[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 121058
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
805 AM EDT TUE SEP 12 2006

TROPICAL WEATHER DISCUSSION FOR NORTH AMERICA...CENTRAL
AMERICA...THE GULF OF MEXICO...THE CARIBBEAN SEA...NORTHEASTERN
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...WEATHER OBSERVATIONS...RADAR...
AND METEOROLOGICAL ANALYSIS.

BASED ON 0600 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
1045 UTC.

...SPECIAL FEATURES...

THE CENTER OF HURRICANE FLORENCE AT 12/0900 UTC WAS LOCATED NEAR
37.2N 62.4W OR ABOUT 365 MILES...585 KM...NORTH-NORTHEAST OF
BERMUDA. FLORENCE IS MOVING TOWARD THE NORTH-NORTHEAST NEAR
17 KT...32 KM/HR. THIS GENERAL MOTION IS EXPECTED TO CONTINUE
OVER THE NEXT 24 HOURS. THE ESTIMATED MINIMUM CENTRAL PRESSURE
IS 980 MB. MAXIMUM SUSTAINED WINDS ARE NEAR 65 KT WITH GUSTS TO
80 KT. FLORENCE IS A CATEGORY ONE HURRICANE ON THE
SAFFIR-SIMPSON SCALE.  PLEASE READ THE LATEST NHC
FORECAST/ADVISORY UNDER AWIPS/WMO HEADERS MIATCMAT1/WTNT21 KNHC
OR THE PUBLIC ADVISORY UNDER MIATCPAT1/WTNT31 KNHC FOR MORE
DETAILS. HURRICANE FORCE WINDS EXTEND OUTWARD UP TO 70
MILES...110 KM...FROM THE CENTER...AND TROPICAL STORM FORCE
WINDS EXTEND OUTWARD UP TO 415 MILES...665 KM. FLORENCE HAS
BECOME INCREASINGLY LESS TROPICAL-LOOKING ON SATELLITE IMAGERY
WITH MOST OF THE CONVECTION DISPLACED TO THE N OF THE CENTER
WITH DRY MID-LEVEL AIR ENTRAINING INTO THE SOUTHERN HALF OF THE
CIRCULATION. FLORENCE IS EXPECTED TO CONTINUE TO SLOWLY LOSE ITS
TROPICAL CHARACTERISTICS AND BECOME A STRONG EXTRATROPICAL
SYSTEM IN ABOUT 24 HOURS.

THE CENTER OF TROPICAL STORM GORDON AT 12/0900 UTC IS NEAR 22.6N
58.3W OR ABOUT 445 MILES/715 KM NORTH-NORTHEAST OF THE LEEWARD
ISLANDS. GORDON IS MOVING TOWARD THE NORTHWEST NEAR 7 KT...13
KM/HR...AND A TURN TO THE NORTH-NORTHWEST IS EXPECTED DURING THE
NEXT 24 HOURS. THE ESTIMATED MINIMUM CENTRAL PRESSURE IS 1000
MB. MAXIMUM SUSTAINED WINDS ARE NEAR 50 KT WITH GUSTS TO 60 KT.
TROPICAL STORM FORCE WINDS EXTEND OUTWARD 75 NM IN THE NE AND 25
NM IN THE SE QUADRANT. PLEASE READ THE LATEST NHC
FORECAST/ADVISORY UNDER AWIPS/WMO HEADERS MIATCMAT2/WTNT22 KNHC
AND THE PUBLIC ADVISORY MIATCPAT2/WTNT32 KNHC FOR MORE DETAILS.
DURING THE OVERNIGHT HOURS...A BALL OF CONVECTION WAS INCREASING
AND CONSOLIDATING NEAR THE CENTER. OVER THE PAST FEW HOURS THE
DEEPEST CONVECTION HAS WEAKENING BUT THE STRUCTURE OF THE BANDS
REMAIN WELL DEFINED. IN ADDITION...THE OUTFLOW LAYER HAS
IMPROVED ESPECIALLY TO THE WEST. THE TROPICAL CYCLONE WILL
LIKELY SPEND ITS LIFE OVER WATER AS IT IS TRACKING TOWARDS A
PROFOUND WEAKNESS LEFT FROM FLORENCE. SOME STRENGTHENING IS
FORECAST AND GORDON COULD BECOME A HURRICANE IN A DAY OR SO.

