIGN ALONG THE WAVE
AXIS...HOWEVER THE WAVE LACKS ANY SIGNIFICANT DEEP CONVECTION.

...ITCZ/MONSOON TROUGH...

THE MONSOON TROUGH EXTENDS FROM THE AFRICAN COAST NEAR 17N16W
ALONG 09N20W TO 12N36W TO 07N41W. THE INTERTROPICAL CONVERGENCE
ZONE AXIS EXTENDS FROM 07N41W TO 06N46W. ISOLATED MODERATE
CONVECTION IS FROM 05N TO 12N BETWEEN 20W AND 27W. SIMILAR
CONVECTION IS FROM 06N TO 10N BETWEEN 45W AND 52W.

...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
OVERNIGHT HOURS AND CONTINUE A SLOW NORTHWESTWARD TRACK DURING
THE DAY SUNDAY. MOSAIC DOPPLER RADAR ACROSS THE NORTH-CENTRAL
GULF INDICATES NUMEROUS SHOWERS AND SCATTERED TSTMS COVER A
BROAD AREA EAST OF THE CIRCULATION CENTER ACROSS THE NE GULF N
OF 25N BETWEEN 83W AND 90W. THIS PRECIPITATION SPREADS INLAND
ACROSS MUCH OF LOUISIANA...SOUTHERN AND CENTRAL MISSISSIPPI...
SOUTHWESTERN ALABAMA...AND THE WESTERN FLORIDA PANHANDLE. THE
LATEST RAINFALL FORECAST IS FOR 10 TO 15 INCHES FROM THE CENTRAL
GULF NORTHWARD INTO THE TENNESSEE RIVER VALLEY THROUGH 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 85W. 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 N OF 15N BETWEEN 76W AND 83W 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 THROUGH THE REMAINDER OF THE WEEKEND.

ATLANTIC OCEAN...
THE MAIN IMPACT IN THE ATLANTIC OCEAN IS TROPICAL STORM KATIA AS
DESCRIBED IN THE SPECIAL FEATURES SECTION ABOVE. WATER VAPOR
IMAGERY INDICATES A FAIRLY ELONGATED MIDDLE TO UPPER LEVEL LOW
CENTERED NEAR 33N71W WITH AXIS DIPPING SOUTHWARD TO 24N ALONG
71W. THIS TROUGHING IS SUPPORTING A WEAK 1014 MB LOW CENTERED
NEAR 33N71W WITH A SURFACE TROUGH EXTENDING S THEN SW FROM THE
LOW ALONG 30N70W TO 27N76W. ISOLATED SHOWERS AND TSTMS ARE
OCCURRING WITHIN 60 NM EITHER SIDE OF THE SURFACE TROUGH...AND
S-SE OF THE BOUNDARY WITHIN 120 NM OF A LINE FROM 32N64W TO THE
CENTRAL BAHAMAS NEAR 24N80W. THE REMAINDER OF THE CENTRAL AND
EASTERN ATLC IS UNDER THE INFLUENCE OF A SURFACE RIDGE ANCHORED
BY A 1025 MB HIGH CENTERED NEAR 34N43W.

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

$$
HUFFMAN



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