[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 230551
TWDAT

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

...SPECIAL FEATURES...

T.D. IVAN WAS UPGRADED TO TROPICAL STORM AT 23/0000 UTC. T.S.
IVAN IS CENTERED OVER THE N GULF OF MEXICO NEAR 27.4N 90.0W AT
23/0300 UTC AND AT 27.7N 90.8W OR ABOUT 230 SE OF THE UPPER
TEXAS COAST AT 23/0600 UTC. IVAN IS MOVING WNW AT 11 KT. MAXIMUM
SUSTAINED WIND SPEED IS 35 KT WITH GUSTS TO 45 KT AND THE
ESTIMATED MINIMUM CENTRAL PRESSURE IS 1007 MB. SEE LATEST NHC
PUBLIC OR FORECAST/ADVISORY UNDER AWIPS/WMO HEADER
MIATCPAT4/WTNT34 OR MIATCMAT4/WTNT24 KNHC FOR MORE DETAILS.
ALTHOUGH IVAN REMAINS FAIRLY DISORGANIZED A WELL DEFINED LOW
LEVEL CENTER WAS REPORTED BY A RECONNAISSANCE PLANE. IVAN
REMAINS UNDER SOUTHERLY SHEAR THAT COULD RELAX CAUSING IVAN TO
INTENSIFY SLIGHTLY BEFORE LANDFALL. ALSO BECAUSE OF THIS SHEAR
THE CONVECTION IS DISPLACED TO THE NE OF THE LOW LEVEL CENTER.
SCATTERED MODERATE/ISOLATED STRONG CONVECTION IS N OF 27.5N TO
JUST INLAND OVER SE LOUISIANA FROM 88.5W-90.5W. SCATTERED
SHOWERS/ISOLATED THUNDERSTORMS ARE APPROACHING THE N GULF COAST
FROM THE FLORIDA PANHANDLE TO LOUISIANA.

HURRICANE JEANNE IS CENTERED NEAR 25.6N 69.3W OR ABOUT 425 NM
EAST OF GREAT ABACO ISLAND AT 23/0300 UTC. JEANNE IS MOVING WSW
AT 4 KT. MAXIMUM SUSTAINED WIND SPEED IS 85 KT WITH GUSTS TO 105
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 HAS A VERY LARGE EYE...APPROXIMATELY 40-45 NM
WIDE...WITH SMALL AREA OF DEEP CONVECTION. STRONG UPPER LEVEL
HIGH OVER THE NE UNITED STATES IS MOVING E TO OVER THE NW ATLC
AND SHOULD BEGIN TO PUSH JEANNE TOWARD THE WEST. THE UPPER LEVEL
OUTFLOW IS GOOD IN ALL BUT THE SE QUADRANT WHERE MODERATE
SUBSIDENCE/DRY AIR IS BEING ADVECTED INTO THE SYSTEM. SCATTERED
MODERATE/ISOLATED STRONG IS WITHIN 60/75 NM FROM THE CENTER OF
THE EYE WITH AN OUTER RAIN BAND WITHIN 30/45 NM OF LINE FROM
26N65W TO 29N69W.

HURRICANE KARL IS CENTERED NEAR 30.0N 47.3W OR ABOUT 1100 NM
WEST-SOUTHWEST OF THE AZORES AT 23/0300 UTC. KARL IS MOVING NNE
AT 19 KT. MAXIMUM SUSTAINED WIND SPEED IS 95 KT WITH GUSTS TO
115 KT AND THE ESTIMATED MINIMUM CENTRAL PRESSURE IS 965 MB. SEE
LATEST NHC FORECAST/ADVISORY UNDER AWIPS/WMO HEADER
MIATCMAT2/WTNT22 KNHC FOR MORE DETAILS. KARL ONCE AGAIN HAS A
DISTINCT EYE ALBEIT SMALL AND OFFSET TO THE WEST SIDE OF THE
DEEP CONVECTION. UPPER LEVEL OUTFLOW REMAINS GOOD IN ALL
QUADRANTS. KARL IS EXPECTED TO CONTINUING MOVING IN A NORTHWARD
DIRECTION AHEAD OF A DEEP LAYERED TROUGH AND WILL THEN MERGE
WITH THE WESTERLYS. SCATTERED MODERATE/STRONG CONVECTION COVERS
AN AREA FROM 27N-35N BETWEEN 42W-49W.

