[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 201037
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
805 AM 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 0600 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
0945 UTC.

...SPECIAL FEATURES...

TROPICAL STORM JEANNE IS CENTERED NEAR 26.0N 71.9W OR ABOUT 285
NM EAST OF GREAT ABACO ISLAND IN THE BAHAMAS AT 20/0900 UTC.
JEANNE IS MOVING NORTH AT 7 KT. MAXIMUM SUSTAINED WIND SPEED IS
50 KT WITH GUSTS TO 60 KT. ESTIMATED MINIMUM CENTRAL PRESSURE IS
992 MB. SEE LATEST NHC PUBLIC ADVISORY OR NHC FORECAST/ ADVISORY
UNDER AWIPS/WMO HEADERS MIATCPAT1/WTNT31 KNHC OR MIATCMAT1/
WTNT21 KNHC FOR MORE DETAILS. CONVECTION NOW IN ALL QUADRANTS
BUT SHOWS LITTLE IN THE WAY OF FURTHER ORGANIZATION. SCATTERED
MODERATE CONVECTION IS WITHIN 60 NM OF OF THE CENTER IN THE SE
QUADRANT. SCATTERED MODERATE/ISOLATED STRONG CONVECTION IS
WITHIN 30/45 NM OF LINE FROM 26N74W-29N68W. THIS CONVECTION IS
AT LEAST 120 NM NE OF THE EASTERN MOST BAHAMA ISLANDS. UPPER
LEVEL OUTFLOW IS GOOD MOSTLY TO THE N OF THE SYSTEM BUT IS
SEVERELY LIMITED TO THE S AS MODERATE SUBSIDENCE/DRY AIR IS
BEING DRAWN ACROSS THE S BAHAMAS INTO JEANNE COURTESY OF A WEAK
MID/UPPER TROUGH OVER THE BAHAMAS.

HURRICANE KARL IS CENTERED NEAR 17.3N 45.5W OR ABOUT 930 NM EAST
OF THE LEEWARD ISLANDS AT 20/0900 UTC MOVING WEST-NORTHWEST AT
8 KT. MAXIMUM SUSTAINED WIND SPEED IS 110 KT WITH GUSTS TO 135
KT. ESTIMATED MINIMUM CENTRAL PRESSURE IS 950 MB. SEE LATEST NHC
FORECAST/ ADVISORY UNDER AWIPS/WMO HEADER MIATCMAT2/WTNT22 KNHC
FOR MORE DETAILS. KARL REMAINS AN IMPRESSIVE SATELLITE SIGNATURE
WITH A VERY SMALL BUT DISTINCT EYE AND STRONG CONVECTION WITHIN
60 NM OF THE CENTER IN THE W SEMICIRCLE. OUTER RAINBANDS REACH
FROM 14N TO 22N BETWEEN 41W AND 49W. KARL IS SITUATED ON THE
SOUTH SIDE OF A LOW/MID LEVEL RIDGE WHICH IS MAINTAINING A
GENERAL WESTWARD MOTION. VERTICAL SHEAR IS STARTING TO IMPINGE
ON THE SW SIDE WITH GOOD UPPER LEVEL OUTFLOW IN THE REMAINING
QUADRANTS.

TROPICAL DEPRESSION THIRTEEN IS CENTERED NEAR 13.5N 34.9W OR
ABOUT 575 NM WEST-SOUTHWEST OF THE CAPE VERDE ISLANDS AT 20/0900
UTC. T.D. THIRTEEN IS MOVING WEST AT 10 KT. MAXIMUM SUSTAINED
WIND SPEED IS 30 KT WITH GUSTS TO 40 KT. ESTIMATED MINIMUM
CENTRAL PRESSURE IS 1005 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 MODERATE/ISOLATED STRONG CONVECTION WITHIN 60/75 NM OF
LINE FROM 13N34W TO 16N37W. SATELLITE IMAGERY SUGGESTS THAT
UPPER-LEVEL OUTFLOW FROM HURRICANE KARL TO THE WEST IS IMPINGING
UPON THE SYSTEM RESULTING IN STRONG WESTERLY SHEAR.

...TROPICAL WAVES...

NONE.

...ITCZ...

ITCZ AXIS EXTENDS ALONG 12N10W 12N18W 6N25W 8N36W 7N60W.
CLUSTERS OF SCATTERED MODERATE/ISOLATED STRONG CONVECTION ARE
FROM 7N-12N BETWEEN 23W-30W AND FROM 5N-8N E OF 16W TO THE COAST
OF AFRICA.
CLUSTERS OF SCATTERED MODERATE CONVECTION ARE FROM 2N-7N BETWEEN
25W-35W.

...DISCUSSION...

