[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 181201
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
805 AM EDT SAT SEP 18 2010

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 0600 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
1015 UTC.

...SPECIAL FEATURES...

HURRICANE IGOR IS CENTERED NEAR 25.6N 63.2W AT 18/1200 UTC OR
ABOUT 475 NM S OF BERMUDA MOVING NW AT 11 KT. ESTIMATED
MINIMUM CENTRAL PRESSURE IS 939 MB. MAXIMUM SUSTAINED WIND SPEED
IS 95 KT WITH GUSTS TO 115 KT. IGOR REMAINS LARGE AND OUTER
RAINBANDS ARE EXPECTED TO BEGIN IMPACTING BERMUDA DURING THE
NEXT 12-18 HRS. SEE LATEST NHC INTERMEDIATE PUBLIC ADVISORY
UNDER AWIPS/WMO HEADERS MIATCPAT1/WTNT31 AND THE FULL
FORECAST/ADVISORY UNDER AWIPS/WMO HEADERS MIATCMAT1/WTNT21 KNHC
FOR MORE DETAILS. NUMEROUS STRONG CONVECTION IS FROM 22N-27N
BETWEEN 61W-65W. NUMEROUS MODERATE/ISOLATED STRONG CONVECTION IS
ELSEWHERE FROM 20N-31N BETWEEN 59W-67W.

TROPICAL STORM JULIA IS CENTERED NEAR 27.4N 50.1W AT 18/0900 UTC
OR ABOUT 1325 NM WSW OF THE AZORES MOVING NW AT 16 KT. ESTIMATED
MINIMUM CENTRAL PRESSURE IS 995 MB. MAXIMUM SUSTAINED WIND SPEED
IS 50 KT WITH GUSTS TO 60 KT. WATER VAPOR IMAGERY AND SATELLITE
DERIVED WINDS INDICATE THAT THE UPPER LEVEL OUTFLOW OF IGOR IS
SHEARING JULIA RESULTING IN THE WEAKENING TO TROPICAL STORM
FORCE. FURTHER WEAKENING IS EXPECTED OVER THE NEXT SEVERAL DAYS.
SEE LATEST NHC FORECAST/ADVISORY UNDER AWIPS/WMO HEADERS
MIATCMAT2/WTNT22 KNHC FOR MORE DETAILS. NUMEROUS STRONG
CONVECTION IS FROM 25N-27N BETWEEN 48W-50W WITH NUMEROUS
MODERATE/ISOLATED STRONG CONVECTION ELSEWHERE FROM 23N-28N
BETWEEN 47W-52W.

KARL HAS NOW BEEN DOWNGRADED TO A REMNANT LOW. THE CENTER OF THE
REMNANTS OF KARL IS NEAR 18.5N 97.6W AT 18/0900 UTC...OR ABOUT
90 NM WSW OF VERACRUZ MEXICO MOVING WSW AT 3 KT. ESTIMATED
MINIMUM CENTRAL PRESSURE IS 1006 MB. MAXIMUM SUSTAINED WIND
SPEED IS 20 KT WITH GUSTS TO 25 KT. SEE THE LAST NHC FORECAST/
ADVISORY UNDER AWIPS/WMO HEADERS MIATCMAT3/WTNT23 KNHC FOR MORE
DETAILS. ONLY A SMALL AREA OF STRONG CONVECTION REMAINS NE OF
THE CENTER OF THE SYSTEM FROM 18N-20N BETWEEN 95W-98W.
HOWEVER...MUCH OF THE DEEP MOISTURE LEFT IN KARLS WAKE REMAINS
ACROSS THE WRN GULF SUPPORTING SCATTERED MODERATE/ISOLATED
STRONG CONVECTION W OF 91W.

...TROPICAL WAVES...

TROPICAL WAVE IS IN THE ERN ATLC EXTENDING FROM THE CAPE VERDE
ISLANDS NEAR 17N25W TO 7N30W MOVING W NEAR 15 KT. SATELLITE
IMAGERY AND SATELLITE DERIVED WINDS SHOW LOW/MID-LEVEL CYCLONIC
FLOW ABOUT THE WAVE AXIS CONCENTRATED NEAR A 1010 MB LOW CENTER
ALONG THE WAVE AXIS NEAR 12N28W. TOTAL PRECIPITABLE WATER
IMAGERY ALSO INDICATES AN AREA OF MAXIMUM MOISTURE SURROUNDING
THE WAVE. SCATTERED MODERATE/STRONG CONVECTION IS MAINLY W OF
THE AXIS FROM 11N-16N BETWEEN 26W-30W.

...ITCZ...

A MONSOONAL TROUGH IS ANALYZED OFF THE W AFRICAN COAST ALONG
8N11W TO 8N26W INDICATING AN AREA WHERE THE WINDS S OF THE AXIS
ARE MAINLY SWLY AS OPPOSED TO TYPICAL ITCZ CONVERGENCE OF SE-NE
WINDS. THE ITCZ AXIS HAS MAINLY BROKEN DOWN DUE TO THE LARGE
SCALE WIND FIELD FROM IGOR AND JULIA. ONLY A PORTION W OF THE
TROPICAL WAVE REMAINS ALONG 10N40W TO 8N51W. SCATTERED
MODERATE/STRONG CONVECTION IS OFF THE AFRICAN COAST FROM 4N-8N
BETWEEN 10W-15W...AND FROM 8N-11N BETWEEN 14W-16W. SIMILAR
ACTIVITY IS FROM 4N-9N BETWEEN 46W-51W. ISOLATED MODERATE/STRONG
CONVECTION IS ALSO FROM 9N-18N BETWEEN 52W-61W EMBEDDED IN
MOISTURE BEING DRAWN NWD BEHIND IGOR.

