[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 231757
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
205 PM EDT THU 23 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 1200 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
1715 UTC.

...SPECIAL FEATURES...

T.S. IVAN IS CENTERED OVER THE NW GULF OF MEXICO NEAR 29.3N
92.8W OR ABOUT 85 SE OF THE PORT ARTHUR TEXAS COAST AT 23/1800
UTC. IVAN IS MOVING NW AT 13 KT. MAXIMUM SUSTAINED WIND SPEED IS
50 KT WITH GUSTS TO 60 KT AND THE ESTIMATED MINIMUM CENTRAL
PRESSURE IS 999 MB. SEE LATEST NHC PUBLIC OR FORECAST/ADVISORY
UNDER AWIPS/WMO HEADER MIATCPAT4/ WTNT34 OR MIATCMAT4/WTNT24
KNHC FOR MORE DETAILS. IVAN REMAINS A POORLY ORGANIZED
CYCLONE...WITH THE ASSOCIATED DEEP CONVECTION TO THE NE OF THE
LOW LEVEL CENTER DUE TO SOUTHERLY SHEAR. SCATTERED
MODERATE/ISOLATED STRONG CONVECTION IS N OF 28.5N TO INLAND OVER
S LOUISIANA. SCATTERED SHOWERS/THUNDERSTORMS ARE APPROACHING THE
N GULF COAST FROM ALABAMA ACROSS LOUISIANA.

HURRICANE JEANNE IS CENTERED NEAR 25.8N 70.0W OR ABOUT 440 M E
OF GREAT ABACO ISLAND AT 23/1800 UTC. JEANNE IS MOVING W AT 4
KT. MAXIMUM SUSTAINED WIND SPEED IS 90 KT WITH GUSTS TO 110 KT
AND THE ESTIMATED MINIMUM CENTRAL PRESSURE 966 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 EYE HAS HAS BECOME A LITTLE MORE RAGGED IN THE
PAST FEW HOURS.  STRONG UPPER LEVEL HIGH OVER THE NE UNITED
STATES CONTINUES TO MOVE E TO SE OVER THE NW ATLC AND HAS BEGUN
TO PUSH JEANNE TOWARD THE WEST. THE OUTFLOW  REMAINS GOOD IN ALL
QUADRANTS. MODERATE SUBSIDENCE/DRY AIR NOW SURROUNDS JEANNE.
SCATTERED MODERATE/ISOLATED STRONG CONVECTION IS WITHIN A 90 NM
RADIUS OF THE CENTER AND WITHIN AN OUTER RAIN

HURRICANE KARL IS CENTERED NEAR 33.8N 43.8W OR ABOUT 980 NM
WEST-SOUTHWEST OF THE AZORES AT 23/1500 UTC. KARL IS MOVING NNE
AT 24 KT. MAXIMUM SUSTAINED WIND SPEED IS 105 KT WITH GUSTS TO
130 KT AND THE ESTIMATED MINIMUM CENTRAL PRESSURE IS 955 MB. SEE
LATEST NHC FORECAST/ADVISORY UNDER AWIPS/WMO HEADER MIATCMAT2/
WTNT22 KNHC FOR MORE DETAILS. KARL'S EYE HAS BECOME VERY
RAGGED...SOME WEAKENING HAS ACCRUED IN THE LAST FEW HOURS.  KARL
IS FORECAST TO BE WEAKEN TO HURRICANE STRENGTH WITHIN 90 NM OF
THE CENTER WITH SCATTERED MODERATE EXTENDING 300 NM FROM THE
CENTER.

TROPICAL STORM LISA IS CENTERED NEAR 12.1N 41.7W OR ABOUT 990 NM
JUST SOUTH OF WEST OF THE CAPE VERDE ISLANDS AT 23/1500 UTC.
LISA IS NOW MOVING W AT 3 KT AND MAXIMUM SUSTAINED WIND SPEED
REMAINS 40 KT WITH GUSTS TO 50 KT. ESTIMATED MINIMUM CENTRAL
PRESSURE IS 1000 MB. SEE LATEST NHC FORECAST/ADVISORY UNDER
AWIPS/WMO HEADER MIATCMAT3/WTNT23 KNHC FOR MORE DETAILS. ON
SATELLITE IMAGERY...LISA REMAINS POORLY ORGANIZED BUT THE DEEP
CONVECTION REMAINS STRONG. LISA IS EXPECTED TO GET BETTER
ORGANIZED AND POSSIBLY INTENSIFY SOMEWHAT OVER THE NEXT 24-36
HOURS  AS HURRICANE KARL MOVES FURTHER AWAY. SCATTERED
MODERATE/ISOLATED STRONG CONVECTION IS WITHIN 130 NM RADIUS.

...TROPICAL WAVES...
NONE.

...ITCZ...

ITCZ EXTENDS ALONG 13N10W 11N22W 11N38W 10N61W. SCATTERED
MODERATE/ ISOLATED STRONG CONVECTION FROM 6N-14N BETWEEN
7W-12W.  SCATTERED MODERATE CONVECTION WITHIN T.S.
LISA...SCATTERED MODERATE/ISOLATED STRONG CONVECTION IS WITHIN
130 NM RADIUS.

