[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 100548
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
205 AM EDT MON SEP 10 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 0000 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY
THROUGH 0515 UTC.

...SPECIAL FEATURE...
THE CENTER OF TROPICAL STORM GABRIELLE AT 10/0300 UTC IS NEAR
36.3N 75.6W...OR ABOUT 65 NM NORTH OF CAPE HATTERAS NORTH
CAROLINA AND ABOUT 385 NM SOUTHWEST OF NANTUCKET MASSACHUSETTS.
GABRIELLE IS MOVING NORTHEAST AT 9 KT. MAXIMUM SUSTAINED WIND
SPEED HAS DECREASED TO 40 KT WITH GUSTS TO 50 KT. THE ESTIMATED
MINIMUM CENTRAL PRESSURE IS 1008 MB. PLEASE REFER TO THE NHC
FORECAST/ADVISORY UNDER AWIPS/WMO HEADERS MIATCMAT2/WTNT22 KNHC
AND/OR THE PUBLIC ADVISORY MIATCPAT2/WTNT32 KNHC FOR MORE
DETAILS. IR IMAGES SHOW CONVECTION ON A STEADY DECLINE OVER THE
PAST SEVERAL HOURS WITH THE ONLY AREA LEFT WELL REMOVED TO THE S
AND SE OF THE CENTER...AND EVEN THIS AREA IS WEAKENING. THE
CIRCULATION SHOWS UP NICELY IN THE SFC DATA WITH SURROUNDING
BUOYS REPORTING 20-30 KT WINDS AT THIS TIME. GIVEN THE STRONG
SHEAR AND SHRINKING TIME OVER WARM WATER THE NHC OFFICIAL
FORECAST SHOWS SOME WEAKENING BEFORE GABRIELLE BECOMES ABSORBED
BY AN EXTRATROPICAL SYSTEM.

...TROPICAL WAVES...

ACTIVE TROPICAL WAVE IS ALONG 37W S OF 15N MOVING W 15 KT OVER
THE PAST 24 HOURS. A 1012 MB LOW IS ANALYZED ALONG THE AXIS NEAR
9N. SATELLITE IMAGES INDICATE THAT THIS LOW IS FAIRLY BROAD
THOUGH IT IS PRODUCING A LARGE AREA OF CONVECTION IN IT'S
VICINITY...ROUGHLY WITHIN 180 NM EITHER SIDE OF THE AXIS. LESS
ORGANIZED CONVECTION EXTENDS FURTHER W WITHIN THE ITCZ. THIS
SYSTEM HAS BECOME A LITTLE BETTER ORGANIZED AND HAS THE
POTENTIAL TO DEVELOP INTO A TROPICAL DEPRESSION DURING THE NEXT
COUPLE OF DAYS.

TROPICAL WAVE IS NEARING THE LESSER ANTILLES ALONG 59W S OF 22N
MOVING W 10-15 KT. MOST OF THE SHOWER ACTIVITY THAT WAS EVIDENT
EARLIER APPEARS TO HAVE DIMINISHED. NIGHT CHANNEL VIS IMAGES
SHOW A WELL DEFINED SMALL CYCLONIC SWIRL ALONG THE NRN PORTION
OF THE WAVE. A PAIR OF SHIP REPORTS INDICATE SOME SFC TURNING
ASSOCIATED WITH THIS SWIRL...THOUGH ITS GREATEST AMPLITUDE IS
LIKELY IN THE MID-LEVELS. FURTHER DEVELOPMENT OF THIS
SYSTEM...IF ANY...IS EXPECTED TO BE SLOW TO OCCUR.

THE NRN PORTION OF A TROPICAL WAVE ALONG 93W/94W EXTENDS INTO
THE BAY OF CAMPECHE S OF 22N MOVING W 10-15 KT. THERE IS A FAIR
AMOUNT OF TURNING AND MOISTURE IN THIS AREA. HOWEVER...IT IS
DIFFICULT TO TELL HOW MUCH OF THIS IS RELATED TO THE WAVE ITSELF
AS THERE IS A WELL DEFINED UPPER TROUGH AND LOW-LEVEL TROUGHING
IN THIS GENERAL AREA AS WELL. MORE ON THIS IN THE GULF OF MEXICO
DISCUSSED BELOW.

...THE ITCZ...
ITCZ AXIS IS CENTERED ALONG 15N17W 12N26W 10N34W 7N46W 6N59W.
BESIDES FOR THE CONVECTION ASSOCIATED WITH THE WELL DEFINED
TROPICAL WAVE APPROACHING 40W...SCATTERED MODERATE IS FROM
7N-12N BETWEEN 41W-54W. AS A SIDE NOTE...A PRELIM LOOK AT THE
DATA SUGGESTS THAT A NEW TROPICAL WAVE LIES OFF THE COAST OF
AFRICA. THIS MAY BE ADDED TO THE NEXT SYNOPTIC MAP.

DISCUSSION...

