[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 200537
TWDAT

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

...SPECIAL FEATURES...

TROPICAL STORM JEANNE IS CENTERED NEAR 25.2N 72.0W OR ABOUT 230
NM EAST OF ELEUTHERA IN THE BAHAMAS AT 20/0300 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 994 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 SATELLITE SIGNATURE CONTINUES TO EVOLVE
WITH A BAND CONVECTION WRAPPING AROUND THE LOW LEVEL CENTER TO
THE NORTH. SCATTERED MODERATE/ISOLATED STRONG CONVECTION IS
WITHIN 30/45 NM OF LINE FROM 25N71W WRAPPING THROUGH 27N72W TO
26N69W. THIS CONVECTION IS AT LEAST 120 NM NE OF THE EASTERN
MOST BAHAMA ISLANDS. UPPER LEVEL OUTFLOW IS GOOD TO THE W AND N
OF THE SYSTEM BUT LIMITED TO THE S AS MODERATE SUBSIDENCE/DRY
AIR IS BEING DRAWN ACROSS THE N BAHAMAS INTO JEANNE COURTESY OF
A WEAK MID/UPPER TROF OVER THE BAHAMAS.

HURRICANE KARL IS CENTERED NEAR 17.2N 45.1W OR ABOUT 980 NM EAST
OF THE LEEWARD ISLANDS AT 20/0300 UTC MOVING WEST-NORTHWEST AT
10 KT. MAXIMUM SUSTAINED WIND SPEED IS 115 KT WITH GUSTS TO 140
KT. 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 STRONG CONVECTION SURROUNDING
THE EYE TO THE SE WITHIN 75 NM. OUTER RAINBANDS REACH FROM 14N
TO 20N BETWEEN 36W AND 48W. KARL IS SITUATED ON THE SOUTH SIDE
OF A MID LEVEL RIDGE WHICH IS MAINTAINING A GENERAL WESTWARD
MOTION. VERTICAL SHEAR REMAINS LOW SHEAR WITH GOOD UPPER LEVEL
OUTFLOW IN ALL QUADRANTS.

TROPICAL DEPRESSION THIRTEEN IS CENTERED NEAR 13.2N 34.1W OR
ABOUT 6O0 NM WEST-SOUTHWEST OF THE CAPE VERDE ISLANDS AT 20/0300
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 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 MODERATE/STRONG CONVECTION ONLY COVERING A SMALL AREA
WITHIN 75 NM OF LINE FROM 11N32W TO 15N36W. SATELLITE IMAGERY
SUGGESTS THAT UPPER-LEVEL OUTFLOW FROM HURRICANE KARL TO THE
WEST IS IMPINGING UPON THE SYSTEM RESULTING IN SOME WESTERLY
SHEAR.

...TROPICAL WAVES...

NONE.

...ITCZ...

ITCZ EMERGES OFF THE COAST OF AFRICA NEAR 10N10W ALONG 5N24W
12N41W 7N60W. SCATTERED MODERATE/ISOLATED STRONG CONVECTION IS
WITHIN A 60 NM RADIUS OF 10.5N27W. AN AREA SCATTERED MODERATE
CONVECTION IS FROM 2N-9N BETWEEN 20W-35W. CLUSTERS OF SIMILAR
CONVECTION ARE WITHIN 60 NM OF 6N FROM 8W-15W.

...DISCUSSION...

