[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 311800
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
205 PM EDT SUN AUG 31 2008

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...METEOROLOGICAL ANALYSIS...WEATHER OBSERVATIONS...AND
RADAR.

BASED ON 1200 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
1715 UTC.

...SPECIAL FEATURES...
HURRICANE GUSTAV IS CENTERED NEAR 25.9N 86.6W AT 31/1800 UTC OR
ABOUT 235 NM...520 KM...SOUTHEAST OF THE MOUTH OF THE
MISSISSIPPI RIVER MOVING NW OR 320 DEG AT 15 KT. THIS GENERAL
MOTION IS EXPECTED TO CONTINUE WITH A DECREASE IN FORWARD SPEED
DURING THE NEXT COUPLE OF DAYS. ON THE FORECAST TRACK...GUSTAV
SHOULD MAKE LANDFALL ON THE NORTHERN GULF COAST ON MONDAY. THE
MINIMUM CENTRAL PRESSURE JUST REPORTED BY A NOAA HURRICANE
HUNTER AIRCRAFT IS 962 MB. MAXIMUM SUSTAINED WIND SPEED IS 100
KT WITH HIGHER GUSTS. PLEASE SEE THE LATEST NHC FORECAST/
ADVISORY UNDER AWIPS/WMO HEADERS MIATCMAT2/ WTNT22 KNHC AND/OR
THE PUBLIC ADVISORY MIATCPAT2/ WTNT32 KNHC FOR MORE DETAILS.
GUSTAV IS AN EXTREMELY DANGEROUS CATEGORY THREE HURRICANE ON THE
SAFFIR-SIMPSON HURRICANE SCALE...AND COULD REGAIN CATEGORY FOUR
STRENGTH LATER TODAY OR TONIGHT. FLUCTUATIONS IN STRENGTH ARE
LIKELY THEREAFTER...BUT GUSTAV IS FORECAST TO REMAIN A MAJOR
HURRICANE UNTIL LANDFALL. GUSTAV IS EXPECTED TO PRODUCE TOTAL
RAINFALL ACCUMULATIONS OF 6 TO 12 INCHES OVER PORTION OF
LOUISIANA...SOUTHERN MISSISSIPPI AND SOUTHERN ARKANSAS...WITH
ISOLATED MAXIMUM AMOUNTS OF UP TO 20 INCHES POSSIBLE THROUGH
WEDNESDAY MORNING. ADDITIONAL RAINFALL AMOUNTS OF ABOUT AN INCH
ARE POSSIBLE OVER FLORIDA KEYS AND SOUTH FLORIDA.

TROPICAL STORM HANNA IS CENTERED NEAR 23.5N 71.1W AT 31/1800 UTC
OR ABOUT 120 NM...240 KM...NORTH OF GRAND TURK ISLAND MOVING
WEST AT 10 KT. ESTIMATED MINIMUM CENTRAL PRESSURE IS 997 MB.
HANNA HAS WEAKENED A BIT MORE. MAXIMUM SUSTAINED WIND SPEED IS
NOW 40 KT WITH HIGHER GUSTS. PLEASE SEE THE LATEST NHC
FORECAST/ADVISORY UNDER AWIPS/WMO HEADERS MIATCMAT3/WTNT23 KNHC
AND/OR THE PUBLIC ADVISORY MIATCPAT3/ WTNT33 KNHC FOR MORE
DETAILS. A BAND OF MODERATE TO STRONG CONVECTION ASSOCIATED WITH
HANNA IS APPROACHING THE SE BAHAMAS. LONG-PERIOD SWELLS FROM
THIS TROPICAL CYCLONE ARE EXPECTED TO INCREASE THE RISK OF
DANGEROUS RIP CURRENTS ALONG PORTIONS OF THE SOUTHEASTERN UNITED
STATES COAST DURING THE NEXT COUPLE OF DAYS.

A TROPICAL WAVE IS ALONG 31W/32W S OF 21N WITH A 1010 MB SURFACE
LOW ALONG THE WAVE AXIS NEAR 16N. AN EARLIER QSCAT PASS CLEARLY
SHOWED THE CYCLONIC CIRCULATION ASSOCIATED WITH THIS SYSTEM WITH
THE STRONGEST WINDS ON THE N SEMICIRCLE. SHOWER AND TSTMS
ACTIVITY HAS INCREASED WITH A CLUSTER OF MODERATE CONVECTION
COVERING THE AREA FROM 18N-20N BETWEEN 31.5W-34W. CONDITIONS
APPEAR TO BE CONDUCIVE FOR DEVELOPMENT AND A TROPICAL DEPRESSION
COULD FORM DURING THE NEXT DAY OR TWO AS THIS SYSTEM MOVES
WESTWARD AT 10 TO 15 KT.

...TROPICAL WAVES...
TROPICAL WAVE IS ALONG 49W/50W S OF 25N MOVING WNW NEAR 10 KT. A
1010 MB LOW IS EMBEDDED ON THE WAVE AXIS NEAR 20.5N50W WHERE AN
EXPOSED SWIRL OF LOW CLOUDS IS NOTED ON VIS SATELLITE IMAGERY.
A LARGE AREA OF CLOUDINESS WITH EMBEDDED SHOWERS EXTENDS FROM
21N-31N BETWEEN 43W-50W. UPPER-LEVEL WINDS ARE FORECAST TO
REMAIN UNFAVORABLE FOR DEVELOPMENT DURING THE NEXT COUPLE OF
DAYS.