THE GULF OF MEXICO...
THERE IS FAIR AMOUNT OF MOISTURE ACROSS THE SE HALF OF THE GULF.
THE CONTRIBUTING UPPER LEVEL COMPONENT IS A HIGHLY STRETCHED
UPPER LEVEL TROUGH WHICH RUNS FROM THE W ATLC TO AN UPPER LOW IN
THE BAY OF CAMPECHE NEAR 22N93W. AN ASSOCIATED LOW-LEVEL TROUGH
BASICALLY LIES DIRECTLY UNDERNEATH THE UPPER AXIS ANALYZED FROM
THE FLORIDA PANHANDLE SWWD ALONG 30N83W 27N89W 24N93W. IR IMAGES
AND LIGHTNING DATA SUGGEST ONLY POCKETS OF SCATTERED SHOWERS AND
TSTMS...MOST ORGANIZED WITHIN 240 NM OF THE UPPER LOW AND IN THE
E GULF FROM 24N-28N BETWEEN THE FL COAST AND 86W. UPPER
CONFLUENCE BETWEEN THE TROUGHING DESCRIBED AND A WELL DEFINED
UPPER HIGH OVER THE S CENTRAL U.S. IS DRYING OUT THE AIR ACROSS
MOST OF THE NW HALF OF THE REGION SUPPORTING FAIR WEATHER.
LOOKING AHEAD OF A COUPLE OF DAYS...THE WEAK SFC TROUGH IN THE
AREA WILL GRADUALLY DISSIPATE AND WILL SOON BE REPLACED BY
ANOTHER TROUGH OR WEAK FRONT PUSHING OFF THE TEXAS COAST. THIS
WILL ALLOW THE PATTERN TO REMAIN WEAK KEEPING WINDS MOSTLY LIGHT.

THE CARIBBEAN SEA...
THE CARIB IS RELATIVELY QUIET THIS EARLY MORNING...ALTHOUGH
THERE ARE A FEW AREAS OF CONVECTION WORTH MENTIONED. THE MOST
PERSISTENT IS AN AREA IN THE S CENTRAL CARIB FROM 12N-15N
BETWEEN 73W-80W. THIS ACTIVITY IS LIKELY RELATED TO SOME ITCZ
ENERGY ENHANCED BY A DIFFLUENT UPPER PATTERN BETWEEN STRONG WLY
FLOW ON THE SW SIDE OF AN UPPER HIGH S OF PUERTO RICO NEAR
16N66W AND LIGHT FLOW ASSOCIATED WITH THE BASE OF AN UPPER LOW
CENTERED NEAR 18N79W. A LINE OF WEAKENING SHOWERS AND TSTMS HAVE
PUSHED S...DRIVEN BY THE UPPER FLOW...WITHIN 60 NM S OF THE
COAST OF HAITI AND CUBA BETWEEN 73W-79W. THIS ACTIVITY IS LIKELY
RELATED TO LEFT OVER EVENING TSTM ACTIVITY OVER THE ISLANDS. IN
THE FAR E CARIB...AN AREA OF CLOUDINESS AND ISOLATED SHOWERS ARE
OVER THE LESSER ANTILLES ASSOCIATED WITH A TROPICAL WAVE. FOR
MORE DETAILS REFER TO THE TROPICAL WAVES SECTION ABOVE.
ELSEWHERE ...SKY CONDITIONS ARE PREDOMINATELY FAIR ALTHOUGH
TYPICAL QUICK MOVING SHOWERS COULD OCCUR JUST ABOUT ANYWHERE.
TRADES ARE MODERATE ACROSS THE REGION WITH 20 KT WINDS CONFINED
TO NEAR THE COLOMBIAN COAST. THESE WINDS ARE ANTICIPATED TO
INCREASE E OF 75W OVER THE NEXT COUPLE OF DAYS AS THE GRADIENT
TIGHTENS.

THE ATLANTIC OCEAN...
A LARGE NEARLY STATIONARY VERTICALLY STACKED LOW PRES SYSTEM IS
LOCATED WELL N OF THE AREA IN THE CENTRAL ATLC. AN ASSOCIATED
SFC TROUGH STRETCHES THROUGH THE AREA EXTENDING FROM 32N37W SW
ALONG 27N46W 25N60W 27N65W. CONVERGENCE ALONG THIS BOUNDARY IS
PRODUCING ISOLATED SHOWERS AND TSTMS WITHIN 45 NM OF THE TROUGH.
THE MOST SIGNIFICANT ASPECT OF THIS TROUGH IS THE LARGE
INTERRUPTION IT HAS PRODUCED IN THE TYPICAL SUBTROPICAL RIDGING.
THIS WEAKNESS HAS ALLOWED SFC WINDS TO BE VERY LIGHT ACROSS THE
BULK OF THE CENTRAL ATLC. SLIGHTER STRONG WINDS ARE DEPICTED ON
QSCAT NEAR THE CARIB ISLANDS AND THE AFRICAN COAST. BOTH OF
THESE ZONES ARE TO THE S OR SE OF MODEST HIGH PRES SYSTEMS.

ALOFT...THE PATTERN IS QUIET MESSY IN THE W ATLC WITH AN UPPER
HIGH LOCATED TO THE W OF BERMUDA NEAR 32N71W...INVERTED
TROUGHING ALONG 69W S OF 28N AND AN UPPER LOW OFF THE NE FLORIDA
COAST. OVERALL THIS PATTERN IS LEADING TO ISOLATED SHOWERS AND
TSTMS ACROSS THE BAHAMAS AND THE ATLC WATERS FROM 24N-29N
BETWEEN 76W-79W. IN THE CENTRAL ATLC...TROUGHING COVERS THE AREA
N OF 23N ASSOCIATED WITH THE DEEP LAYERED LOW MENTIONED ABOVE. A
MID LEVEL LOW HAS DEVELOPED E OF THE LESSER ANTILLES. IN THE E
ATLC...A DOMINATED RIDGE IS IN CONTROL CENTERED NEAR 22N26W
PROVIDING FAIR WEATHER FOR MUCH OF THAT AREA.

$$
CANGIALOSI




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