[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 180559
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
205 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 0000 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
0500 UTC.

...SPECIAL FEATURES...

HURRICANE IGOR IS CENTERED NEAR 24.9N 62.4W AT 18/0600 UTC OR
ABOUT 460 NM SSE OF BERMUDA MOVING NW AT 11 KT. ESTIMATED
MINIMUM CENTRAL PRESSURE IS 942 MB. MAXIMUM SUSTAINED WIND SPEED
IS 95 KT WITH GUSTS TO 115 KT. IGOR CONTINUES TO POSE A THREAT
TO BERMUDA. 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 21N-26N
BETWEEN 60W-65W. NUMEROUS MODERATE/ISOLATED STRONG CONVECTION IS
ELSEWHERE FROM 21N-30N BETWEEN 57W-66W.

TROPICAL STORM JULIA IS CENTERED NEAR 26.0N 49.2W AT 18/0300 UTC
OR ABOUT 1335 NM WSW OF THE AZORES MOVING NW AT 14 KT. ESTIMATED
MINIMUM CENTRAL PRESSURE IS 991 MB. MAXIMUM SUSTAINED WIND SPEED
IS 60 KT WITH GUSTS TO 75 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 24N-26N BETWEEN 48W-50W WITH NUMEROUS
MODERATE/ISOLATED STRONG CONVECTION ELSEWHERE FROM 24N-27N
BETWEEN 46W-51W...AND FROM 21N-24N BETWEEN 50W-52W.

KARL HAS NOW BEEN DOWNGRADED TO A TROPICAL DEPRESSION. THE
CENTER OF T.D. KARL IS NEAR 18.6N 97.4W AT 18/0300 UTC...OR
ABOUT 50 NM ESE OF PUEBLA MEXICO MOVING WSW AT 6 KT. ESTIMATED
MINIMUM CENTRAL PRESSURE IS 1000 MB. MAXIMUM SUSTAINED WIND
SPEED IS 30 KT WITH GUSTS TO 40 KT. SEE LATEST NHC FORECAST/
ADVISORY UNDER AWIPS/WMO HEADERS MIATCMAT3/WTNT23 KNHC FOR MORE
DETAILS. KARL IS EXPECTED TO DISSIPATE SOON AS IT APPROACHES THE
MOUNTAINS OF SRN MEXICO. ONLY A SMALL AREA OF STRONG CONVECTION
REMAINS NEAR THE CENTER OF THE SYSTEM. HOWEVER...MUCH OF THE DEEP
MOISTURE ASSOCIATED WITH KARL REMAINS ACROSS THE WRN GULF
SUPPORTING SCATTERED MODERATE/ISOLATED STRONG CONVECTION W OF
89W.

...TROPICAL WAVES...

TROPICAL WAVE IS IN THE ERN ATLC EXTENDING FROM THE CAPE VERDE
ISLANDS NEAR 18N23W TO 8N28W MOVING W NEAR 15 KT. SATELLITE
IMAGERY AND SATELLITE DERIVED WINDS SHOW LOW/MID-LEVEL CYCLONIC
FLOW ABOUT THE WAVE AXIS CONCENTRATED NEAR A 1009 MB LOW CENTER
ALONG THE WAVE AXIS NEAR 12N26W. AN ASCAT SCATTEROMETER PASS
CONFIRMS THE CYCLONIC WIND SHIFT W OF THE WAVE AXIS. TOTAL
PRECIPITABLE WATER IMAGERY ALSO INDICATES AN AREA OF ENHANCED
MOISTURE SURROUNDING THE WAVE. SCATTERED MODERATE/STRONG
CONVECTION IS MAINLY W OF THE AXIS FROM 11N-15N BETWEEN 26W-29W.

...ITCZ...

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
ALONG 9N31W TO 9N43W REMAINS. HOWEVER...NO DEEP CONVECTION
RESIDES IN THIS AREA. SCATTERED MODERATE/ISOLATED STRONG
CONVECTION IS FARTHER W FROM 5N-9N BETWEEN 43W-50W. ISOLATED
MODERATE/STRONG CONVECTION IS ALSO FROM 9N-19N BETWEEN 51W-61W
EMBEDDED IN MOISTURE BEING DRAWN NWD BEHIND IGOR. A SURGE OF
SCATTERED MODERATE/STRONG CONVECTION IS ALSO ALONG THE WRN COAST
OF AFRICA FROM 4N-15N BETWEEN 10W-15W.

...DISCUSSION...

GULF OF MEXICO...
SIGNIFICANT MOISTURE LIES ACROSS THE WRN GULF IN THE WAKE OF
T.D. KARL...NOW INLAND OVER MEXICO. SCATTERED SHOWERS/ISOLATED
THUNDERSTORMS ARE W OF 88W S OF 28N. THIS ACTIVITY IS EXPECTED
TO DRIFT WWD AND REMAIN IMPACTING THE FAR WRN GULF OVER THE NEXT
COUPLE OF DAYS. FAIR WEATHER PREVAILS E OF 88W 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 ASSOCIATED WITH 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 AND JAMAICA. SIMILAR
ACTIVITY IS IN THE FAR SW CARIBBEAN OFF THE COAST OF PANAMA NEAR
AN EXTENSION OF THE E PACIFIC MONSOONAL TROUGH ALONG 10N TO THE
COAST OF COLOMBIA. CYCLONIC SURFACE FLOW FROM THE CIRCULATION OF
HURRICANE IGOR IS INFLUENCING THE NE CARIBBEAN PRODUCING WLY
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 ASSOCIATED 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. HURRICANE IGOR IS TO THE E AND N OF
THE LEEWARD ISLANDS. TROPICAL STORM JULIA IS E OF THE 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-19N
BETWEEN 51W-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 19N39W 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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