TROPICAL STORM LISA IS CENTERED NEAR 13.2N 41.2W OR ABOUT 1000
NM WEST OF THE CAPE VERDE ISLANDS AT 23/0300 UTC. LISA IS NEAR
STATIONARY AND MAXIMUM SUSTAINED WIND SPEED IS 45 KT WITH GUSTS
TO 55 KT. ESTIMATED MINIMUM CENTRAL PRESSURE IS 1000 MB. THE
TROPICAL DISTURBANCE PREVIOUSLY LOCATED NEAR 12.5N37.0W HAS
MERGED WITH T.S. LISA AND THE ENTIRE SYSTEM WILL REMAIN
DESCRIBED AS LISA. SEE LATEST NHC FORECAST/ADVISORY UNDER
AWIPS/WMO HEADER MIATCMAT3/WTNT23 KNHC FOR MORE DETAILS. ON
SATELLITE IMAGERY...LISA IS NOT WELL ORGANIZED BUT THE DEEP
CONVECTION RELATES OTHERWISE. THE SATELLITE IMAGERY ALSO
INDICATES THAT LISA CONTINUES TO BE ADVERSELY AFFECTED BY
NORTHERLY SHEAR ON THE SOUTH SIDE OF AN UPPER LEVEL HIGH NEAR
20N48W. WITH THE MERGER OF THE TROPICAL DISTURBANCE FROM THE
EAST...THE SYSTEM IS UNDERGOING SOME REORGANIZATION AND MAY
BECOME BETTER ORGANIZED OVER THE NEXT DAY OR TWO. NUMEROUS
STRONG CONVECTION IS WITHIN A 60 NM RADIUS OF 15N40W. SCATTERED
MODERATE/STRONG CONVECTION COVERS THE REMAINDER OF THE AREA FROM
11N-16N BETWEEN 38W-44W.

...TROPICAL WAVES...
NONE.

...ITCZ...

ITCZ EXTENDS ALONG 15N10W 8N22W 13N35W 9N45W 8N63W. THIS AXIS IS
DISRUPTED BY T.S LISA. SCATTERED MODERATE/ISOLATED STRONG
CONVECTION IS WITHIN 30 NM OF LINE FROM 8N26W-10N28W...FROM
13N30W-15N33W...AND WITHIN A 90 NM RADIUS OF 3.5N18W. SCATTERED
THUNDERSTORMS DOT THE REMAINDER OF THE AREA FROM 1N-10N E OF
29W.

...DISCUSSION...

GULF OF MEXICO...
ASIDE FROM ACTIVITY ASSOCIATED WITH THE T.S. IVAN...WELL DEFINED
MID/UPPER LEVEL ELONGATED LOW IS LOCATED OVER THE W GULF NEAR
23N95W. A MID/UPPER LEVEL RIDGE CENTERED IN THE NW CARIBBEAN IS
PRODUCING STRONG S FLOW FROM 86W-92W. THIS IS PRODUCING THE
SOUTHERLY SHEAR OF IVAN. THE RIDGE NOW EXTENDS TO OVER THE SE
UNITED STATES AND WILL CONTINUE TO BUILD N AS IT SHIFTS TO THE W
OVER THE NEXT 48 HOURS. THE UPPER LOW WILL REMAIN ESSENTIALLY
STATIONARY BUT BECOME NARROWER AND EVEN MORE ELONGATED. THIS
EVOLUTION SHOULD PRODUCE SOME IMPROVEMENT IN THE MID-UPPER LEVEL
ENVIRONMENT OVER T.S. IVAN. AT THE SURFACE...T.S. IVAN TRAILS A
REMNANT FRONTAL BOUNDARY/SURFACE TROUGH ESE OVER THE FLORIDA
KEYS TO THE CENTRAL BAHAMAS NEAR 22N75W. THE BOUNDARY COUPLED
WITH THE TROPICAL MOISTURE ADVECTED IN THE SOUTHERLY FLOW IS
PRODUCING SCATTERED SHOWERS/ISOLATED THUNDERSTORMS S OF 25N FROM
79W-93W.

