[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 210001
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
805 PM EDT MON 20 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 1800 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
2315 UTC.

...SPECIAL FEATURES...

TROPICAL STORM JEANNE HAS BEEN UPGRADED TO A HURRICANE CENTERED
NEAR 27.4N 71.2W OR ABOUT 370 MILES... 595 KM...EAST-NORTHEAST
OF GREAT ABACO ISLAND AT 20/2100 UTC. JEANNE IS MOVING NE AT 6
KT. MAXIMUM SUSTAINED WIND SPEED IS 75 KT WITH GUSTS TO 90 KT
AND THE ESTIMATED MINIMUM CENTRAL PRESSURE IS 983 MB. SEE LATEST
NHC PUBLIC ADVISORY OR NHC FORECAST/ ADVISORY UNDER AWIPS/WMO
HEADERS MIATCPAT1/WTNT31 KNHC OR MIATCMAT1/ WTNT21 KNHC FOR MORE
DETAILS.  SATELLITE IMAGERY INDICATES THAT JEANNE IS BECOMING
BETTER ORGANIZED.  DEEP CONVECTION HAS FORMED NORTH OF THE
SYSTEM AND IS WRAPPING AROUND THE WESTERN SIDE CURRENTLY WITHIN
70 NM OVER THE NW SEMICIRCLE.  CONVECTION OVER THE SE QUADRANT
REMAINS WEAK.  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 RESULTING IN THE DEVELOPMENT OF
SCATTERED MODERATE CONVECTION WELL NE OF JEANNE FROM 28N TO 32N
BETWEEN 62W-70W.  THE UPPER TROUGH IS ALSO ENHANCING POLEWARD
OUTFLOW BUT A SECOND...MUCH WEAKER...UPPER TROUGH OVER THE
BAHAMAS IS RESTRICTING EQUATORWARD OUTFLOW.

HURRICANE KARL IS CENTERED NEAR 18.6N 47.1W OR ABOUT  965
MILES...1550 KM...EAST-NORTHEAST OF THE LESSER ANTILLES AT
20/2100 UTC. KARL IS NOW MOVING NORTHWEST AT 10 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.  WATER VAPOR IMAGERY INDICATES THAT VERTICAL
SHEAR AND SUBSIDENCE ASSOCIATED WITH AN UPPER TROUGH TO THE WEST
OF KARL HAS BEGUN IMPINGING UPON THE EXTREME W EXTENT OF THE
SYSTEM AS EVIDENCED BY SOME RESTRICTION OF THE UPPER LEVEL
OUTFLOW. HOWEVER...THE SHEAR HAS NOT YET IMPACTED THE CORE OF
THE HURRICANE AS THE EYE REMAINS DISTINCT AND THE OVERALL
CONVECTIVE PATTERN UNCHANGED. IN FACT...CLOUD TOP TEMPERATURES
HAVE COOLED SLIGHTLY OVER THE LAST FEW HOURS.  NUMEROUS STRONG
CONVECTION ENCIRCLES THE CENTER WITHIN 50 NM OVER THE NW
SEMICIRCLE AND 100 NM OVER THE SE SEMICIRCLE. SCATTERED
RAINBANDS EXTEND NWD TO 23N AND SWD TO 14N BETWEEN 40W-50W.

TROPICAL STORM LISA IS CENTERED NEAR 13.6N 35.9W OR ABOUT 870
MILES...1395 KM...WEST OF THE CAPE VERDE ISLANDS AT 20/2100 UTC.
LISA IS MOVING WEST AT 10 KT. MAXIMUM SUSTAINED WIND SPEED IS 55
KT WITH GUSTS TO 65 KT AND THE ESTIMATED MINIMUM CENTRAL
PRESSURE IS 994 MB. SEE LATEST NHC FORECAST/ADVISORY UNDER
AWIPS/WMO HEADER MIATCMAT3/WTNT23 KNHC FOR MORE DETAILS. LISA
REMAINS A VERY COMPACT SYSTEM WITH ASSOCIATED SCATTERED
MODERATE/ISOLATED STRONG CONVECTION ONLY COVERING A SMALL AREA
FROM 12.5N-14N BETWEEN 36W-38W. DESPITE ITS SIZE...LISA APPEARS
BETTER ORGANIZED IN SATELLITE IMAGERY WITH THE LOW LEVEL CENTER
MORE EMBEDDED WITHIN THE CDO.

