[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 211752
TWDAT

TROPICAL WEATHER DISCUSSION
NWS NATIONAL HURRICANE CENTER MIAMI FL
205 PM EDT WED SEP 21 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 1715 UTC.

...SPECIAL FEATURES...

THE CENTER OF TROPICAL STORM OPHELIA AT 21/1500 UTC IS NEAR
13.0N 43.6W...OR ABOUT 1050 NM TO THE EAST OF THE EASTERN
CARIBBEAN SEA ISLANDS. OPHELIA IS MOVING WEST 14 KT. THE MAXIMUM
SUSTAINED WIND SPEEDS ARE 50 KT WITH GUSTS TO 60 KT. THE
ESTIMATED MINIMUM CENTRAL PRESSURE IS 1005 MB. PUBLIC ADVISORIES
ABOUT OPHELIA ARE ISSUED UNDER WMO HEADER WTNT31 KNHC AND UNDER
AWIPS HEADER MIATCPAT1. FORECAST/ADVISORIES ABOUT OPHELIA ARE
ISSUED UNDER WMO HEADER WTNT21 KNHC AND UNDER AWIPS HEADER
MIATCMAT1. NUMEROUS STRONG CONVECTIVE PRECIPITATION IS FROM 12N
TO 14N BETWEEN 41W AND 43W. THIS PRECIPITATION RANGES FROM 90 NM
TO 120 NM AWAY FROM THE SYSTEM CENTER IN THE EASTERN SEMICIRCLE.
AN UPPER LEVEL TROUGH PASSES THROUGH 33N28W TO 29N34W 25N42W AND
26N51W. UPPER LEVEL CYCLONIC FLOW THAT IS MOVING AROUND THE
TROUGH REACHES 19N46W...STILL ABOUT 385 NM TO THE NORTH-NORTHWEST
OF OPHELIA.

...TROPICAL WAVES...

A TROPICAL WAVE IS ALONG 19N21W...ACROSS THE CAPE VERDE
ISLANDS...TO 9N27W. ISOLATED MODERATE RAINSHOWERS TO POSSIBLE
THUNDERSTORMS ARE FROM 4N TO 13N BETWEEN 22W AND 36W. SOME OF
THIS PRECIPITATION ALSO IS RELATED TO THE MONSOON TROUGH.

...THE MONSOON TROUGH/THE ITCZ...

THE MONSOON TROUGH REACHES THE AFRICAN COAST NEAR 19N16W TO
18N17W. IT CONTINUES EVENTUALLY FROM 10N25W TO 9N28W AND 12N36W.
ISOLATED MODERATE RAINSHOWERS TO POSSIBLE THUNDERSTORMS ARE
FROM 4N TO 13N BETWEEN 22W AND 36W...AND FROM 6N TO 12N
BETWEEN 40W AND 52W.

...DISCUSSION...

THE GULF OF MEXICO...
THE SURFACE PRESSURE GRADIENT IS BROAD AND FLAT. A SURFACE
TROUGH IS ALONG 83W/84W FROM 16N TO 24N. THIS TROUGH HAS BEEN
MOVING WESTWARD FOR THE LAST FEW DAYS. AN UPPER LEVEL TROUGH
PASSES THROUGH CENTRAL TEXAS INTO CENTRAL MEXICO. THIS TROUGH
MAY BE THE TROUGH THAT WAS SUPPORTING A TEXAS GULF COASTAL
PLAINS COLD FRONT 24 HOURS AGO. THAT FRONT EVENTUALLY DISSIPATED
FROM 22/0000 UTC TO 22/0600 UTC. WIDELY SCATTERED MODERATE
RAINSHOWERS TO ISOLATED STRONG THUNDERSTORMS COVER THE GULF
WATERS TO THE NORTH OF 24N TO THE EAST OF 91W. RAINSHOWERS
ARE POSSIBLE TO THE NORTH OF 26N TO THE WEST OF 90W.