A STRONG TROPICAL WAVE IS LOCATED OFF THE COAST OF AFRICA ALONG
20W/21W S OF 19N. A 1008 MB LOW PRES SYSTEM IS ALONG THE WAVE
NEAR 13N. THIS SYSTEM IS FAIRLY LARGE WITH ITS BROAD CYCLONIC
ROTATION COVERING AN AREA OF AT LEAST A FEW HUNDRED NM. SHOWER
ACTIVITY WAS GENERALLY ON THE DECREASE LAST EVENING...HOWEVER
SCATTERED MODERATE TO STRONG CONVECTION HAS FIRED AND EXPANDED
SIGNIFICANTLY OVER THE LAST SEVERAL HOURS TO THE SOUTH AND WEST
OF THE ANALYZED SFC LOW FROM 9N-15N BETWEEN 19W-25W. A QUIKSCAT
PASS NEAR 0700 UTC SHOWED GUSTY WINDS S OF THE LOW. IT WAS ALSO
HELPFUL IN LOCATING THE LOW CENTER WHICH WAS ADJUSTED TO THE NW
FROM THE 00 UTC MAP. THIS SYSTEM IS SHOWING SIGNS OF
ORGANIZATION AND HAS THE POTENTIAL TO BECOME A TROPICAL
DEPRESSION OVER THE NEXT DAY OR SO AS IT MOVES WESTWARD 10 TO 15
KT.

...TROPICAL WAVES...

A TROPICAL WAS ADJUSTED SLIGHTLY AHEAD ALONG 36W S OF 18N MOVING
W 10 TO 15 KT. THIS ADJUSTMENT WAS BASED ON SATELLITE IMAGERY
AND SFC OBSERVATIONS THAT SHOWED A FAIR AMOUNT OF LOW-MID LEVEL
CYCLONIC TURNING ABOUT THE AXIS NEAR 7N. ONLY ISOLATED SHOWERS
ARE NEAR THE WAVE AXIS. METEOSAT8 HOVMOLLER DIAGRAMS WHERE VERY
HELPFUL IN THE PLACEMENT OF THE AXIS.

A TROPICAL WAVE IS ALONG 46W S OF 16N MOVING W NEAR 10 KT. THIS
WAVE IS LOW AMPLITUDE AND DIFFICULT TO LOCATE WITH HIGH LEVEL
CLOUDS STREAMING ACROSS THIS FEATURE IN A PRONOUNCED SWLY FLOW
MASKING ANY LOW-MID LEVEL SIGNATURE. SCATTERED SHOWERS AND TSTMS
HAVE INCREASED OVER THE PAST FEW HOURS FROM 12N-15N BETWEEN
43W-49W.

A TROPICAL WAVE HAS MOVED INTO THE E CARIBBEAN ALONG 62W S OF
16N MOVING W NEAR 15 KT. THIS WAVE SPLIT SUNDAY EVENING WITH THE
NRN EXTENSION NOW T.S. GORDON. THE WAVE IS LOW AMPLITUDE AND
BARELY DISCERNIBLE ON NIGHT CHANNEL VIS IMAGES. ONLY ISOLATED
SHOWERS ARE IN THE VICINITY OF THE AXIS.

...THE ITCZ...
ITCZ AXIS IS CENTERED ALONG 10N22W 9N34W 9N44W 10N60W. BESIDES
FOR THE CONVECTION DISCUSSED IN THE TROPICAL WAVES
SECTION...SCATTERED MODERATE CONVECTION IS INLAND OVER SOUTH
AMERICA S OF 8N BETWEEN 58W-70W.

...DISCUSSION...

THE GULF OF MEXICO...
THE WEATHER HAS CHANGED LITTLE ACROSS THE GULF OVER THE PAST FEW
DAYS. AN UPPER LEVEL HIGH IS NEARLY STATIONARY OVER CENTRAL
MEXICO NEAR 24N103W. THIS ANTICYCLONE HAS RIDGING THAT EXTENDS E
ALONG 26N/27N. UPPER DIFFLUENT AIR BETWEEN THE FLOW AROUND THIS
HIGH AND THE WESTERLIES OVER THE SRN U.S. IS HELPING TO SUPPORT
ISOLATED SHOWERS AND TSTMS BETWEEN 25N-30N ACROSS THE GULF. THE
MOST PERSISTENT ACTIVITY IS IN THE E GULF FROM 26N-28N BETWEEN
83W-86W BUT EVEN THIS AREA HAS DIMINISHED THIS MORNING.
SCATTERED SHOWERS AND TSTMS HAVE DEVELOPED OVER NRN MEXICO/S
TEXAS FROM 25N-28N BETWEEN 97W-101W WHERE UPPER DIFFLUENCE IS
SLIGHTLY STRONGER.  AN UPPER LEVEL LOW IS MOVING W IN THE BAY OF
CAMPECHE WITH SCATTERED SHOWERS AND TSTMS ASSOCIATED WITH
IT...MOST ORGANIZED OVER THE LANDMASS OF S MEXICO. AT THE
SURFACE...HIGH PRES RIDGING EXTENDS FROM SE CANADA AND THE NE
U.S. SOUTHWESTWARD INTO THE ERN GULF. E/SE WINDS ARE FAIRLY
LIGHT ON THE SW PERIPHERY OF THE SFC RIDGE. THIS RIDGE WILL PUSH
E AS A COLD FRONT ENTERS THE N GULF ON WED. SIMILAR WEATHER IS
EXPECTED THRU TONIGHT AS THE UPPER LEVEL PATTERN IS NOT EXPECTED
TO CHANGE MUCH.

