[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 251240
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
805 AM 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 0600 UTC SURFACE ANALYSIS AND
SATELLITE IMAGERY THROUGH 1045 UTC.

...SPECIAL FEATURES...

AT 8 AM EDT...1200Z...THE CENTER OF HURRICANE JEANNE WAS LOCATED
BY A RECONNAISSANCE PLANE NEAR LATITUDE 26.5 NORTH...LONGITUDE
77.0 WEST JUST OVER MARSH HARBOUR...ABACO ISLAND IN THE
NORTHWESTERN BAHAMAS.  THIS POSITION IS ALSO ABOUT 190
MILES...310 KM...EAST OF THE SOUTHEASTERN COAST OF FLORIDA...
MOVING W AT 12 KT. MAXIMUM SUSTAINED WIND SPEED IS 90 KT WITH
GUSTS TO 110 KT AND THE MINIMUM CENTRAL PRESSURE IS 958 MB. SEE
LATEST NHC PUBLIC ADVISORY OR NHC FORECAST/ADVISORY UNDER
AWIPS/WMO HEADERS MIATCPAT1/WTNT31 KNHC OR MIATCMAT1/WTNT21 KNHC
FOR MORE DETAILS. WELL DEFINED EYE REMAINS WITH THE ASSOCIATED
DEEP CONVECTION MAINLY TO THE S OF THE CENTER. STRONG UPPER
LEVEL HIGH IS NOW CENTERED NEAR JEANNE WITH RIDGE EXTENDING N TO
WELL OVER E CANADA. THE OUTFLOW STILL REMAINS GOOD IN ALL BUT
THE S QUADRANT. MODERATE SUBSIDENCE/DRY AIR REMAINS AROUND
JEANNE IN ALL BUT THE E QUADRANT. AS JEANNE MOVES OVER THE
WARMER WATER OF THE GULF STREAM FURTHER INTENSIFICATION IS
POSSIBLE BEFORE LANDFALL. SCATTERED STRONG CONVECTION IS WITHIN
90 NM IN THE S SEMICIRCLE. SCATTERED MODERATE/ISOLATED STRONG
CONVECTION IS WITHIN 150 NM AROUND THE REMAINDER OF THE SYSTEM.

TROPICAL DEPRESSION LISA WAS UPGRADED AGAIN TO TROPICAL STORM AT
25/0900 UTC. T.S. JEANNE IS CENTERED NEAR 15.2N 45.2W OR ABOUT
925 NM EAST OF THE OUTER LESSER ANTILLES AT 25/0900 UTC MOVING
NW AT 8 KT. MAXIMUM SUSTAINED WIND SPEED IS 35 KT WITH GUSTS TO
45 KT AND 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
REMAINS EXPOSED TO THE NW OF THE ASSOCIATED DEEP CONVECTION. AS
IN THE LAST COUPLE OF DAYS...LISA CONTINUES TO EXPERIENCE
NORTHEASTERLY SHEAR WHICH ACCOUNTS FOR THE DISPLACEMENT OF THE
DEEP CONVECTION. SCATTERED MODERATE/ISOLATED STRONG CONVECTION
COVERS THE AREA WITHIN 100 NM OF LINE FROM 12N46W-15N42W.

...TROPICAL WAVES...
TROPICAL WAVE W OF THE CAPE VERDE ISLANDS IS ALONG 28W/29W S OF
19N MOVING W 10-15 KT. A BROAD LOW/MID LEVEL CIRCULATION IS
OBSERVED ALONG THE WAVE ABOUT 16N. CLASSIC SATELLITE SIGNATURE
IS OBSERVED ON INFRARED SATELLITE IMAGERY. SCATTERED SHOWERS/
ISOLATED THUNDERSTORMS ARE E OF THE AXIS FROM 14N-18N BETWEEN
23W-28W INCLUDING THE CAPE VERDE ISLANDS.

...ITCZ...

ITCZ EXTENDS ALONG 18N10W 15N20W 12N33W 15N42W 1053W 11N70W.
OTHER THAN THE TROPICAL WAVE AND T.D. LISA...AREA OF SCATTERED
MODERATE/ISOLATED STRONG CONVECTION IS WITHIN 120/150 NM OF
LINE FROM 2N31W-8N26W. SMALL CLUSTERS OF SIMILAR CONVECTION ARE
FROM 3N-8N BETWEEN 21W-26W.

...DISCUSSION...

