[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 090605
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
205 AM EDT SUN SEP 09 2007

TROPICAL WEATHER DISCUSSION FOR NORTH AMERICA...CENTRAL
AMERICA...THE GULF OF MEXICO...THE CARIBBEAN SEA...NORTHERN
SECTIONS OF SOUTH AMERICA...AND THE ATLANTIC OCEAN TO THE
AFRICAN COAST FROM THE EQUATOR TO 32N. THE FOLLOWING INFORMATION
IS BASED ON SATELLITE IMAGERY...METEOROLOGICAL ANALYSIS...
WEATHER OBSERVATIONS...AND RADAR.

BASED ON 1800 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY
THROUGH 0515 UTC.

...SPECIAL FEATURE...
THE CENTER OF TROPICAL STORM GABRIELLE AT 09/0600 UTC WAS NEAR
33.5N 75.9W OR ABOUT 75 NM SSE OF CAPE LOOKOUT NORTH CAROLINA.
GABRIELLE IS NOW MOVING N-NW NEAR 10 KT. A TURN TOWARD THE NORTH
IS EXPECTED LATER TODAY. THE CENTER OF GABRIELLE SHOULD MOVE
OVER OR VERY NEAR THE COAST OF NORTH CAROLINA LATE THIS MORNING
OR EARLY THIS AFTERNOON.  HOWEVER...THE OUTER RAIN BANDS ARE
ALREADY SPREADING ONSHORE AT THIS TIME. THE ESTIMATED MINIMUM
CENTRAL PRESSURE AS MEASURED BY AN AIR FORCE RESERVE UNIT
RECONNAISSANCE AIRCRAFT IS 1005 MB. THE MAXIMUM SUSTAINED WIND
SPEEDS ARE 35 KT WITH GUSTS TO 45 KT. SOME STRENGTHENING IS
FORECAST BEFORE THE CENTER REACHES THE NORTH CAROLINA COAST.
PLEASE REFER TO THE NHC FORECAST/ADVISORY UNDER AWIPS/WMO
HEADERS MIATCMAT2/WTNT22 KNHC AND THE PUBLIC ADVISORY UNDER
MIATCPAT2/WTNT32 KNHC FOR MORE DETAILS...INCLUDING THE LATEST
WATCH AND WARNING INFORMATION. NUMEROUS MODERATE CONVECTION IS
MOSTLY IN THE W SEMICIRCLE FROM 32N-34W BETWEEN 75.5W-78W.
SCATTERED MODERATE...IN SPIRAL RAINBANDS...IS ELSEWHERE FROM
32N-35N BETWEEN 74W-78W.

...TROPICAL WAVES...

AN ATLANTIC OCEAN TROPICAL WAVE IS ALONG 29W/30W SOUTH OF 17N
MOVING WEST NEAR 15 KT. A RATHER ILL DEFINED 1012 MB LOW IS
ALONG THE WAVE AXIS NEAR 10N...WHICH IS MORE OR LESS A MEAN
CENTER OF AN ELONGATED AREA OF CYCLONIC TURNING THAT HAS AN
ASSOCIATED TROUGH AXIS STRETCHING ENE FROM 7N43W TO NEAR 14N20W.
THE DEEPEST CONVECTION ASSOCIATED WITH THE WAVE IS TO THE W OF
THE AXIS...WITH SCATTERED MODERATE FROM 7N-12N BETWEEN 31W-36W.
ISOLATED SHOWERS/TSTMS ARE ELSEWHERE WITHIN 150 NM EITHER SIDE
OF THE AXIS. THIS SYSTEM HAS CHANGED LITTLE IN ORGANIZATION
DURING THE PAST 24 HOURS...BUT STILL HAS THE POTENTIAL FOR SOME
DEVELOPMENT DURING THE NEXT FEW DAYS.

