[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 180005
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
805 PM EDT FRI SEP 17 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 1800 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
2345 UTC.

...SPECIAL FEATURES...

HURRICANE KARL IS NOW DOWNGRADED TO TROPICAL STORM. THIS SYSTEM
IS INLAND OVER MEXICO CENTERED NEAR 18.8N 97.1W AT 18/0000 UTC
OR ABOUT 75 MI..115 KM E OF PUEBLA MEXICO MOVING WSW AT 8 KT.
ESTIMATED MINIMUM CENTRAL PRESSURE IS 995 MB. MAXIMUM SUSTAINED
WIND SPEED IS 60 KT WITH GUSTS TO 80 KT. SEE LATEST NHC
INTERMEDIATE PUBLIC ADVISORY UNDER AWIPS/WMO HEADERS
MIATCPAT3/WTNT33 AND THE FULL FORECAST/ ADVISORY UNDER AWIPS/WMO
HEADERS MIATCMAT3/WTNT23 KNHC FOR MORE DETAILS. THIS SYSTEM
CONTINUES TO PRODUCE NUMEROUS STRONG CONVECTION OVER THE MEXICO
REGION CAUSING LIFE THREATENING FLASH FLOODS AND MUD
SLIDES...ESPECIALLY IN AREAS OF MOUNTAINOUS TERRAIN. THE OUTER
BANDS OF MODERATE TO STRONG CONVECTION COVER THE REMAINDER OF
THE AREA INCLUDING THE WESTERN HALF OF THE GULF OF MEXICO W OF
88W.

HURRICANE IGOR IS CENTERED NEAR 24.2N 61.3W AT 18/0000 UTC OR
ABOUT 600 MI SSE OF BERMUDA MOVING NW AT 9 KT. ESTIMATED MINIMUM
CENTRAL PRESSURE IS 947 MB. MAXIMUM SUSTAINED WIND SPEED IS 89
KT WITH GUSTS TO 120 KT. IGOR CONTINUES TO POSE A THREAT TO
BERMUDA. SEE LATEST NHC FORECAST/ADVISORY UNDER AWIPS/WMO
HEADERS MIATCMAT1/WTNT21 KNHC FOR MORE DETAILS. NUMEROUS STRONG
CONVECTION IS FROM 23N-26N BETWEEN 60W-63W. SCATTERED MODERATE
CONVECTION COVERS THE REMAINDER OF THE AREA FROM 21N-28N BETWEEN
58W-64W.

HURRICANE JULIA IS CENTERED NEAR 25.2N 48.2W AT 17/2100 UTC OR
ABOUT 1525 MI WSW OF THE AZORES MOVING WNW AT 16 KT. ESTIMATED
MINIMUM CENTRAL PRESSURE IS 987 MB. MAXIMUM SUSTAINED WIND SPEED
IS 65 KT WITH GUSTS TO 80 KT. SATELLITE IMAGERY SHOWS THE UPPER
OUTFLOW OF IGOR IS SHEARING JULIA AND THEREFORE THIS SYSTEM IS
EXPECTED TO CONTINUE TO WEAKEN OVER THE NEXT 24 HOURS. SEE
LATEST NHC FORECAST/ADVISORY UNDER AWIPS/WMO HEADERS
MIATCMAT2/WTNT22 KNHC FOR MORE DETAILS. SCATTERED MODERATE TO
STRONG CONVECTION IS FROM 22N-26N BETWEEN 45W-50W.

...TROPICAL WAVES...

A TROPICAL WAVE IS ALONG 23W S OF 19N MOVING W AT 10 KT.
SATELLITE IMAGERY AND DERIVED WINDS SHOW CYCLONIC TURNING IN
THE VICINITY OF THE WAVE N OF 12N. AN EMBEDDED LOW IS ON THE
WAVE AXIS NEAR 12N23W. A DEEP LAYERED MOISTURE SURROUNDS THE
WAVE NOTED  ON TOTAL PRECIPITABLE WATER IMAGERY. SCATTERED
MODERATE TO ISOLATED STRONG CONVECTION IS FROM 7N-14N BETWEEN
22W AND 32W. HOWEVER...THE CONVECTION ASSOCIATED WITH THE WAVE
IS ALSO EMBEDDED IN THE MONSOONAL TROUGH COVERING A LARGER AREA
IN THE TROPICAL ATLC.

...ITCZ...

