[Tropical] Tropical Weather Discussion

[Nashville EMWIN]

AXNT20 KNHC 022351
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
805 PM EDT THU 02 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 1800 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
2315 UTC.

...SPECIAL FEATURES...

CATEGORY FOUR HURRICANE FRANCES CENTERED NEAR 24.3N 75.1W...OR
65 MILES SE OF NORTHERN CAT ISLAND AND 355 MILES ESE OF THE
LOWER FLORIDA EAST COAST...AT 03/0000 UTC MOVING WNW 8 KT.
MAXIMUM SUSTAINED WIND SPEED HAS DECREASED JUST A BIT TO 120 KT
WITH GUSTS TO 145 KT. MINIMUM CENTRAL PRESSURE REPORTED FROM A
RECONNAISSANCE AIRPLANE IS 948 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. FRANCES CONTINUES ITS RAMPAGE ACROSS THE
FAR EASTERN BAHAMA ISLANDS...CROSSING SAN SALVADOR AROUND 2000
UTC WITH SUSTAINED WINDS OF 120 MPH...AND IT IS NOW HEADING FOR
CAT ISLAND AND ELEUTHERA ISLAND. THE LAST FEW VISIBLE IMAGES OF
THE HURRICANE CONTINUE TO SHOW NEARLY PERFECT STRUCTURE AND
EXPANSIVE OUTFLOW ESPECIALLY IN THE NRN SEMICIRCLE. THE EYE
BECAME A LITTLE RAGGED AND OBSCURED AS IT PASSED OVER SAN
SALVADOR...BUT IT IS NOT CERTAIN AT THIS TIME IF THE HURRICANE
IS WEAKENING A BIT OR IT IS JUST GOING THROUGH ANOTHER EYEWALL
REPLACEMENT CYCLE. ONE ENCOURAGING NOTE...THE AIRCRAFT
RECONNAISSANCE FROM EARLIER THIS AFTERNOON DID FIND A HIGHER
CENTRAL PRESSURE AND SLIGHTLY WEAKER WINDS SO IT WILL BE
INTERESTING TO SEE IF THIS TREND CONTINUES. CONVECTION REMAINS
STRONG...IF NOT A LITTLE LESS SYMMETRICAL...AROUND THE CORE OF
FRANCES WITH NUMEROUS MODERATE/STRONG FROM 22N-27N BETWEEN
72W-77W.

THE HURRICANE HAS BEEN WOBBLING A LITTLE ALONG ITS FORECAST
TRACK AND THIS IS EXPECTED AS THE HURRICANE CONTINUES TO MOVE
ACROSS THE NRN BAHAMAS AND TOWARDS THE FLORIDA COAST. REMEMBER
THAT ANY OF THESE WOBBLES COULD BRING THE HURRICANE INLAND
ANYWHERE ALONG THE WARNING AREA. RESIDENTS IN EVACUATION ZONES
AND IN MOBILE HOMES WITHIN THE WARNING AREA ARE URGED TO FOLLOW
THE DIRECTION OF LOCAL COUNTY EMERGENCY MANAGERS.

TROPICAL DEPRESSION NINE HAS DEVELOPED NEAR 9.7N 29.1W...OR
ABOUT 555 MILES SW OF THE CAPE VERDE ISLANDS...AT 02/2100 UTC
MOVING W 17 KT. MAXIMUM SUSTAINED WIND SPEED IS 25 KT WITH GUSTS
TO 35 KT. ESTIMATED MINIMUM CENTRAL PRESSURE IS 1009 MB. SEE
LATEST NHC FORECAST/ADVISORY UNDER AWIPS/WMO HEADERS
MIATCMAT4/WTNT24 KNHC FOR MORE DETAILS. THE DEPRESSION HAS
MAINTAINED A LARGE CLUSTER OF CONVECTION OVER THE PAST 24 HRS OR
SO AND UPPER LEVEL OUTFLOW IS IMPRESSIVE FOR A SYSTEM WHICH JUST
RECENTLY MOVED OFF THE COAST OF AFRICA. EVEN THOUGH IT HAS BEEN
ZIPPING ALONG QUICKLY TO THE W...THE BULK OF THE TSTMS ARE
ACTUALLY ORIENTED TO THE W OF THE LOW-LEVEL CIRCULATION.
NUMEROUS MODERATE/STRONG CONVECTION FROM 7N-12N BETWEEN
28W-32.5W.

...TROPICAL WAVES...

TROPICAL WAVE LOCATED OVER THE CENTRAL ATLC ALONG 42W S OF 26N
MOVING W 15 KT. A 1013 MB LOW IS CENTERED ALONG THE WAVE AXIS
NEAR 19N42W BUT IS FORECAST TO WEAKEN AS IT CONTINUES ACROSS THE
CNTRL ATLC BASIN. THE WAVE/LOW IS LOCATED TO THE SE OF A LARGE
MID/UPPER LOW...AND STRONG SLY FLOW HAS SHEARED ALL THE TSTMS UP
TO 175 NM TO THE N OF THE LOW-LEVEL CENTER. WIDELY SCATTERED
MODERATE CONVECTION FROM 20N-26N BETWEEN 37W-44W.

TROPICAL WAVE BETWEEN BARBADOS AND THE REST OF THE LESSER
ANTILLES ALONG 60W...THEN BENDING BACK ALONG 16N60W 24N57W. THE
WAVE IS BECOMING INCREASINGLY INFLUENCED BY NW/W SHEAR AS A
LARGE UPPER LOW ROTATES WWD TOWARDS THE NRN LEEWARD ISLANDS. DRY
AIR NEAR THE LOW IS LIMITING DEEP CONVECTION...WHICH IS
PRIMARILY RESTRICTED SE OF BARBADOS NEAR THE ITCZ. ISOLATED
SHOWERS ARE LOCATED FROM 16N-24N BETWEEN 54W-62W BUT ARE LARGELY
ASSOCIATED WITH THE UPPER LOW.

