[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 130556 AAA
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
205 AM EDT WED SEP 13 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...
TROPICAL STORM GORDON HAS BEEN UPGRADED TO A HURRICANE...THE
THIRD OF THE 2006 SEASON. THE CENTER OF HURRICANE GORDON AT
13/0300 UTC WAS NEAR 24.4N 57.9W OR ABOUT 565 NM/905 KM
NORTH-NORTHEAST OF THE LEEWARD ISLANDS. GORDON IS MOVING
NORTHWARD AT 8 KT AND THIS MOTION IS EXPECTED TO CONTINUE
THROUGH WED. THE ESTIMATED MINIMUM CENTRAL PRESSURE IS 987 MB.
THE MAXIMUM SUSTAINED WIND SPEEDS ARE 65 KT WITH GUSTS TO 80 KT.
GORDON IS A CATEGORY ONE HURRICANE ON THE SAFFIR-SIMPSON SCALE.
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 IS A VERY COMPACT
TROPICAL CYCLONE WITH HURRICANE FORCE WINDS EXTENDING OUTWARD
WITHIN 20 NM IN THE NE QUADRANT AND TROPICAL STORM FORCE WINDS
WITHIN 75 NM. SCATTERED MODERATE CONVECTION STRETCHES WITHIN 150
NM OF THE CENTER. AN INTERMITTENT EYE FEATURE HAS NOW BECOME
APPARENT ON CONVENTIONAL SATELLITE IMAGERY. SOME ADDITIONAL
STRENGTHENING IS FORECAST DURING THE NEXT 24 HOURS. GORDON IS
ALREADY ON THE W PERIPHERY OF THE SUBTROPICAL RIDGE AND EXPECTED
TO REMAIN IN THE OPEN ATLANTIC.

THE CENTER OF TROPICAL DEPRESSION EIGHT AT 13/0300 UTC WAS NEAR
11.8N 25.3W OR ABOUT 215 NM/350 KM SOUTH-SOUTHWEST OF THE
SOUTHERNMOST CAPE VERDE ISLANDS. T.D. EIGHT IS MOVING WEST AT 14
KT AND THIS GENERAL MOTION IS EXPECTED TO CONTINUE FOR THE NEXT
24 HOURS WITH SOME INCREASE IN FORWARD SPEED. THE ESTIMATED
MINIMUM CENTRAL PRESSURE IS 1007 MB. THE MAXIMUM SUSTAINED WINDS
REMAIN NEAR 30 KT WITH GUSTS TO 40 KT. THE DEPRESSION COULD
BECOME A TROPICAL STORM ON WEDNESDAY. PLEASE READ THE LATEST NHC
FORECAST/ADVISORY UNDER AWIPS/WMO HEADERS MIATCMAT3/WTNT23 KNHC
AND THE PUBLIC ADVISORY MIATCPAT3/WTNT33 KNHC FOR MORE DETAILS.
UNLIKE GORDON...T.D. EIGHT IS A VERY BROAD ELONGATED FEATURE
WITH ITS CYCLONIC FLOW ENVELOPE COVERING A REGION OF SEVERAL
HUNDRED NM WIDE. CONVECTION IS LIMITED NEAR THE CENTER OF THE
BROAD CIRCULATION...HOWEVER THERE IS AN ORGANIZED BROKEN BAND TO
THE SE OF THE CENTER AND A FAIR AMOUNT OF CONVECTION TO THE N
AND W BUT SOME OF THIS ACTIVITY APPEARS TO BE MOVING AWAY FROM
THE CIRCULATION RATHER THAN WRAPPING AROUND. ONLY SLOW
INTENSIFICATION IS FORECAST IN THE SHORT-TERM BECAUSE THE LARGE
CYCLONE WILL LIKELY TAKE SOME TIME TO CONSOLIDATE.

...TROPICAL WAVES...

A TROPICAL WAVE HAS BEEN ADJUSTED AHEAD ALONG 40W SOUTH OF 15N
MOVING WEST 10 TO 15 KT. THERE IS SOME SLIGHT CYCLONIC TURNING
IN THE SCATTERED SHOWER AND TSTM ACTIVITY JUST AHEAD OF THE
ANALYZED AXIS FROM 6N-8N BETWEEN 40W-43W. A FEW SHIP
OBSERVATIONS HELP LOCATE THE WAVE POSITION. OVERALL...THIS WAVE
IS POORLY STRUCTURED AND IS NOT IN A CONDUCIVE UPPER LEVEL
ENVIRONMENT FOR SIGNIFICANT DEVELOPMENT.

