[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 091757
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
205 PM EDT WED SEP 09 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 1200 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
1700 UTC.

...SPECIAL FEATURES...

HURRICANE FRED IS CENTERED NEAR 13.9N 33.4W AT 09/1500 UTC OR OR
ABOUT 470 NM W OF THE SOUTHERNMOST CAPE VERDE ISLANDS MOVING NW
AT 11 KT. ESTIMATED MINIMUM CENTRAL PRESSURE IS 958 MB. MAXIMUM
SUSTAINED WINDS HAVE INCREASED TO 105 KT WITH GUSTS TO 130 KT
MAKING FRED A CATEGORY THREE HURRICANE ON THE SAFFIR-SIMPSON
SCALE. SCATTERED MODERATE/STRONG CONVECTION IS FROM 10N-17N
BETWEEN 30W-35W. SEE LATEST NHC FORECAST/ ADVISORY UNDER
AWIPS/WMO HEADERS MIATCMAT2/WTNT22 KNHC FOR MORE DETAILS.

...TROPICAL WAVES...

TROPICAL WAVE IS EXTENDS FROM E OF PUERTO RICO NEAR 18N65W TO
14N67W 9N67W MOVING W NEAR 18 KT. THE WAVE COINCIDES WITH A DEEP
LAYER MOISTURE MAXIMUM OBSERVED IN TOTAL PRECIPITABLE WATER
IMAGERY. NO DEEP CONVECTION IS CURRENTLY ASSOCIATED WITH THE
WAVE. HOWEVER...SCATTERED SHOWERS ARE FROM 18N-21N BETWEEN
63W-66W.

TROPICAL WAVE IS ALONG 86W S OF 19N MOVING W NEAR 20 KT. THIS
WAVE REMAINS DIFFICULT TO LOCATE DUE TO DRY AIR ALOFT ACROSS THE
CENTRAL AND WRN CARIBBEAN. NO DEEP CONVECTION IS CURRENTLY
ASSOCIATED WITH THE WAVE.

...ITCZ...

THE ITCZ AXIS IS CENTERED ALONG 14N15W 16N29W 10N35W 6N44W
6N61W. SCATTERED MODERATE/ISOLATED STRONG CONVECTION IS FROM
10N-15N BETWEEN 15W-20W. ISOLATED MODERATE CONVECTION IS FROM
4N-5N BETWEEN 45W-49W.

...DISCUSSION...

GULF OF MEXICO...
A SURFACE TROUGH IS ACROSS THE NRN GULF EXTENDING FROM THE
MISSISSIPPI COAST NEAR 30N89W ALONG SRN LOUISIANA TO 28N91W.
SURFACE CONVERGENCE NEAR THE TROUGH AS WELL AS UPPER LEVEL
DIFFLUENT FLOW BETWEEN AN UPPER LEVEL RIDGE COVERING THE
MAJORITY OF THE GULF CENTERED OVER MEXICO NEAR 20N101W AND AN
UPPER LEVEL TROUGH OVER THE ERN CONUS AND W ATLC CENTERED OVER W
VIRGINIA NEAR 38N80W ARE SUPPORTING SCATTERED
SHOWERS/THUNDERSTORMS ACROSS THE NW GULF N OF 25N W OF 85W.
ISOLATED SHOWERS/THUNDERSTORMS ARE ALSO IN THE SW GULF S OF 22N
W OF 94W. A SURFACE TROUGH EXTENDS FROM THE SW N ATLC ACROSS S
FLORIDA CONTINUING TO WRN CUBA. SURFACE CONVERGENCE NEAR THE
TROUGH IS SUPPORTING ISOLATED SHOWERS/POSSIBLE THUNDERSTORMS
ACROSS THE FAR SE GULF AND STRAITS OF FLORIDA S OF 25N E OF 83W.
EXPECT THE SRN PORTION OF THIS TROUGH TO DRIFT WWD THU AND
DISSIPATE FRI.

