[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 250556
TWDAT

TROPICAL WEATHER DISCUSSION
NWS NATIONAL HURRICANE CENTER MIAMI FL
205 AM EDT SUN SEP 25 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
0445 UTC.

...SPECIAL FEATURES...

TROPICAL STORM OPHELIA IS CENTERED NEAR 18.3N 58.4W AT 25/0300
UTC OR ABOUT 270 NM E OF THE NORTHERN LEEWARD ISLANDS MOVING
W-NW AT 10 KT. ESTIMATED MINIMUM CENTRAL PRESSURE IS 1007 MB.
MAXIMUM SUSTAINED WIND SPEED IS 40 KT WITH GUSTS TO 50 KT.
PLEASE SEE LATEST NHC FORECAST/ADVISORY UNDER AWIPS/WMO HEADERS
MIATCMAT1/WTNT21 KNHC FOR MORE DETAILS. OPHELIA CONTINUES TO BE
SHEARED WITH THE DEEP CONVECTION WELL REMOVED FROM THE CENTER.
SCATTERED STRONG CONVECTION IS FROM 16N-19N BETWEEN 52W-55W WITH
SCATTERED MODERATE/ISOLATED STRONG CONVECTION FROM 17N-21N
BETWEEN 51W-57W.

TROPICAL STORM PHILIPPE IS CENTERED NEAR 11.6N 28.8W AT 25/0300
UTC OR ABOUT 320 NM SW OF THE SOUTHERNMOST CAPE VERDE ISLANDS
MOVING W-NW AT 11 KT. ESTIMATED MINIMUM CENTRAL PRESSURE IS 1006
MB. MAXIMUM SUSTAINED WIND SPEED IS 35 KT WITH GUSTS TO 45 KT.
PLEASE SEE LATEST NHC FORECAST/ADVISORY UNDER AWIPS/WMO HEADERS
MIATCMAT2/WTNT22 KNHC FOR MORE DETAILS. SCATTERED MODERATE/
ISOLATED STRONG CONVECTION IS FROM 9N-12N BETWEEN 28W-30W AND
FROM 10N-13N BETWEEN 31W-32W.

...TROPICAL WAVES...

TROPICAL WAVE IS ANALYZED ALONG 39W/40W BETWEEN 10N-19N MOVING W
NEAR 10 KT. WAVE IS TRAPPED BETWEEN TROPICAL STORMS OPHELIA AND
PHILIPPE RESULTING IN THE WAVE SLOWING DOWN. WAVE REMAINS WELL
DEFINED IN THE UPPER LEVEL SATELLITE WINDS WITH A WEAK SIGNATURE
IN THE LOW CLOUDS ON SATELLITE IMAGERY. NO ASSOCIATED SHOWERS/
CONVECTION.

...ITCZ/MONSOON TROUGH...

THE MONSOON TROUGH EXTENDS ACROSS AFRICA ENTERING THE E TROPICAL
ATLC NEAR 20N16W TO 17N19W. SCATTERED MODERATE/ISOLATED STRONG
CONVECTION IS WITHIN A 45 NM RADIUS OF 15N20.5W WITH CLUSTERS OF
SIMILAR CONVECTION WITHIN 120 NM ALONG THE COAST OF LIBERIA AND
SIERRA LEONE.

...DISCUSSION...

GULF OF MEXICO...
THE WEAKENING STATIONARY FRONT EXTENDS INTO THE GULF ACROSS THE
FLORIDA PANHANDLE JUST W OF TALLAHASSEE ALONG 30N88W TO 28N90W
SUPPORTED BY A BROAD UPPER TROUGH THAT COVERS E HALF OF THE US
TO THE EASTERN SEABOARD AND INTO THE GULF N OF 23N GIVING THE
GULF SE FLOW ALOFT. THE MOST OF N GULF IS DOMINATED BY STRONG
SUBSIDENCE AND DRY STABLE AIR THUS THE FRONT IS NOT PRODUCING
ANY SHOWERS. A SURFACE TROUGH EXTENDS ACROSS THE SE GULF FROM
26N85W TO 23N90W GENERATING SCATTERED SHOWERS/ISOLATED
THUNDERSTORMS SE OF A LINE FROM CEDAR KEY FLORIDA TO 24N91W. THE
REMAINDER OF THE GULF REMAINS UNDER REMARKABLY CLEAR SKIES AGAIN
TONIGHT. THE WEAKENING STATIONARY FRONT WILL GRADUALLY DISSIPATE
THROUGH SUN NIGHT. HIGH PRESSURE WILL BUILD IN THE WAKE OF THE
FRONT THROUGH TUE AND SHIFT N WED AND THU.