...DISCUSSION...

GULF OF MEXICO...
ASIDE FROM ACTIVITY ASSOCIATED WITH THE T.S. IVAN...MID/UPPER
LEVEL ELONGATED LOW IS LOCATED OVER THE W GULF NEAR 20N94W. A
MID/UPPER LEVEL RIDGE CENTERED IN THE NW CARIBBEAN CONTINUES TO
PUSHING NORTHWARD INTO THE GULF TO THE GA/AL BOARDER...THIS
RIDGE CONTINUES TO PRODUCE STRONG S FLOW FROM 85W-92W WHICH IS
PRODUCING SHEAR OVER IVAN.  THE UPPER LOW WILL REMAIN
ESSENTIALLY STATIONARY BUT BECOME NARROWER AND EVEN MORE
ELONGATED WITHIN THE NEXT 24-36 HOURS. THIS EVOLUTION SHOULD
PRODUCE SOME IMPROVEMENT IN THE MID-UPPER LEVEL ENVIRONMENT OVER
T.S. IVAN AND REDUCING THE UPPER LEVEL SHEAR. AT THE
SURFACE...T.S. IVAN TRAILS A REMNANT SURFACE TROUGH SE ALONG
28N91W OVER  W CUBA TO NEAR 20N80W. THE BOUNDARY COUPLED WITH
THE TROPICAL MOISTURE ADVECTED IN THE SOUTHERLY FLOW IS
PRODUCING SCATTERED SHOWERS/THUNDERSTORMS S OF 27N FROM 83W-94W.

THE CARIBBEAN SEA...
LARGE MID/UPPER LEVEL HIGH OVER THE NW CARIBBEAN BETWEEN THE W
TIP OF CUBA AND THE YUCATAN PENINSULA NEAR 20N85W CONTINUES TO
DOMINATE ALL BUT THE E CARIBBEAN...WHERE A COL OR AN AREA OF
WEAKNESS BETWEEN THE UPPER/MID LEVEL HIGH IN THE E W CARIBBEAN
AND AN UPPER/MID LEVEL HIGH OVER THE CENTRAL ATLANTIC PRODUCES
STRONG SUBSIDENCE AND DRY TRANQUIL WEATHER. WIDELY SCATTERED
MODERATE CONVECTION CONTINUES S OF 10N TO INLAND OVER PANAMA
FROM 77W-79W.  ISOLATED MODERATE CONVECTION  WITHIN 60 NM OF THE
AXIS OF THE TROUGH EXTENDS FROM THE GULF SE OVER CUBA NEAR
20N80W.

SUBTROPICAL ATLANTIC...
STRONG...LARGE DEEP LAYERED HIGH IS SITUATED SE OF THE
WASHINGTON D.C. NEAR 37N75W...THIS IS PRODUCING STRONG
ANTICYCLONIC FLOW AROUND THE HIGH  PREVENTING HURRICANE JEANNE
FROM MOVING NORTHWARD. THE HIGH IS ALSO PROVIDING STRONG
SUBSIDENCE AND DRY AIR TO MUCH OF THE W ATLANTIC.  THE LARGE
DEEP LAYERED TROUGH OVER THE CENTRAL ATLC REMAINS N OF 30N AND
IS LIFTING NE. THE ASSOCIATED SURFACE COLD FRONT CONTINUES TO
DISSIPATING ALONG 30N65W 27N58W 30N50W AND THEN CONTINUES N OF
THE AREA... ELSEWHERE OVER THE W ATLC...BROAD/FLAT MID-LEVEL
TROUGH IS NOW WESTERLY ZONAL FROM BETWEEN HURRICANE KARL AND
HURRICANE JEANNE. OVER THE REMAINDER OF THE CENTRAL ATLC...LARGE
AND HIGH AMPLITUDE MID/UPPER LEVEL RIDGE CONTINUES TO BUILD N TO
THE E OF HURRICANE KARL. THE RIDGE IS ANCHORED BY AN LARGE
MID/UPPER LEVEL HIGH NEAR 19N51W AND IS ALSO PRODUCING NORTHERLY
SHEAR OVER T.S. LISA. MID/UPPER LEVEL TROUGH REMAINS OVER THE E
ATLC ALONG 32N23W JUST W OF THE CANARY ISLANDS TO JUST W OF THE
CAPE VERDE ISLANDS NEAR 12N26W. SURFACE SUBTROPICAL RIDGE
REMAINS LARGELY DISRUPTED OVER THE W ATLC BUT IS WELL
ESTABLISHED OVER THE E ATLC THROUGH THE AZORES S TO 15N30W.

TROPICAL ATLANTIC...
MID/UPPER LEVEL RIDGE EXTENDS E/W ALONG 20N BUT IS DISRUPTED/
SPLIT NEAR 27W BY THE S EXTENT OF A MID/UPPER LEVEL TROUGH TO
THE NORTH.

$$
JP



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