[Tropical] Tropical Weather Discussion

[Nashville EMWIN]

AXNT20 KNHC 011756
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
205 PM EDT WED 01 SEP 2004

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...WEATHER OBSERVATIONS...RADAR...AND
METEOROLOGICAL ANALYSIS.

BASED ON 1200 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
1715 UTC.

...SPECIAL FEATURES...

AT 2PM AST/EDT OR 01/1800 UTC...HURRICANE FRANCES IS CENTERED
NEAR 21.8N 70.4W...OR ABOUT 60 MILES/85 KM...EAST OF GRAND TURK
ISLAND...0R 700 MILES/1125 KM...EAST-SOUTHEAST OF THE FLORIDA
EAST COAST. FRANCES CONTINUES TO MOVE WNW 15 MPH...AROUND THE
SOUTHERN PERIPHERY OF SUBTROPICAL RIDGE AND NE OF WEAKENING
MID-UPPER LOW CENTERED NEAR 24.5N 78W. MAXIMUM SUSTAINED WIND
SPEED IS 140 MPH/220 KM/HR AND AS ALWAYS THERE WILL BE HIGHER
GUSTS. THE LATEST MINIMUM CENTRAL PRESSURE MEASURED BY
RECONNAISSANCE IS 941 MB. SEE THE LATEST NHC PUBLIC ADVISORY OR
FORECAST/ADVISORY ISSUED UNDER AWIPS/WMO HEADERS
MIATCPAT1/WTNT31 KNHC OR MIATCMAT1/WTNT21 KNHC FOR MORE DETAILS
AND WARNING INFORMATION.

FRANCES HAS AN IMPRESSIVE AND CLASSIC SATELLITE SIGNATURE
COMPLETE WITH 25 NM DIAMETER EYE...WITH SPIRAL BANDS CONTINUOUS
OVER 360 DEG...AND UPPER OUTFLOW NOTED AS FAR NORTH AS BERMUDA.
A TRAILING FEEDER BAND EXTENDS WELL TO THE SE...AND WILL BE
SHIFTING W THROUGH MOST OF THE WINDWARD AND LEEWARD ISLANDS BY
LATE THIS AFTERNOON. SUBJECTIVE AND OBJECTIVE DVORAK
CLASSIFICATIONS RUNNING 6 TO 6.5. SURROUNDING CLOUD TOP
TEMPERATURES REMAIN IN THE -70 TO -80 DEG CELSIUS RANGE. FRANCES
CONTINUES TO TRACK THROUGH FAVORABLE UPPER LEVEL ENVIRONMENT...
AND ALTHOUGH ALREADY A CAT 4 HURRICANE...COULD STILL STRENGTHEN
SLIGHTLY WITH EYEWALL FLUCTUATIONS. NO DOUBT TODAYS SATELLITE
IMAGES WILL BE RE-PRODUCED BECOMING AN EXCELLENT HURRICANE
AWARENESS TOOL IN THE FUTURE.

TROPICAL STORM GASTON DECLARED EXTRATROPICAL THIS MORNING AND
THEREFORE DROPPED FROM THIS DISCUSSION.

...TROPICAL WAVES...

TROPICAL LOW PRES ADDED TO 1200 UTC ANALYSIS AT 10N20W...MOST
LIKELY ASSOCIATED WITH A TROPICAL WAVE THAT HAS NOT PASSED
THROUGH THE CAPE VERDE ISLANDS AS YET. A 600 NM DIAMETER
CYCLONIC CIRCULATION NOTED WITH SCATTERED MODERATE TO STRONG
CONVECTION OBSERVED WITHIN 90 NM OF 10.5N23W. IF THIS CONVECTION
PERSISTS A TROPICAL DEPRESSION WILL FORM.

TROPICAL WAVE OVER THE E ATLC ALONG 34.5W S OF 23N MOVING W AT
20 KT WITH SCATTERED STRONG CONVECTION CONCENTRATED IN ONE
CLUSTER WITHIN 15 NM OF 19.5N33.5W. ENVIRONMENTAL PRES
INDICATES THE ACCOMPANYING LOW PRES WAS ABOUT 1013 MB AT 1200
UTC AND LOCATED AT 19.1N 34.6W. ALTHOUGH A COUPLE OF TENTHS
BANDING MEASURED THIS MORNING THE SYSTEM IS EXPERIENCING WLY
SHEAR AND THUS DEVELOPMENT IS ARRESTED.

TROPICAL WAVE IS ESTIMATED S OF 17N ALONG 56W MOVING WEST AT 15
KT. THE WAVE IS ENHANCING CONVECTION ALONG THE ITCZ S OF 10N.
UPPER SUBSIDENCE IS SUPPRESSING CONVECTION N OF 10N.

...ITCZ...
ITCZ AXIS IS CENTERED ALONG 8N8E 6N11W TO THE LOW PRES AT 10N23W
TO 12N37W 8N47W 11N53W 8N54W. ASIDE FROM ACTIVITY DESCRIBED NEAR
THE TROPICAL WAVES...WIDELY SCATTERED MODERATE ISOLATED STRONG
CONVECTION NOTED WITHIN 120 NM OF AXIS E OF 1E AND BETWEEN 42W
AND 50W.

