[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 210619
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
205 AM EDT TUE 21 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...

HURRICANE JEANNE CENTER AT 21/0300 UTC NEAR 27.4N 70.6W OR
ABOUT 405 MILES/655 KM EAST OF GREAT ABACO ISLAND. JEANNE IS
BEGINNING TO SLOW DOWN AND IS MOVING EAST 2 KT. JEANNE IS
ENCOUNTERING VERY WEAK STEERING CURRENTS AND LIKELY WILL BEGIN
TO MEANDER FOR SEVERAL DAYS. MAXIMUM SUSTAINED WIND SPEED 75 KT
GUSTS 90 KT. ESTIMATED MINIMUM CENTRAL PRESSURE 982 MB. SEE
LATEST NHC PUBLIC ADVISORY OR NHC FORECAST/ADVISORY UNDER
AWIPS/WMO HEADERS MIATCPAT1/WTNT31 KNHC OR MIATCMAT1/WTNT21 KNHC
FOR MORE DETAILS. SCATTERED TO NUMEROUS STRONG SHOWERS AND
THUNDERSTORMS IN THE SOUTHWESTERN SEMICIRCLE WITHIN 60 TO 80 NM
RADIUS...AND WITHIN 120 TO 180 NM RADIUS IN THE NORTHEASTERN
SEMICIRCLE. JEANNE IS LOCATED SOUTH OF A MID-LATITUDE TROUGH
MOVING OFF THE NE UNITED STATES COAST WITH ATTENDANT COLD FRONT
TRAILING SWD JUST N OF THE HURRICANE INTO FLORIDA.  MOISTURE
ASSOCIATED WITH JEANNE IS STREAMING NEWD AHEAD OF THE UPPER
TROUGH/FRONTAL BOUNDARY. THE UPPER TROUGH ALSO IS ENHANCING
POLEWARD OUTFLOW BUT A SECOND...MUCH WEAKER...UPPER TROUGH
OVER THE BAHAMAS IS RESTRICTING EQUATORWARD OUTFLOW.

HURRICANE KARL CENTER AT 21/0300 UTC NEAR 19.1N 47.4W OR ABOUT
950 MILES/1530 KM...EAST-NORTHEAST OF THE LESSER ANTILLES.
KARL HAS RE-STRENGTHENED TO CATEGORY 4 STATUS...MOVING NORTHWEST
9 KT. MAXIMUM SUSTAINED WIND SPEED 120 KT GUSTS 145 KT. ESTIMATED
MINIMUM CENTRAL PRESSURE 938 MB. FLUCTUATIONS IN INTENSITY ARE
POSSIBLE DURING THE NEXT 24 HOURS. HURRICANE FORCE WINDS EXTEND
OUTWARD UP TO  70 MILES...110 KM...FROM THE CENTER...AND
TROPICAL STORM FORCE WINDS EXTEND OUTWARD UP TO 200 MILES...
325 KM. SEE LATEST NHC FORECAST/ADVISORY UNDER AWIPS/WMO HEADER
MIATCMAT2/WTNT22 KNHC FOR MORE DETAILS. NUMEROUS STRONG SHOWERS
AND THUNDERSTORMS FROM 17.5N TO 20.5N BETWEEN 45W AND 48W. WATER
VAPOR IMAGERY INDICATES THAT VERTICAL SHEAR AND SUBSIDENCE
ASSOCIATED WITH AN UPPER TROUGH TO THE WEST OF KARL ARE
IMPINGING UPON THE EXTREME WESTERN EXTENT OF THE SYSTEM AS
EVIDENCED BY SOME RESTRICTION OF THE UPPER LEVEL OUTFLOW. THE
SHEAR IS NOT IMPACTING THE CORE OF THE HURRICANE AS THE EYE
REMAINS DISTINCT AND THE OVERALL CONVECTIVE PATTERN UNCHANGED.
WIDELY SCATTERED TO SCATTERED MODERATE/ISOLATED STRONG SHOWERS
AND THUNDERSTORMS ELSEWHERE FROM 16N TO 24N BETWEEN 43W AND 50W.

