[Tropical] Tropical Weather Discussion

[Nashville EMWIN]

AXNT20 KNHC 041745
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
205 PM EDT SAT 04 SEP 2004

TROPICAL WEATHER DISCUSSION FOR N AMERICA...CENTRAL
AMERICA...GULF OF MEXICO...CARIBBEAN SEA...NORTHEASTERN  SECTIONS
OF S AMERICA...AND ATLC 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...
HURRICANE FRANCES AT 2PM EDT/1800 UTC...WAS NEAR LATITUDE 26.9N
...LONGITUDE 79.0W.  ALTHOUGH FRANCES HAS BEEN NEARLY STATIONARY
THE PAST FEW HOURS SHE IS EXPECTED TO RESUME A WESTWARD MOVEMENT
AT ABOUT 5 MPH. THE CURRENT POSITION IS ABOUT 70 MILES E OF PALM
BEACH FLORIDA. MAXIMUM SUSTAINED WIND SPEED 105 MPH/ 165 KM/HR
WITH HIGHER GUSTS. THE WIND FIELD HAS EXPANDED WITH HURRICANE
FORCE WINDS WITHIN 105 NM OF CENTER AND TROPICAL STORM FORCE
WINDS OUT 185 NM FROM CENTER. THE LATEST MINIMUM CENTRAL
PRESSURE MEASURED WAS 962 MB. SEE LATEST NHC PUBLIC ADVISORY
UNDER AWIPS/WMO HEADERS MIATCPAT1/ WTNT31 KNHC AND THE
FORECAST/ADVISORY UNDER HEADERS MIATCMAT1/WTNT21 KNHC FOR
ADDITIONAL INFORMATION. NUMEROUS STRONG CONVECTION NOTED IN
SEVERAL BANDS OVER THE N SEMICIRCLE. THE WESTERN MOST BANDS HAVE
BEEN MOVING ONSHORE THE FLORIDA E COAST ALL MORNING WITH TWO
SIGNIFICANT RAIN BANDS NOW MOVING BACK OFFSHORE THE W COAST OF
FLORIDA FROM NEAR SARASOTA TO S OF KEY WEST. AN INTENSE SOLID
OUTERBAND IS NOW MOVING SE THROUGH THE STRAITS OF FLORIDA
TOWARDS THE CAY SAL BANK.

TROPICAL STORM IVAN IS CENTERED NEAR 8.9N 38.9W AT 04/1500 UTC
MOVING W AT 16 KT. THE MAXIMUM SUSTAINED WIND SPEED IS 50 KT
WITH GUSTS TO 60 KT. ESTIMATED MINIMUM CENTRAL PRESSURE IS 997
MB. SEE LATEST NHC FORECAST/ADVISORY UNDER AWIPS/WMO HEADERS
MIATCMAT4/WTNT24 KNHC FOR MORE DETAILS. THIS MORNINGS SATELLITE
CLASSIFICATION MEASURED 7/10 BANDING AGAIN INDICATING THAT THE
INTENSITY IS NEARLY CONSTANT AT 50 KT. THIS BANDING IS STILL
PRESENT. AN UPPER ANTICYCLONE IS CENTERED NEAR 17N40W WITH A
RIDGE EXTENDING SW TO A CREST AT 11N52W. THUS UPPER LEVEL
CONDITIONS WILL REMAIN FAVORABLE FOR CONTINUED STRENGTHENING OF
IVAN TO HURRICANE STATUS IN ABOUT 30 HOURS.

...TROPICAL WAVES...

LOW PRES...ABOUT 1017 MB...CONTINUES NEAR 25N47W...ORIGINALLY
SPAWNED ALONG THE NORTHERN EXTENSION OF A HIGH LATITUDE TROPICAL
WAVE THAT IS CURRENTLY ANALYZED AS A TROUGH EXTENDING FROM
14N49W TO 31N45W. THIS LOW LEVEL SYSTEM IS DRIFTING W UNDER A
TROPICAL UPPER TROUGH...TUTT...RESULTING IN A CONVECTIVE BLOWUP
WITHIN 300 NM OF 27N43W. THE CONVECTION IS SHEARED WELL TO THE
NE OF THE EXPOSED LOW LEVEL CIRCULATION CENTER. GUIDANCE MOVES
THE LOW PRES N TO NEAR 30N47W IN 24 HOURS LIKELY IN RESPONSE TO
A BAROCLINIC BOUNDARY N OF THE FORECAST AREA. THE AREA WILL BE
MONITORED CLOSELY HAS GUIDANCE INDICATES A DECREASE IN SHEAR IN
ABOUT 24 HOURS.