AN ATLANTIC OCEAN TROPICAL WAVE IS ALONG 54W/55W SOUTH OF 21N
MOVING WEST 10-15 KT. THIS WAVE CONTINUES TO SHOW UP WELL IN
SATELLITE IMAGERY AND THE SURROUNDING BUOY OBS...WITH A BROAD
INVERTED V PATTERN NOTED. SCATTERED MODERATE CONVECTION IS OVER
THE N PORTION OF THE AXIS FROM 14N-19N BETWEEN 54W-59W. THIS
ACTIVITY IS EXPECTED TO AFFECT THE NRN LESSER ANTILLES/LEEWARD
ISLANDS LATE SUN INTO MON.

A WESTERN CARIBBEAN SEA TROPICAL WAVE IS ALONG 88W SOUTH OF 22N
MOVING WEST NEAR 15 KT. THE AXIS OF THE WAVE IS NOW MOSTLY
INLAND OVER CENTRAL AMERICA. THE WAVE REMAINS DIFFICULT TO
LOCATE FOR THE MOST PART WITH ITS POSITION BASED MAINLY ON
FORWARD EXTRAPOLATION. HOWEVER...SOME OF THE ASSOCIATED
MOISTURE/VORTICITY MAY HAVE ENHANCED THE ACTIVITY IN THE SRN
GULF.

...THE ITCZ...
AXIS CENTERED ALONG 14N17W 10N28W 6N42W 9N61W. BESIDES FOR THE
ACTIVITY NOTED WITH THE TROPICAL WAVE SEVERAL HUNDRED MILES SW
OF THE CAPE VERDE ISLANDS...SCATTERED MODERATE/ISOLATED STRONG
CONVECTION IS WITHIN 300 NM N OF THE AXIS BETWEEN 36W-46W.
SIMILAR ACTIVITY IS JUST OFF THE COAST OF AFRICA FROM 8N-18N E
OF 21W. SOME OF THIS MAY BE ASSOCIATED WITH THE NEXT TROPICAL
WAVE...BUT I STILL DO NOT HAVE A GOOD FEEL FOR THIS WAVE SO WILL
WAIT FOR MORE EVIDENCE AND VISIBLE IMAGERY BEFORE ADDING TO THE
MAP.

DISCUSSION...

THE GULF OF MEXICO...
THE MAIN AREA OF WEATHER TONIGHT IS IN THE SE GULF ASSOCIATED
WITH A WEAK SURFACE TROUGH AND AN UPPER LOW. DISORGANIZED
SCATTERED SHOWERS/ISOLATED TSTMS ARE GENERALLY OVER THE S/SE
GULF S OF 28N E OF 89W. THE MOST CONCENTRATED AREA OF MODERATE
CONVECTION IS JUST OFFSHORE SW FLORIDA. THE MOST PRONOUNCED AREA
OF LOW TO MID LEVEL VORTICITY IS JUST N OF THE YUCATAN CHANNEL
NEAR 23N87W. AS OF 09/0300 UTC THE SFC TROUGH AXIS IS ANALYZED
ALONG 23N89W TO THE COAST OF FLORIDA NEAR 27N82W...AND CONTINUES
THROUGH CENTRAL FLORIDA TO JUST OFFSHORE CAPE CANAVERAL IN THE
ATLC. UPPER-LEVEL WINDS ARE NOT CURRENTLY FAVORABLE FOR
DEVELOPMENT. THE REMAINDER OF THE GULF IS RATHER TRANQUIL WITH
WINDS MOSTLY 15 KT OR LESS AND SEAS 4' OR LESS. VERY DRY/STABLE
MID TO UPPER AIR IS OVER THE NE GULF...BEING ADVECTED SW BY NE
UPPER FLOW BETWEEN THE UPPER LOW JUST E OF CENTRAL FLORIDA...AND
THE UPPER HIGH OVER ERN TEXAS. THE WEAK SFC TROUGHING WILL
DOMINATE OVER THE NEXT DAY OR SO AS IT MOVES SLOWLY NW. THIS
WILL KEEP WINDS MOSTLY ON THE LIGHT TO MODERATE SIDE...THOUGH
SCATTERED SHOWERS/TSTMS ANTICIPATED NEAR THE TROUGHING.

