[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 240545
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
205 AM EDT FRI 24 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 0000 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
0315 UTC.

...SPECIAL FEATURES...

T.S. IVAN WAS DOWNGRADED TO TROPICAL DEPRESSION AT 24/0300 UTC.
IVAN IS NOW INLAND ALONG THE COAST OF LOUISIANA NEAR 29.8N 93.5W
JUST S OF LAKE CHARLES AT 24/0300 UTC MOVING NW AT 7 KT. MAXIMUM
SUSTAINED WIND SPEED IS 30 KT WITH GUSTS TO 40 KT AND THE
ESTIMATED MINIMUM CENTRAL PRESSURE IS 1002 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 SYSTEM...WITH LITTLE DEEP CONVECTION. SCATTERED
SHOWERS/THUNDERSTORMS ARE INLAND OVER LOUISIANA AND TEXAS WITHIN
45 NM OF THE BORDER.

HURRICANE JEANNE IS CENTERED NEAR 26.1N 71.2W OR ABOUT 325 NM
EAST OF GREAT ABACO ISLAND AT 24/0600 UTC MOVING W AT 5 KT.
MAXIMUM SUSTAINED WIND SPEED IS 90 KT WITH GUSTS TO 110 KT AND
THE ESTIMATED MINIMUM CENTRAL PRESSURE IS 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.
WELL DEFINED BUT SMALL EYE REMAINS ALTHOUGH THE ASSOCIATED DEEP
CONVECTION HAS DIMINISHED OVER THE PAST FEW HOURS. STRONG UPPER
LEVEL HIGH JUST OFF THE NE UNITED STATES CONTINUES TO MOVE SE
OVER THE NW ATLC AND IS PUSHING JEANNE TO THE WEST TOWARDS THE
BAHAMAS AND FLORIDA. THE OUTFLOW REMAINS GOOD IN ALL QUADRANTS.
MODERATE SUBSIDENCE/DRY AIR SURROUNDS JEANNE HOPEFULLY HAMPERING
FURTHER INTENSIFICATION ALTHOUGH A MORE FAVORABLE ENVIRONMENT
WILL BE ENCOUNTERED AS THE SYSTEM MOVES FURTHER WEST. AT THAT
TIME JEANNE COULD INTENSIFY. SCATTERED MODERATE/ISOLATED STRONG
CONVECTION IS WITHIN 75 NM OF THE CENTER IN THE E SEMICIRCLE.

HURRICANE KARL IS CENTERED NEAR 38.7N 41.5W OR ABOUT 650 NM WEST
OF THE AZORES AT 24/0300 UTC MOVING NNE AT 26 KT. MAXIMUM
SUSTAINED WIND SPEED IS 80 KT WITH GUSTS TO 100 KT AND THE
ESTIMATED MINIMUM CENTRAL PRESSURE IS 963 MB. SEE LATEST NHC
FORECAST/ADVISORY UNDER AWIPS/WMO HEADER MIATCMAT2/WTNT22 KNHC
FOR MORE DETAILS. THE EYE HAS BECOME VERY LARGE WITH THE LOW
LEVEL CENTER BECOMING DETACHED FROM THE MORE OBVIOUS MID LEVEL
CIRCULATION. KARL IS FORECAST TO GO EXTRATROPICAL OVER THE NEXT
12 HOURS AND WILL CONTINUE TO WEAKEN OVER THE NEXT SEVERAL DAYS.
KARL REMAINS UNDER STRONG SOUTHERLY SHEAR WHICH IS LIMITING DEEP
CONVECTION. THEREFORE...VERY LITTLE IN THE WAY OF DEEP
CONVECTION REMAINS. SCATTERED SHOWERS/ISOLATED THUNDERSTORMS
COVERS AN AREA FROM WITHIN 150 NM OF A LINE FROM 28N46W TO
44N34W.

TROPICAL DEPRESSION LISA IS CENTERED NEAR 14.7N 42.0W OR ABOUT
1050 NM WEST OF THE CAPE VERDE ISLANDS AT 24/0300 UTC MOVING WNW
AT 6 KT. MAXIMUM SUSTAINED WIND SPEED IS 30 KT WITH GUSTS TO 40
KT AND ESTIMATED MINIMUM CENTRAL PRESSURE IS 1003 MB. SEE LATEST
NHC FORECAST/ADVISORY UNDER AWIPS/WMO HEADER MIATCMAT3/WTNT23
KNHC FOR MORE DETAILS. THE LOW LEVEL CENTER IS MOSTLY EXPOSED TO
THE N OF THE ASSOCIATED DEEP CONVECTION. LISA CONTINUES TO
EXPERIENCE NORTHERLY SHEAR WHICH ACCOUNTS FOR THE DISPLACEMENT
OF THE DEEP CONVECTION. NUMEROUS STRONG CONVECTION IS WITHIN A
45 NM RADIUS OF 12.5N42W. SCATTERED STRONG CONVECTION IS WITHIN
30 NM OF 14N FROM 41.5W-43.5W. SCATTERED MODERATE/ISOLATED
STRONG CONVECTION COVERS THE AREA FROM 8N-13N BETWEEN 40W-46W.

...TROPICAL WAVES...
TROPICAL WAVE IS OVER THE CAPE VERDE ISLANDS ALONG 23W/24W S OF
17N MOVING W 10-15 KT. SATELLITE SIGNATURE IS ABSENT DUE TO
UPPER LEVEL SOUTHERLY SHEAR. ISOLATED SHOWERS DOT THE AREA.

...ITCZ...

