[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 260001
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
805 PM EDT SAT 25 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...

HURRICANE JEANNE CENTERED NEAR 27.1N 79.3W...OR ABOUT 80 MILES
SE OF VERO BEACH FLORIDA AND 65 MILES ESE OF FT. PIERCE
FLORIDA...AT 26/0000 UTC MOVING W TO WNW 12 KT. MAXIMUM
SUSTAINED WIND SPEED IS 100 KT WITH GUSTS TO 120 KT. LATEST
MINIMUM CENTRAL PRESSURE MEASURED BY A NOAA HURRICANE HUNTER
PLANE IS 951 MB. SEE LATEST NHC PUBLIC ADVISORY OR NHC
FORECAST/ADVISORY UNDER AWIPS/WMO HEADERS MIATCPAT1/WTNT31 KNHC
OR MIATCMAT1/WTNT21 KNHC FOR MORE DETAILS. THE STRONGEST
CONVECTION WITHIN THE EYEWALL HAS WEAKENED A BIT OVER THE PAST
SEVERAL HOURS...YET JEANNE REMAINS A POWERFUL CATEGORY 3
HURRICANE CAPABLE OF WIDESPREAD WIND DAMAGE AND STORM SURGE
FLOODING. WSR-88D IMAGERY FROM MIAMI AND MELBOURNE FLORIDA
INDICATE THAT THE EYE IS SOMEWHAT OBLONG...ABOUT 40 NM BY 28
NM...WITH ABOUT A 60 NM WIDE CORE OF STRONG CONVECTION WHICH IS
NOW MOVING ONSHORE THE S/CNTRL COAST OF E FLORIDA. THE S SIDE OF
THE HURRICANE IS THE WETTER SIDE OF THE STORM...WITH INDISTINCT
SPIRAL BANDING SWEEPING ACROSS S FLORIDA TOWARDS THE NORTHERN
BAHAMAS. TO THE N...ISOLATED FAST-MOVING SHOWERS ARE MOVING FROM
THE ATLC WATERS ACROSS THE REMAINDER OF N/CNTRL FLORIDA.
NUMEROUS MODERATE/STRONG CONVECTION EXTENDS WITHIN 120 NM OF THE
CENTER...AND WIDELY SCATTERED MODERATE IS IN BANDS ELSEWHERE
FROM 24N-30N BETWEEN 76W-82W.

TROPICAL STORM LISA IS CENTERED NEAR 17.2N 45.8W...OR ABOUT 1445
MILES W OF THE CAPE VERDE ISLANDS...AT 25/2100 UTC MOVING NNW 9
KT. MAXIMUM SUSTAINED WIND SPEED IS 35 KT WITH GUSTS TO 45 KT.
ESTIMATED MINIMUM CENTRAL PRESSURE IS 1002 MB. SEE LATEST NHC
FORECAST/ADVISORY UNDER AWIPS/WMO HEADER MIATCMAT3/WTNT23 KNHC
FOR MORE DETAILS. THE LOW LEVEL CENTER OF LISA REMAINS PARTIALLY
EXPOSED TO THE W OF THE STRONG CONVECTION...WHICH IS BECOMING A
LITTLE BIT MORE INTENSE. THE STORM IS LOCATED ON THE EASTERN
PERIPHERY OF A MID/UPPER TROF...AND ASSOCIATED DRY AIR AND NWLY
SHEAR IS DISPLACING THE CONVECTION TO THE E. SCATTERED
MODERATE/STRONG CONVECTION FROM 13N-19N BETWEEN 41W-46W.

...TROPICAL WAVES...

TROPICAL WAVE LOCATED ABOUT 300 NM W OF THE CAPE VERDE ISLANDS
ALONG 30W/31W S OF 18N MOVING W 10-15 KT. A WELL-DEFINED
LOW-LEVEL CIRCULATION HAS DEVELOPED ALONG THE WAVE AXIS NEAR
15N31W WITH A FEW ISOLATED TSTMS OCCASIONALLY POPPING NEAR THE
CENTER. THERE APPEARS TO BE DRY AIR BEING ENTRAINED INTO THE
CIRCULATION FROM THE WEST...WHICH IS PROBABLY LIMITING
CONVECTION N OF 9N. OTHERWISE...THERE IS ENHANCED ITCZ
CONVECTION NEAR THE WAVE BETWEEN 21W-34W. ISOLATED SHOWERS/TSTMS
FROM 14N-17N BETWEEN 28W-31W WITH UPPER LEVEL CIRRUS EXTENDING
AWAY FROM THE WAVE N OF 18N BETWEEN 20W-26W.

...ITCZ...

ITCZ AXIS EXTENDS OFF THE COAST OF SIERRA LEONE ALONG 7.5N13W
15N27W...THEN ALONG 6N32W 11N42W INTO THE CIRCULATION OF T.S.
LISA...THEN RE-ESTABLISHED W OF GUYANA ALONG 8N60W 8N80W. WIDELY
SCATTERED MODERATE CONVECTION ALIGNED ALONG AND UP TO 200 NM
INLAND OF THE AFRICAN COAST FROM 5N-14N. SCATTERED MODERATE FROM
2N-7N BETWEEN 21W-33W. WIDELY SCATTERED TO SCATTERED MODERATE
OVER GUYANA...VENEZUELA...AND N COLOMBIA. WIDELY SCATTERED OVER
THE SW CARIBBEAN FROM 10N-12N BETWEEN 73W-80W.