...THE ITCZ...
THE ITCZ AXIS IS ANALYZED ALONG 11N15W 13N27W 10N34W 11N50W
10N62W. SCATTERED MODERATE/ISOLATED STRONG CONVECTION IS MOVING
OFF THE AFRICAN COAST FROM 9N-13N EAST OF 19W. SCATTERED
MODERATE CONVECTION IS WITHIN 100 NM SE OF LINE 14N27W 10N35W
9N40W.

...DISCUSSION...

GULF OF MEXICO...
ALL THE ATTENTION REMAINS FOCUSED ON GUSTAV THAT IS FORECAST TO
MAKE LANDFALL ALONG THE LOUISIANA COAST THIS MONDAY AS A MAJOR
HURRICANE. SEE SPECIAL FEATURES FOR DETAILS. WEATHER CONDITIONS
WILL GRADUALLY DETERIORATE ALONG THE NORTHERN GULF COAST BUT
MAINLY FROM CAMERON LOUISIANA EWD TO THE ALABAMA-FLORIDA BORDER
WHERE A HURRICANE WARNING REMAINS IN EFFECT. PREPARATIONS TO
PROTECT LIFE AND PROPERTY SHOULD BE RUSHED TO COMPLETION.
RAIN...WINDS AND WAVES WILL BE ON INCREASE. CURRENTLY NOAA
BUOY...42003...LOCATED IN THE EASTERN GULF IS REPORTING
SUSTAINED WINDS OF 50 KT AND WAVE HEIGHTS OF 34 FEET WHILE PRES
HAS FALLEN TO 992 MB. OUTER RAINBANDS ASSOCIATED WITH THE
OVERALL CIRCULATION OF GUSTAV WILL CONTINUE TO AFFECT THE STATE
OF FLORIDA WITH THE THREAT OF ISOLATED TORNADOES. ISOLATED
SHOWERS ARE SEEN ACROSS THE WESTERN HALF OF THE GULF UNDER A
N-NW WIND FLOW. A MID-UPPER LEVEL RIDGE ANCHORED ON A HIGH OVER
THE NW BAHAMAS IS STEERING GUSTAV NWWD. THE RIDGE COVERS THE SE
CONUS...THE WESTERN ATLC WEST OF 70W...CUBA...THE EASTERN GULF
AND THE FLORIDA PENINSULA. AN-UPPER-LEVEL LOW IS TO THE WEST OF
GUSTAV OVER THE WESTERN GULF NEAR 24N92W PRODUCING MODERATE TO
STRONG SUBSIDENCE.

CARIBBEAN SEA...
GUSTAV AS A POWERFUL AND DESTRUCTIVE CATEGORY FOUR HURRICANE
WITH SUSTAINED WINDS OF 150 MPH...240 KM/H MOVED YESTERDAY
ACROSS WESTERN CUBA DURING THE AFTERNOON AND EVENING HOURS. THIS
AFTERNOON IT CONTINUES TO MOVE AWAY FROM CUBA BUT A FEW NARROW
RAINBANDS ARE STILL AFFECTING THE ISLAND. SEE SPECIAL FEATURES
ABOVE. ELSEWHERE...SCATTERED SHOWERS REMAIN OVER THE NRN LEEWARD
ISLANDS AND THE VIRGIN ISLANDS ASSOCIATED WITH OUTER RAINBANDS
OF T.S. HANNA. IN THE UPPER LEVELS...MOSTLY EASTERLY FLOW IS
NOTED OVER THE CARIBBEAN MOSTLY DUE TO OUTFLOW FROM GUSTAV AND
HANNA. UPPER LEVEL MOISTURE/HIGH CLOUDS ARE OVER THE CENTRAL
CARIBBEAN .

ATLANTIC OCEAN...
T.S. HANNA AND THE TROPICAL WAVES ARE THE MAIN FEATURES IN THE
TROPICAL ATLANTIC. WV IMAGERY INDICATED THAT THE UPPER-LEVEL LOW
THAT HAS BEEN LIMITING THE INTENSIFICATION OF HANNA OVER THE
PAST FEW DAYS HAS BEGUN TO DROP SOUTHWARD TOWARD HISPANIOLA...
WHICH MAY ALLOW HANNA TO TRANSITION BACK INTO A FULL WARM CORE
TROPICAL CYCLONE LATER TODAY. AN AREA OF SCATTERED MODERATE
CONVECTION HAS DEVELOPED EAST OF THE LEEWARD ISLANDS LIKELY DUE
TO UPPER DIFFLUENCE RELATED TO AN UPPER-LEVEL HIGH LOCATED JUST
N OF PUERTO RICO. AN UPPER-LEVEL TROUGH IS TO THE EAST EXTENDING
FROM AN UPPER-LEVEL LOW SITUATED NEAR 27N50W...AND IS PRODUCING
STRONG SLY WINDS OVER THE TROPICAL WAVE/LOW LOCATED ALONG
49W/50W. AN UPPER LEVEL HIGH IS OVER THE E ATLANTIC NEAR
22N35W.`

$$
GR





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