TROPICAL STORM LISA CENTER AT 21/0300 UTC NEAR 13.8N 37.9W OR
ABOUT 940 MILES/1515 KM WEST OF THE CAPE VERDE ISLANDS. LISA
IS MOVING WEST 10 KT. MAXIMUM SUSTAINED WIND SPEED 50 KT GUSTS
60 KT. ESTIMATED MINIMUM CENTRAL PRESSURE 998 MB. SEE LATEST NHC
FORECAST/ADVISORY UNDER AWIPS/WMO HEADER MIATCMAT3/WTNT23 KNHC
FOR MORE DETAILS. LISA REMAINS A VERY COMPACT SYSTEM WITH
ASSOCIATED NUMEROUS STRONG SHOWERS AND THUNDERSTORMS FROM 13N
TO 14N BETWEEN 37W AND 38W.

...TROPICAL WAVES...

TROPICAL WAVE ALONG 28W/29W SOUTH OF 17N MOVING WEST 15 KT.
WIDELY SCATTERED MODERATE TO ISOLATED STRONG SHOWERS AND
THUNDERSTORMS FROM 5N TO 13N BETWEEN 29W AND 35W. A MIDDLE TO
UPPER LEVEL TROUGH STRETCHES FROM A CYCLONIC CIRCULATION CENTER
NEAR 31N15W JUST NORTH OF THE CANARY ISLANDS TO AN ILL-DEFINED
CYCLONIC CENTER NEAR 21N24W TO 16N26W AT THE WESTERN EDGE OF
THE CAPE VERDE ISLANDS.

...ITCZ...

ITCZ FROM AFRICA NEAR 17N16W TO 11N 26W...BEING DISRUPTED BY
THE 28W/29W TROPICAL WAVE...FROM 9N31 TO 12N35W...THEN COMES
T.S. LISA...FROM 13N45W TO 8N57W TO 9N64W...AND IN THE SOUTH-
WESTERN CARIBBEAN SEA FROM 10N72W TO 9N 83W. WIDELY SCATTERED
MODERATE TO ISOLATED STRONG SHOWERS AND THUNDERSTORMS FROM 5N
TO 7N BETWEEN 20W AND 24W. ISOLATED MODERATE SHOWERS AND
THUNDERSTORMS FROM 3N TO 7N BETWEEN 10W AND 20W.

...DISCUSSION...

GULF OF MEXICO...
MID/UPPER LEVEL TROUGH WHICH MOVED OFF THE E COAST OF THE UNITED
STATES YESTERDAY HAS AMPLIFIED SW INTO THE GLFMEX WITH AXIS
EXTENDING FROM NORTHERN FLORIDA TO THE SOUTHWESTERN GULF OF
MEXICO. SURFACE STATIONARY FRONT ALONG LINE THROUGH 30N67W
30N73W 28N76W 27N79W 26N82W AND 27N84W. THE UPPER TROUGH IS
ACCOMPANIED BY SIGNIFICANTLY DRIER AIR IN THE MIDDLE TO UPPER
LEVELS COVERING ALL BUT THE EXTREME SE PORTION OF THE GLFMEX.
SURFACE 1009 MB LOW PRESSURE CENTER NEAR 26N79W OFF THE
SOUTHEASTERN COAST OF FLORIDA. THERE ARE NO SIGNS OF
DEVELOPMENT. SCATTERED MODERATE SHOWERS AND THUNDERSTORMS FROM
27.5N TO 29N BETWEEN 76.5W AND 80.5W EARLIER WATER VAPOR IMAGES
WERE INDICATING THAT THE UPPER TROUGH IS FRACTURING FORMING A
BROAD UPPER LOW OVER THE E GLFMEX.  THIS UPPER LOW IS EXPECTED
TO DRIFT SLOWLY WESTWARD PRODUCING AN INCREASINGLY DIVERGENT
PATTERN OVER THE N GLFMEX DURING THE NEXT 24 HOURS. THIS SHOULD
ALLOW INCREASING CLOUDINESS AND SHOWERS/THUNDERSTORMS PRIMARILY
NORTH OF 25N.