THE CARIBBEAN SEA...
A SURFACE TROUGH IS ALONG 83W/84W FROM 16N TO 24N. STRONG
CONVECTIVE PRECIPITATION THAT HAD BEEN WITHIN 100 NM OF THE
WESTERN SEMICIRCLE OF LA ISLA DE LA JUVENTUD OF CUBA ABOUT
FIVE HOURS AGO HAS WEAKENED AND DISSIPATED. AN UPPER LEVEL
TROUGH PASSES THROUGH THE ATLANTIC OCEAN NEAR 32N64W...ABOUT
60 NM TO THE EAST OF BERMUDA...TO 27N66W...TO 24N74W...TO
SOUTHEASTERN CUBA NEAR 27N78W. AN UPPER LEVEL TROUGH IS ALONG
17N73W 13N78W...TO 9N80W ALONG THE PANAMA COAST. UPPER LEVEL
CYCLONIC WIND FLOW COVERS THE CARIBBEAN SEA TO THE WEST OF 70W.
THE MONSOON TROUGH PASSES THROUGH COLOMBIA ALONG 10N76W TO
10N82W...AND THEN NORTHWESTWARD BEYOND NORTHWESTERN NICARAGUA.
WIDELY SCATTERED MODERATE RAINSHOWERS TO ISOLATED STRONG
THUNDERSTORMS ARE TO THE SOUTH OF 13N BETWEEN 80W AND 83W.
ISOLATED MODERATE RAINSHOWERS ARE FROM 13N TO THE SOUTHERN
COASTS OF JAMAICA AND HISPANIOLA BETWEEN 70W AND 81W...AND
FROM JAMAICA TO CUBA BETWEEN THE WINDWARD PASSAGE TO THE
CAYMAN ISLANDS. A 1011 MB LOW PRESSURE CENTER IS NEAR 18N61W.
THIS LOW PRESSURE CENTER IS NOT EXPECTED TO DEVELOP INTO
A TROPICAL CYCLONE DURING THE NEXT 48 HOURS. IT WILL CONTINUE
MOVING WESTWARD 15 TO 20 MILES PER HOUR. ANY DEEP CONVECTIVE
PRECIPITATION THAT WAS ACCOMPANYING THIS LOW CENTER FIVE HOURS
HAS DISSIPATED. A NEW CELL OF CONVECTIVE PRECIPITATION HAS
DEVELOPED ALONG THE NORTHERN SHORES OF GUADELOUPE.

THE ATLANTIC OCEAN...
A SURFACE TROUGH IS ALONG THE U.S.A. COAST FROM 31N NEAR GEORGIA
TO VIRGINIA. SCATTERED MODERATE RAINSHOWERS ARE WITHIN 90 NM OF
THE U.S.A. COAST. AN UPPER LEVEL TROUGH PASSES THROUGH THE
ATLANTIC OCEAN NEAR 32N64W...ABOUT 60 NM TO THE EAST OF
BERMUDA...TO 27N66W...TO 24N74W...TO SOUTHEASTERN CUBA NEAR
27N78W. AN UPPER LEVEL TROUGH PASSES THROUGH 33N28W TO 29N34W
25N42W AND 26N51W. UPPER LEVEL CYCLONIC FLOW THAT IS MOVING
AROUND THE TROUGH REACHES 19N46W...STILL ABOUT 385 NM TO THE
NORTH-NORTHWEST OF OPHELIA. SCATTERED MODERATE TO STRONG
CONVECTIVE PRECIPITATION IS FROM 22N TO 24N BETWEEN 65W AND
67W...AND FROM 27N TO 29N BETWEEN 60W AND 62W. ISOLATED MODERATE
RAINSHOWERS ARE ELSEWHERE FROM 20N TO 27N BETWEEN 62W AND 74W.
RAINSHOWERS ARE POSSIBLE ALSO ELSEWHERE TO THE NORTH OF 20N TO
THE WEST OF 70W IN SURFACE CONFLUENT WIND FLOW AND AFTERNOON
HEATING. RAINSHOWERS ARE POSSIBLE FROM 20N TO 30N BETWEEN 50W
AND 60W...AND FROM 30N TO 34N BETWEEN 27W AND 30W.

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

$$
MT





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