[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 120604
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
205 AM EDT SUN 12 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
0345 UTC.

...SPECIAL FEATURE...
HURRICANE IVAN REMAINS A CATEGORY 5 STORM. IVAN IS CENTERED NEAR
18.4N 80.4W OR 90 MILES SE OF GRAND CAYMAN AT 12/0600 UTC MOVING
WNW AT 7 KT. MAXIMUM SUSTAINED WIND SPEED IS 145 KT WITH GUSTS
TO 175 KT. MINIMUM CENTRAL PRESSURE REPORTED BY AIR FORCE
RESERVE UNIT HURRICANE HUNTER AIRCRAFT IS 910 MB. SEE LATEST NHC
PUBLIC ADVISORY OR NHC FORECAST/ ADVISORY UNDER AWIPS/WMO
HEADERS MIATCPAT4/WTNT34 KNHC OR MIATCMAT4/WTNT24 KNHC FOR MORE
DETAILS. IVAN CONTINUES TO BE A VERY SYMMETRICAL SYSTEM WITH
GOOD OUTFLOW IN ALL QUADRANTS. NUMEROUS STRONG CONVECTION IS
WITHIN 60 NM OF THE CENTER WITH SCATTERED MODERATE/ISOLATED
STRONG CONVECTION COVERING THE REMAINDER OF THE AREA WITHIN 150
NM OF LINE FROM SE CUBA NEAR 21N76W TO JUST OFF THE COAST OF
HONDURAS NEAR 15N93W. IVAN COULD POSSIBLY INTENSIFY MORE OVER
THE BUT IS EXPECTED TO WEAKEN IN THE GULF OF MEXICO 2 TO 3 DAYS
FROM NOW.

...TROPICAL WAVES...
TROPICAL WAVE IN THE E ATLC ALONG 32W/33W S OF 21N MOVING W
15-20 KT. BROAD CYCLONIC ROTATION IS OBSERVED ON INFRARED
SATELLITE IMAGERY WITH CLUSTERS OF SCATTERED MODERATE/ISOLATED
STRONG CONVECTION FROM 5N-10N BETWEEN 29W-38W.

TROPICAL WAVE IN THE W TROPICAL ATLC ALONG 52W/53W S OF 19N
MOVING W 15-20 KT. BROAD CYCLONIC ROTATION IS BEING DISTORTED BY
A STRONG UPPER LEVEL LOW N OF THE WAVE. SCATTERED MODERATE/
STRONG CONVECTION IS WITHIN 60/75 NM OF LINE FROM 11N45W-17N53W.

TROPICAL WAVE IN THE E CARIBBEAN ALONG 63W/64W S OF 22N MOVING W
10 KT WITH A 1011 MB LOW ALONG THE WAVE NEAR 17N. LOW LEVEL
CYCLONIC CIRCULATION IS OBSERVED IN ASSOCIATION WITH THE LOW
ALONG THE WAVE WHICH IS DEVELOPING SCATTERED STRONG CONVECTION
WITHIN A 75/90 NM RADIUS OF 16.5N64W.

...ITCZ...
ITCZ AXIS EXTENDS ALONG 11N10W 6N23W 9N32W 10N52W. SCATTERED
MODERATE/STRONG CONVECTION MOVING OFF THE COAST OF AFRICA WITHIN
60 NM FROM 5N-10N. CLUSTERS OF SCATTERED MODERATE/ISOLATED
STRONG CONVECTION FROM 3N-10N BETWEEN 14W-22W.