THE CARIBBEAN SEA...
VERY LITTLE DEEP CONVECTION IS AFFECTING THE CARIBBEAN TONIGHT.
ISOLATED SHOWERS/TSTMS ARE...HOWEVER...IN THE NW CARIBBEAN N OF
17N W OF 73W. THIS ACTIVITY IS ASSOCIATED WITH THE MOIST
ENVIRONMENT S OF THE SFC TROUGHING IN THE SE GULF. FURTHER
SUPPORT IS BEING LENT BY DIVERGENCE ALOFT BETWEEN THE UPPER LOW
NEARING CENTRAL FLORIDA AND RIDGING OVER THE NW CARIBBEAN. THIS
MOISTURE IS MOSTLY EXPECTED TO MOVE N OF THE AREA BY MON.
ANOTHER SMALL AREA OF SCATTERED TSTMS IS JUST OFF THE COAST OF
NICARAGUA FROM 12N-14N BETWEEN 82W-84W WHICH APPEARS TO BE
PUSHING SLOWLY INLAND. SHOWER ACTIVITY ELSEWHERE IS ISOLATED AND
MOSTLY SHALLOW IN NATURE. HOWEVER...CONVECTION ASSOCIATED WITH
THE TROPICAL ATLC WAVE ALONG 54W WILL AFFECT THE NE CARIBBEAN
LATE SUN AND MON. TRADES ARE ON THE LIGHT TO MODERATE
SIDE...WITH TO A WEAKER THAN NORMAL GRADIENT IN PLACE IN
RESPONSE TO THE TROUGHING OVER THE GULF/FLORIDA AND T.S.
GABRIELLE. A SLIGHT INCREASE IN TRADES EXPECTED THROUGH EARLY
WEEK AS MORE TYPICAL RIDGING BUILDS N/NE OF THE AREA.

THE ATLANTIC OCEAN...
T.S. GABRIELLE IS NOW N OF THE AREA JUST OFFSHORE THE SOUTHERN
NORTH CAROLINA COAST. HOWEVER...THE AFFECTS PERSIST. ALTHOUGH
THE WINDS ARE NOT PARTICULARLY STRONG IN THE AREA...NOW MOSTLY
15 KT OR BELOW...A MODERATE RESIDUAL NE SWELL CONTINUES TO
AFFECT THE WRN ATLC WITH THE OUTER CANAVERAL BUOY 41010
REPORTING 7 FT SEAS AT 10 SECONDS. THE NAH WW3 SEEMS TO BE
HANDLING THIS EVENT FAIRLY WELL AND SUGGESTS THE SWELL WILL
SUBSIDE STEADILY DURING THE DAY TODAY AS GABRIELLE CONTINUES
MOVING WELL N OF THE AREA.

THE SFC TROUGHING FROM THE GULF EXTENDS INTO THE WRN
ATLC...WHICH IS GENERATING SCATTERED SHOWERS AND TSTMS S OF 27N
W OF 72W. THIS ACTIVITY IS AFFECTING THE BAHAMAS AND SOUTH
FLORIDA...AND IS GENERALLY EXPECTED TO SPREAD N THROUGH MON. THE
ACTIVITY IS ALSO BEING SUPPORTED BY LIFT ASSOCIATED WITH THE
UPPER LOW NEAR 28N79W. THE NEXT AREA OF INTEREST IS THE SLOW
MOVING FRONT ALONG 32N39W 26N55W 31N64W. SCATTERED SHOWERS AND
ISOLATED TSTMS NOTED WITHIN 90 NM OF THIS BOUNDARY...AND MOST
CONCENTRATED NEAR 26N49W...JUST AHEAD OF THE ASSOCIATED DEEP
LAYER TROUGHING THAT EXTENDS S/SW FROM THE WELL DEFINED LOW NEAR
41N44W. THIS ACTIVITY GENERALLY EXPECTED TO DIMINISH OVER THE
NEXT COUPLE OF DAYS AS THE FRONT BECOMES DIFFUSE. THE REMAINDER
OF THE SFC PATTERN IS DOMINATED BY WEAK RIDGING...WITH A 1021 MB
HIGH CENTERED NEAR 29N25W.

$$
WILLIS




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