THE CARIBBEAN SEA...
LARGE MID/UPPER LEVEL HIGH OVER THE NW CARIBBEAN ROUGHLY HALFWAY
IN BETWEEN JAMAICA AND THE YUCATAN PENINSULA NEAR 19N83W
CONTINUES TO DOMINATE ALL BUT THE E CARIBBEAN WHERE A WEAK
INVERTED TROUGH EXTENDS FROM W VENEZUELA TO W PUERTO RICO/MONA
PASSAGE. DEEP CONVECTION CONTINUES OVER HONDURAS AND THE YUCATAN
PENINSULA WITH ISOLATED THUNDERSTORMS OFF THE COAST OF PANAMA...
HISPANIOLA...AND ALONG THE S COAST OF CUBA. E CARIBBEAN IS
UNDER STRONG SUBSIDENCE/DRY AIR WHICH IS LIMITING SHOWER
ACTIVITY OVER THE LESSER ANTILLES.

SUBTROPICAL ATLANTIC...
STRONG...LARGE DEEP LAYERED HIGH IS SITUATED NEAR THE WASHINGTON
D.C. AREA WITH THE ANTICYCLONIC FLOW COVERING ALL OF THE NW
ATLANTIC. THIS HIGH IS PREVENTING HURRICANE JEANNE FROM MOVING
NORTHWARD. THE LARGE DEEP LAYERED TROUGH OVER THE CENTRAL ATLC
REMAINS N OF 30N AND IS BEGINNING TO LIFT NE. THE ASSOCIATED
SURFACE COLD FRONT NOW EXTENDS THROUGH 32N48W...VERY CLOSE TO
HURRICANE KARL...SW TO 27N60W WHERE IT CONTINUES NE AROUND
JEANNE IN THE W ATLC AS A STATIONARY FRONT TO 29N70W THEN
DISSIPATES S TO 25N75W. HURRICANE JEANNE CONTINUES TO PULL
THE W EXTENT OF THIS BOUNDARY S OVER FLORIDA RESULTING IN MUCH
DRIER AIR OVER A PORTION OF THE SW ATLC E OF THE BAHAMAS TO
HURRICANE JEANNE. ELSEWHERE OVER THE W ATLC...BROAD/FLAT
MID-LEVEL TROUGH HAS BEEN CARVED OUT BY THE COMBINED EFFECT OF
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 20N48W WHICH IS
PRODUCING NORTHERLY SHEAR OVER T.S. LISA. MID/UPPER LEVEL TROUGH
REMAINS OVER THE E ATLANTIC JUST W OF THE CANARY ISLANDS ALONG
25W S TO OVER THE CAPE VERDE ISLANDS. SURFACE SUBTROPICAL RIDGE
REMAINS LARGELY DISRUPTED OVER THE W ATLC BUT IS WELL
ESTABLISHED OVER THE E ATLC FROM THE AZORES S TO 20N35W. A 1026
MB HIGH PRESSURE OVER THE E UNITED STATES AND A 1020 MB HIGH
PRESSURE N OF BERMUDA ARE PRODUCING STRONG NE FLOW OVER THE W
ATLC NORTH AND WEST OF HURRICANE JEANNE.

TROPICAL ATLANTIC...
MID/UPPER LEVEL RIDGE EXTENDS E/W ALONG 20N BUT IS
DISRUPTED/SPLIT NEAR 25W BY THE S EXTENT OF A MID/UPPER LEVEL
TROUGH TO THE NORTH.

$$
WALLACE


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