CARIBBEAN SEA...
STRONG MIDDLE TO UPPER LEVEL RIDGE NOW COVERS ALL BUT THE
EXTREME NW CARIBBEAN WHERE A TROUGH OVER THE E GLFMEX CLIPS THE
AREA. THE MEAN RIDGE AXIS EXTENDS FROM HISPANIOLA SW OVER
CENTRAL AMERICA NEAR HONDURAS. ANTICYCLONIC FLOW AROUND THE
RIDGE HAS PUSHED VERY DRY MIDDLE TO UPPER LEVEL AIR FROM THE
TROPICAL ATLC WESTWARD INTO THE EASTERN CARIBBEAN SEA...NOW
EAST OF 75W.
THROUGH
31N70W TO 29N73W 27N79W 27N85W.
A WEAK LOWER TO MIDDLE LEVEL TROUGH TRAILING SWD FROM HURRICANE
IVAN OVER THE ATLC CONTINUES TO SPARK CONVECTION OVER E CUBA AND
W HISPANIOLA.  THE UPPER RIDGE IS EXPECTED TO REMAIN ESSENTIALLY
STATIONARY OVER THE NEXT 2 DAYS.

SUBTROPICAL ATLANTIC...
STRONG MID/UPPER LEVEL TROUGH JUST N OF THE AREA EXTENDS SWD
OVER THE W ATLC FROM THE CANADIAN MARITIMES TO JUST OFF THE
MID-ATLANTIC COAST. SURFACE STATIONARY FRONT THROUGH 31N70W TO
29N73W 27N79W 27N85W. AREA OF STRONG MIDDLE TO UPPER LEVEL
SUBSIDENCE REMAINS JUST N OF THE AREA. SHIFTING EWD...UPPER
LEVEL RIDGE JUST E OF JEANNE EXTENDS NEWD BEYOND 32N55W.  THE
RIDGE IS CURRENTLY PROVIDING A FAVORABLE ENVIRONMENT FOR JEANNE
TO INTENSIFY. ADDITIONALLY...ANTICYCLONIC FLOW IS ALLOWING
MOISTURE FROM JEANNE TO SURGE NEWD OVER BERMUDA. OVER THE
CENTRAL ATLC...MID/UPPER LEVEL TROUGH ENTERS AREA ALONG 32N50W
EXTENDING SWD ALONG 51W TO 20N.  A HIGH AMPLITUDE MID/UPPER
LEVEL RIDGE EXTENDS FROM JUST E OF KARL NWD ALONG 40W COVERING
THE AREA WITH ANTICYCLONIC FLOW FROM 35W TO 50W. A MID/UPPER
LEVEL TROUGH COVERS THE REMAINDER OF THE AREA E OF 35W WITH
ASSOCIATED MID-LEVEL SUBSIDENCE AND DRY AIR BLANKETING THE E
ATLC.  AT THE SURFACE...SUBTROPICAL RIDGE ENTERS AREA IN BETWEEN
HURRICANE KARL AND HURRICANE JEANNE ALONG 30N50W SW TO
HISPANIOLA.

TROPICAL ATLANTIC...
MID/UPPER LEVEL RIDGING WHICH TYPICALLY EXTENDS E/W ACROSS THE
AREA REMAINS DISRUPTED BY HURRICANE KARL AND TROPICAL STORM
LISA. A WEAK RIDGE EXTENDS E/W ALONG 13N/14N FROM CAPE VERDE TO
40W. THE RIDGE IS PRODUCING DEEP LAYERED ELY FLOW TO THE SOUTH.

$$
MT




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