[Tropical] Tropical Weather Discussion

[Nashville EMWIN]

AXNT20 KNHC 020003
TWDAT

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

...SPECIAL FEATURES...

HURRICANE FRANCES CENTERED NEAR 22.3N 71.4W...OR ABOUT 40 MILES
NNE OF GRAND CAICOS ISLAND AND 625 MILES ESE OF THE SE COAST OF
FLORIDA...AT 02/0000 UTC MOVING WNW 12 KT. MAXIMUM SUSTAINED
WIND SPEED REMAINS AT 120 KT WITH GUSTS TO 145 KT. ESTIMATED
MINIMUM CENTRAL PRESSURE REPORTED BY A RECONNAISSANCE AIRCRAFT
IS 938 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 TO RADIATE IMPRESSIVE UPPER LEVEL CIRRUS OVER
THE NRN...ERN...AND SRN QUADRANTS EXTENDING OUTWARD UP TO 500 NM
AWAY FROM THE CENTER. THE OUTFLOW IS SLIGHTLY MORE RESTRICTED TO
THE W OF THE HURRICANE...ABOUT 225 NM AWAY...AS IT RUNS INTO THE
DRIER AIR NEAR AN UPPER TROF BETWEEN THE BAHAMAS AND FLORIDA.
THE INNER CORE OF FRANCES HAS BEEN CYCLING THROUGH BURSTS OF
CONVECTION AND POSSIBLY AN EYEWALL REPLACEMENT CYCLE THROUGH THE
AFTERNOON HOURS WITH THE EYE SHRINKING TO ABOUT 8 NM WIDE AT
2045Z AND RECENTLY EXPANDING BACK TO 16 NM WIDE AS OF 2315Z.
NUMEROUS MODERATE/STRONG CONVECTION IS NOW WITHIN 120 NM N...120
NM E...160 NM S...AND 90 NM W OF THE CENTER. VERY HEAVY RAINFALL
AND STRONG WINDS ARE NOW AFFECTING THE TURKS AND CAICOS ISLANDS
AND WILL CONTINUE TO SPREAD ACROSS THE REST OF THE SOUTHERN
BAHAMAS DURING THE NEXT SEVERAL HOURS.

THE COLDEST CLOUD TOPS...COLDER THAN ABOUT -70C...ARE ONCE AGAIN
WRAPPING ENTIRELY AROUND THE EYE AND IT SEEMS THAT THE
SHORT-TERM TREND IS FOR THE STORM TO MAINTAIN ITS CURRENT STATUS
OR EVEN GAIN A LITTLE STRENGTH. IN ADDITION...WATER TEMPERATURES
AROUND 29C NEAR THE STORM BECOME INCREASINGLY WARMER NEAR THE
BAHAMAS AND OFF THE SE FLORIDA COAST...AS HIGH AS 32C...SO ALONG
WITH FAVORABLE UPPER LEVEL CONDITIONS IT DOES NOT SEEM LIKELY
THAT THIS HURRICANE WILL LOSE MUCH STRENGTH AS IT HEADS TO THE
NW. RESIDENTS AND VISITORS TO THE BAHAMAS AND FLORIDA ARE URGED
TO FOLLOW THE DIRECTIONS OF LOCAL EMERGENCY MANAGERS AND BE
PREPARED TO EXPERIENCE TROPICAL STORM OR HURRICANE CONDITIONS
THROUGH THE NEXT SEVERAL DAYS.


A 1012 MB LOW IS CENTERED ABOUT 600 NM WNW OF THE CAPE VERDE
ISLANDS NEAR 19N36W ALONG A TROPICAL WAVE WHICH EXTENDS FROM
13N37W TO 26N33W. SHOWER AND TSTM ACTIVITY HAS BEEN PERSISTENT
TO THE N OF THE LOW WITH SCATTERED MODERATE CONVECTION FROM
19N-23N BETWEEN 33W-39W. HOWEVER...STRONG UPPER LEVEL SWLY WINDS
ARE AFFECTING THE SYSTEM (CIMSS ESTIMATES UPWARDS OF 50-60 KT OF
SHEAR NW OF THE LOW). TROPICAL CYCLONE DEVELOPMENT IS POSSIBLE
WITHIN THE NEXT 36 HOURS IF THE LOW CAN WITHSTAND THE SHEAR.

