[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 270001
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
805 PM EDT SUN 26 SEP 2004

TROPICAL WEATHER DISCUSSION FOR NORTH AMERICA...CENTRAL
AMERICA...GULF OF MEXICO...CARIBBEAN SEA...NORTHEASTERN SECTIONS
OF SOUTH 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 1800 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
2315 UTC.

...SPECIAL FEATURES...

TROPICAL STORM JEANNE IS CENTERED NEAR 29.4N 82.7W...OR ABOUT 10
MILES S OF BRONSON FLORIDA AND 30 MILES SW OF GAINESVILLE
FLORIDA...AT 27/0000 UTC MOVING NNW 11 KT. MAXIMUM SUSTAINED
WIND SPEED HAS DECREASED TO 50 KT WITH GUSTS TO 60 KT. ESTIMATED
MINIMUM CENTRAL PRESSURE IS 978 MB. SEE LATEST NHC PUBLIC
ADVISORY OR NHC FORECAST/ADVISORY UNDER AWIPS/WMO HEADERS
MIATCPAT1/WTNT31 KNHC OR MIATCMAT1/WTNT21 KNHC FOR MORE DETAILS.
JEANNE HAS MAINTAINED A TIGHT CIRCULATION EVEN AS IT CONTINUES
TO MOVE INLAND OVER PARTS OF N FLORIDA. RADAR IMAGERY INDICATES
SOME DRYING ON THE S SIDE OF THE STORM WITH THE HEAVIEST SHIELD
OF RAIN NOW SPIRALING ACROSS N FLORIDA (N OF CEDAR KEY-OCALA-
DAYTONA BEACH LINE)...EXTREME SE GEORGIA...AND THE FAR NE GULF
OF MEXICO WATERS. WIDELY SCATTERED SHOWERS ARE LOCATED ACROSS
CNTRL PARTS OF THE STATE FROM ABOUT TAMPA BAY TO ORLANDO AND
CAPE CANAVERAL...WHILE SOME LEFTOVER FEEDER BANDS ARE SWINGING
ACROSS S FLORIDA INTO THE ATLC WATERS. NUMEROUS MODERATE/
SCATTERED STRONG CONVECTION FROM 28N-32N BETWEEN 80W-85W.

TROPICAL STORM LISA IS CENTERED NEAR 19.7N 46.1W...OR ABOUT 1475
MILES WNW OF THE CAPE VERDE ISLANDS...26/2100 UTC MOVING N AT 8
KT. MAXIMUM SUSTAINED WIND SPEED IS 45 KT WITH GUSTS TO 55 KT.
ESTIMATED MINIMUM CENTRAL PRESSURE IS 1000 MB. SEE LATEST NHC
FORECAST/ADVISORY UNDER AWIPS/WMO HEADER MIATCMAT3/WTNT23 KNHC
FOR MORE DETAILS. LISA CONTINUES TO SIT ON THE NE PERIPHERY
OF A LARGE MID/UPPER LEVEL HIGH CENTERED TO THE E OF THE LESSER
ANTILLES...AND EASTERLY SHEAR CONTINUES TO PARTIALLY EXPOSE THE
LOW-LEVEL CENTER JUST TO THE W OF THE STRONGEST CONVECTION. THE
CONVECTION HAD BEEN RAGGED FOR MOST OF THE DAY...BUT A NEW BURST
OF STRONG CONVECTION IS NOW DEVELOPING NO MORE THAN ABOUT 50 NM
NE OF THE CENTER. WIDELY SCATTERED MODERATE/ISOLATED STRONG
CONVECTION FROM 15N-22N BETWEEN 40W-46W.

...TROPICAL WAVES...

TROPICAL WAVE LOCATED ABOUT 600 NM W OF THE CAPE VERDE ISLANDS
ALONG 35W/36W S OF 20N MOVING W 10-15 KT. A WEAK 1010 MB LOW IS
CENTERED ALONG THE AXIS NEAR 15N36W. THE WAVE IS APPROACHING THE
STRONGER CIRCULATION ASSOCIATED WITH T.S. LISA AND SO THE SFC
LOW SHOULD BEGIN TO WEAKEN AS IT GETS STRETCHED TO THE N. A FEW
SHOWERS HAVE BEEN DEVELOPING UP TO 300 NM E OF THE WAVE BUT
OVERALL THE ATMOSPHERE HAS BEEN TOO DRY TO SUPPORT MUCH TSTM
ACTIVITY.

...ITCZ...

ITCZ AXIS EXTENDS OFF THE COAST OF SENEGAL DIPPING S ALONG
14N17W 7N25W 10N30W...THEN RE-ESTABLISHED S OF T.S. LISA ALONG
10N47W 7N65W 8N80W. SCATTERED MODERATE CONVECTION OVER SW MALI
AND THE COASTAL REGIONS FROM GUINEA-BISSAU TO GHANA. ISOLATED
MODERATE WITHIN 175 NM NW OF AXIS BETWEEN 18W-21W. ISOLATED
SHOWERS/TSTMS FROM 4N-9N BETWEEN 12W-25W. ISOLATED SHOWERS/TSTMS
FROM 1N-7N BETWEEN 31W-40W. SCATTERED MODERATE OVER MOST OF
VENEZUELA. SCATTERED MODERATE/STRONG ALONG THE COLOMBIAN COAST
AND ADJACENT WATERS FROM 8N-13N BETWEEN 72W-80W.