THE TROPICAL WAVE ALONG 72W S OF 22N IS MOVING W ABOUT 12 KT.
THE WAVE AXIS IS DIFFICULT TO ACCURATELY LOCATE AS BROAD
CYCLONIC TURNING CONTINUES IN THE TRADE WIND CUMULUS MOVING W
THROUGH THE CENTRAL CARIBBEAN WATERS. ADDITIONALLY...WIDESPREAD
CONVECTION OVER VENEZUELA AND COLOMBIA IS MASKING THE WAVE AXIS.

...ITCZ...

ITCZ AXIS IS CENTERED ALONG 5N10W 6N53W. OTHER THAN T.S. IVAN
CONVECTION...SCATTERED MODERATE AND ISOLATED STRONG CONVECTION
IS OBSERVED FROM 4N-9N BETWEEN 26W-30W.

...DISCUSSION...

GULF OF MEXICO...
AN UPPER LOW HAS CUT OFF NEAR 23N96W AND IS MOVING W. AN UPPER
ANTICYCLONE IS NEAR 28N94W AND ANOTHER NEAR 23N91W. BROAD UPPER
SUBSIDENCE IS NOTED OVER MOST OF THE GULF WITH ONLY ISOLATED
SHOWERS AND TSTMS NOTED W OF 89W. THE MOISTURE PLUME ASSOCIATED
WITH HURRICANE FRANCES IS SPREADING W ACROSS FLORIDA S OF 27N.
OUTER RAIN BANDS FROM FRANCES ARE MOVING OFFSHORE THE S FLORIDA
W COAST.

CARIBBEAN...
AN UPPER CYCLONE IS NEAR 14N87W AND MOVING W ACROSS HONDURAS AT
THE MOMENT. AN UPPER LEVEL ANTICYCLONE IS DISSIPATING NEAR
20N83W. STRONG UPPER SUBSIDENCE IS OBSERVED N OF 15N W OF 80W
AND S OF 15N W OF 77W. ELSEWHERE W OF 65W...THE UPPER LEVELS
ARE DOMINATED BY THE ANTICYCLONIC OUTFLOW FROM HURRICANE FRANCES
WITH DEBRIS MOISTURE SPREADING SW ACROSS THE CENTRAL WATERS. A
MID TO UPPER LEVEL CYCLONE IS CENTERED NEAR 14N63W AND IS
ENHANCING CONVECTION OVER THE CARIBBEAN E OF 70W.

REMAINDER OF ATLANTIC...
AN UPPER LEVEL TROUGH LIES NEARLY STATIONARY ALONG 32N8W 23N23W
TO 14N27W...AND IS IDENTIFIED BY MODERATE TO STRONG UPPER
SUBSIDENCE WITHIN 75 NM EITHER SIDE OF ITS AXIS. AN UPPER
CYCLONE HAS CUT OFF NEAR 28N28W AND IS MOVING S WITH TIME. AN
UPPER ANTICYCLONE IS NOTED AT 23N41W WITH A RIDGE AMPLIFYING
N-NE TO A SHARP CREST AT 34N34W. ASSOCIATED UPPER DIFFLUENCE IS
ENHANCING SCATTERED CONVECTION NE OF THE SURFACE LOW NEAR
25N47W. AN UPPER CYCLONE IS POSITIONED JUST TO THE W OF THE
RIDGE NEAR 27N54W WITH A TROUGH S TO THE CARIBBEAN UPPER CYCLONE
NEAR 14N63W. STRONG UPPER SUBSIDENCE IS NOTED WITHIN 480 NM
EITHER SIDE OF LINE 18N67W 26N60W 29N45W...AND FROM 24N-12N
BETWEEN 65W-28W.

$$
NELSON





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