...ITCZ...

ITCZ AXIS EMERGES W OF LIBERIA ALONG 6N10W 6N20W 10N42W 8N60W.
ISOLATED SHOWERS/TSTMS WITHIN 45 NM OF THE AXIS BETWEEN 8W-11W
AND 19W-23W. ISOLATED TSTMS WITHIN 120 NM S OF THE AXIS BETWEEN
36W-38W. SCATTERED MODERATE CONVECTION 200 NM N OF THE AXIS
BETWEEN 53W-58W. WIDELY SCATTERED MODERATE OVER PARTS OF NW
GUYANA AND E VENEZUELA. ISOLATED TSTMS ALONG THE COLOMBIA COAST
AND E PANAMA.

...DISCUSSION...

GULF OF MEXICO...
MUCH LIKE YESTERDAY...WIDELY SCATTERED SHOWERS AND TSTMS
CONTINUE TO DOT THE LANDSCAPE. MOST OF THE ACTIVITY SEEMS TO
HAVE SHIFTED A LITTLE FARTHER W OVER THE W GULF...ALONG A SFC
TROF WHICH EXTENDS FROM LAKE CHARLES LOUISIANA SWD TO 23N94W.
THERE IS A WEAK WIND SHIFT ALONG THIS BOUNDARY BUT MOST OF THE
WINDS ACROSS THE GULF HAVE TURNED TO THE E/NE IN ADVANCE OF
HURRICANE FRANCES. WIDELY SCATTERED SHOWERS ARE ALSO LOCATED
OVER MUCH OF THE AREA BETWEEN FLORIDA AND 90W DUE TO THE
PRESENCE OF DEEP-LAYERED MOISTURE. A COL REGION IN THE UPPER
LEVELS IS CENTERED NEAR 26N90W...SEPARATING A RIDGE AXIS ALONG A
E/CNTRL MEXICO TO CNTRL FLORIDA LINE FROM TWO TROFS OVER THE
LOWER MISSISSIPPI VALLEY AND THE BAY OF CAMPECHE.

CARIBBEAN...
WEATHER CONDITIONS REMAIN DRY OVER MUCH OF THE CARIBBEAN WATERS
WITH STRONG SUBSIDENCE W OF 68W. PART OF THE ANTICYCLONIC UPPER
LEVEL OUTFLOW FROM FRANCES IS EXPANDING SWD ACROSS
HISPANIOLA...E CUBA...AND JAMAICA BUT EVEN MORE DRY AIR IS ABOUT
TO MOVE ACROSS THE NRN LEEWARD ISLANDS IN ADVANCE OF AN ATLC
UPPER LOW. THESE DRY CONDITIONS ARE EXPECTED TO CONTINUE AS THE
ATLC UPPER LOW MOVES IN. HOWEVER...THE LOW LEVELS MAY MOISTEN UP
A BIT IN THE SLY FLOW IN THE WAKE OF FRANCES.

WEST ATLANTIC...
SEE SPECIAL FEATURES FOR DISCUSSION ON HURRICANE FRANCES.

REMAINDER OF SUBTROPICAL ATLANTIC...
A COUPLET OF MID/UPPER LOWS ARE CENTERED NE OF THE NRN LEEWARD
ISLANDS NEAR 20N56W AND 29N47W AND ARE COMBINING FORCES TO DRAW
DEEP MOISTURE NWD OVER THE CNTRL ATLC AND DRIER AIR SWD BETWEEN
50W-66W. IN ADDITION...THE STRONG SLY FLOW TO THE E OF THE LOWS
IS PRODUCING STRONG VERTICAL SHEAR OVER THE TROPICAL WAVE/LOW
ALONG 42W...AND THIS HAS PREVENTED THE SYSTEM FROM DEVELOPING
INTO A TROPICAL DEPRESSION. TO THE E...A WELL-DEFINED UPPER
LEVEL HIGH HAS DEVELOPED NEAR 19N34W AND DEEP-LAYERED TROUGHING
IS PLUNGING FROM THE COAST OF PORTUGAL SWD PAST THE CANARY
ISLANDS TO 24N. THIS TROF IS SUPPORTING A COLD FRONT WHICH LIES
ALONG THE COAST OF MOROCCO THEN WWD TO 31N20W.

TROPICAL ATLANTIC...
THE UPPER LOW CENTERED NE OF THE LEEWARD ISLANDS NEAR 19N56W IS
PRODUCING STRONG WLY UPPER FLOW FROM THE WINDWARD ISLANDS EWD TO
45W...WHICH WILL KEEP THIS AREA OF THE ATLC NON-CONDUCIVE FOR
TROPICAL DEVELOPMENT. HOWEVER...STRONG RIDGING AND DEEP-LAYERED
ELY FLOW OVER THE E ATLC HAS PROMPTED THE DEVELOPMENT OF
TROPICAL DEPRESSION NINE JUST SW OF THE CAPE VERDE ISLANDS. THIS
RIDGE IS EXPECTED TO EXPAND WWD ACROSS THE ATLC AND WILL MAKE
THE ENVIRONMENT NEAR THE LESSER ANTILLES CONDUCIVE FOR FURTHER
STRENGTHENING OF THE DEPRESSION. FARTHER E...A SQUALL LINE HAS
DEVELOPED OVER PARTS OF W AFRICA EXTENDING FROM SE MAURITANIA TO
THE GUINEA/IVORY COAST LINE...AND SOME OF THESE STORMS MAY
APPROACH THE ATLC WATERS LATER TONIGHT OR TOMORROW.

$$
BERG


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