...DISCUSSION...
GULF OF MEXICO...
A MID TO UPPER ANTICYCLONE ALONG THE S CAROLINA COAST HAS
RIDGE EXTENDING SW ACROSS N FLORIDA INTO THE CENTRAL GULF OF
MEXICO NEAR 25N88W. THE CENTRAL GULF IS DOMINATED BY A UPPER
LEVEL TROUGH S FROM A WEAK UPPER CYCLONE NEAR 32N91W ALONG
26N90W TO A WEAK UPPER CYCLONE AT 20N89W. A SECOND SHORT WAVE
NOTED ALONG 32N93W TO A BASE AT 28N93W. AT THE SURFACE A TROUGH
EXTENDS ALONG 30N85W TO 21N90W. TO THE E OF THE RESULTANT DEEP
LAYERED TROUGH A FEW SHOWERS AND TSTMS ARE ENHANCED. THIS
CONVECTION IS MOVING W OVER THE WATERS S OF 24N INCLUDING THE
STRAITS OF FLORIDA...BUT ARE MOVING ANTICYCLONICALLY NW THEN N
OVER THE WATERS N OF 24N.

THE ANTICYCLONE FROM HURRICANE HOWARD IN THE E PACIFIC EXTENDS E
ALONG 21N106W TO A SHARP CREST AT 27N92W. WIDELY SCATTERED
SHOWERS AND A FEW TSTMS ARE ENHANCED W OF 92W.

CARIBBEAN SEA...
A TROUGH EXTENDS SE FROM THE UPPER CYCLONE OVER THE YUCATAN AT
20N89W TO A WEAK UPPER CYCLONE AT 18N86W...THEN CONTINUES SE...
BUT IS WEAKENING...TO YET ANOTHER UPPER CYCLONE NEAR 10N78W.
SMALL UPPER ANTICYCLONE NOTED NEAR 13N83W SHIFTING W WITH TIME.
A FEW SHOWERS NOTED W OF THIS TROUGH OVER THE GULF OF
HONDURAS...BUT SCATTERED CONVECTION NOTED SW OF THIS TROUGH OVER
THE WATERS S OF 13N. A TRAILING FEEDER BAND FROM HURRICANE
FRANCES EXTENDS WELL TO THE SE ACROSS THE WINDWARD AND LEEWARD
ISLANDS...BUT SHOULD SHIFT W OF THESE ISLANDS BY LATE THIS
AFTERNOON. HOWEVER THE US AND BRITISH VIRGIN ISLANDS...AND
PUERTO RICO WILL EXPERIENCE THIS TRAIN ECHO CONVECTION FROM THE
S-SE WELL INTO THE EARLY EVENING HOURS TONIGHT AND HISPANIOLA
WILL LIKELY SEE THE SAME ON THU. THE UPPER LEVELS OVER THE
REMAINDER OF THE CARIBBEAN SEA IS DOMINATED BY THE UPPER
ANTICYCLONE ACCOMPANIED BY STRONG SUBSIDENCE FROM HURRICANE
FRANCES WITH CONVECTION SUPPRESSED TO A FEW SHOWERS AT BEST.

SUBTROPICAL ATLANTIC OCEAN...
AN UPPER TROUGH IS NOTED ALONG 32N75W TO 23N80W. A FEW SHOWERS
CONTINUE N OF 29N W OF 78W. THE UPPER CYCLONE NEAR 24N79W HAS
ALMOST WEAKENED TO AN INVERTED TROUGH AND IS SHIFTING SLOWLY W
THROUGH THE STRAITS OF FLORIDA. ANY EFFECT THIS UPPER LOW HAD ON
STEERING FOR HURRICANE FRANCES IS RAPIDLY DECREASING. THE UPPER
LEVELS BETWEEN 74W AND 58W ARE OF COURSE DOMINATED BY THE
IMPRESSIVE OUTFLOW FROM FRANCES. AN UPPER TROUGH EXTENDS ALONG
33N10W 31N26W THROUGH A SMALL UPPER CYCLONE AT 31.5N36W THEN SW
THROUGH A LARGE UPPER CYCLONE AT 24N47W. WIDELY SCATTERED
SHOWERS AND ISOLATED TSTMS ARE ENHANCED OVER THE W SEMICIRCLE OF
THIS CYCLONE...ROUGHLY WITH 150 NM EITHER SIDE OF LINE 16N48W
26N51W. AN UPPER ANTICYCLONE OVER AFRICA NEAR 27N1E HAS A RIDGE
EXTENDING W TO NEAR 23N24W.

TROPICAL ATLANTIC...
ASIDE FROM HURRICANE FRANCES AND ITCZ CONVECTION...WIDELY
SCATTERED SHOWERS AND ISOLATED TSTMS ARE NOTED FROM 14N-23N
BETWEEN 53W AND 31W.

$$
NELSON


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