[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 131758
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
205 PM EDT TUE SEP 13 2005

TROPICAL WEATHER DISCUSSION FOR NORTH AMERICA...CENTRAL
AMERICA...GULF OF MEXICO...CARIBBEAN SEA...NORTHEASTERN 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
1715 UTC.

...SPECIAL FEATURE...

TROPICAL STORM OPHELIA IS CENTERED NEAR 32.5N 78.0W...OR 110 NM
S OF WILMINGTON NORTH CAROLINA...AT 13/1800 UTC MOVING NNW 3 KT.
ESTIMATED MINIMUM CENTRAL PRESSURE IS 989 MB. MAXIMUM SUSTAINED
WIND SPEED IS 60 KT WITH GUSTS TO 75 KT. SEE LATEST NHC
FORECAST/ADVISORY UNDER AWIPS/WMO HEADERS MIATCMAT1/WTNT21 KNHC
AND THE PUBLIC ADVISORY UNDER HEADERS MIATCPAT1/WTNT31 KNHC FOR
MORE DETAILS. OPHELIA'S STRUCTURE HAS GREATLY IMPROVED SINCE
YESTERDAY AND IT APPEARS THAT THE STORM HAS FINALLY BEEN ABLE TO
ISOLATE ITSELF FROM THE DRY AIR LOCATED OVER THE SOUTHEAST
UNITED STATES. CONVECTIVE BANDS HAVE BEEN WRAPPING AROUND THE
STORM ALTHOUGH THE CLOUD SYSTEM CENTER REMAINS RAGGED WITH DRY
AIR TRAPPED IN THE MIDDLE. UPPER LEVEL OUTFLOW IS RELATIVELY
CIRCULAR BUT IS STRONGEST TO THE E OF THE STORM DUE TO A 35-40
KT NELY OUTFLOW JET. NUMEROUS MODERATE/STRONG CONVECTION IN
BANDS IS FROM 30N-34N BETWEEN 74W-80W. WSR-88D IMAGERY FROM
WILMINGTON AND CHARLESTON SHOWS A 60 NM WIDE BAND OF CONVECTION
ON THE NW SIDE OF OPHELIA THAT IS JUST BRUSHING THE COASTLINE
BETWEEN CAPE FEAR AND BULLS BAY SOUTH CAROLINA. THIS ACTIVITY
WILL CONTINUE TO SPREAD INLAND AS OPHELIA SLOWLY HEADS N TOWARDS
THE NORTH CAROLINA COAST.

...TROPICAL WAVES...

EAST ATLANTIC TROPICAL WAVE ALONG 34W S OF 17N MOVING W 10 KT.
THE WAVE IS STILL LOW LATITUDE BUT HAS BEGUN TO ACQUIRE A
STRONGER LOW-LEVEL CIRCULATION AS IT BECOMES MORE EMBEDDED IN
THE TRADE WIND FLOW REGIME. SCATTERED SHOWERS/TSTMS FROM 10N-15N
BETWEEN 33W-39W.

CENTRAL ATLANTIC TROPICAL WAVE TILTED ALONG 8N49W 15N48W 21N45W
MOVING W 10 KT. THE WAVE CONTINUES TO DISPLAY A WELL-DEFINED AND
SHARP CIRCULATION...BUT IT CONTINUES TO BE AFFECTED BY MODERATE
SWLY SHEAR THAT IS KEEPING ALL CONVECTION TO THE E. SCATTERED
SHOWERS/TSTMS ARE NEAR THE ITCZ FROM 11N-14N BETWEEN 40W-47W.

WEST CARIBBEAN TROPICAL WAVE ALONG 81W S OF 20N MOVING W 15 KT.
THE WAVE IS MOVED AHEAD MAINLY BASED ON CONTINUITY SINCE IT HAS
A RELATIVELY POOR SIGNATURE OVER THE CARIBBEAN. HOWEVER...THE
CURRENT POSITION MAY BE SLIGHTLY BEHIND BASED ON AN IMPROVING
CIRCULATION NOTED OVER AND JUST SW OF COSTA RICA. SCATTERED
MODERATE CONVECTION FROM 10N-13N BETWEEN 81W-86W.

TROPICAL WAVE ALONG 97W/98W HAS MOVED SW OF THE AREA BASED ON A
CIRCULATION NOTED S OF ACAPULCO.

...ITCZ...

ITCZ AXIS IS CENTERED ALONG 17N10W 9N20W 8N33W 13N46W...THEN
ALONG 10N76W 9N85W. WIDELY SCATTERED MODERATE CONVECTION FROM
5N-10N BETWEEN 14W-20W. WIDELY SCATTERED MODERATE WITHIN 75 NM
OF A LINE FROM 6N20W 3N28W 8N40W. SCATTERED MODERATE OVER THE SW
CARIBBEAN FROM 10N-13N BETWEEN 75W-80W.

...DISCUSSION...

GULF OF MEXICO...
TROPICAL STORM OPHELIA IS SLOWLY PULLING AWAY TOWARDS THE
CAROLINA COAST BUT STILL HAS A BROAD ENOUGH CIRCULATION TO PULL
DRIER CONTINENTAL AIR SWD OVER FLORIDA AND THE NE GULF. THE
DRIEST AIR EXTENDS FROM SW GEORGIA SE TO JUST N OF LAKE
OKEECHOBEE WHERE THE UPPER LEVEL SUBSIDENCE IS GREATEST. TO THE
W...AN UPPER LEVEL TROUGH/SHEAR AXIS STRETCHES FROM VERACRUZ
MEXICO TO SE LOUISIANA...AND IS PULLING SOME MOISTURE NWD OVER
THE E/CENTRAL GULF. ISOLATED SHOWERS ARE LOCATED OVER THE
CENTRAL GULF...AND A CLUSTER OF SCATTERED MODERATE HAS DEVELOPED
OVER THE BAY OF CAMPECHE FROM 19N-21.5N BETWEEN 93W-95W. THIS
PATTERN IS EXPECTED TO BE MAINTAINED FOR THE NEXT 48 HRS OR
SO...WITH A DRIER SURGE OF AIR MOVING IN FROM THE N BY THU.

