[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 192359
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
805 PM EDT SUN 19 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 CENTERED NEAR 24.5N 72.3W OR ABOUT 145
MILES/210 KM EAST-SOUTHEAST OF SAN SALVADOR IN THE BAHAMAS AT
19/2100 UTC. JEANNE IS MOVING NORTH 7 KT. MAXIMUM SUSTAINED WIND
SPEED 45 KT WITH GUSTS TO 55 KT AND THE ESTIMATED MINIMUM
CENTRAL PRESSURE 996 MB. SEE LATEST NHC PUBLIC ADVISORY OR NHC
FORECAST/ ADVISORY UNDER AWIPS/WMO HEADERS MIATCPAT1/WTNT31 KNHC
OR MIATCMAT1/WTNT21 KNHC FOR MORE DETAILS.  THE OVERALL
SATELLITE SIGNATURE HAS CHANGED LITTLE DURING THE LAST SEVERAL
HOURS. THERE WAS A BURST OF DEEP CONVECTION NEAR THE CENTER
BETWEEN 1900-2100 UTC BUT CLOUD TOP TEMPERATURES HAVE SINCE
WARMED. CURRENTLY JEANNE IS PRODUCING AN AREA OF SCATTERED TO
LOCALLY NUMEROUS STRONG CONVECTION NE OF THE BAHAMAS FROM
23N-28N BETWEEN 68W-74W. THIS ACTIVITY IS PULLING AWAY FROM THE
BAHAMAS WITH ONLY UPPER LEVEL CIRRUS CLOUDS REMAINING.
UPPER-LEVEL OUTFLOW IS GOOD TO THE NORTH BUT SOMEWHAT RESTRICTED
TO THE SOUTH COURTESY OF A WEAK UPPER TROUGH OVER THE BAHAMAS.

HURRICANE KARL IS CENTERED NEAR 17.0N 44.0W MOVING
WEST-NORTHWEST 9 KT. MAXIMUM SUSTAINED WIND SPEED HAS INCREASED
TO 115 KT WITH GUSTS TO 140 KT MAKING KARL THE FOURTH CATEGORY
FOUR HURRICANE THIS SEASON. THE ESTIMATED MINIMUM CENTRAL
PRESSURE IS 944 MB. SEE LATEST NHC FORECAST/ADVISORY UNDER
AWIPS/WMO HEADER MIATCMAT2/WTNT22 KNHC FOR MORE DETAILS. KARL IS
MAINTAINING AN IMPRESSIVE SATELLITE SIGNATURE WITH A DISTINCT
EYE AND INTENSE SURROUNDING CONVECTION WITHIN 90 NM RADIUS.
OUTER RAINBANDS REACH AS FAR NORTH AS 21N AND SOUTH TO 13N
BETWEEN 39W AND 47W. KARL IS SITUATED ON THE SOUTH SIDE OF A
MID- LEVEL RIDGE WHICH IS MAINTAINING A GENERAL WESTWARD MOTION.
VERTICAL SHEAR REMAINS LOW SHEAR AND A 50 KT UPPER LEVEL JET TO
THE NE IS PROVIDING EXCELLENT POLEWARD OUTFLOW.

NEWLY FORMED T.D. THIRTEEN IS CENTERED NEAR 13.3N 33.2W...OR
ABOUT 645 MILES...1035 KM...WEST-SOUTHWEST OF THE CAPE VERDE
ISLANDS AT 19/2100 UTC.  THE DEPRESSION IS MOVING TOWARD THE
WEST AT 10 KT. MAXIMUM SUSTAINED WINDS ARE 30 KT WITH GUSTS TO
40 KT AND THE ESTIMATED MINIMUM CENTRAL PRESSURE IS 1004 MB. SEE
LATEST NHC FORECAST/ADVISORY UNDER AWIPS/WMO HEADER
MIATCMAT3/WTNT23 KNHC FOR MORE DETAILS. T.D. THIRTEEN IS A
FAIRLY COMPACT SYSTEM WITH ASSOCIATED SCATTERED TO LOCALLY
NUMEROUS STRONG CONVECTION ONLY COVERING A SMALL AREA FROM
12.5N-15.5N BETWEEN 31W-35W. SATELLITE IMAGERY SUGGESTS THAT
UPPER-LEVEL OUTFLOW FROM HURRICANE KARL TO THE WEST IS IMPINGING
UPON THE SYSTEM RESULTING IN SOME SHEAR.  CONVECTION NEAR THE
CENTER HAS BEEN WEAKENING OVER THE LAST SEVERAL HOURS.

