[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 031755
TWDAT

TROPICAL WEATHER DISCUSSION
NWS NATIONAL HURRICANE CENTER MIAMI FL
205 PM 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 1200 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
1745 UTC.

...SPECIAL FEATURES...

TROPICAL STORM LEE IS NEARLY STATIONARY CENTERED NEAR 29.3N
91.8W AT 03/1800 UTC OR ABOUT 39 NM SW OF MORGAN CITY LOUISIANA
AND ABOUT 56 NM S OF LAFAYETTE LOUISIANA. ESTIMATED MINIMUM
CENTRAL PRESSURE IS 991 MB. MAXIMUM SUSTAINED WIND SPEED IS 50
KT WITH GUSTS TO 60 KT. DOPPLER RADAR AND LIGHTNING DATA
INDICATE A BROAD BAND OF NUMEROUS MODERATE AND ISOLATED STRONG
CONVECTION FOCUSED ON THE EASTERN SEMI-CIRCLE OF THE STORM
BETWEEN 83W-92W N OF 23N TO INLAND OVER SE LOUISIANA...SOUTHERN
MISSISSIPPI...EXTREME SOUTHWESTERN ALABAMA...AND THE FAR WESTERN
FLORIDA PANHANDLE. SIMILAR CONVECTION IS AROUND THE LOW LEVEL
CIRCULATION AFFECTING THE EASTERN COASTAL WATERS OF TEXAS INTO
THE WESTERN LOUISIANA COAST E OF 94W. 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-FORCE WINDS EXTEND OUTWARD UP TO 230 MILES FROM
THE CENTER. A STORM SURGE WILL RAISE WATER LEVELS BY AS MUCH AS
3 TO 5 FEET ABOVE GROUND LEVEL ALONG THE LOUISIANA COAST...AND
BY AS MUCH AS 2 TO 4 FEET ABOVE GROUND LEVEL ALONG THE
MISSISSIPPI AND ALABAMA COASTS INCLUDING MOBILE BAY.

HURRICANE KATIA IS CENTERED NEAR 19.6N 55.8W AT 03/1500 UTC OR
ABOUT 485 MI...785 KM ENE OF THE NORTHERN LEEWARD ISLANDS MOVING
NW AT 9 KT. ESTIMATED MINIMUM CENTRAL PRESSURE IS 989 MB.
MAXIMUM SUSTAINED WIND SPEED IS 65 KT WITH GUSTS TO 80 KT. SEE
LATEST NHC FORECAST/ADVISORY UNDER AWIPS/WMO HEADER
MIATCMAT2/WTNT22 KNHC FOR MORE DETAILS. SCATTERED MODERATE AND
ISOLATED STRONG CONVECTION IS FROM 17N TO 23N BETWEEN 52W-59W.
HURRICANE-FORCE WINDS EXTEND OUTWARD UP TO 35 MILES...55
KM...FROM THE CENTER...AND TROPICAL-STORM-FORCE WINDS EXTEND
OUTWARD UP TO 175 MILES...280 KM. A GENERAL NW MOTION IS
EXPECTED TO CONTINUE THROUGH MONDAY WITH KATIA REMAINING WELL
NORTH OF THE LEEWARD ISLANDS. HOWEVER...WELLS GENERATED BY KATIA
ARE AFFECTING THE LESSER ANTILLES AND COULD BEGIN TO AFFECT
BERMUDA BY TONIGHT OR SUNDAY. THESE SWELLS ARE LIKELY TO CAUSE
LIFE-THREATENING SURF AND RIP CURRENT CONDITIONS.


...TROPICAL WAVE...

TROPICAL WAVE IS ANALYZED FROM 21N33W TO A 1010 MB LOW ON THE
SOUTHERN EXTENT OF THE WAVE NEAR 11N33W MOVING W-NW 10-15 KT.
THIS SYSTEM IN EMBEDDED IN A SURGE OF DEEP MOISTURE NOTICED ON
WATER VAPOR IMAGERY. HOWEVER...AN UPPER LEVEL ANTI-CYCLONIC
CIRCULATION IS TO THE NW OF THIS FEATURE PROVIDING MID-UPPER
LEVEL SUBSIDENCE AND THEREFORE THE CONVECTION IS LIMITED TO A
FEW ISOLATED SHOWERS AND THUNDERSTORMS IN THE VICINITY OF THE
WAVE AXIS N OF 13N.