GULF OF MEXICO...
LATE FALL PATTERN REMAINS OVER THE GULF WITH A STRONG MID/UPPER
LEVEL TROUGH EXTENDING FROM THE CANADIAN MARITIMES THROUGH THE W
ATLC ACROSS NE FLORIDA TO THE SE GULF OVER THE YUCATAN
PENINSULA. A SURFACE COLD FRONT ENTERS THE REGION FROM A 1009 MB
LOW NEAR 31N76W TO INLAND OVER FLORIDA JACKSONVILLE AND DAYTONA
BEACH THEN NW ACROSS THE FLORIDA PANHANDLE TO THE ALABAMA/
GEORGIA BORDER. SCATTERED SHOWERS/ISOLATED THUNDERSTORMS ARE
DEVELOPING ALONG THE FRONT W OF 79W TO INLAND OVER FLORIDA. A
SURFACE TROUGH EXTENDS FROM 28N74W ACROSS THE N BAHAMAS ALONG
25N79W OVER THE FLORIDA KEYS TO THE E GULF NEAR 26N83W.
UNUSUALLY DRY AIR THROUGHOUT THE ENTIRE DEPTH OF THE ATMOSPHERE
LIES NORTH OF THE YUCATAN AND W CUBA FROM 81W TO 94W. OVER THE W
GULF...A HIGH AMPLITUDE MID/UPPER LEVEL HIGH IS OVER NW MEXICO
WITH A RIDGE EXTENDING ACROSS THE CENTRAL UNITED STATES INTO
CANADA. ASSOCIATED STRONG N FLOW AROUND THE E PERIPHERY OF THE
RIDGE PREVAILS W OF 94W WITH THE ONLY SIGNIFICANT WEATHER OF
NOTE BEING WIDELY SCATTERED SHOWERS/ ISOLATED THUNDERSTORMS OVER
THE BAY OF CAMPECHE S OF 21N. THE E GULF TROUGH IS EXPECTED TO
CONTINUE TO AMPLIFY TO THE W THEN SW AS THE RIDGE OVER MEXICO
BUILDS OVER THE NE UNITED STATES.

CARIBBEAN SEA...
WEAK MID/UPPER LEVEL TROUGH EXTENDS FROM OVER THE BAHAMAS SE TO
JUST S OF JEANNE. THIS IS BRINGING DRIER AIR INTO JEANNE AND
ONLY WIDELY ISOLATED SHOWERS TO E CUBA. OVER THE CARIBBEAN...
BROAD ANTICYCLONIC FLOW COVERS THE CARIBBEAN WITH NE FLOW E OF
LINE FROM PUERTO RICO SW TO N CENTRAL COLOMBIA USHERING IN
MODERATE SUBSIDENCE/DRY AIR OVER THE E CARIBBEAN INCLUDING THE
THE LEEWARD AND WINDWARD ISLANDS. THE EAST TO NORTHEAST FLOW
OVER THE REMAINDER OF THE CARIBBEAN IS USHERING IN TROPICAL
MOISTURE. CLUSTERS OF SCATTERED STRONG CONVECTION ARE INLAND
OVER NW VENEZUELA...NE COLOMBIA AND WITHIN 75 NM ALONG THE W
COAST OF COLOMBIA...WHICH INCLUDES LAKE MARACAIBO. CLUSTERS OF
SCATTERED SHOWERS/THUNDERSTORMS DOT THE W CARIBBEAN FROM
71W-85W. THIS SCENARIO WILL REMAIN WILL REMAIN WITH A MID/UPPER
LEVEL HIGH FORMING IN THE NE CARIBBEAN THEN DRIFTING WESTWARD.

SUBTROPICAL ATLANTIC...
STRONG MID/UPPER LEVEL TROUGH CONTINUES TO PROGRESS E OVER THE W
ATLC FROM THE CANADIAN MARITIMES N OF THE REGION COURTESY OF THE
UPPER LEVEL HIGH ASSOCIATED WITH T.S. JEANNE. JEANNE IS SITUATED
BENEATH A WELL-DEFINED UPPER LEVEL HIGH WITH RIDGE EXTENDING NE
TO BEYOND 32N60W. FURTHER EAST...AMPLIFYING MID/UPPER LEVEL
TROUGH ENTERS AREA ALONG 32N53W S TO 19N56W. MID/UPPER LEVEL
MOISTURE AND HIGH CLOUDINESS COVERS THE CENTRAL/WESTERN ATLC N
OF 20N FROM 49W TO OVER T.S. JEANNE. A HIGH AMPLITUDE MID/UPPER
LEVEL RIDGE EXTENDS FROM OVER KARL N ALONG 42W COVERING THE AREA
WITH ANTICYCLONIC FLOW FROM 33W TO 50W. THE MID/UPPER LEVEL
TROUGH COVERS THE REMAINDER OF THE E ATLC WITH A SERIES OF
MID/UPPER LEVEL LOWS CENTERED NEAR 24N28W...OVER THE CANARY
ISLANDS NEAR 29N16W...AND A THIRD N OF THE REGION NEAR 37N29W.
AT THE SURFACE...SUBTROPICAL RIDGE EXTENDS FROM 32N40W W TO
30N60W.A SURFACE TROUGH EXTENDS FROM A WEAK 1018 MB LOW N OF THE
REGION THROUGH 32N32W WSW TO 28N41W.

TROPICAL ATLANTIC...
ASIDE FROM ACTIVITY ASSOCIATED WITH HURRICANE KARL AND T.D.
THIRTEEN...CONVECTION IS LIMITED TO A SMALL AREA WITHIN THE ITCZ
E OF 35W. 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 12N/13N WHILE
A WEAK UPPER TROUGH LIES W OF KARL FROM TRINIDAD/TOBAGO TO
19N51W.

$$
WALLACE



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