...DISCUSSION...
GULF OF MEXICO...
DEEP LAYERED TROUGH COVERS THE EAST HALF OF THE UNITED STATES E
OF TEXAS AND THE EXTREME N GULF. UPPER LEVEL LOWS HAVE BEEN
ROTATING THROUGH THIS TROUGH OVER THE PAST FEW DAYS AS IT MOVES
OVER THE FAR E COAST OF THE U.S. RESULTING IN BANDS OF STRONG
SUBSIDENCE/DRY AIR...EXTENDING N FROM GEORGIA THROUGH THE
CAROLINAS...AND MORE MOVING S ACROSS OKLAHOMA INTO E TEXAS. THIS
CYCLONIC FLOW COUPLED WITH THE FLOW FROM AN UPPER LEVEL HIGH
OVER NORTH-CENTRAL MEXICO IS BRINGING STRONG SUBSIDENCE/DRY AIR
TO THE NW GULF N OF 25N W OF 90W. WEAK TROUGH REMAINS OVER THE
BAY OF CAMPECHE S OF 24N FROM 91W TO 96W. A MID/UPPER LEVEL HIGH
CENTERED JUST N OF THE YUCATAN CHANNEL NEAR 22N87W COVERS THE E
GULF AND THUS FUNNELING TROPICAL MOISTURE OVER THE NE GULF AND
THE FLORIDA PENINSULA. SCATTERED CLUSTERS OF SCATTERED SHOWERS/
ISOLATED THUNDERSTORMS DOT THE ENTIRE GULF EXCEPT IN THE NW
CORNER.

CARIBBEAN...
MAIN FEATURE IN THE CARIBBEAN...AS OVER THE PAST SEVERAL
DAYS...IS HURRICANE IVAN. IVAN HAS SLOWED OVER THE LAST 24 HOURS
DUE TO THE MID/UPPER LEVEL HIGH TO THE W CENTERED IN THE YUCATAN
CHANNEL DISCUSSED ABOVE. BROAD UPPER LEVEL HIGH IS OVER IVAN
WITH A RIDGE AXIS EXTENDING E CROSSING THE GREATER ANTILLES NEAR
THE MONA PASSAGE INTO THE CENTRAL ATLC. CLUSTERS OF SCATTERED
MODERATE/ISOLATED STRONG CONVECTION ARE S OF 17N W OF 72W OVER
CENTRAL AMERICA AND COLOMBIA IN ASSOCIATION WITH THE OUTER
RAINBANDS OF IVAN.

SUBTROPICAL ATLANTIC...
RIDGE AXIS EXTENDS FROM THE MID/UPPER LEVEL HIGH OVER THE
YUCATAN CHANNEL ACROSS FLORIDA NEAR 27N80W INTO THE W ATLC TO
BEYOND 32N74W. DOWNSLOPE ANTICYCLONIC FLOW COUPLED WITH THE
UPPER LEVEL LOW TO THE E IS PRODUCING MODERATE SUBSIDENCE/DRY
AIR OVER PORTIONS OF THE W ATLC ACROSS THE N BAHAMAS INTO THE
STRAITS OF FLORIDA. BROAD UPPER LEVEL LOW IS IN THE CENTRAL/
WESTERN ATLC ABOUT 150 NM S OF BERMUDA NEAR 30N65W WITH CYCLONIC
FLOW CUT OFF FROM THE MID-OCEANIC TROUGH FROM LAST NIGHT.
CYCLONIC FLOW COVERS THE AREA N OF 23N FROM 57W-71W. RIDGE AXIS
EXTENDING FROM THE CARIBBEAN NEAR THE MONA PASSAGE NE ALONG
24N56W TO 30N52W. THE UPSLOPE ANTICYCLONIC FLOW COMBINED WITH
THE CYCLONIC FLOW FROM THE UPPER LOW S OF BERMUDA IS PRODUCING
LARGE CLUSTERS OF SCATTERED MODERATE/STRONG CONVECTION FROM
18N-33N BETWEEN 50W-63W. THE MID-OCEANIC TROUGH IS NOW LIMITED
TO THE E ATLC N OF 23N FROM 23W-42W.

TROPICAL ATLANTIC...
MID/UPPER RIDGE AXIS EXTENDS ACROSS THE TROPICAL ATLC FROM OVER
AFRICA THROUGH A MID/UPPER LEVEL HIGH OVER THE CAPE VERDE
ISLANDS NEAR 15N23W TO A SECOND HIGH NEAR 15N44W. THE CULL
BETWEEN THE TWO HIGHS IS PRODUCING MODERATE SUBSIDENCE/DRY AIR
FROM 10N-20N BETWEEN 30W-40W.

$$
WALLACE


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