THE THE ITCZ/MONSOONAL HAS BROKEN DOWN OVER THE PAST SEVERAL
DAYS DUE TO THE LARGE SCALE WIND FIELD FROM HURRICANES IGOR AND
JULIA. RESIDUAL WIDELY SCATTERED MODERATE CONVECTION IS HOWEVER
FROM 7N TO 14N BETWEEN 22W AND 40W. A SURGE OF SCATTERED
MODERATE TO STRONG CONVECTION WILL MOVE OFF THE COAST OF WEST
AFRICA FROM 5N TO 14N OVER THE NEXT FEW HOURS.

...DISCUSSION...

GULF OF MEXICO...
ALTHOUGH HURRICANE KARL IS INLAND OVER MEXICO...REMNANT OUTER
BANDS FROM THIS SYSTEM CONTINUE TO SPREAD ACROSS MOST OF THE
CENTRAL AND WESTERN GULF PRODUCING SCATTERED HEAVY SHOWERS AND
THUNDERSTORMS W OF 88W. THIS AREA OF CONVECTION IS EXPECTED TO
CONTINUE TO MOVE WESTWARD ACROSS THE WESTERN HALF OF THE GULF
OVER THE NEXT 24 HOURS. FAIR WEATHER CONDITIONS ARE PRESENT
ACROSS THE REMAINDER OF THE GULF WITH A FEW ISOLATED SHOWERS
EMBEDDED IN THE EASTERLY 5-15 KT FLOW. THE UPPER LEVEL RIDGE OF
HIGH PRESSURE OVER THE SE CONUS WEAKENED IN RESPONSE OF THE
PASSAGE OF KARL OVER THE GULF THESE PAST SEVERAL DAYS.
HOWEVER...COMPUTER MODELS SUGGEST THIS UPPER LEVEL FEATURE WILL
REBUILD OVER THE SE CONUS AND PROMOTE FAIR WEATHER TO THE EAST
AND CENTRAL GULF WHILE SOME REMNANT CONVECTION ASSOCIATED WITH
KARL WILL CONTINUE OVER THE FAR WEST BASIN THROUGH EARLY NEXT
WEEK.

CARIBBEAN SEA...
FAIR WEATHER CONDITIONS WITH A FEW ISOLATED SHOWERS ARE OBSERVED
ACROSS MOST OF THE BASIN...DUE TO DRY STABLE AIR ALOFT CAPTURED
ON WATER VAPOR IMAGERY...SHOWING THE STRONGEST AREA OF
SUBSIDENCE BETWEEN 74W AND 84W N OF 12N. MONSOONAL TROUGHINESS
IS NOTED OVER NORTHERN SOUTH AMERICA GENERATING SCATTERED
SHOWERS AND THUNDERSTORMS TO THE FAR SW CARIBBEAN S OF 12N W
OF 76W...AND ALSO ALONG THE COASTAL WATERS OF VENEZUELA AND
COLOMBIA TO 20 NM OFFSHORE. CYCLONIC 10-15 KT SURFACE FLOW IS
OVER THE EASTERN BASIN E OF 70W DUE TO THE LARGE SCALE WIND
FIELD FROM HURRICANE IGOR. COMPUTER MODELS INDICATE THIS LARGE
SCALE WIND FIELD WILL DRAG CONSIDERABLE MOISTURE ACROSS THE ESE
CARIBBEAN GENERATING SCATTERED MODERATE TO STRONG CONVECTION
OVER THIS REGION IN THE NEXT 12 TO 24 HOURS.

ATLANTIC OCEAN...
HURRICANES IGOR AND JULIA TOGETHER WITH A TROPICAL WAVE OVER THE
EAST TROPICAL ATLC ARE THE PRIMARY SURFACE FEATURES OVER THE
ATLANTIC. IGOR CONTINUES TO POSE A THREAT TO BERMUDA. SATELLITE
IMAGERY SHOWS THE UPPER OUTFLOW OF IGOR IS STARTING TO SHEAR
JULIA. A LARGE AREA OF AFRICAN DUST FROM THE SAHARA REGION IS
NOTED ON SATELLITE IMAGERY...COVERING MOST OF THE EASTERN ATLC
FROM 14N TO 28N BETWEEN THE COAST OF AFRICA AND 41W. THIS
SAHARAN AIR LAYER...ALONG WITH THE EAST ATLC UPPER LEVEL RIDGE
SUPPORTING THE SUB-TROPICAL 1027 MB HIGH LOCATED NEAR
40N38W...ARE KEEPING FAIR WEATHER CONDITIONS IN THIS REGION.


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

$$

GARCIA



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