THE CARIBBEAN SEA...
QUIET WEATHER CONTINUES IN THE CARIBBEAN TONIGHT WITH PLENTY OF
DRY STABLE UPPER LEVEL AIR NOTED ON WATER VAPOR IMAGES BETWEEN
75W AND 85W. THIS REGION LIES IN AN AREA OF UPPER LEVEL RIDGING
WITH AN ANTICYCLONE CENTERED NEAR 20N85W. E OF 75W...BROKEN
DEBRIS MOISTURE FROM THE ATLC TROPICAL CYCLONES HAS PUSHED
SOUTHWARD BETWEEN AN UPPER LOW JUST N OF THE LEEWARD ISLANDS AND
THE UPPER HIGH IN THE NW CARIBBEAN. HOWEVER...DEEP MOISTURE IS
VERY LIMITED WITH ONLY ISOLATED SHOWERS FOUND IN THE HIGH LEVEL
MOISTURE PLUME. THE ONLY CONVECTION NOTED IN THE REGION IS IN
THE SW CARIBBEAN S OF 12N W OF 75W...HIGHLY CONTRIBUTED TO THE
ITCZ. AT THE SFC...TRADE WINDS APPEAR TO BE MOSTLY IN THE 10 TO
20 KT RANGE WITH LITTLE CHANGE IN THESE WINDS EXPECTED THRU
MID-WEEK. GFS SLOWLY SHIFTS THE DRY AIR WEST OVER THE NEXT FEW
DAYS WITH SOME INCREASE IN TROPICAL MOISTURE ACROSS THE LESSER
ANTILLES.

THE ATLANTIC OCEAN..
HURRICANE FLORENCE HAS MOVED N OF THE AREA BUT HAS HELPED TO
PUSH A SURGE OF N/NE WINDS AND COOLER/DRIER AIR SOUTHWARD OFF
THE EAST COAST...AS THE STORM INTERACTS WITH A STRONG 1031 MB
HIGH OVER SOUTHEASTERN CANADA. A COLD FRONT HAS BEEN ADDED TO
THE 00 UTC ANALYSIS IN ASSOCIATION WITH THIS SURGE OF AIR FROM
THE NORTH. AN EARLIER QUIKSCAT PASS SHOWS THIS SURGE NICELY WITH
WINDS IN EXCESS OF 20 KT BEHIND THE SURGE AND 10-15 KT TO THE S.
THIS LARGE FETCH OF NE WINDS WILL CONTINUE TO GENERATE A
MODERATE TO STRONG NE SWELL FOR THE SW NORTH ATLANTIC THROUGH
MIDWEEK...AND DANGEROUS SURF CONDITIONS FOR BEACHES EXPOSED TO
NE SWELL. THIS WILL SLOWLY SUBSIDE THROUGH THE SECOND PART OF
THE WEEK...SEE STATEMENTS FROM LOCAL WEATHER SERVICE OFFICES FOR
MORE INFO.  TROPICAL STORM GORDON LIES ABOUT 1000 NM TO THE SE
OF THE FLORENCE AND IS TRACKING NW INTO THE PROFOUND WEAKNESS IN
THE SUBTROPICAL RIDGE LEFT BEHIND FROM FLORENCE. SCATTERED
MODERATE CONVECTION LIES FROM 20N-25N BETWEEN 55W-59W. A
WELL-DEFINED UPPER LEVEL LOW IS SPINNING NEAR 29N40W MOVING
WESTWARD. THIS UPPER LOW IS ALSO WEAKENING THE SUBTROPICAL
RIDGE. ISOLATED TO SCATTERED SHOWERS ARE SPIRALING CYCLONICALLY
AROUND THE LOW FROM 27N-34N BETWEEN 36W-45W. AN UPPER HIGH IS
MOVING WESTWARD OFF THE AFRICAN COAST WITH A HIGH CENTER NEAR
25N25W AND RIDGING EXTENDING TO 34W. AT THE SFC...A 1026 MB HIGH
IS CENTERED JUST S OF THE AZORES WITH RIDGING COVERING THE
CENTRAL AND EASTERN SUBTROPICAL ATLC.

$$
CANGIALOSI




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