CARIBBEAN...
THE UPPER LEVEL FLOW OVER THE CARIBBEAN IS DOMINATED BY A LARGE
UPPER LOW CENTERED JUST S OF JAMAICA NEAR 17N76W. THE DEEPEST
MOISTURE IS CURRENTLY LOCATED OVER THE SW CARIBBEAN WHERE
SEVERAL CLUSTERS OF TSTMS HAVE DEVELOPED FROM THE COAST OF
COLOMBIA TO COSTA RICA AND NICARAGUA. ELSEWHERE...THERE ARE SOME
PATCHES OF UPPER MOISTURE MOVING AROUND THE CIRCULATION
ASSOCIATED WITH THE UPPER LOW...BUT LOW-LEVEL CONDITIONS ARE
GENERALLY TOO DRY FOR WIDESPREAD CONVECTIVE ACTIVITY. ISOLATED
SHOWERS STRETCH FROM W CUBA ACROSS THE CAYMAN ISLANDS TO THE
GULF OF HONDURAS...AND ANOTHER PATCH OF SHOWERS (FROM CONVECTION
THAT FIRED ALONG AN OLD ATLANTIC FRONTAL BOUNDARY YESTERDAY) IS
DISSIPATING UP TO 300 NM W OF THE WINDWARD ISLANDS. A NARROW
SWATH OF DRY AIR WILL CONTINUE TO STRETCH E/W ACROSS THE
CARIBBEAN WATERS FOR THE NEXT SEVERAL DAYS...BUT A WEAK SURFACE
TROUGH MAY TRIGGER A FEW SHOWERS/TSTMS OVER THE NRN LEEWARD
ISLANDS AND GREATER ANTILLES STRETCHING INTO THE ATLC THROUGH
THE REST OF THE WEEK.

WEST ATLANTIC...
TROPICAL STORM OPHELIA IS SLOWLY MOVING N TOWARDS THE CAROLINA
COAST AND IS SHEDDING SEVERAL SURFACE TROUGHS TO ITS S AND SE.
ONE TROUGH LIES NEAR THE INTERSECTION WITH THE SUBTROPICAL RIDGE
ALONG 24N76W 31N72W WITH SCATTERED SHOWERS/TSTMS AND EMBEDDED
WIDELY SCATTERED MODERATE FROM 22N-32N BETWEEN 68W-73W. ANOTHER
TROUGH IS ASSOCIATED WITH A MORE WELL-DEFINED WIND SHIFT AND
EXTENDS FROM JUST OFF THE FLORIDA KEYS NE TO 28N75W. ISOLATED
TSTMS HAVE JUST BEGUN TO DEVELOP SPORADICALLY ALONG THIS
BOUNDARY. WEAK HIGH PRES EXTENDS E OF OPHELIA AND ITS TRAILING
TROUGHS BUT A DEEP MID-LATITUDE TROUGH DIGGING INTO THE CENTRAL
ATLC IS BREAKING THE RIDGE DOWN. A SURFACE TROUGH IS EXPECTED TO
DEVELOP NEAR PUERTO RICO OVER THE NEXT 24 HRS AND THEN MOVE NW
OVER THE BAHAMAS...WHICH COULD INCREASE THE CHANCE OF
SHOWERS/TSTMS OVER THE AREA THROUGH THE WEEKEND.

CENTRAL/EAST ATLANTIC...
AN UNSEASONABLY STRONG UPPER LEVEL TROUGH HAS DUG DOWN OVER THE
SUBTROPICAL WATERS N OF 22N BETWEEN 40W-70W BUT APPEARS
RELATIVELY STATIONARY AT THE MOMENT. THE TROUGH HAD BEEN PUSHING
A COLD FRONT THROUGH THE AREA BUT ITS HALTED AMPLIFICATION HAS
CAUSED THE FRONT TO BECOME STATIONARY ALONG 31N37W 27N45W
22N57W. SCATTERED MODERATE CONVECTION HAS DEVELOPED ALONG THE
TAIL END OF THE FRONT FROM 19N-23N BETWEEN 53W-58W...AND MORE
WIDELY SCATTERED SHOWERS/TSTMS ARE WITHIN 75 NM OF THE FRONT N
OF 23N. AN UPPER LEVEL LOW IS LOCATED NEAR 20N45W AT THE NRN END
OF THE CENTRAL ATLC TROPICAL WAVE AND IS BEING PULLED NWD AHEAD
OF THE UPPER TROUGH. AN UPPER HIGH HAS DEVELOPED DEEP IN THE
TROPICS NEAR 13N34W AND IS PROVIDING A FAIRLY DECENT ENVIRONMENT
ABOVE THE TROPICAL WAVE ALONG 34W. ELSEWHERE...AN UPPER TROUGH
LIES JUST OFF THE AFRICAN COAST ALONG 32N11W TO THE CANARY
ISLANDS TO 19N23W AND APPEARS TO BE INCREASING UPPER LEVEL
OUTFLOW FARTHER S OFF THE COAST OF GUINEA.

$$
BERG


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