[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 120549
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
205 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 0000 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
0530 UTC.

...SPECIAL FEATURES...

THE CENTER OF HURRICANE FLORENCE AT 12/0300 UTC WAS LOCATED NEAR
35.8N 63.9W OR ABOUT 245 MILES...315 KM...NORTH-NORTHEAST OF
BERMUDA. FLORENCE IS MOVING TOWARD THE NORTH-NORTHEAST NEAR 16
KT...30 KM/HR. THIS GENERAL MOTION WITH SOME INCREASE IN FORWARD
SPEED IS EXPECTED TUESDAY. THE ESTIMATED MINIMUM CENTRAL
PRESSURE IS 974 MB. MAXIMUM SUSTAINED WINDS ARE NEAR 75 KT WITH
GUSTS TO 90 KT. FLORENCE IS A CATEGORY ONE HURRICANE ON THE
SAFFIR-SIMPSON SCALE. SOME WEAKENING IS FORECAST DURING THE NEXT
24 HOURS. 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. FLORENCE IS A
LARGE HURRICANE. HURRICANE FORCE WINDS EXTEND OUTWARD UP TO 70
MILES...110 KM...FROM THE CENTER...AND TROPICAL STORM FORCE
WINDS EXTEND OUTWARD UP TO 290 MILES...465 KM. WINDS AT BERMUDA
WILL CONTINUE TO DECREASE THRU THE NIGHT. FLORENCE HAS BECOME
INCREASINGLY LESS HEALTHY-LOOKING ON SATELLITE IMAGERY WITH MOST
OF THE CONVECTION TO THE N OF THE CENTER. THIS SYSTEM WILL
SLOWLY BEGIN TO LOSE ITS TROPICAL CHARACTERISTICS AND BECOME A
STRONG EXTRATROPICAL SYSTEM IN ABOUT 2 DAYS.

THE CENTER OF TROPICAL STORM GORDON AT 12/0300 UTC IS NEAR 22.1N
57.9W OR ABOUT 425 MILES/690 KM NORTHEAST OF THE LEEWARD
ISLANDS. GORDON IS MOVING TOWARD THE NORTHWEST NEAR 8 KT...15
KM/HR...AND THIS MOTION IS EXPECTED TO CONTINUE FOR THE NEXT 24
HOURS. THE ESTIMATED MINIMUM CENTRAL PRESSURE IS 1000 MB.
MAXIMUM SUSTAINED WINDS HAVE INCREASED TO 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.
GORDON APPEARS TO BE ON A STRENGTHENING TREND WITH CONVECTION
INCREASING AND CONSOLIDATING. THE COLDEST CLOUD TOPS ARE BETWEEN
-75 AND -80 C NEAR THE CENTER. 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
DURING THE NEXT 24 HOURS AND GORDON COULD BECOME A HURRICANE IN
A DAY OR TWO.

A STRONG TROPICAL WAVE IS LOCATED JUST OFF THE COAST OF AFRICA
ALONG 17W/18W S OF 18N. A 1009 MB LOW PRES SYSTEM IS ALONG THE
WAVE NEAR 12N. THIS SYSTEM IS FAIRLY LARGE WITH ITS BROAD
CYCLONIC ROTATION COVERING AN AREA OF A FEW HUNDRED NM. SHOWER
ACTIVITY WAS GENERALLY ON THE DECREASE THIS EVENING...HOWEVER
SCATTERED MODERATE CONVECTION HAS FIRED OVER THE LAST FEW HOURS
TO THE W OF THE ANALYZED SFC LOW FROM 10N-14N BETWEEN 20W-22W.
THIS SYSTEM HAS THE POTENTIAL TO DEVELOP DURING THE NEXT DAY OR
TWO AS IT MOVES WESTWARD 10-15 KT.

...TROPICAL WAVES...

A TROPICAL IS ALONG 34W S OF 17N MOVING W 10 TO 15 KT. SLIGHT
LOW-MID LEVEL CYCLONIC TURNING IS NOTED ABOUT THE AXIS N OF 11N.
THE BEST TURNING APPEARS TO BE MAINLY IN THE MID-LEVELS JUST
AHEAD OF THE ANALYZED POSITION NEAR 7N. ONLY ISOLATED SHOWERS
ARE NEAR THE WAVE AXIS. DESPITE THE POOR STRUCTURE OF THE
WAVE...THERE IS GOOD CONFIDENCE IN THE PLACEMENT OF THE AXIS
USING METEOSAT8 HOVMOLLER DIAGRAMS.

A TROPICAL WAVE IS ALONG 45W 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 DIMINISHED A GREAT DEAL SINCE YESTERDAY BUT APPEAR TO BE
MAKING A SLIGHT COMEBACK OVER THE PAST HOUR OR TWO FROM 12N-15N
BETWEEN 43W-49W.

A TROPICAL WAVE HAS MOVED INTO THE E CARIBBEAN ALONG 61W 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 11N22W 10N31W 9N41W 11N60W. BESIDES
FOR THE CONVECTION DISCUSSED IN THE TROPICAL WAVES
SECTION...SCATTERED MODERATE CONVECTION IS INLAND OVER SOUTH
AMERICA S OF 8N BETWEEN 61W-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
SCATTERED SHOWERS AND TSTMS BETWEEN 25N-30N ACROSS THE GULF.
HOWEVER...MUCH OF THIS HAS BEEN DIMINISHING OVER THE PAST FEW
HOURS. THE MOST PERSISTENT ACTIVITY IS IN THE E GULF FROM
26N-28N BETWEEN 83W-86W WHERE UPPER DIFFLUENCE IS SLIGHTLY
STRONGER.  AN UPPER LEVEL LOW IS MOVING W ENTERING THE BAY OF
CAMPECHE WITH WEAKENING SCATTERED SHOWERS ASSOCIATED WITH IT. 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 ON MONDAY 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 W OF 75W.
THIS REGION LIES IN AN AREA OF UPPER LEVEL RIDGING WITH AN
ANTICYCLONE CENTERED NEAR 20N83W. 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 74W...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 W 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. A 23Z 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. NUMEROUS
MODERATE CONVECTION LIES FROM 21N-24N BETWEEN 55W-59W. A
WELL-DEFINED UPPER LEVEL LOW IS SPINNING NEAR 29N39W 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-42W. AN UPPER HIGH IS
MOVING WESTWARD OFF THE AFRICAN COAST WITH A HIGH CENTER NEAR
25N24W AND RIDGING EXTENDING TO 33W. AT THE SFC...A 1027 MB HIGH
IS CENTERED JUST S OF THE AZORES WITH RIDGING COVERING THE
CENTRAL AND EASTERN SUBTROPICAL ATLC.

$$
CANGIALOSI








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