...DISCUSSION...

GULF OF MEXICO...
A WEAK SFC TROF IS BEING PROPELLED SWWD OVER THE WESTERN GULF OF
MEXICO DUE TO THE STRONG CIRCULATING FLOW EMANATING FROM
HURRICANE JEANNE FARTHER E. THE TROF IS SEMI-ATTACHED TO THE
REMNANTS OF T.D. IVAN...WHICH ARE LUMBERING ACROSS PARTS OF THE
TEXAS COAST...AND IS TRIGGERING ISOLATED SHOWERS OVER THE W GULF
PRIMARILY W OF 90W. THE TROF IS COLLOCATED WITH A MID/UPPER
LEVEL LOW CENTERED ABOUT 280 NM SE OF HOUSTON TEXAS AND MOST OF
THE SHOWERS ARE LOCATED WITHIN THE UNSTABLE ATMOSPHERE NEAR THIS
FEATURE. FARTHER E...RADAR IMAGERY SHOWS ONLY A FEW SHOWERS FROM
HURRICANE JEANNE MOVING OFF THE FLORIDA W COAST AT THE MOMENT.
STRONG SUBSIDENCE IS OCCURRING AHEAD OF THE HURRICANE AND HAS
LIMITED CLOUD COVER OVER THE E GULF...FOR NOW.

CARIBBEAN AND FAR W ATLANTIC...
OF COURSE THE MAIN CONCERN PRESENTLY IS HURRICANE JEANNE WHICH
IS MOVING AWAY FROM THE NORTHERN BAHAMAS TOWARD THE FLORIDA EAST
COAST. THE HURRICANE LIES TO THE N OF A MID/UPPER TROF WHICH
EXTENDS FROM THE SOUTHERN BAHAMAS TO THE SW OF JAMAICA...AND THE
ELY FLOW ON THE N SIDE OF THIS FEATURE IS ENHANCING THE OUTFLOW
OVER THE SW QUADRANT OF JEANNE. A WEAK SFC TROF IS LOCATED IN
THE SAME GENERAL AREA AS THE UPPER TROF...AND THIS HAS ALLOWED
WIDELY SCATTERED MODERATE CONVECTION TO DEVELOP OVER THE
SOUTHERN BAHAMAS...HISPANIOLA...THE WINDWARD PASSAGE...AND
JAMAICA. ELSEWHERE...A FEW ISOLATED SHOWERS ARE EASING OVER THE
WINDWARD ISLANDS BUT PREDOMINANTLY MODERATE/STRONG SUBSIDENCE
OVER THE E CARIBBEAN IS KEEPING THE AREA DRY.

SUBTROPICAL ATLANTIC...
A LARGE UPPER LEVEL CYCLONIC VORTEX IS CENTERED OVER THE N ATLC
NEAR 37N44W WITH THE BASE OF THE TROF EXTENDING SWD INTO THE
AREA...AND A RE-INFORCING SHORTWAVE ALONG 32N POISED TO MOVE IN
SHORTLY. A TROF AT THE SFC ALSO EXTENDS ACROSS THE AREA...ALONG
30N40W 24N55W 27N67W...AND A NARROW SWATH OF DEEP-LAYERED
MOISTURE IS ENHANCING ISOLATED SHOWERS/TSTMS WITHIN 90 NM OF THE
TROF W OF 45W. MORE WIDELY SCATTERED MODERATE CONVECTION IS N OF
24N BETWEEN 35W-45W. FARTHER E...TWO STRONG UPPER RIDGES ARE
ANCHORED ALONG 36W AND FROM CNTRL MAURITANIA TO THE CANARY
ISLANDS...WITH A CYCLONIC SHEAR AXIS IN BETWEEN EXTENDING FROM
THE AZORES SWD ALONG 30N25W 19N27W TO A WEAK CUT-OFF LOW NEAR
THE CAPE VERDES. HIGH LEVEL CIRRUS WITH PERHAPS ISOLATED SHOWERS
OR LIGHT DRIZZLE EXTENDS FROM THE CAPE VERDES NWD BETWEEN
20W-27W.

TROPICAL ATLANTIC...
A LARGE MID/UPPER LEVEL HIGH IS CENTERED ABOUT 375 NM E OF THE
LESSER ANTILLES NEAR 15N54W WITH MODERATE SUBSIDENCE OVER THE
ENTIRE AREA W OF 47W. T.S. LISA AND ITS ASSOCIATED CONVECTION IS
LOCATED BETWEEN 40W-50W...AND AN UPPER LEVEL RIDGE HAS DEVELOPED
DOWNSTREAM ALONG 10N44W 16N39W 20N40W WITH ENHANCED OUTFLOW NOW
ON THE E AND S SIDE OF THE STORM. DEEP UPPER LEVEL TROUGHING
EXTENDS TO THE CAPE VERDE ISLANDS BETWEEN 20W-35W AND THE
SUBSIDENCE TO THE W OF THE AXIS...OR W OF 26W...IS KEEPING MOST
OF THE TROPICAL AREA DRY. AN EQUALLY LARGE UPPER LEVEL TROF IS
LOCATED S OF THE EQUATOR...AND AN AREA OF DIVERGENCE BETWEEN THE
TWO TROFS IS SUPPORTING ENHANCED ITCZ CONVECTION BETWEEN 20W-30W.

$$
BERG


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