[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 030601
TWDAT

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

...SPECIAL FEATURES...

TROPICAL STORM LEE IS CENTERED NEAR 28.5N 91.8W AT 03/0600 UTC
OR 150 NM WSW OF THE MOUTH OF THE MISSISSIPPI RIVER AND ABOUT 80
NM SSW OF MORGAN CITY LOUISIANA MOVING N AT 4 KT. ESTIMATED
MINIMUM CENTRAL PRESSURE IS 997 MB. MAXIMUM SUSTAINED WIND
SPEED IS 45 KT WITH GUSTS TO 55 KT. MOSAIC DOPPLER RADAR AND
LIGHTNING DATA INDICATE NUMEROUS MODERATE AND ISOLATED STRONG
CONVECTION IS FROM 27N TO 31N BETWEEN 88W AND 92W...MAINLY
LOCATED IN THE NE QUADRANT OF LEE...AND OVER INLAND PORTIONS OF
SE LOUISIANA...SOUTHERN MISSISSIPPI AND EXTREME SOUTHWESTERN
ALABAMA. ANOTHER CONVECTIVE BAND OF SCATTERED MODERATE
CONVECTION IS FROM 24N TO 28N BETWEEN 84W AND 88W. 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 18.5N 54.3W AT 03/0300 UTC OR
500 NM E OF THE NORTHERN LEEWARD ISLANDS MOVING NW AT 10 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 16N TO 23N BETWEEN 51W AND
56W. SEE LATEST NHC FORECAST/ADVISORY UNDER AWIPS/WMO HEADER
MIATCMAT2/WTNT22 KNHC FOR MORE DETAILS.

...TROPICAL WAVES...

TROPICAL WAVE IS ANALYZED FROM 18N30W TO A 1011 MB LOW ON THE
SOUTHERN EXTENT OF THE WAVE AND EMBEDDED WITHIN THE MONSOON
TROUGH NEAR 10N32W MOVING W-NW AT 15 KT. TOTAL PRECIPITABLE
WATER IMAGERY INDICATES MAXIMUM VALUES ALIGN ALONG THE WAVE AXIS
WITH ISOLATED MODERATE CONVECTION OCCURRING WITHIN 120 NM WEST
OF THE WAVE AXIS.

...ITCZ/MONSOON TROUGH...

THE MONSOON TROUGH EXTENDS FROM THE AFRICAN COAST NEAR 17N16W
ALONG 12N24W TO 07N37W TO 09N42W. THE MONSOON TROUGH THEN
RESUMES IN THE WESTERN CARIBBEAN SEA NEAR 13N76W TO 11N84W.
ISOLATED MODERATE CONVECTION IS FROM 06N TO 09N BETWEEN 22W AND
26W.

...DISCUSSION...

GULF OF MEXICO...
THE MAIN AREA OF INTEREST IN THE GULF IS TROPICAL STORM LEE AS
IT IS FORECAST TO CONTINUE SLOWLY MOVING NORTHWARD THROUGH THE
OVERNIGHT HOURS INTO MIDDAY SATURDAY. MOSAIC DOPPLER RADAR
ACROSS THE NORTH-CENTRAL GULF INDICATES NUMEROUS SHOWERS AND
SCATTERED TSTMS COVER A LARGE AREA N OF 27N BETWEEN 88W AND 92W.
THIS PRECIPITATION SPREADS INLAND ACROSS SE LOUISIANA...SOUTHERN
MISSISSIPPI...AND EXTREME SW ALABAMA. THE LATEST RAINFALL
FORECAST IS FOR 10 TO 15 INCHES OVER SOUTHERN LOUISIANA...
SOUTHERN MISSISSIPPI AND SOUTHERN ALABAMA THROUGH 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 THE OVERNIGHT HOURS INTO 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 AND
EXTREME SOUTHERN MISSISSIPPI AND ALABAMA THROUGH THE OVERNIGHT
HOURS. 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 EVENING. 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 70W WITH E-SE TRADES AT THE SURFACE IN
THE RANGE OF 10 TO 20 KT WHICH ARE EXPECTED TO PERSIST
THROUGHOUT 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 72W.
THIS TROUGHING IS SUPPORTING A WEAK 1009 MB LOW CENTERED NEAR
33N66W WITH A SURFACE TROUGH EXTENDING SW FROM THE LOW ALONG
30N69W TO 28N77W. ISOLATED SHOWERS ARE WITHIN 45 NM EITHER SIDE
OF THE SURFACE TROUGH...AND EAST OF THE BOUNDARY N OF 26N
BETWEEN 61W AND 66W. THE REMAINDER OF THE CENTRAL AND EASTERN
ATLC IS UNDER THE INFLUENCE OF A SURFACE RIDGE ANCHORED BY A
1027 MB HIGH CENTERED NEAR 33N40W.

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

$$
HUFFMAN



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