...TROPICAL WAVES...

TROPICAL WAVE LOCATED NEAR THE CAPE VERDE ISLANDS FROM 2N23W TO
16N19W MOVING W ABOUT 15 KT. A 1010 MB LOW IS CENTERED ALONG THE
WAVE AXIS NEAR 10N22W WITH SCATTERED MODERATE/STRONG CONVECTION
FROM 7N-12N BETWEEN 22W-27W. SEVERAL NUMERICAL MODELS STRENGTHEN
THIS SYSTEM OVER THE ATLC WATERS SO IT WILL BE WATCHED FOR
FURTHER DEVELOPMENT.

SEE SPECIAL FEATURES FOR TROPICAL WAVE ALONG 36W/37W.

TROPICAL WAVE LOCATED ABOUT 200 NM E OF THE LEEWARD/WINDWARD
ISLANDS ALONG 57W S OF 20N MOVING W 15 KT. A BROAD CYCLONIC
CIRCULATION IS NOTED E OF THE ISLANDS WITH SHOWERS/TSTMS
CENTERED ABOUT 200 NM NE OF THE WAVE AXIS IN ASSOCIATION WITH A
MID/UPPER LOW OVER THE CENTRAL ATLC.

...ITCZ...

ITCZ AXIS IS CENTERED ALONG 7N10W 11N31W 8N44W 10N55W 10N80W.
SCATTERED MODERATE CONVECTION 375 NM N OF THE AXIS OVER PARTS OF
GUINEA...SIERRA LEONE...AND LIBERIA MAY DRIFT WWD OVER THE ATLC
WATERS THROUGH THE NIGHT. WIDELY SCATTERED SHOWERS/TSTMS WITHIN
120 NM OF THE AXIS BETWEEN 50W-55W. SCATTERED MODERATE OVER ERN
AND SRN VENEZUELA. SCATTERED MODERATE WITHIN 30 NM OF THE
COLOMBIAN COAST BETWEEN 73W-76W.

...DISCUSSION...

GULF OF MEXICO...
WIDELY SCATTERED SHOWERS AND TSTMS ARE DISTRIBUTED ACROSS MOST
OF THE GULF THIS EVENING AND ARE FOCUSED IN TWO MAIN AREAS...
NEAR THE W COAST OF FLORIDA AND OFF THE TEXAS/MEXICO COAST. A
REMNANT FRONTAL BOUNDARY THAT HAS BEEN OVER THE N GULF WATERS
HAS DEGENERATED INTO A TROF ALONG 31N84W 22N92W BUT THIS FEATURE
CONTINUES TO WEAKEN WITH NO CLEAR WIND SHIFT OR CLOUD BOUNDARY.
NONETHELESS...WIDELY SCATTERED MODERATE CONVECTION EXTENDS E OF
THE TROF OVER FLORIDA AND THE E GULF FROM 22N-29N BETWEEN
81W-88W. OTHER WIDELY SCATTERED SHOWERS/TSTMS ARE FARTHER W FROM
19N-28N BETWEEN 92W-100W. THE UPPER LEVELS ARE DOMINATED BY TWO
RIDGES...ONE FROM THE E GULF TO THE CAROLINA COAST...AND THE
OTHER CENTERED OVER CNTRL MEXICO. A SHORTWAVE TROF IS SANDWICHED
BETWEEN THE RIDGES NEAR LOUISIANA AND THE N GULF WATERS...AND
THIS IS THE FEATURE THAT IS WEAKENING THE ATLC RIDGE JUST ENOUGH
TO ALLOW HURRICANES FRANCES OUT IN THE ATLC TO MAKE A MORE NWWD
TRACK OVER THE NEXT COUPLE OF DAYS. AS FAR AS FLORIDA GOES...THE
OFFICIAL FORECAST TRACK OF FRANCES TAKES THE HURRICANE VERY
CLOSE TO OR INLAND OVER THE STATE BY THE WEEKEND. STAY TUNED FOR
ADDITIONAL INFORMATION.

