[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 121205
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
805 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 0600 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
1115 UTC.

...SPECIAL FEATURE...
HURRICANE IVAN IS CENTERED NEAR 18.8N 81.2W OR 35 MILES S OF
GRAND CAYMAN AT 12/1200 UTC MOVING WNW AT 7 KT. MAXIMUM
SUSTAINED WIND SPEED IS 135 KT WITH GUSTS TO 165 KT. MINIMUM
CENTRAL PRESSURE REPORTED BY AIR FORCE RESERVE UNIT HURRICANE
HUNTER AIRCRAFT IS 919 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 BUT THE NE
QUADRANT. NUMEROUS STRONG CONVECTION IS WITHIN 120 NM OF THE
CENTER IN THE SW SEMICIRCLE. SCATTERED MODERATE/ STRONG
CONVECTION COVERS THE REMAINDER OF THE AREA WITHIN 175 NM OF
LINE FROM SE CUBA NEAR 21N77W TO THE COAST OF HONDURAS NEAR
15N84W. IVAN COULD POSSIBLY RE-INTENSIFY TO CATEGORY 5 STATUS
OVER THE NEXT 24 HOURS AS FLUCTUATIONS IN INTENSITY ARE LIKELY
AND WILL CONTINUE TO BE A MAJOR HURRICANE IN THE GULF OF MEXICO.

...TROPICAL WAVES...
TROPICAL WAVE IN THE E ATLC ALONG 33W S OF 21N MOVING W 10-15
KT. BROAD INVERTED V CURVATURE IS OBSERVED ON SATELLITE IMAGERY
WITH CLUSTERS OF SCATTERED MODERATE/ISOLATED STRONG CONVECTION
FROM 12N-24N BETWEEN 29W-33W.

TROPICAL WAVE IN THE W TROPICAL ATLC ALONG 53W/54W S OF 19N
MOVING W 10-15 KT. BROAD CYCLONIC ROTATION CONTINUES TO BE
DISTORTED BY A STRONG UPPER LEVEL LOW N OF THE WAVE. SCATTERED
MODERATE/ISOLATED STRONG CONVECTION IS WITHIN 90/120 NM OF LINE
FROM 12N46W-19N56W.

TROPICAL WAVE IN THE E CARIBBEAN ALONG 65W S OF 22N MOVING W
10-15 KT WITH A 1010 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 45/60 NM OF LINE FROM 16N63W-18N64W INCLUDING PORTIONS
OF THE LEEWARD ISLANDS.

...ITCZ...
ITCZ AXIS EXTENDS ALONG 18N13W 10N25W 9N43W 12N61W. LARGE
CLUSTERS OF SCATTERED MODERATE/ISOLATED STRONG CONVECTION ARE
MOVING OFF THE COAST OF AFRICA WITHIN 90 NM FROM 4N-12N. SMALL
CLUSTERS OF SIMILAR CONVECTION ARE WITHIN 90 NM OF LINE FROM
12N52W-20N59W. CLUSTERS OF SCATTERED MODERATE TO SCATTERED
MODERATE/ISOLATED STRONG CONVECTION ARE FROM 4N-10N BETWEEN
15W-52W.

...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 CONTINUE TO
ROTATE THROUGH THIS TROUGH AS IT MOVES OFF THE 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
LOUISIANA AND MISSISSIPPI. THIS CYCLONIC FLOW COUPLED WITH THE
FLOW FROM AN UPPER LEVEL NEAR STATIONARY HIGH OVER NORTH-CENTRAL
MEXICO IS BRINGING STRONG SUBSIDENCE/DRY AIR TO THE NW GULF N OF
26N W OF 92W. THE WEAK TROUGH OVER THE BAY OF CAMPECHE IS
DEVELOPING INTO A CLOSED MID/UPPER LEVEL LOW NEAR 20N94W.
CYCLONIC FLOW COVERS THE AREA S OF 25N FROM 92W-98W. A MID/UPPER
LEVEL HIGH CENTERED JUST N OF THE YUCATAN PENINSULA NEAR 23N88W
COVERS THE E GULF AND THUS FUNNELING TROPICAL MOISTURE ACROSS
THE CENTRAL GULF FROM THE BAY OF CAMPECHE TO ACROSS THE FLORIDA
PENINSULA. SCATTERED SHOWERS/ISOLATED THUNDERSTORMS ARE OVER THE
SW GULF WITHIN 150/175 NM OF  LINE FROM 30N90W TO 19N95W.

CARIBBEAN...
MAIN FEATURE IN THE CARIBBEAN...AS OVER THE PAST SEVERAL
DAYS...IS HURRICANE IVAN. IVAN CONTINUES IT SLOW MOVEMENT ACROSS
THE NW CARIBBEAN MOSTLY DUE TO THE MID/UPPER LEVEL HIGH TO THE W
CENTERED N OF THE YUCATAN PENINSULA DISCUSSED ABOVE. BROAD UPPER
LEVEL HIGH IS OVER IVAN WITH A RIDGE AXIS EXTENDING E CROSSING
THE GREATER ANTILLES NEAR HISPANIOLA INTO THE CENTRAL ATLC.
SCATTERED SHOWERS/ISOLATED THUNDERSTORMS ARE S OF 17N W OF 84W
TO OVER CENTRAL AMERICA.

SUBTROPICAL ATLANTIC...
RIDGE AXIS EXTENDS FROM THE MID/UPPER LEVEL HIGH N OF THE
YUCATAN PENINSULA ACROSS CENTRAL FLORIDA NEAR 28N80W INTO THE W
ATLC TO BEYOND 32N75W. 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 THROUGH
THE STRAITS OF FLORIDA INTO THE YUCATAN CHANNEL. BROAD UPPER
LEVEL LOW IS IN THE CENTRAL/WESTERN ATLC ABOUT 150 NM SSE OF
BERMUDA NEAR 30N66W WITH CYCLONIC FLOW COVERING THE AREA N OF
23N FROM 60W-72W. RIDGE AXIS EXTENDING FROM THE CARIBBEAN ACROSS
HISPANIOLA NE ALONG 22N62W TO 30N55W. THE UPSLOPE ANTICYCLONIC
FLOW COMBINED WITH THE CYCLONIC FLOW FROM THE UPPER LOW SSE OF
BERMUDA IS PRODUCING LARGE CLUSTERS OF SCATTERED MODERATE/STRONG
CONVECTION IN THE AREA N OF 20N BETWEEN 50W-64W. THE MID-OCEANIC
TROUGH LIMITED TO THE E ATLC IS N OF 23N FROM 25W-44W WITH AN
EMBEDDED UPPER LOW NEAR 29N33W.

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 15N24W TO A SECOND HIGH NEAR 14N45W. THE CULL
BETWEEN THE TWO HIGHS IS PRODUCING MODERATE SUBSIDENCE/DRY AIR
WITHIN 200 NM OF LINE FROM 11N42W TO 20N33W.

$$
WALLACE



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