[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 MON SEP 12 2005

TROPICAL WEATHER DISCUSSION FOR NORTH AMERICA...CENTRAL
AMERICA...GULF OF MEXICO...CARIBBEAN SEA...NORTHEASTERN SECTIONS
OF SOUTH AMERICA...AND ATLANTIC 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 OPHELIA IS CENTERED NEAR 31.2N 76.6W...OR ABOUT 180 NM
ESE OF CHARLESTON SOUTH CAROLINA AND ABOUT 235 NM SSW OF CAPE
HATTERAS NORTH CAROLINA...AT 12/0600 UTC MOVING SLOWLY W 4 KT.
ESTIMATED MINIMUM CENTRAL PRESSURE IS 983 MB. MAXIMUM SUSTAINED
WIND SPEED IS 65 KT WITH GUSTS TO 80 KT. SEE LATEST NHC
FORECAST/ADVISORY UNDER AWIPS/WMO HEADERS MIATCMAT1/WTNT21 KNHC
AND THE PUBLIC ADVISORY UNDER HEADERS MIATCPAT1/WTNT31 KNHC FOR
MORE DETAILS. THE SATELLITE IMAGERY DOES NOT INDICATE A TYPICAL
HURRICANE PRESENTATION...BUT THE HURRICANE WINDS WERE CONFIRMED
BY AN AIR FORCE RECONNAISSANCE AIRCRAFT. DRY AIR CONTINUES TO BE
WRAPPED INTO THE CENTER OF OPHELIA THUS FURTHER LIMITING
CONVECTION. ONE AREA OF SCATTERED MODERATE/ISOLATED STRONG
CONVECTION IS E OF THE CENTER WITHIN A 60/75 NM RADIUS OF
30.5N71.5W. SCATTERED SHOWERS/THUNDERSTORMS ARE FOUND FROM
28N-34N BETWEEN 67W-80W.

...TROPICAL WAVES...

ATLC TROPICAL WAVE IS ALONG 43W/44W S OF 22N MOVING W 15 KT.
SATELLITE IMAGERY CLEARLY DEFINES THE WAVE AXIS IN THE LOW LEVEL
CLOUDS S OF 20N AND TILTED SLIGHTLY NE/SW. WAVE IS SURROUNDED BY
A LARGE AREA OF AFRICAN DUST AND DRY UPPER AIR...SO LITTLE IN
THE WAY OF CONNECTION CAN BE MAINTAINED.

E CARIBBEAN TROPICAL WAVE IS ALONG 72W S OF 22N MOVING W 15 KT.
WAVE IS BENEATH AN UPPER LEVEL INVERTED TROUGH OVER THE CENTRAL
CARIBBEAN...THUS MASKING THE SATELLITE SIGNATURE. THE DRY UPPER
AIR ACROSS THE CENTRAL PORTION OF THE CARIBBEAN IS RESTRICTING
ANY CONVECTION TO OVER THE GREATER ANTILLES AND OVER COLOMBIA.

W CARIBBEAN TROPICAL WAVE IS ALONG 87W S OF 21N MOVING W 15 KT.
WAVE IS BENEATH STRONG S FLOW JUST W OF AN UPPER LEVEL HIGH
ADVECTING TROPICAL MOISTURE WELL INTO THE GULF OF MEXICO. WITH
THE DIFFLUENCE ALOFT...CONVECTION IS MORE ASSOCIATED TO THE
UPPER HIGH THAN THE TROPICAL WAVE.

...ITCZ...

ITCZ AXIS IS CENTERED ALONG 8N11W 5N20W 10N35W 10N50W 12N62W.
SCATTERED MODERATE/ISOLATED STRONG CONVECTION IS WITHIN 90/120
NM OF THE AXIS FROM 18W-24W AND WITHIN 60 NM OF THE AXIS FROM
30W-34W. CLUSTERS OF SIMILAR CONVECTION ARE WITHIN 200 NM OF THE
AXIS FROM 34W-40W.

...DISCUSSION...

GULF OF MEXICO...
UPPER LEVEL RIDGING OVER THE FAR W AND FAR E GULF IS GENERATING
AN UPPER LOW OVER THE CENTRAL GULF NEAR 26N92W. THE UPPER RIDGE
TO THE W EXTENDS ALONG THE NE COAST OF MEXICO OVER E TEXAS INTO
ARKANSAS. A MID/UPPER HIGH IN THE NW CARIBBEAN EXTENDS A RIDGE
ACROSS E CUBA TO THE FLORIDA PANHANDLE. WITH THIS SCENARIO...DRY
CONTINENTAL AIR COVERS THE N GULF N OF 26N E OF 88W AND N OF 23N
FROM 86W-94W. SURFACE RIDGING FROM THE SE UNITED STATES IS
PRODUCING MODERATE NE TO E SURFACE WINDS ACROSS THE GULF. THUS
THE GULF REMAINS RATHER CLEAR TONIGHT WITH SOME ISOLATED SHOWERS
OVER THE W GULF W OF 94W DUE TO DIFFLUENCE BETWEEN THE W RIDGE
AND UPPER LOW. THE UPPER HIGH OVER THE NW CARIBBEAN WILL MOVE
INTO THE GULF AND DOMINATE THE AREA BY MID WEEK. THE HIGHEST
POTENTIAL FOR CONVECTION WILL BE TO THE W OF THE UPPER HIGH AS
IT MOVES ACROSS THE GULF.