CARIBBEAN...
WITH THE CIRCULATION OF HURRICANE FRANCES NOW N OF
HISPANIOLA...MOST OF THE AREA IS ACTUALLY EXPERIENCING FAIRLY
NICE WEATHER. THE DEEP-LAYERED FLOW IS MOSTLY FROM THE EAST BUT
EXTENSIVE CIRRUS OUTFLOW FROM THE HURRICANE HAS EXPANDED SWD
ACROSS HISPANIOLA TO ABOUT 14N/15N BETWEEN 68W-75W. THE
SLIGHTEST HINT OF AN UPPER TROF IS OBSERVED IN THE CIMSS
SATELLITE-DERIVED WIND VECTORS FROM THE VENEZUELAN ISLANDS NEWD
TO THE VIRGIN ISLANDS. A FEW SHOWERS/TSTMS ARE LOCATED WITHIN
100 NM OF THE PANAMA COAST AS WELL AS NEAR THE YUCATAN CHANNEL
BUT OTHERWISE MODERATE/STRONG SUBSIDENCE S OF THE HURRICANE IS
SUPPRESSING DEEP CONVECTION.

WEST ATLANTIC...
THE MAIN CONCERN AT THE MOMENT IS UNDERSTANDABLY HURRICANE
FRANCES. THE STRUCTURE AND EFFECTS OF THE STORM IS EXPLAINED IN
THE SPECIAL FEATURES SECTION ABOVE. ELSEWHERE W OF 60W...THE
UPPER LOW WHICH HAD BEEN MOVING ACROSS THE BAHAMAS SINCE
YESTERDAY HAS PRETTY MUCH BECOME AN OPEN TROF BETWEEN THE
BAHAMAS AND FLORIDA AND IS ADDING TO THE WEAKNESS IN THE
MID-LEVEL RIDGE WHICH IS ALLOWING FRANCES TO NOW TAKE A MORE WNW
OR NW TRACK.

SUBTROPICAL ATLANTIC E OF 60W...
THERE ARE A FEW AREAS OF CONVECTION WHICH HAVE DEVELOPED OVER
THE AREA AND ARE STRONGLY INFLUENCED BY A VIGOROUS MID/UPPER LOW
CENTERED NEAR 26N46W. A LARGE AREA OF DRY AIR IS PLASTERED
BETWEEN THE LOW AND HURRICANE FRANCES FROM 54W-62W.
HOWEVER...BROAD UPPER DIFFLUENCE S OF THE LOW HAS ENHANCED
SCATTERED MODERATE CONVECTION FROM 16N-23N BETWEEN 45W-53W. IN
ADDITION...MOIST SWLY FLOW SE OF THE LOW IS PROVIDING A GOOD
ENVIRONMENT FOR SCATTERED MODERATE CONVECTION TO FORM ALONG  THE
E ATLC TROPICAL WAVE/LOW BUT IT SEEMS THE VERTICAL SHEAR IS
PROHIBITING TROPICAL DEVELOPMENT. ELSEWHERE...BROAD WLY FLOW
EXTENDS FROM 35W EWD TO AFRICA WITH THE BASE OF AN UPPER TROF
DIGGING SWD PAST MADEIRA ISLAND TOWARDS THE CANARY ISLANDS.
EXCEPT FOR INCREASED HIGH CLOUDINESS NEAR THE COAST OF MOROCCO
HOWEVER...THE ATMOSPHERE IS TOO DRY TO SUPPORT HEAVY
SHOWERS/TSTMS IN THE AREA.

TROPICAL ATLANTIC...
BROAD UPPER LEVEL TROUGHING EXTENDS E OF THE LEEWARD/WINDWARD
ISLANDS BETWEEN 40W-60W...S OF THE CENTRAL ATLC UPPER LOW...WITH
SCATTERED MODERATE CONVECTION HAVING DEVELOPED N OF 16N BETWEEN
42W-51W. HOWEVER...A STRONG 50 KT NLY JET IS ADVECTING DRY AIR
WELL TO THE S INTO THE TROPICS JUST E OF THE ISLANDS AND THIS IS
LIMITING THE AMOUNT OF DEEP CONVECTION ALONG THE ITCZ. FARTHER
E...A LARGE UPPER LEVEL ANTICYCLONE IS CENTERED ABOUT 200/300 NM
W OF THE CAPE VERDE ISLANDS WITH THE DEEPEST AND MOST MOIST ELY
FLOW S OF 13N.

$$
BERG


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