...TROPICAL WAVES...

TROPICAL WAVE IS INTRODUCED OVER THE FAR E ATLC ALONG 28W S OF
14N MOVING W NEAR 15 KT.  SATELLITE IMAGERY SHOWS A BROAD YET
WELL-DEFINED LOW LEVEL CIRCULATION WHICH HAS BECOME BETTER
ORGANIZED DURING THE DAY.  EARLIER WIDELY SCATTERED CONVECTION
HAS BECOME BETTER CONSOLIDATED NEAR THE CENTER AND A LOOSELY
ORGANIZED BAND NOW APPEARS TO BE FORMING TO THE NW.  THE
ENVIRONMENT APPEAR FAVORABLE FOR ADDITIONAL DEVELOPMENT.

...ITCZ...

ITCZ AXIS EXTENDS ALONG 11N1W 9N25W 12N35W THEN DISRUPTED BY
T.S. LISA AND HURRICANE KARL BETWEEN 35W-45W. ITCZ BECOMES
REESTABLISHED ALONG 11N45W 7N60W 8N80W. ASIDE FROM ACTIVITY WITH
TROPICAL WAVE NEAR 28W...NONE SIGNIFICANT.

...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 N FLORIDA TO THE BAY OF CAMPECHE. ATTENDANT
SURFACE COLD FRONT IS PUSHING SWD OVER THE W ATLC AND FLORIDA
JUST S OF LAKE OKEECHOBEE. 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.  AS A
RESULT...DEEP CONVECTION IS PRIMARILY CONFINED OVER INTERIOR
MEXICO AND THE YUCATAN PENINSULA WHERE MOISTURE IS MORE
PREVALENT. AT THE SURFACE...1008 MB LOW WHICH FORMED FROM THE
REMNANTS OF T.D. IVAN IS LOCATED JUST OFF THE SE COAST OF
FLORIDA NEAR THE ISLAND OF BIMINI IN THE BAHAMAS.  WHILE THERE
ARE NO SIGNS OF DEVELOPMENT...THE SYSTEM IS PRODUCING SCATTERED
TO LOCALLY NUMEROUS SHOWERS/THUNDERSTORMS ALONG THE E COAST OF
FLORIDA PRIMARILY FROM PALM BEACH NWD TO CAPE CANAVERAL. THIS
ACTIVITY SHOULD SPREAD SLOWLY WESTWARD ACROSS CENTRAL PORTIONS
OF FLORIDA TONIGHT WITH LOCALLY HEAVY RAINFALL.  LATEST WATER
VAPOR ANALYSIS INDICATES 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 N 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 ADVECTED VERY DRY MIDDLE TO UPPER LEVEL AIR FROM THE
TROPICAL ATLC WESTWARD INTO THE E CARIBBEAN...NOW E OF 75W.
THIS HAS RESULTED IN DECREASED AFTERNOON SHOWERS/THUNDERSTORMS
ESPECIALLY OVER THE EXTREME SE CARIBBEAN AND WINDWARD ISLANDS.
FURTHER W...WEAK DIFFLUENT FLOW ON THE EQUATORWARD SIDE OF THE
UPPER RIDGE IS PRODUCING AREAS OF CONVECTION OVER N PORTIONS OF
S AMERICA AND MUCH OF CENTRAL AMERICA.  ELSEWHERE...A WEAK LOWER
TO MID-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. ATTENDANT SURFACE COLD FRONT ENTERS THE AREA
NEAR 32N60W EXTENDING WSW AROUND HURRICANE JEANNE TO SE FLORIDA
NEAR PALM BEACH.  THE S EXTENT OF THE TROUGH HAS BECOME NEARLY
STATIONARY AS IT ENCOUNTERS THE UPPER LEVEL OUTFLOW ASSOCIATED
WITH HURRICANE JEANNE.  ACCORDINGLY...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.

$$
RHOME



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