CARIBBEAN SEA...
AN UPPER LOW IS OVER THE NW CARIBBEAN CENTERED NEAR THE CAYMAN
ISLANDS GENERATING SCATTERED SHOWERS/ISOLATED THUNDERSTORMS N OF
LINE FROM JAMAICA TO THE NE TIP OF THE YUCATAN PENINSULA TO OVER
CUBA. AN UPPER RIDGE IS OVER THE SW CARIBBEAN EXTENDING FROM E
PANAMA TO NE NICARAGUA PROVIDING A DIFFLUENT ENVIRONMENT TO
GENERATE SCATTERED SHOWERS/ISOLATED THUNDERSTORMS FROM 12N-18N W
OF 81W TO OVER CENTRAL AMERICA AND IN THE GULF OF HONDURAS. AN
UPPER LOW LOCATED N OF THE DOMINICAN REPUBLIC EXTENDS S OVER THE
NE CARIBBEAN. THE MONSOON TROUGH EXTENDS ACROSS THE SW CARIBBEAN
FROM COLOMBIA NEAR 11N76W INTO THE E PACIFIC REGION ACROSS COSTA
RICA NEAR 10N84W GENERATING SCATTERED SHOWERS/ISOLATED
THUNDERSTORMS S OF 12N BETWEEN 72W-84W. THIS IS LEAVING THE
REMAINDER OF THE CARIBBEAN UNDER CLEAR SKIES AGAIN TONIGHT.
TROPICAL STORM OPHELIA WILL CONTINUE TO MOVE NE OF THE LEEWARD/
VIRGIN ISLANDS THROUGH MON NIGHT. A WEAK TROPICAL WAVE IS
EXPECTED TO ENTER THE THE E CARIBBEAN THU.

ATLANTIC OCEAN...
A NARROW UPPER RIDGE IS OVER THE FAR W ATLC FROM THE CENTRAL
BAHAMAS TO NEAR 31N76W PROVIDING A DIFFLUENT ENVIRONMENT ALOFT
WITH A SURFACE TROUGH EXTENDING FROM JUST W OF GRAND BAHAMA
ISLAND THROUGH A WEAK 1012 MB LOW NEAR 29N78W TO BEYOND 32N78W.
SCATTERED SHOWERS/ISOLATED THUNDERSTORMS ARE S OF 28N ACROSS THE
THE BAHAMA ISLANDS TO OVER CUBA BETWEEN 74W-80W WITH ISOLATED
SHOWERS COVERING THE AREA N OF 28N BETWEEN 75W-81W. A BROAD
UPPER RIDGE DOMINATES THE W ATLC ANCHORED JUST N OF BERMUDA
PROVIDING DRY STABLE AIR OVER THE AREA N OF 25N BETWEEN 50W-75W.
AN UPPER TROUGH EXTENDS FROM AN UPPER LOW IN THE SW ATLC N OF
THE DOMINICAN REPUBLIC NEAR 21N69W TO OVER THE E CARIBBEAN BUT
IS ONLY PRODUCING POSSIBLE ISOLATED SHOWERS. A BROAD SURFACE
RIDGE DOMINATES THE REMAINDER OF THE ATLC N OF 22N BETWEEN
37W-73W ANCHORED BY 1024 MB HIGH JUST NE OF BERMUDA. AN UPPER
TROUGH DIPS S OVER THE E ATLC N OF 24N BETWEEN 20W-45W
SUPPORTING A DISSIPATING COLD FRONT THAT ENTERS THE REGION NEAR
32N28W TO 29N35W GENERATING SCATTERED SHOWERS/ISOLATED
THUNDERSTORMS WITHIN 90 NM E OF THE FRONT. A WEAK SURFACE RIDGE
COVERS THE REMAINDER OF THE E ATLC ANCHORED BY A 1020 MB HIGH
NEAR MADEIRA ISLANDS. THE SURFACE TROUGH/LOW IN THE W ATLC WILL
SLOWLY LIFT N OF THE AREA THROUGH SUN. TROPICAL STORM OPHELIA
WILL TRACK NW THROUGH MON NIGHT THEN TURN MORE NORTHERLY THROUGH
THU EVENING. THE WEAK TROPICAL WAVE IS EXPECTED TO MOVE ACROSS
THE W TROPICAL ATLC REACHING THE E CARIBBEAN THU.

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

$$
PAW





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