[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 091817
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
205 PM EDT FRI SEP 09 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 1200 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
1715 UTC.

...SPECIAL FEATURES...

TROPICAL STORM OPHELIA WAS CENTERED NEAR 29.5N 78.9W OR ABOUT
130 SM E OF DAYTONA BEACH FLORIDA...AT 09/1500 UTC MOVING NNE AT
4 KT. THE ESTIMATED MINIMUM CENTRAL PRESSURE IS 983 MB. MAXIMUM
SUSTAINED WIND SPEED IS 55 KT WITH GUSTS TO 65 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. OPHELIA IS SLOWLY MOVING AWAY FROM THE FLORIDA
EAST COAST BUT THE CENTER REMAINS WELL DEFINED ON THE EDGE OF
THE WSR-88D RADAR IMAGERY FROM MELBOURNE. DESPITE THE WELL
DEFINED APPEARANCE IN RADAR AND SATELLITE IMAGERY...
RECONNAISSANCE AIRCRAFT THIS MORNING ONLY FOUND TROPICAL
STORM FORCE WINDS IN THE CYCLONE. HOWEVER....OPHELIA IS FORECAST
TO RE-STRENGTHEN INTO A HURRICANE WITHIN THE NEXT 12-24 HOURS. A
TROUGH MOVING OFF THE NE U.S. COAST IS CURRENTLY STEERING
OPHELIA NEWD BUT THE TROUGH IS EXPECTED TO BYPASS THE STORM IN
24-48 HOURS WITH OPHELIA REMAINING IN A WEAK STEERING
ENVIRONMENT. SCATTERED MODERATE/STRONG CONVECTION IS WITHIN 90
NM OF CENTER OVER THE SW SEMICIRCLE AND 60 NM NE SEMICIRCLE.  A
BAND OF SCATTERED MODERATE/ISOLATED STRONG CONVECTION IS WITHIN
75 NM OF LINE 32N75W TO 31N79W.

NATE WAS DOWNGRADED TO A TROPICAL STORM AT 1500 UTC.  AT
09/1500...NATE WAS CENTERED NEAR 34.3N 54.6W...OR 605 SM ENE OF
BERMUDA.  NATE IS MOVING ENE AT 21 KT WITH AN ESTIMATED MINIMUM
CENTRAL PRESSURE OF 988 MB. MAXIMUM SUSTAINED WIND SPEED IS 60
KT WITH GUSTS TO 75 KT. SEE LATEST NHC FORECAST/ADVISORY UNDER
AWIPS/WMO HEADERS MIATCMAT5/WTNT25 KNHC FOR MORE DETAILS.
NATE IS NOW WELL EMBEDDED WITHIN THE MID-LATITUDE WESTERLIES
AND IS RAPIDLY MOVING ENE AS RESULT. THE WESTERLIES HAVE
SHEARED NATE WITH THE LOW LEVEL CLOUD CENTER NOW EXPOSED TO
THE SW OF THE REMAINING DEEP CONVECTION. WATER VAPOR IMAGERY
ALSO INDICATES THAT SOME DRY MID LEVEL AIR IS BEING PULLED INTO
THE CIRCULATION.  NATE IS FORECAST TO CONTINUE WEAKENING WHILE
MOVING ENE. NATE IS EXPECTED TO BECOME EXTRATROPICAL WITHIN
THE NEXT 2-3 DAYS. SCATTERED MODERATE CONVECTION IS WITHIN
180 NM OF CENTER OVER THE NE SEMICIRCLE.

TROPICAL STORM MARIA IS CENTERED NEAR 40.9N 42.7W...OR 655 SM SE
OF CAPE RACE NEWFOUNDLAND...AT 09/1500 UTC MOVING NE AT 13 KT.
ESTIMATED MINIMUM CENTRAL PRESSURE IS 988 MB. MAXIMUM SUSTAINED
WIND SPEED IS 55 KT WITH GUSTS TO 65 KT. SEE LATEST NHC
FORECAST/ADVISORY UNDER AWIPS/WMO HEADERS MIATCMAT4/WTNT24 KNHC
FOR MORE DETAILS. MARIA REMAINS A VERY RESILIENT SYSTEM OVER THE
NORTH ATLANTIC. COLDER CLOUD TOPS/CONVECTION CONTINUE TO WRAP
AROUND THE CENTER OF MARIA. AN INTERMITTENT EYE-LIKE FEATURE HAS
BEEN SEEN IN SATELLITE IMAGERY. MARIA IS FORECAST TO BEGIN
ACCELERATING NEWD BECOMING A STRONG EXTRATROPICAL SYSTEM OVER
THE NEXT 24 TO 36 HOURS. SCATTERED MODERATE CONVECTION IS WITHIN
150 NM OF CENTER EXCEPT OVER THE SW QUADRANT.