CARIBBEAN...
AN UPPER HIGH IS LOCATED OVER THE CAYMAN ISLANDS NEAR 19N81W
GIVING THE FAR W CARIBBEAN S FLOW ADVECTING TROPICAL MOISTURE
OVER THE AREA. THIS IS GENERATING SCATTERED SHOWERS/
THUNDERSTORMS W OF 83W WITH THE STRONGEST STORMS BEING OVER THE
NE YUCATAN PENINSULA. AN UPPER LEVEL INVERTED TROUGH OVER THE
CENTRAL CARIBBEAN ALONG 70W...MASKING THE TROPICAL WAVE IN THAT
AREA...IS GENERATING SIMILAR SHOWERS/THUNDERSTORMS FROM HAITI TO
CENTRAL CUBA...MAINLY OFFSHORE N OF JAMAICA. A UPPER HIGH IN THE
CENTRAL ATLC EXTENDS S OVER THE W TROPICAL ATLC AND E CARIBBEAN
N OF 10N E OF 66W. THIS IS DRAWING DRY UPPER AIR ACROSS THE
LESSER ANTILLES INTO THE CARIBBEAN. THE LARGEST AND STRONGEST
AREA OF WEATHER IS OVER THE SW CARIBBEAN WHERE A 1006 MB LOW
CENTERED OVER N COLOMBIA AND THE ITCZ AXIS CROSSES N SOUTH
AMERICA AND ACROSS PANAMA AND COSTA RICA. SCATTERED STRONG
CONVECTION IS INLAND AND ALONG THE IMMEDIATE COAST OF COLOMBIA
AND E PANAMA E OF 77W. SCATTERED MODERATE/STRONG CONVECTION IS S
OF 13N W OF 81W TO INLAND OVER W PANAMA...COSTA RICA...AND
NICARAGUA. EXPECT THE HIGHEST POTENTIAL OF CONVECTION OVER THE
SW CARIBBEAN FROM COLOMBIA TO OVER CENTRAL AMERICA AS THE
INVERTED UPPER TROUGH MOVES WESTWARD AND THE RIDGING OVER THE
CENTRAL ATLC MOVES W TO ENCOMPASS THE MOST OF THE CARIBBEAN BY
MIDWEEK.

ATLANTIC...
HURRICANE OPHELIA REMAINS ARE AREA OF FOCUS STILL THIS WEEK AS
IT SLOWLY LEAVES THE BAHAMAS AND FLORIDA AREA WITH DRIER AIR
THAN THE FIRST OF LAST WEEK. A DEEP LAYERED TROUGH DIGS S INTO
THE W/CENTRAL ATLC N OF 27N FROM 48W-62W. THIS IS DRAWING UPPER
MOISTURE FROM OVER OPHELIA EASTWARD AND WITH THE DRY AIR BEING
DRAWN INTO THE CENTER IS DISPLACING THE HEAVIEST SHOWERS/
THUNDERSTORMS E OF HURRICANE OPHELIA. A COLD FRONT ASSOCIATED
WITH THE DEEP LEVEL TROUGH ENTERS THE AREA NEAR 32N54W TO
31N58W. SCATTERED MODERATE/ISOLATED STRONG CONVECTION IS WITHIN
45/60 NM RADIUS OF 28N58.5W. TO THE S OF THE DEEP LAYERED TROUGH
IS AN UPPER HIGH LOCATED NE OF THE LEEWARD ISLANDS NEAR 20N60W
COVERING THE AREA FROM 10N-27N BETWEEN 50W-70W INCLUDING THE E
CARIBBEAN. DIFFLUENCE TO THE W IS GENERATING CLUSTERS OF
SCATTERED MODERATE/ISOLATED STRONG CONVECTION FROM 19N-28N
BETWEEN 63W-70W. A VERY NARROW DEEP LAYERED TROUGH EXTENDS FROM
AND UPPER LOW IN THE NE ATLC NEAR 32N35W SW TO A SECOND LARGER
UPPER LOW IN THE TROPICAL ATLC NEAR 18N45W. THE ASSOCIATED COLD
FRONT EXTENDS THROUGH 32N35W SW TO 25N49W. THE ATLC WATERS E OF
THIS FRONT IS COVERED IN AFRICAN DUST...THUS ONLY ISOLATED LOW
LEVEL SHOWERS CAN BE MAINTAINED. AN UPPER LEVEL TROUGH COVERS
THE REMAINDER OF THE NE ATLC N OF 20N E OF 30W AND AN UPPER
LEVEL HIGH COVERS THE E TROPICAL ATLC S OF 20N E OF 40W WITH THE
RIDGE AXIS EXTENDING OFF AFRICA ALONG 12N/13N.

$$
WALLACE


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