GULF OF MEXICO...
A PATTERN MORE TYPICAL OF LATE FALL PREVAILS OVER THE GULF WITH
A MID/UPPER LEVEL TROUGH EXTENDING FROM THE CANADIAN MARITIMES
THROUGH THE W ATLC ACROSS FLORIDA INTO THE SE GULF TO OVER THE
YUCATAN PENINSULA. A SECOND SURFACE COLD FRONT ENTERS THE REGION
FROM A 1009 MB LOW NEAR 31N75W TO INLAND OVER FLORIDA NEAR
JACKSONVILLE. A DISSIPATING STATIONARY FRONT THAT WILL SOON BE A
SURFACE TROF EXTENDS FROM 30N73W ACROSS THE N BAHAMAS TO OVER
FLORIDA NEAR MIAMI TO THE E GULF NEAR 27N85W. UNUSUALLY DRY AIR
THROUGHOUT THE ENTIRE DEPTH OF THE ATMOSPHERE LIES NORTH OF THE
YUCATAN AND W CUBA FROM 80W TO 90W. 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 90W WITH THE ONLY SIGNIFICANT WEATHER OF NOTE
BEING WIDELY SCATTERED SHOWERS OVER THE SW GULF INTO THE BAY OF
CAMPECHE S OF 25N. THE E GULF TROF IS EXPECTED TO AMPLIFY TO THE
W THEN SW AS THE RIDGE OVER MEXICO BUILDS OVER THE NE UNITED
STATES.

CARIBBEAN SEA...
WEAK MID/UPPER LEVEL TROF EXTENDS FROM OVER THE BAHAMAS ESE TO
JUST S OF JEANNE PRODUCING CLUSTERS OF STRONG THUNDERSTORMS OVER
CUBA E OF 80W. OVER THE CARIBBEAN...BROAD ANTICYCLONIC FLOW
COVERS THE CARIBBEAN WITH NORTHERLY FLOW E OF 70W USHERING IN
MODERATE SUBSIDENCE/DRY AIR OVER THE AREA INCLUDING THE MOST OF
THE LEEWARD ISLANDS AND ALL OF THE WINDWARD ISLANDS. THE EAST TO
NORTHEAST FLOW OVER THE REMAINDER OF THE CARIBBEAN IS USHERING
IN TROPICAL MOISTURE. NUMEROUS STRONG CONVECTION IS INLAND OVER
NW VENEZUELA AND NE COLOMBIA INCLUDING LAKE MARACAIBO. CLUSTERS
OF SCATTERED MODERATE/ISOLATED STRONG CONVECTION COVERS CENTRAL
AMERICA AND THE ADJACENT COASTAL WATERS. ISOLATED LOW LEVEL
SHOWERS DOT THE WATERS OF THE CARIBBEAN W OF 70W. 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 BUT IS NO LONGER IN 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 FROM THE BAHAMAS NE TO BEYOND BERMUDA. FURTHER
EAST...AMPLIFYING MID/UPPER LEVEL TROF ENTERS AREA ALONG 32N54W
S TO 20N57W. MID/UPPER LEVEL MOISTURE AND HIGH CLOUDINESS
ASSOCIATED WITH JEANNE IS STREAMING E AROUND THE BASE OF THIS
TROF WITH SCATTERED SHOWERS/THUNDERSTORMS FROM 17N-26N BETWEEN
60W-70W AND N OF 22N BETWEEN 48W-56W. A HIGH AMPLITUDE MID/UPPER
LEVEL RIDGE EXTENDS FROM OVER KARL N ALONG 43W COVERING THE AREA
WITH ANTICYCLONIC FLOW FROM 33W TO 50W. THE MID/UPPER LEVEL
TROF COVERS THE REMAINDER OF THE E ATLC WITH A SERIES OF
MID/UPPER LEVEL LOWS CENTERED NEAR 24N30W...OVER THE CANARY
ISLANDS NEAR 29N17W...AND A THIRD N OF THE REGION NEAR 37N29W.
AT THE SURFACE...SUBTROPICAL RIDGE EXTENDS FROM 32N45W W TO
30N65W.A SURFACE TROF EXTENDS FROM A WEAK 1020 MB LOW N OF THE
REGION THROUGH 32N31W WSW TO 28N42W.

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 13N/14N WHILE
A WEAK UPPER TROUGH LIES W OF KARL FROM TRINIDAD/TOBAGO TO
20N52W.

$$
WALLACE


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