[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 222351
TWDAT

TROPICAL WEATHER DISCUSSION
NWS NATIONAL HURRICANE CENTER MIAMI FL
805 PM EDT THU SEP 22 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 1800 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY
THROUGH 2315 UTC.

...SPECIAL FEATURES...

THE CENTER OF TROPICAL STORM OPHELIA AT 22/2100 UTC IS NEAR
13.8N 48.9W...OR ABOUT 770 NM ESE OF THE LEEWARD ISLANDS.
OPHELIA IS MOVING WEST NEAR 11 KT. MAXIMUM SUSTAINED WIND SPEED
IS 55 KT WITH GUSTS TO 65 KT. THE ESTIMATED MINIMUM CENTRAL
PRESSURE IS 994 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. THE STORM
CONTINUES TO BE SHEARED BY AN UPPER LEVEL TROUGH TO THE W WHICH
IS DISPLACING THE CONVECTION TO THE ERN HALF OF THE STORM. A
CLUSTER OF STRONG CONVECTION IS FROM 14N-17N BETWEEN 46W-48W.
SCATTERED MODERATE/STRONG CONVECTION IS FROM 10N-13N BETWEEN
44W-47W. NUMEROUS MODERATE CONVECTION IS ELSEWHERE FROM 14N-19N
BETWEEN 42W-49W.

...TROPICAL WAVES...

TROPICAL WAVE IS W OF THE CAPE VERDE ISLANDS ALONG 20N29W TO
11N32W MOVING W NEAR 15 KT. SATELLITE IMAGERY AND SATELLITE
DERIVED WINDS INDICATE BROAD CYCLONIC FLOW IN THE LOW-MID LEVELS
AROUND THE WAVE AXIS. A RECENT WINDSAT SCATTEROMETER PASS ALSO
INDICATES SURFACE CYCLONIC FLOW AROUND THE AXIS. TOTAL
PRECIPITABLE WATER IMAGERY INDICATES THAT ENHANCED DEEP LAYER
MOISTURE ACCOMPANIES THE WAVE ALSO EXTENDING WELL N OF THE WAVE
AXIS. ISOLATED MODERATE/STRONG CONVECTION IS W OF THE WAVE AXIS
FROM 10N-12N BETWEEN 33W-38W.

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

A SMALL PORTION OF THE MONSOON TROUGH EXTENDS FROM NEAR THE
COAST OF AFRICA AT 8N17W WHERE SOME EVIDENT MID-LEVEL CYCLONIC
TURNING IS OCCURRING CONTINUING TO E OF THE TROPICAL WAVE AXIS
NEAR 10N30W. A CLUSTER OF NUMEROUS STRONG CONVECTION IS MOVING
OFF THE AFRICAN COAST FROM 10N-13N BETWEEN 14W-18W. SCATTERED
MODERATE/STRONG CONVECTION IS S OF THE AXIS FROM 4N-7N BETWEEN
18W-24W.

...DISCUSSION...

THE GULF OF MEXICO...
A LONGWAVE UPPER LEVEL TROUGH MOVING ACROSS THE CENTRAL UNITED
STATES IS IMPACTING THE WEATHER IN THE ERN GULF OF MEXICO.
DIFFLUENCE AROUND THE ERN SIDE OF THE UPPER TROUGH IS SUPPORTING
A LARGE AREA OF STRONG SHOWERS/THUNDERSTORMS ACROSS CENTRAL
FLORIDA AND THE IMMEDIATE OFFSHORE WATERS FROM 26N-30N E OF 85W.
THE UPPER TROUGH IS ALSO SUPPORTING A SURFACE TROUGH EXTENDING
FROM SE LOUISIANA INTO THE BAY OF CAMPECHE ALONG 29N91W TO
21N92W. ISOLATED SHOWERS/THUNDERSTORMS ARE E OF THE SURFACE
TROUGH N OF 23N E OF 90W. THE REMAINDER OF THE WRN GULF IS UNDER
MOSTLY FAIR CONDITIONS DUE TO DRY AIR ALOFT. EXPECT THE SURFACE
TROUGH IS REMAIN SOMEWHAT STATIONARY BEFORE BEING ABSORBED BY A
COLD FRONT THAT WILL MOVE ACROSS THE AREA ON SATURDAY. MOIST
CONDITIONS WILL REMAIN OVER THE ERN GULF OF MEXICO.