...TROPICAL WAVES...

NONE.

...ITCZ...

ITCZ EMERGES OFF THE COAST OF AFRICA NEAR 12N15W EXTENDING WSW
ALONG 11N25W THEN BECOMING DISRUPTED BY T.D. THIRTEEN AND
HURRICANE KARL. AXIS BECOME REESTABLISHED ALONG 10N43W 9N50W
13N65W 10N80W.  WIDELY SCATTERED MODERATE CONVECTION OFF THE SW
COAST OF AFRICA FROM 4N-10N BETWEEN 17W-31W.

...DISCUSSION...

GULF OF MEXICO...
A PATTERN MORE TYPICAL OF LATE FALL PREVAILS OVER THE GLFMEX
WITH A MID-UPPER LEVEL TROUGH EXTENDING FROM THE W ATLC OVER S
FLORIDA INTO THE SE GLFMEX. ATTENDANT SURFACE COLD FRONT PULLS
UP STATIONARY OVER FLORIDA NEAR LAKE OKEECHOBEE WEAKENING OVER
THE GLFMEX ALONG 27N82W 23N85W 22N90W.  UNUSUALLY DRY AIR
THROUGHOUT THE ENTIRE DEPTH OF THE ATMOSPHERE LIES NORTH OF THE
FRONTAL BOUNDARY LIMITING SIGNIFICANT CONVECTION TO A SMALL AREA
OF AFTERNOON SHOWERS/THUNDERSTORMS WHICH OCCURRED EARLIER TODAY
OVER S FLORIDA.  OVER THE W GLFMEX...A HIGH AMPLITUDE MID-UPPER
LEVEL RIDGE RESIDES OVER INTERIOR MEXICO EXTENDING INTO THE
CENTRAL UNITED STATES.  ASSOCIATED STRONG NLY FLOW AROUND THE E
PERIPHERY OF THE RIDGE PREVAILS W OF 90W WITH THE ONLY
SIGNIFICANT WEATHER OF NOTE BEING WIDELY SCATTERED
SHOWERS/THUNDERSTORMS OVER THE SW GLFMEX AND BAY OF CAMPECHE S
OF 23N.  THE E GLFMEX TROUGH IS EXPECTED TO AMPLIFY A LITTLE
FURTHER S ALLOWING DRY AIR TO CONTINUE FILTERING SWD OVER E
GLFMEX DURING THE NEXT 24 HOURS.  HOWEVER...AN AREA OF HIGH LOW
LEVEL MOISTURE CURRENTLY OVER THE W ATLC SHOULD MOVE SW OVER N
PORTIONS OF FLORIDA TONIGHT.

CARIBBEAN SEA...
WEAK DEEP LAYERED TROUGH TRAILS SWD FROM T.S. JEANNE OVER E CUBA
AND THE W CARIBBEAN TO CENTRAL AMERICA NEAR THE
HONDURAS/NICARAGUA BORDER. THIS FEATURE IS PRODUCING SCATTERED
MODERATE CONVECTION OVER HISPANIOLA...E CUBA...AND JAMAICA WITH
WIDELY SCATTERED SHOWERS/THUNDERSTORMS OVER THE OPEN WATERS
WITHIN 150 NM OF A LINE FROM THE WINDWARD PASSAGE TO CENTRAL
NICARAGUA.  SCATTERED MODERATE TO STRONG CONVECTION IS ALSO
NOTED OVER ALL OF CENTRAL AMERICA WITH THE STRONGEST AND MOST
NUMEROUS ACTIVITY CURRENTLY FOCUSED NEAR THE UPPER TROUGH AXIS
OVER NICARAGUA/HONDURAS.  FURTHER E...STRONG MID-LEVEL RIDGE
OVER THE CENTRAL ATLC EXTENDS INTO THE E CARIBBEAN NEAR THE
VIRGIN ISLANDS TO NEAR 15N80W. MODERATE SUBSIDENCE AND DRY AIR E
OF 70W IS CAPPING SIGNIFICANT ACTIVITY.  THE WEAK TROUGH
TRAILING FROM T.S. JEANNE OVER THE W CARIBBEAN IS EXPECTED TO
SLOWLY WEAKEN AND DRIFT WESTWARD DURING THE NEXT 24-36 HOURS
WITH STRONG MID-UPPER LEVEL RIDGING BUILDING WESTWARD IN ITS
WAKE.