...TROPICAL WAVES...

E ATLC TROPICAL WAVE IS ALONG 26W S OF 19N MOVING W 15 KT WITH
A VERY WEAK AND BROAD 1014 MB LOW ALONG THE WAVE NEAR 13N. THE
WAVE REMAINS EMBEDDED WITHIN A DRY/STABLE ENVIRONMENT WITH NO
ASSOCIATED CONVECTION. THE DRY STABLE LAYER IS ASSOCIATED WITH
A LARGE AREA OF AFRICAN DUST THAT COVERS MUCH OF THE EASTERN
ATLC N OF 10N.

CENTRAL ATLC TROPICAL WAVE IS ALONG 8N52W 18N51W 23N50W MOVING
WNW 10-15 KT. WAVE HAS A SW/NE TILT AND A LARGE AMPLITUDE THAT
REACHES WELL INTO THE SUBTROPICS. WAVE IS ALSO EMBEDDED WITHIN
THE AREA OF AFRICAN DUST...SO THERE IS LITTLE ASSOCIATED SHOWER
OR TSTM ACTIVITY. WEST OF THE WAVE THERE IS AN AREA OF SCATTERED
SHOWERS/TSTMS THAT EXTENDS FROM EAST OF THE WINDWARD ISLANDS
NEAR 12.5N56W ACROSS THE ISLAND INTO THE E CARIBBEAN NEAR
13.5N64W. THIS ACTIVITY IS PRIMARY ASSOCIATED WITH CONVERGENCE
ALONG THE ITCZ WHICH HAS MOVED NORTHWARD ACROSS THE LEEWARD
ISLANDS.

E CARIBBEAN TROPICAL WAVE IS NEAR THE EAST END OF PUERTO RICO
ALONG 65W/66W S OF 20N MOVING W 10 KT. THIS WAVE IS INTERACTING
WITH A LARGE UPPER LEVEL LOW CENTERED OVER N OF PUERTO RICO AND
IS PRODUCING SCATTERED SHOWERS/THUNDERSTORMS FROM THE TURKS AND
CAICOS SE TO THE DOMINICAN REPUBLIC AND PUERTO RICO. THE UPPER
LOW IS EXPECTED TO MOVE WNW JUST NORTH OF THE SE BAHAMAS SAT
MORNING.

CARIBBEAN TROPICAL WAVE IS ALONG 81W S OF 20N MOVING W 5-10 KT.
THIS WAVE REMAINS WEAK WITHIN ONLY SCATTERED MODERATE/ISOLATED
STRONG CONVECTION LOCATED OVER THE SW CARIBBEAN NEAR FROM
10N-12N W OF 81W. THE WAVE MAY ENHANCE SHOWERS/THUNDERSTORMS
OVER PARTS OF CENTRAL AMERICAN THROUGH THE WEEKEND AS THE WAVE
MOVES WESTWARD.

...ITCZ...

ITCZ AXIS IS CENTERED ALONG 16N16W 14N23W 8N30W 8N45W 9N52W...
THEN NW 12N60W...THEN ILL-DEFINED INTO THE LEEWARD ISLANDS.
SCATTERED MODERATE WITHIN 30 NM OF LINE FROM 9N19W TO 7N21W.
WIDELY SCATTERED MODERATE CONVECTION IS WITHIN 75 NM OF THE
AXIS FROM 42W-47W. SCATTERED MODERATE CONVECTION IS WITHIN
90 NM OF THE AXIS FROM 55W-62W.

...DISCUSSION...