CARIBBEAN SEA...
A SURFACE TROUGH EXTENDS FROM THE SW N ATLC TO WRN CUBA NEAR
23N82W CONTINUING TO 19N82W. SURFACE CONVERGENCE NEAR THE TROUGH
IS SUPPORTING SCATTERED SHOWERS/THUNDERSTORMS FROM 19N-22N
BETWEEN 78W-83W MAINLY S OF CUBA. THE REMAINDER OF THE WRN AND
CENTRAL CARIBBEAN IS EXPERIENCING GENERALLY FAIR WEATHER UNDER
DRY SUBSIDENT AIR DUE TO NLY FLOW AROUND AN UPPER LEVEL RIDGE
OVER THE NW CARIBBEAN. AN UPPER LEVEL TROUGH EXTENDS FROM AN
UPPER LEVEL LOW N OF HISPANIOLA NEAR 23N68W CONTINUING ACROSS
HISPANIOLA TO THE SW CARIBBEAN NEAR 10N83W. MOIST SWLY FLOW
AROUND THIS UPPER TROUGH IS DRAWING TROPICAL MOISTURE AND HIGH
CLOUDS FROM PANAMA TO PUERTO RICO. SURFACE CONVERGENCE NEAR THE
E PACIFIC ITCZ AND A 1008 MB LOW OVER NRN COLOMBIA NEAR 8N75W IS
SUPPORTING SCATTERED SHOWERS/THUNDERSTORMS ACROSS THE SW
CARIBBEAN S OF 11N BETWEEN 75W-81W. MODERATE TO FRESH TRADE
WINDS ARE ACROSS MUCH OF THE BASIN BECOMING STRONG IN THE ERN
CARIBBEAN. EXPECT THE TROPICAL WAVE ALONG 67W TO CONTINUE WWD.

ATLANTIC OCEAN...
A SURFACE TROUGH ENTERS THE DISCUSSION AREA NEAR 32N74W AND
EXTENDS TO S FLORIDA NEAR 25N80W CONTINUING TO W CUBA NEAR
23N82W. SURFACE CONVERGENCE NEAR THE TROUGH IS SUPPORTING
SCATTERED SHOWERS/THUNDERSTORMS WITHIN 300 NM SE OF THE TROUGH
AXIS. THIS ACTIVITY IS ALSO ENHANCED BY UPPER LEVEL DIFFLUENCE
AND MOIST SWLY FLOW ALOFT AROUND AN UPPER LEVEL TROUGH EXTENDING
FROM THE NW BAHAMAS TO AN UPPER LEVEL LOW OVER W VIRGINIA NEAR
38N80W. SCATTERED SHOWERS/THUNDERSTORMS ARE ALSO FROM 19N-22N
BETWEEN 59W-61W DUE TO SURFACE CONVERGENCE NEAR AN AREA OF
SURFACE LOW PRESSURE NEAR 20N62W AS WELL AS UPPER LEVEL
DIFFLUENCE BETWEEN AN UPPER LEVEL LOW N OF HISPANIOLA NEAR
23N68W AND AN UPPER LEVEL RIDGE CENTERED NEAR 30N51W. A 1020 MB
SURFACE HIGH IS CENTERED NEAR 30N59W. A 1016 MB LOW NEAR 32N43W
INTRUDES THE SURFACE RIDGE. A STATIONARY FRONT EXTENDS FROM THE
LOW CENTER ALONG 29N46W 28N52W. NO SHOWERS ARE CURRENTLY
ASSOCIATED WITH THE FRONT. A SURFACE TROUGH EXTENDS FROM 24N41W
TO 16N42W. ISOLATED SHOWERS ARE ALONG THE TROUGH AXIS. THE
TROUGH IS SUPPORTED BY AN UPPER LEVEL TROUGH EXTENDING FROM
17N54W TO 31N37W. ISOLATED SHOWERS ARE N OF 29N BETWEEN 26W-33W
AHEAD OF A STATIONARY FRONT N OF THE DISCUSSION AREA. ELSEWHERE
ACROSS THE ATLC...HURRICANE FRED REMAINS THE DOMINANT FEATURE.
SEE SPECIAL FEATURES ABOVE. ELSEWHERE IN THE UPPER LEVELS...AN
UPPER LEVEL RIDGE DOMINATES E OF 50W WHICH IS ENHANCING
CONVECTION ASSOCIATED WITH HURRICANE FRED.

$$
WALTON





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