SUBTROPICAL ATLANTIC...
STRONG MID-UPPER LEVEL TROUGH CONTINUES TO PROGRESS EWD OVER THE
W ATLC FROM THE CANADIAN MARITIMES SWD IN BETWEEN THE SE UNITED
STATES AND BERMUDA.  THE TROUGH IS ACCOMPANIED BY VERY DRY AIR
IN THE MIDDLE TO UPPER LEVELS.  THE S EXTENT OF THE TROUGH...S
OF 30N...APPEARS NEARLY STATIONARY IN WATER VAPOR IMAGERY AS IT
ENCOUNTERS UPPER LEVEL OUTFLOW ASSOCIATED WITH T.S. JEANNE NE OF
THE BAHAMAS.  JEANNE IS SITUATED BENEATH A WELL-DEFINED UPPER
LEVEL RIDGE EXTENDING FROM THE BAHAMAS NEWD TO BEYOND BERMUDA.
MID-LEVEL WEAKNESS ASSOCIATED WITH JEANNE TRAILS SWD OVER THE S
BAHAMAS AND E CUBA.  FURTHER E...AMPLIFYING UPPER LEVEL TROUGH
ENTERS AREA ALONG 30N56W SWD TO 20N63W.  MID-UPPER LEVEL
MOISTURE AND HIGH CLOUDINESS ASSOCIATED WITH JEANNE IS STREAMING
EWD INTO THE BASE OF THIS TROUGH WITH SCATTERED
SHOWERS/THUNDERSTORMS FROM 19N-23N BETWEEN 61W-65W.  A SECOND
AREA OF SCATTERED SHOWERS/THUNDERSTORMS IS LOCATED FROM 25N-31N
BETWEEN 50W-56W. THE MID-OCEANIC TROUGH ENTERS AREA OVER THE FAR
E ATLC IN BETWEEN THE AZORES AND CANARY ISLANDS EXTENDING SW
ALONG 25N40W THEN WEAKENING W OF HURRICANE KARL.  ENHANCED UPPER
LEVEL WLY FLOW ASSOCIATED WITH THE MID-OCEANIC TROUGH IS
ASSISTING OUTFLOW FROM KARL.  AT THE SURFACE...SUBTROPICAL RIDGE
EXTENDS FROM 32N45W TO 30N70W.  COLD FRONT LIES OVER THE W ATLC
FROM 32N72W TO THE FLORIDA E COAST NEAR 27N80W.

TROPICAL ATLANTIC...
ASIDE FROM ACTIVITY ASSOCIATED WITH HURRICANE KARL AND THE NEWLY
FORMED T.D. THIRTEEN...CONVECTION IS LIMITED TO A SMALL AREA
WITHIN THE ITCZ E OF 30W.  MID-UPPER LEVEL RIDGING WHICH
TYPICALLY EXTENDS E/W ACROSS THE AREA IS DISRUPTED BY KARL AND
T.D. THIRTEEN.  A WEAK RIDGE LIES JUST S OF THE CAPE VERDE
ISLANDS ALONG 13N/14N WHILE A WEAK UPPER TROUGH LIES W OF KARL
FROM TRINIDAD/TOBAGO TO 20N50W.

$$
RHOME


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