[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 031158
TWDAT

TROPICAL WEATHER DISCUSSION
NWS NATIONAL HURRICANE CENTER MIAMI FL
805 AM EDT SAT SEP 03 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 29.4N 92.0W AT 03/1200 UTC
OR 13 NM SSE OF INTRACOASTAL CITY LOUISIANA AND ABOUT 39 NM S OF
NEW IBERIA LOUISIANA MOVING N-NW AT 6 KT. ESTIMATED MINIMUM
CENTRAL PRESSURE IS 995 MB. MAXIMUM SUSTAINED WIND SPEED IS 50
KT WITH GUSTS TO 60 KT. MOSAIC DOPPLER RADAR AND LIGHTNING DATA
INDICATE TWO MAIN BANDS OF NUMEROUS MODERATE AND ISOLATED STRONG
CONVECTION ON THE EASTERN SEMI-CIRCLE OF THE STORM BETWEEN
84W-92W N OF 24N TO INLAND OVER SE LOUISIANA...SOUTHERN
MISSISSIPPI...EXTREME SOUTHWESTERN ALABAMA...AND THE FAR WESTERN
FLORIDA PANHANDLE. 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 19.3N 55.1W AT 03/0900 UTC OR
460 NM E OF THE NORTHERN LEEWARD ISLANDS MOVING NW AT 9 KT.
ESTIMATED MINIMUM CENTRAL PRESSURE IS 988 MB. MAXIMUM SUSTAINED
WIND SPEED IS 65 KT WITH GUSTS TO 80 KT. SCATTERED MODERATE AND
ISOLATED STRONG CONVECTION IS FROM 18N TO 23N BETWEEN 51W AND
57W. SEE LATEST NHC FORECAST/ADVISORY UNDER AWIPS/WMO HEADER
MIATCMAT2/WTNT22 KNHC FOR MORE DETAILS.

...TROPICAL WAVES...

TROPICAL WAVE IS ANALYZED FROM 21N31W TO A 1010 MB LOW ON THE
SOUTHERN EXTENT OF THE WAVE AND EMBEDDED WITHIN THE MONSOON
TROUGH NEAR 11N33W 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 18N16W
ALONG 11N18W TO 11N32W TO 05N43W. THE INTERTROPICAL CONVERGENCE
ZONE AXIS EXTENDS FROM 05N43W TO 04N51W. ISOLATED MODERATE
CONVECTION IS FROM 10N TO 13N BETWEEN 17W AND 21W.

...DISCUSSION...

GULF OF MEXICO...
THE MAIN AREA OF INTEREST IN THE GULF IS TROPICAL STORM LEE AS
IT IS FORECAST TO CONTINUE SLOWLY MOVING NORTH-NORTHWESTWARD
THIS MORNING INTO THE LATTER PART OF SATURDAY. MOSAIC DOPPLER
RADAR ACROSS THE NORTH-CENTRAL GULF INDICATES NUMEROUS SHOWERS
AND SCATTERED TSTMS COVER A LARGE AREA N OF 28N BETWEEN 85W AND
93W. THIS PRECIPITATION SPREADS INLAND ACROSS SE LOUISIANA...
SOUTHERN MISSISSIPPI...EXTREME SW ALABAMA...AND THE FAR WESTERN
FLORIDA PANHANDLE. THE LATEST RAINFALL FORECAST IS FOR 10 TO 15
INCHES OVER SOUTHERN LOUISIANA...SOUTHERN MISSISSIPPI AND
SOUTHERN ALABAMA THROUGH LATE SUNDAY WITH POSSIBLE ISOLATED
MAXIMUM AMOUNTS OF 20 INCHES. THESE RAINS ARE EXPECTED TO CAUSE
EXTENSIVE FLOODING. TROPICAL STORM FORCE WINDS ARE EXPECTED TO
REACH LAND IN THE TROPICAL STORM WARNING AREA THROUGH SATURDAY
EVENING. A STORM SURGE OF 2 TO 5 FT ABOVE GROUND LEVEL IS
EXPECTED ALONG THE NORTHERN GULF COAST IN AREAS OF ONSHORE
FLOW...AND DANGEROUS RIP CURRENTS ARE ALSO LIKELY ALONG THE
NORTHERN GULF COAST. ISOLATED TORNADOES ARE POSSIBLE OVER
PORTIONS OF SOUTHERN LOUISIANA...SOUTHERN MISSISSIPPI AND
ALABAMA....AND THE FAR WESTERN FLORIDA PANHANDLE THROUGH THE DAY
SATURDAY. 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 CENTRAL AND
WESTERN CARIBBEAN AS AN UPPER LEVEL ANTICYCLONE IS POSITIONED
OVER THE SOUTH-CENTRAL GULF OF MEXICO THIS MORNING. UPPER LEVEL
DIVERGENCE IS AIDING IN SUSTAINING CONVECTION ASSOCIATED WITH
TROPICAL STORM LEE...HOWEVER THE NORTHERLY FLOW IS PROVIDING FOR
RATHER SUBDUED CONDITIONS OVER MUCH OF THE CARIBBEAN. MIDDLE TO
UPPER LEVEL CONVECTIVE DEBRIS MOISTURE AND CLOUDINESS ARE NOTED
ON SATELLITE IMAGERY W OF 74W WITH E-SE TRADES AT THE SURFACE IN
THE RANGE OF 10 TO 20 KT WHICH ARE EXPECTED TO PERSIST THROUGH
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 AMPLIFIED MIDDLE TO UPPER LEVEL
TROUGH IS LOCATED OVER THE SW NORTH ATLC WITH AXIS ALONG 71W.
THIS TROUGHING IS SUPPORTING A WEAK 1010 MB LOW CENTERED NEAR
34N68W WITH A SURFACE TROUGH EXTENDING S THEN SW FROM THE LOW
ALONG 31N68W TO 28N76W. ISOLATED SHOWERS ARE WITHIN 45 NM EITHER
SIDE OF THE SURFACE TROUGH...AND E-SE OF THE BOUNDARY N OF 25N
BETWEEN 61W AND 69W. THE REMAINDER OF THE CENTRAL AND EASTERN
ATLC IS UNDER THE INFLUENCE OF A SURFACE RIDGE ANCHORED BY A
1025 MB HIGH CENTERED NEAR 33N42W.

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

$$
HUFFMAN




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