[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 112354
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
805 PM EDT FRI SEP 11 2009

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
2315 UTC.

...SPECIAL FEATURES...

TROPICAL STORM FRED IS CENTERED NEAR 18.1N 34.6W AT 11/2100 UTC
OR ABOUT 715 MILES...1150 KM...WEST-NORTHWEST OF THE CAPE VERDE
ISLANDS DRIFTING NE AT 2 KT. LITTLE MOTION IS EXPECTED OVER THE
NEXT COUPLE OF DAYS. ESTIMATED MINIMUM CENTRAL PRESSURE IS 987
MB. MAXIMUM SUSTAINED WINDS HAVE DECREASED TO 60 KT WITH GUSTS
TO 75 KT. FURTHER WEAKENING OF FRED IS EXPECTED. SEE LATEST NHC
FORECAST/ ADVISORY UNDER AWIPS/WMO HEADERS MIATCMAT2/WTNT22 KNHC
FOR MORE DETAILS. SCATTERED MODERATE/STRONG CONVECTION IS FROM
17N-21N BETWEEN 32W-36W.

...TROPICAL WAVES...

TROPICAL WAVE IS ALONG 21W S OF 20N MOVING W NEAR 15 KT. A 1010
MB LOW IS ALONG THE WAVE AXIS NEAR 12N. SATELLITE IMAGERY AND AN
EARLIER QUIKSCAT PASS CONFIRMED THE LOCATION OF THE LOW
CIRCULATION. ISOLATED MODERATE CONVECTION IS FROM 14N-17N
BETWEEN 20W-25W.

TROPICAL WAVE IS ALONG 81W S OF 19N MOVING W NEAR 18 KT. THE
WAVE FOLLOWS A MAXIMUM IN DEEP LAYER MOISTURE OBSERVED IN TOTAL
PRECIPITABLE WATER IMAGERY. THE WAVE HAS MOVED UNDER MOIST SLY
FLOW ALOFT AROUND AN UPPER LEVEL LOW S OF GUATEMALA WHICH HAS
ENHANCED A LARGE CLUSTER OF SCATTERED MODERATE TO STRONG
CONVECTION FROM 8N-14N BETWEEN 83W-88W.  THE CONVECTION MAY BE
MORE ASSOCIATED WITH UPPER LEVEL DIFFLUENT FLOW THAN SURFACE
CONVERGENCE NEAR THE WAVE. WIDELY SCATTERED MODERATE CONVECTION
IS ALSO CLOSER TO THE WAVE AXIS FROM 11N-15N BETWEEN 80W-83W.

...ITCZ...

THE ITCZ AXIS IS CENTERED ALONG 11N15W 7N26W 14N34W 11N50W
10N62W. BESIDES THE CONVECTION MENTIONED IN THE SPECIAL FEATURE
SECTION AND THE TROPICAL WAVE SECTION...WIDELY SCATTERED
MODERATE CONVECTION IS ALONG THE COAST OD WEST AFRICA FROM
12N-15N BETWEEN 16W-19W. ISOLATED MODERATE CONVECTION IS FROM
4N-9N BETWEEN 24W-29W.

...DISCUSSION...

GULF OF MEXICO...
AS OF 2100 UTC...A SURFACE TROUGH IS OVER THE NW GULF OF MEXICO
FROM 29N92W TO A 1010 MB SURFACE LOW IS ANALYZED OFF THE TEXAS
COAST NEAR 29N93W TO 27N97W. THIS SYSTEM IS SUPPORTED BY AN
UPPER LEVEL TROUGH FORMING OVER MEXICO AND TEXAS EXTENDING INTO
THE FAR W CARIBBEAN. SURFACE CONVERGENCE NEAR THE SURFACE LOW
AND TROUGH ALONG WITH UPPER LEVEL DIFFLUENCE BETWEEN THE UPPER
TROUGH AND AN UPPER LEVEL RIDGE DOMINATING THE CENTRAL GULF ARE
SUPPORTING SCATTERED SHOWERS/THUNDERSTORMS ACROSS MUCH OF THE
GULF N OF 22N. EXPECT SHOWERS/THUNDERSTORMS TO CONTINUE OVER THE
NEXT 24 HOURS AS THE TROUGH MOVES NW.

CARIBBEAN SEA...
A TROPICAL WAVE IS OVER THE W CARIBBEAN. SEE ABOVE. FRESH TO
STRONG TRADEWINDS ARE OVER THE CARIBBEAN AND CENTRAL AMERICA.
CLUSTERS OF SCATTERED MODERATE TO STRONG CONVECTION ARE OVER
CUBA...THE YUCATAN CHANNEL...AND THE YUCATAN PENINSULA N OF 20N
BETWEEN 77W-89W. SIMILAR CONVECTION IS OVER N COLOMBIA FROM
8N-12N BETWEEN 73W-76W. SCATTERED SHOWERS ARE OVER PUERTO RICO
AND HISPANIOLA. IN THE UPPER LEVELS...AN UPPER LEVEL TROUGH IS
OVER THE W CARIBBEAN W OF 80W WITH SIGNIFICANT UPPER LEVEL
MOISTURE. WESTERLY UPPER LEVEL FLOW WITH STRONG SUBSIDENCE IS
OVER THE REMAINDER OF THE CARIBBEAN. EXPECT...CONTINUED
CONVECTION OVER THE W CARIBBEAN AND CENTRAL AMERICA W OF 85W
OVER THE NEXT 24 HOURS AS THE TROPICAL WAVE MOVES W.

ATLANTIC OCEAN...
A SURFACE TROUGH IS OFF THE COAST OF FLORIDA ALONG 32N72W
29N80W. SCATTERED SHOWERS ARE WITHIN 60 NM OF THE TROUGH AXIS S
OF 30N. A 1020 MB HIGH IS OVER THE W ATLANTIC NEAR 29N64W. A
COLD FRONT IS FURTHER E ALONG 32N41W 29N50W 32N60W. SCATTERED
SHOWERS ARE WITHIN 60 NM OF THE FRONT. A 1020 MB HIGH IS OVER
THE E ATLANTIC NEAR 38N20W. IN THE UPPER LEVELS...AN UPPER LEVEL
LOW IS OVER THE W ATLANTIC N OF PUERTO RICO NEAR 24N65W. UPPER
LEVEL DIFFLUENCE NW OF THE CENTER IS PRODUCING WIDELY SCATTERED
MODERATE CONVECTION E OF THE BAHAMAS FROM 24N-29N BETWEEN
68W-74W. ANOTHER UPPER LEVEL LOW IS OVER THE CENTRAL ATLANTIC
NEAR 21N44W PRODUCING SW SHEAR OVER T.S. FRED. A LARGE UPPER
LEVEL HIGH IS OVER THE TROPICAL E ATLANTIC NEAR THE CAPE VERDE
ISLANDS AT 19N21W.

$$
FORMOSA







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