GULF OF MEXICO...
LARGE UPPER LEVEL REMAINS NEARLY STATIONARY OVER MAINLAND MEXICO
NEAR 26N104W.  THIS LOW IS ADVECTING TROPICAL MOISTURE FROM THE
E PACIFIC NE ACROSS SOUTHERN MEXICO AND INTO THE WESTERN GULF OF
MEXICO. NARROW UPPER RIDGE AXIS OVER THE W GULF IS PRODUCING AN
AREA OF UPPER LEVEL DIFFLUENCE. AT THE SURFACE... TWO WEAK LOWS
ARE LOCATED ALONG A TROUGH ALONG 96W/97W. ONE LOW IS ALONG THE
COAST OF S TEXAS NEAR 26N WITH THE OTHER OFF THE COAST OF MEXICO
NEAR 23N. THE SURFACE TROUGH AND AREA OF UPPER DIFFLUENCE IS
PRODUCING SCATTERED SHOWERS/THUNDERSTORMS THAT ARE LOCATED
WITHIN 150 NM OF THE TROUGH. ANOTHER SURFACE TROUGH EXTENDS
FROM OPHELIA'S CIRCULATION SW THROUGH THE STRAIGHTS OF FLORIDA
AND THE GULF ALONG 24N81W 25N90W TO 27N93W. THE TROUGH IS
SUPPORTING WIDELY SCATTERED SHOWERS/TSTMS WITH 60 NM OF THE
AXIS. THIS TROUGH DELINEATES AN AREA OF SLIGHTLY DRIER AREA TO
THE NORTH AROUND THE WESTERN SIDE OF OPHELIA'S CIRCULATION.
THIS DRIER AIR IS SUPPORTED BY DRY AIR/SUBSIDENCE SEEN IN THE
MID LEVELS IN WATER VAPOR IMAGERY OVER THE SE U.S. AND THE NE
GULF OF MEXICO N OF 26N E OF 90W.

CARIBBEAN...
THE FLOW OVER THE CARIBBEAN IS BEING DOMINATED BY TWO UPPER
LOWS...ONE OVER THE NW CARIBBEAN NEAR THE CAYMAN ISLANDS NEAR
19N83W. THE SECOND UPPER LOW IS ACTUALLY CENTERED OVER THE ATLC
JUST SE OF THE SE BAHAMAS...BUT THE FLOW AROUND THE LOW EXTENDS
SOUTH INTO THE EASTERN CARIBBEAN. WESTERLY FLOW SOUTH OF THE NW
CARIBBEAN LOW IS ADVECTING SOME HIGH LEVEL MOISTURE FROM THE
EAST PACIFIC ACROSS CENTRAL AMERICA INTO THE EXTREME SW
CARIBBEAN.

WEST ATLANTIC...
AN NARROW UPPER HIGH/RIDGE IS LOCATED E OF T.S. OPHELIA AND NE
OF THE NORTHERN MOST BAHAMA ISLANDS NEAR 28N75W. THIS UPPER HIGH
IS PRODUCING A GENERALLY FAVORABLE OUTFLOW PATTERN OVER OPHELIA.
THE UPPER LOW PREVIOUSLY MENTIONED SE OF THE BAHAMAS IS CENTERED
NEAR 20.5N67W. MOST OF THE SHOWER/TSTMS ACTIVITY ASSOCIATED WITH
THIS LOW IS THE SOUTH NEAR HISPANIOLA/PUERTO RICO. NORTH THE
UPPER LOW DRY AIR/SUBSIDENCE IS SEEN IN WATER VAPOR IMAGERY.

EAST/CENTRAL ATLANTIC...
LARGE WELL DEFINE MID/UPPER HIGH IS CENTERED NEAR 25N52W. THIS
HIGH DOMINATES THE FLOW OVER THE AREA BETWEEN 40W-60W. NEARLY
STATIONARY UPPER TROUGH EXTENDS FROM SW OF THE CANARY ISLANDS
SW ALONG PAST THE CAPE VERDE ISLANDS. AN UPPER LOW IS SEEN IN
WATER VAPOR IMAGERY NEAR NEAR 21N36W WHICH IS REINFORCING THE
OVERALL TROUGHING PATTERN OVER THE FAR EASTERN ATLC. VISIBLE
SATELLITE IMAGES CONTINUE TO SHOW THAT THE LARGE AREA OF
SAHARAN DUST REMAINS OVER MUCH OF THE TROPICAL EAST ATLC.

$$
BROWN


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