...ITCZ/MONSOON TROUGH...

THE MONSOON TROUGH EXTENDS INLAND ACROSS WEST AFRICA...ENTERING
THE ATLC OCEAN THROUGH THE COAST OF SENEGAL NEAR 14N17W ALONG
11N20W TO 12N24W. THE BROAD CYCLONIC WIND FIELD ASSOCIATED TO
THE TROPICAL WAVE HAS BECOME MORE APPARENT OVER THE PAST 6
HOURS. ALSO...SURFACE RIDGING AXIS OVER THE FAR E ATLC WAS ABLE
TO CUT THROUGH THE MONSOON TROUGH. THESE TWO FEATURES MADE THE
OCEANIC MONSOON TROUGH TO BREAK AND WEAKEN. THEREFORE...THE
MONSOON TROUGH AXIS PREVIOUSLY ANALYZED ALONG THE SOUTHERN
EXTENSION OF THE TROPICAL WAVE HAS BEEN REMOVED. THE BROAD
CYCLONIC FIELD ONLY ALLOWS FOR A SMALL PORTION OF THE ITCZ TO
DEVELOP FROM 6N40W TO 5N50W. SCATTERED MODERATE CONVECTION IS
FROM 8N TO 12N BETWEEN 17W AND 24W. ISOLATED MODERATE
CONVECTION IS WITHIN 90 NM ON EITHER SIDE OF THE ITCZ.

...DISCUSSION...

GULF OF MEXICO...
THE MAIN AREA OF INTEREST IN THE GULF IS TROPICAL STORM LEE
IMPACTING THE WATERS ALONG NORTHERN GULF COAST STATES BETWEEN
83W-94W. FOR MORE INFORMATION PLEASE SEE SPECIAL FEATURES ABOVE.

CARIBBEAN SEA...
MOSTLY FAIR WEATHER CONDITIONS ARE NOTED ACROSS THE CARIBBEAN
THIS AFTERNOON ON VISIBLE SATELLITE IMAGERY...ESPECIALLY ACROSS
THE EASTERN BASIN E OF 70W...WHERE WATER VAPOR IMAGERY SHOWS THE
GREATEST MID-UPPER LEVEL DRYNESS. OBSERVATIONS ACROSS THE BASIN
SHOW 10-15 KT EASTERLY TRADES WITH A FEW ISOLATED LOW TOP
SHOWERS E OF 77W. THIS FLOW TURNS SOUTHERLY W OF 77W IN RESPONSE
TO THE BROAD LOWER PRESSURE FIELD ASSOCIATED TO TROPICAL STORM
LEE. SCATTERED SHOWERS AND ISOLATED THUNDERSTORMS ARE DEVELOPING
ALONG THE COASTAL WATERS OF COSTA RICA AND NICARAGUA WITHIN
50-120 NM...IN CLOSE PROXIMITY TO THE MONSOON TROUGH INLAND OVER
CENTRAL AMERICA.

ATLANTIC OCEAN...
THE MAIN AREA OF INTEREST IN THE ATLANTIC OCEAN IS HURRICANE
KATIA DESCRIBED IN THE SPECIAL FEATURES SECTION ABOVE. WATER
VAPOR IMAGERY INDICATES A MID-UPPER LEVEL TROUGH/LOW LOCATED
OVER THE SW NORTH ATLC. THIS FEATURE IS SUPPORTING A WEAK
SURFACE TROUGH EXTENDING SW ALONG 31N68W TO 27N76W. ISOLATED
SHOWERS ARE WITHIN 25 NM EITHER SIDE OF THE SURFACE TROUGH.
SCATTERED SHOWERS AND ISOLATED THUNDERSTORMS ARE TO THE ESE OF
THIS SURFACE TROUGH N OF 25N BETWEEN 60W-69W. THIS IS DUE TO LOW
LEVEL MOISTURE CONVERGENCE AND MID/UPPER LEVEL LIFT ASSOCIATED
TO THE UPPER TROUGH. THE REMAINDER OF THE CENTRAL AND EASTERN
ATLC IS UNDER THE INFLUENCE OF A BROAD SURFACE RIDGE...ANCHORED
BY A 1025 MB HIGH CENTERED NEAR 33N41W.

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

$$

GARCIA




This weather bulletin was brought to you by:
www.nashvilleweather.net