...DISCUSSION...

GULF OF MEXICO...
SLOWLY-WEAKENING TROPICAL STORM JEANNE IS MOVING N OVER THE
FLORIDA PENINSULA WITH HEAVY SPIRAL BANDS SWEEPING ACROSS THE
FAR NE PARTS OF THE GULF OF MEXICO WATERS...NE OF A LINE FROM
APALACHICOLA TO TAMPA BAY. FARTHER W...JEANNE'S CIRCULATION IS
DRAWING DRIER CONTINENTAL AIR SWD OVER THE CNTRL GULF...WITH
AMSU AND SSM/I IMAGERY BOTH SHOWING PWAT VALUES LOWERING BELOW
1.25" AND AGREEING WITH RADIOSONDE DATA FROM STATIONS ALONG THE
GULF COAST. THIS IS PARTIALLY DUE TO MODERATE SUBSIDENCE UP TO
500 NM TO THE SW OF JEANNE ALONG A MID/UPPER LEVEL TROF
EXTENDING FROM SW LOUISIANA TO NEAR THE YUCATAN PENINSULA.
ELSEWHERE...A REMNANT SFC TROF IS BEING PUSHED SWD OVER THE BAY
OF CAMPECHE WHILE TRIGGERING ISOLATED SHOWERS GENERALLY WITHIN
150 NM OF THE MEXICAN COAST.

CARIBBEAN...
SHOWERS/TSTMS ARE FOCUSING ALONG A BOUNDARY FROM CNTRL CUBA TO
THE GULF OF HONDURAS AS STRONGER EASTERLY FLOW BECOMES
RE-ESTABLISHED OVER THE E/CNTRL CARIBBEAN IN THE WAKE OF
JEANNE...AND CONVERGES WITH LIGHTER WLY FLOW OVER THE NW
CARIBBEAN. WIDELY SCATTERED SHOWERS/TSTMS ARE N OF 17N BETWEEN
76W-84W AND EXTEND ACROSS CNTRL CUBA AND THE CAYMAN ISLANDS. A
BROAD MID/UPPER LOW IS CENTERED OFF THE W TIP OF JAMAICA...WHICH
IS ENHANCING THIS SHOWER ACTIVITY. UPPER LEVEL DIVERGENCE TO THE
S OF THIS FEATURE IS ALSO ENHANCING ITCZ CONVECTION OVER N
COLOMBIA AND PULLING IT NWD OVER THE SW CARIBBEAN WATERS.

SUBTROPICAL ATLANTIC...
STRONG UPPER LEVEL RIDGING IS BUILDING NWD FROM THE BAHAMAS TO
THE SE UNITED STATES COAST IN THE WAKE OF JEANNE...AND SOME OF
THE STORM'S OUTFLOW IS BEING PULLED SEWD ON THE E SIDE OF THE
RIDGE. A BROAD UPPER TROF REMAINS OVER THE W/CNTRL ATLANTIC WITH
THE AXIS ALONG 32N47W 24N66W AND MUCH DRIER AIR SWEEPING IN
BEHIND IT. A REMNANT TROF...PUSHED S BY THE UPPER LEVEL
FEATURE...IS STILL DRAPED ALONG 32N36W 23N60W 30N70W. SCATTERED
SHOWERS/TSTMS EXTEND WITHIN 70 NM OF THE TROF E OF 50W AND
WITHIN 90 NM OF THE TROF W OF 60W. A BUILDING RIDGE IS LOCATED E
OF THE UPPER TROF EXTENDING FROM T.S. LISA NEWD BEYOND 32N31W
WITH A 70+ KT JET RIDING UP THE W SIDE OF THE AXIS INTO THE N
ATLC. FARTHER E...A PAIR OF MID/UPPER LOWS ARE SPIRALING ACROSS
AND NEAR THE AREA...NEAR 22N26W AND 35N16W...CONNECTED BY A
SHEAR AXIS WHICH STRETCHES E/W ACROSS THE CANARY ISLANDS.

TROPICAL ATLANTIC...
AN EXPANSIVE MID/UPPER LEVEL HIGH REMAINS ENTRENCHED E OF THE
LESSER ANTILLES NEAR 14N53W WITH DRY AIR ACROSS THE ENTIRE AREA
W OF 48W. BROAD CYCLONIC FLOW EXTENDS INTO THE AREA FROM THE N
BETWEEN AFRICA AND 35W...AND A SHEAR AXIS STRETCHES SW OF THIS
FEATURE ALONG 10N32W EQ45W. ITCZ CONVECTION IS MUCH MORE
SPORADIC AND LESS INTENSE COMPARED TO THE PAST SEVERAL
DAYS...PRIMARILY BECAUSE THERE IS VERY LITTLE DIVERGENCE IN THE
UPPER LEVELS OF THE ATMOSPHERE.

$$
BERG





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