THE CARIBBEAN SEA...
STRONG SHOWERS/THUNDERSTORMS ARE ACROSS THE YUCATAN
PENINSULA...CUBA...JAMAICA...AND HISPANIOLA THIS EVENING MOST
LIKELY THE RESULT OF WIDESPREAD DEEP MOISTURE AND DAYTIME
HEATING. SOME OF THE ACTIVITY OVER HISPANIOLA IS ALSO INFLUENCED
BY A WEAK 1012 MB DISSIPATING LOW CURRENTLY JUST S OF THE
DOMINICAN REPUBLIC NEAR 18N70W. A LARGE CLUSTER OF
SHOWERS/ISOLATED THUNDERSTORMS IS ALSO E OF NICARAGUA AND COSTA
RICA FROM 10N-13N BETWEEN 79W-83W WITH SCATTERED ACTIVITY ACROSS
MUCH OF CENTRAL AMERICA. THE LARGE CLUSTER IS INFLUENCE BY UPPER
LEVEL DIFFLUENCE AROUND AN UPPER LEVEL TROUGH WITH AXIS DOWN
CENTRAL AMERICA. SOME OF THE ACTIVITY IS ALSO INFLUENCED BY THE
MONSOON TROUGH EXTENDING ACROSS THE COSTA RICA/PANAMA BORDER TO
NRN COLOMBIA. ISOLATED SHOWERS ARE ALSO EMBEDDED WITHIN THE 15
KT TRADEWIND FLOW OVER THE ERN CARIBBEAN. MUCH OF THE CARIBBEAN
WILL REMAIN UNDER MOIST CONDITIONS OVER THE NEXT COUPLE OF DAYS
WITH SOME DRY AIR AHEAD OF OPHELIA MOVING INTO THE ERN CARIBBEAN.

THE ATLANTIC OCEAN...
THE AREA OF SHOWERS/THUNDERSTORMS ACROSS THE ERN GULF OF MEXICO
AND FLORIDA EXTEND INTO THE ATLC WATERS NW OF A LINE FROM 27N80W
TO 32N77W ASSOCIATED WITH A LONGWAVE UPPER LEVEL TROUGH MOVING
ACROSS THE CENTRAL UNITED STATES. A BROAD SURFACE RIDGE COVERS
THE REMAINDER OF THE W/CENTRAL ATLC SUPPORTED BY AN UPPER LEVEL
RIDGE CENTERED NEAR 31N71W. HOWEVER...AN INVERTED UPPER TROUGH
TO THE S ACROSS ERN CUBA AND THE NW BAHAMAS IS PROVIDING
DIFFLUENCE ALOFT TO SUPPORT SCATTERED SHOWERS/THUNDERSTORMS N OF
THE ERN BAHAMAS FROM 22N-27N BETWEEN 68W-75W. ANOTHER UPPER
LEVEL TROUGH IS OVER THE CENTRAL ATLC ALONG 53W. A SHORTWAVE
TROUGH EXTENDS OFF THE MAIN TROUGH SUPPORTING ANOTHER AREA OF
SCATTERED SHOWERS/THUNDERSTORMS FROM 23N-28N BETWEEN 60W-64W
FARTHER E...TROPICAL STORM OPHELIA IS IMPACTING THE CENTRAL
TROPICAL ATLC. THE AFOREMENTIONED UPPER TROUGH ALONG 53W
CONTINUES TO SHEAR OPHELIA. A SURFACE TROUGH HAS FORMED TO THE S
OF THE STORM ALONG 10N49W TO 8N55W SUPPORTING ISOLATED
SHOWERS/THUNDERSTORMS WITHIN 120 NM EITHER SIDE OF THE AXIS.
WEAK SURFACE RIDGING COVERS THE ERN ATLC AROUND A 1023 MB HIGH
BETWEEN THE AZORES ISLANDS AND MADEIRA ISLANDS. ALOFT...AN UPPER
LEVEL RIDGE IS CENTERED TO THE E OF OPHELIA NEAR 17N38W.

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

$$
WALTON




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