ITCZ EXTENDS ALONG 14N10W 10N26W 13N40W 10N60W 11N70W. OTHER
THAN T.D. LISA...SCATTERED MODERATE/ISOLATED STRONG CONVECTION
IS MOVING OFF THE COAST OF AFRICA FROM 13N-16N. CLUSTERS OF
SIMILAR CONVECTION ARE WITHIN 120 NM OF LINE FROM 4N13W-8N26W-
14N35W.

...DISCUSSION...

GULF OF MEXICO...
MID/UPPER HIGH IS OVER THE E PACIFIC WITH ANTICYCLONIC FLOW
COVERING MEXICO W OF 97W. MID/UPPER LEVEL HIGH IS CENTERED OVER
THE YUCATAN CHANNEL NEAR 23N86W CONTINUING TO PUSH NORTHWARD. A
RIDGE AXIS EXTENDS N ACROSS TO THE E GULF OVER THE SE UNITED
STATES. THIS RIDGE CONTINUES TO PRODUCE STRONG SOUTHERLY SHEAR
OVER IVAN. A NARROW TROUGH IS INDUCED BETWEEN THESE TWO UPPER
HIGHS ALONG 95W. AT THE SURFACE...A N/S SURFACE TROUGH EXTENDS
FROM NEAR IVAN TO THE NW YUCATAN PENINSULA. THE SOUTHERLY UPPER
LEVEL FLOW COUPLED WITH TROPICAL MOISTURE IS CREATING SHOWERS/
STRONG THUNDERSTORMS OVER THE S GULF S OF 26N FROM 84W-90W. A
WEAKNESS/TROUGH OVER THE FLORIDA PENINSULA IS A RESULT FROM THE
UPPER HIGH OVER THE YUCATAN CHANNEL AND THE HIGH OVER HURRICANE
JEANNE. THIS IS PRODUCING STRONG SUBSIDENCE AND DRY AIR AT ALL
LEVELS OVER FLORIDA GIVING WAY CLEAR SKIES TONIGHT BUT WILL
BECOME CLOUDIER AS JEANNE CONTINUES TO MOVE WEST.

THE CARIBBEAN SEA AND W TROPICAL ATLANTIC...
LARGE MID/UPPER LEVEL HIGH CENTERED OVER THE YUCATAN CHANNEL
COVERS THE CARIBBEAN WITH ANTICYCLONIC FLOW W OF 75W. A LARGE
MID/UPPER LEVEL HIGH IS OVER THE W TROPICAL ATLC ABOUT 450 NM W
OF THE LEEWARD ISLANDS NEAR 19N54W. ANTICYCLONIC FLOW COVERS THE
AREA FROM 40W-65W. A TROUGH IS INDUCED BETWEEN THESE TWO UPPER
HIGHS ALONG 73W THAT EXTENDS N TO JUST S OF JEANNE. STRONG
SUBSIDENCE/DRY AIR COVERS THE E CARIBBEAN AND TROPICAL ATLC FROM
53W-68W. CLUSTERS OF THUNDERSTORMS DOT THE OUTER PERIPHERY OF
THE W CARIBBEAN OVER HISPANIOLA...CUBA...HONDURAS...PANAMA...
COLOMBIA...AND W VENEZUELA INCLUDING LAKE MARACAIBO. ONLY
ISOLATED LOW LEVEL SHOWERS ARE OVER THE LESSER ANTILLES.

SUBTROPICAL ATLANTIC AND THE E TROPICAL
ATLANTIC...STRONG...LARGE MID/UPPER LEVEL HIGH IS SITUATED
WITHIN 130 NM OFF THE COAST OF VIRGINIA NEAR 37N73W WITH STRONG
ANTICYCLONIC FLOW W OF 65W THUS PREVENTING HURRICANE JEANNE FROM
MOVING NORTHWARD. THE HIGH IS ALSO PROVIDING STRONG SUBSIDENCE/
DRY AIR TO THE W ATLANTIC N OF 30N. THE LARGE DEEP LAYERED
TROUGH OVER THE CENTRAL ATLC REMAINS N OF 26N BETWEEN 41W-65W
AND CONTINUES TO LIFT NE. ELSEWHERE OVER THE CENTRAL ATLC...A
LARGE MID/UPPER LEVEL HIGH IS CENTERED NEAR 19N54W IN THE
TROPICAL ATLC WITH ANTICYCLONIC FLOW S OF 25N FROM 40W-65W. A
RIDGE AXIS EXTENDS FROM NEAR 24N44W NE TO WELL BEYOND 32N35W.
THIS UPPER LEVEL HIGH IS PRODUCING NORTHERLY SHEAR OVER T.D.
LISA. MID/UPPER LEVEL LOW IS OVER THE E ATLANTIC NEAR 28N28W
WITH A TROUGH EXTENDING S TO 10N30W. LARGE MID/UPPER LEVEL HIGH
IS INLAND OVER W AFRICA WITH ANTICYCLONIC FLOW COVERING THE E
ATLC E OF 23W. AT THE SURFACE...THE SURFACE SUBTROPICAL RIDGE
OVER THE W ATLC IS WELL N OF THE REGION. A SURFACE TROUGH
SEPARATES THE SUBTROPICAL RIDGE OVER THE E ATLC AND EXTENDS FROM
34N38W SW ALONG 26N45W THEN W TO 26N59W. THE RIDGE EXTENDS
THROUGH THE AZORES S TO 20N34W. SCATTERED SHOWERS AND POSSIBLE
ISOLATED THUNDERSTORMS ARE WITHIN 90 NM OF THE SURFACE TROUGH.

$$
WALLACE



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