...DISCUSSION...

GULF OF MEXICO...
SIGNIFICANT MOISTURE LIES ACROSS THE WRN GULF IN THE WAKE OF
KARL...NOW A REMNANT LOW OVER INLAND SRN MEXICO. SCATTERED
SHOWERS/ISOLATED THUNDERSTORMS ARE W OF 91W S OF 28N. THIS
ACTIVITY IS EXPECTED TO DRIFT WWD AND REMAIN IMPACTING THE FAR
WRN GULF OVER THE NEXT COUPLE OF DAYS. A SURFACE TROUGH HAS
FORMED ALONG THE TEXAS COASTLINE FURTHER ENHANCING
SHOWER/THUNDERSTORM ACTIVITY IN THE FAR NW GULF. FAIR WEATHER
PREVAILS E OF 91W DUE TO SUBSIDENCE ALOFT AROUND THE PERIPHERY
OF AN UPPER LEVEL RIDGE COVERING MUCH OF THE BASIN. WATER VAPOR
IMAGERY ALSO INDICATES DRY AIR BEING DRAWN AROUND THE ERN EDGE
ACROSS FLORIDA AND THE W ATLC. AS THE MOISTURE LEFT BEHIND BY
KARL PROPAGATES WWD...FAIR WEATHER SHOULD SPREAD IN BEHIND IT.

CARIBBEAN SEA...
MOSTLY FAIR WEATHER COVERS MUCH OF THE CARIBBEAN TONIGHT UNDER
THE INFLUENCE OF A DRY AND STABLE AIRMASS OVER THE WRN HALF OF
THE BASIN AROUND AN UPPER LEVEL INVERTED TROUGH CENTERED OVER
THE SW CARIBBEAN. AN UPPER LEVEL RIDGE COVERS THE ERN HALF OF
THE AREA CENTERED OVER THE WINDWARD ISLANDS. A FEW ISOLATED
SHOWERS/THUNDERSTORMS ARE S OF CUBA FROM 19N-21N BETWEEN
80W-82W. SHOWERS/THUNDERSTORMS ARE ALSO OFF THE COAST OF
COLOMBIA S OF 13N BETWEEN 72W-77W NEAR AN EXTENSION OF THE E
PACIFIC MONSOONAL TROUGH ALONG 11N TO THE COAST OF COLOMBIA.
CYCLONIC SURFACE FLOW FROM THE CIRCULATION OF HURRICANE IGOR IS
INFLUENCING THE NE CARIBBEAN PRODUCING SW-W WINDS UP TO 15 KT
ACROSS THE NE ISLANDS. LARGE SWELLS ARE ALSO IMPACTING
HISPANIOLA...PUERTO RICO...THE VIRGIN ISLANDS...AND THE LEEWARD
ISLANDS IN ASSOCIATION WITH IGOR. A FEW SHOWERS/THUNDERSTORMS
REMAIN ACROSS THE WINDWARD ISLANDS ASSOCIATED WITH MOISTURE
BEHIND DRAWN NWD BY IGOR. SOME OF THIS MOISTURE IS FORECAST TO
MOVE WWD INCREASING THE CHANCES OF ENHANCED SHOWER/THUNDERSTORM
ACTIVITY ACROSS THE ERN CARIBBEAN.

ATLANTIC OCEAN...
THE FAR W ATLC IS EXPERIENCING MOSTLY FAIR WEATHER ASSOCIATED
WITH DRY AIR AND SUBSIDENCE ALOFT AROUND AN UPPER LEVEL RIDGE
COVERING THE GULF OF MEXICO. TO THE E...HURRICANE IGOR IS N OF
THE LEEWARD ISLANDS. TROPICAL STORM JULIA IS E OF IGOR. SEE
SPECIAL FEATURES FOR MORE DETAILS ON BOTH OF THESE SYSTEMS. E OF
THE LESSER ANTILLES MOISTURE IS BEING DRAWN NWD IN THE WAKE OF
IGOR SUPPORTING AREAS OF SHOWERS/THUNDERSTORMS FROM 9N-18N
BETWEEN 52W-61W. E OF JULIA...SURFACE RIDGING PREVAILS AROUND A
1028 MB HIGH SW OF THE AZORES ISLANDS PROVIDING GENERALLY FAIR
WEATHER ACROSS THE E ATLC N OF THE TROPICAL TROPICAL WAVE NEAR
THE CAPE VERDE ISLANDS. ALOFT...A WEAK UPPER LEVEL RIDGE IS E OF
JULIA NEAR 20N40W WITH A LONGWAVE UPPER TROUGH EXTENDING FROM
PORTUGAL TO THE CAPE VERDE ISLANDS.

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

$$
WALTON






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