GULF OF MEXICO...
BROAD DEEP LAYERED TROUGH EXTENDS FROM THE THE GREAT LAKES
THROUGH THE MID WEST OF THE UNITED STATES INTO TEXAS. A
SHORTWAVE TROUGH AXIS EXTENDS FROM CENTRAL COAST OF TEXAS INTO
THE GULF THROUGH A UPPER LEVEL LOW CENTERED NEAR 26N93W
CONTINUING S INTO THE BAY OF CAMPECHE NEAR 21N93W. THIS
SHORTWAVE TROUGH IS A RESULT OF THE MID/UPPER LEVEL HIGH OVER
THE E PACIFIC AND THE MID/UPPER LEVEL HIGH CENTERED JUST N OF
THE YUCATAN PENINSULA NEAR 23N88W. THE RIDGE AXIS FROM THE
YUCATAN HIGH IS BEING NARROWED BY THE APPROACH OF THE UPPER
LEVEL HIGH OVER HURRICANE JEANNE. AN INDUCED INVERTED TROUGH
OVER THE FAR E GULF IS A RESULT OF THE ABOVE UPPER HIGHS. STRONG
SUBSIDENCE/DRY AIR IS OVER THE E GULF E OF 86W TO THE FLORIDA
PENINSULA. THIS DRY AIR IS GIVING WAY AS JEANNE CONTINUES TO
MOVE WESTWARD. THE HIGH LAYERED CLOUDS ARE OVER THE S FLORIDA
PENINSULA AND THE OUTER MOST RAINBANDS ARE APPROACHING THE
COAST. ONLY SCATTERED SHOWERS/ISOLATED THUNDERSTORMS REMAIN IN
THE NW GULF N OF 26N FROM 91W-95W WHICH IS A RESULT OF THE
SURFACE TROUGH THAT IS THE REMNANT OF IVAN. ISOLATED
THUNDERSTORMS ARE ALONG THE COAST OF THE BAY OF CAMPECHE.

THE CARIBBEAN SEA AND W TROPICAL ATLANTIC...
THE MID/UPPER LEVEL HIGH N OF THE YUCATAN PENINSULA COVERS THE
FAR NW CARIBBEAN WITH ANTICYCLONIC FLOW W OF 85W. A MID/UPPER
LEVEL HIGH CENTERED OVER NW VENEZUELA IS BRINGING ANTICYCLONIC
FLOW OVER THE CENTRAL CARIBBEAN FROM 64W-81W. AN INDUCED
MID/UPPER LEVEL LOW/TROUGH IS A RESULT OVER THE UPPER HIGH OVER
VENEZUELA AND THE HIGH OVER JEANNE IN THE W ATLC. THIS TROUGH
EXTENDS FROM N OF HISPANIOLA NEAR 22N74W W TO A LOW CENTERED S
OF CUBA NEAR 20N79W THEN SW TO 16N83W. THIS IS PRODUCING
SCATTERED SHOWERS/ISOLATED THUNDERSTORMS OVER HAITI...THE
WINDWARD PASSAGE...TO OVER THE TURKS AND CAICOS ISLANDS. A
MID/UPPER LEVEL HIGH OVER THE W TROPICAL ATLC ABOUT 475 NM W OF
THE LEEWARD ISLANDS NEAR 16N53W. ANTICYCLONIC FLOW COVERS THE
AREA FROM 47W-63W INCLUDING THE LEEWARD AND WINDWARD ISLANDS.
MODERATE TO STRONG SUBSIDENCE/DRY AIR COVERS THE E CARIBBEAN
INTO THE TROPICAL ATLC FROM 48W-70W. SCATTERED LOW LEVEL
SHOWERS/THUNDERSTORMS ARE OVER THE LESSER ANTILLES S OF 16N
INCLUDING TRINIDAD AND TOBAGO.

SUBTROPICAL ATLANTIC AND THE E TROPICAL
HURRICANE JEANNE AND THE UPPER LEVEL HIGH OVER HER DOMINATE THE
W ATLC. THE LARGE DEEP LAYERED TROUGH OVER THE CENTRAL ATLC IS
NOW N OF 25N BETWEEN 38W-65W WITH A LARGE UPPER LEVEL LOW
CENTERED NEAR 40N49W. THIS TROUGH WILL REMAIN NEARLY STATIONARY
OVER THE NEXT 12 TO 24 HOURS BEFORE IT BEGINS TO LIFT NE AGAIN.
ELSEWHERE OVER THE CENTRAL ATLC...A MID/UPPER LEVEL HIGH IS
CENTERED NEAR 16N53W IN THE TROPICAL ATLC WITH ANTICYCLONIC FLOW
S OF 24N FROM 47W-63W. THIS UPPER LEVEL HIGH CONTINUES TO
PRODUCE NORTHEASTERLY SHEAR OVER T.S. LISA. A RIDGE AXIS
EXTENDS FROM NEAR 24N44W NE TO WELL BEYOND 32N34W. MID/UPPER
LEVEL LOW IS OVER THE E ATLANTIC NEAR 32N27W WITH A TROUGH
EXTENDING S TO 12N30W. THE ABOVE UPPER HIGH AND TROUGH HAVE BEEN
NEAR STATIONARY FOR ALMOST 24 HOURS AND WILL REMAIN SO FOR AT
LEAST THE NEXT 12...THE UPPER LOW IS STARTING TO MOVE N OUT OF
THE REGION. LARGE MID/UPPER LEVEL HIGH IS INLAND OVER W AFRICA
NEAR 19N7W WITH ANTICYCLONIC FLOW COVERING THE E ATLC E OF 20W.
AT THE SURFACE...A COLD FRONT ENTERS THE CENTRAL ATLC NEAR
32N49W EXTENDING W TO 31N59W. A SURFACE TROUGH EXTENDS ACROSS
THE CENTRAL ATLC SE OF THE ABOVE FRONT NEAR 32N38W SW TO 26N45W
THEN W ALONG 27N61W TO 26N68W. THE SUBTROPICAL RIDGE EXTENDS
JUST E OF THE AZORES THROUGH 32N24W SW TO 22N35W. CLUSTERS OF
SHOWERS/THUNDERSTORMS ARE WITHIN 120 NM OF THE SURFACE TROUGH.

$$
WALLACE





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