A TROPICAL WAVE IS ALONG 49W SOUTH OF 14N MOVING WEST NEAR 10 KT
OVER THE LAST 24 HOURS. THIS WAVE HAS BEEN CHALLENGING TO TRACK
AS IT CONTINUES TO BE A LOW AMPLITUDE FEATURE. THE WAVE IS
BARELY IDENTIFIABLE ON SATELLITE IMAGERY...SURFACE OBS AND
QUIKSCAT DATA. SCATTERED SHOWERS AND TSTMS ARE NEAR THE BASE OF
THE ANALYZED AXIS FROM 5N-7N BETWEEN 48W-51W.

A TROPICAL WAVE IS ALONG 57W SOUTH OF 18N MOVING WEST NEAR 10
KT. UNLIKE THE TWO WAVES TO ITS EAST...THIS ONE IS VERY EASY TO
FIND WITH A CLASSIC INVERTED V-SHAPE SEEN ON SATELLITE IMAGES.
SCATTERED SHOWERS AND TSTMS ARE WITHIN 180 NM OF THE WAVE AXIS.
SOME OF THIS MOISTURE WILL BE SPREADING ACROSS THE LESSER
ANTILLES LATER TODAY.

A TROPICAL WAVE IS IN THE CARIBBEAN ALONG 67W SOUTH OF 16N
MOVING WEST NEAR 15 KT. THIS WAVE IS WEAK WITH ONLY A SLIGHT
HINT OF LOW-MID CYCLONIC TURNING NEAR THE WAVE AXIS. CONVECTION
IS MOSTLY INLAND OVER SOUTH AMERICA ASSOCIATED WITH THE ITCZ.

...THE ITCZ...
ITCZ IS CENTERED ALONG 16N16W 10N28W 7N39W 8N50W 10N63W. BESIDES
FOR THE CONVECTION ASSOCIATED WITH T.D. EIGHT AND THE TROPICAL
WAVES...SCATTERED MODERATE CONVECTION IS OVER SOUTH AMERICA FROM
3-9N BETWEEN 58W-67W AND OVER WRN COLOMBIA FROM 6N-11N BETWEEN
71W-77W.

...DISCUSSION...

THE GULF OF MEXICO...
LITTLE IN THE WAY OF ANY SIGNIFICANT PATTERN CHANGE HAS OCCURRED
OVER THE PAST FEW DAYS IN THE GULF OF MEXICO. AN ELONGATED MID
TO UPPER LEVEL HIGH IS CENTERED IN THE WRN GULF WITH RIDGING
EXTENDING TO NEAR 87W ALONG 26N/27N. ANOTHER SMALLER MID/UPPER
HIGH IS OVER THE FAR SE GULF. UPPER DIFFLUENT AIR BETWEEN THESE
FEATURES AND THE WESTERLY FLOW OVER THE SRN UNITED STATES IS
HELPING TO SUPPORT THE SCATTERED MODERATE CONVECTION IN THE NW
GULF FROM 25N-28N BETWEEN 93W-100W. SOME SFC CYCLONIC WIND
SHIFTS WHERE NOTED IN SFC OBSERVATIONS IN THIS AREA AND A WEAK
TROUGH WAS ADDED TO THE 0300 UTC ANALYSIS ALONG 25N96W 28N93W.
SCATTERED SHOWERS AND TSTMS ARE ALSO IN THE NE GULF FROM 25N-31N
BETWEEN 83W-88W WHERE UPPER DIFFLUENCE IS SLIGHTLY STRONGER. A
MID TO UPPER LEVEL LOW IS MOVING SLOWLY W THROUGH THE BAY OF
CAMPECHE CENTERED NEAR 20N94W...THAT HAS SCATTERED SHOWERS/TSTMS
MAINLY ON THE MOIST E SIDE OF THE CIRCULATION FROM 17N-22N
BETWEEN 90W-93W. AT THE SURFACE...HIGH PRES RIDGING EXTENDS
SWWARD FROM SE CANADA TO THE NE GULF. SFC WINDS ARE FAIRLY LIGHT
AND VARIABLE. THE WEATHER PATTERN WILL BE CHANGING AS A COLD
FRONT ENTERS THE N GULF LATE WED. GFS INDICATES THAT THIS FRONT
WILL LIKELY DIG TO NEAR 25N BEFORE BECOMING STATIONARY AND
LIFTING OUT.

THE CARIBBEAN SEA...
CONDITIONS REMAIN QUIET ACROSS THE CARIBBEAN TONIGHT WITH AN
ABUNDANT AMOUNT OF DRY STABLE UPPER LEVEL AIR NOTED ON WATER
VAPOR IMAGES W OF 76W. A FEW LEFT OVER PATCHES OF CLOUDS AND
ISOLATED SHOWERS FROM LATE EVENING TSTMS OVER CUBA ARE MOVING
SOUTHWARD DRIVEN BY NLY UPPER LEVEL FLOW BETWEEN AN ANTICYCLONE
OVER THE YUCATAN PENINSULA AND A LARGE UPPER LEVEL LOW IN THE E
CARIBBEAN. OTHERWISE...MID-HIGH LEVEL CLOUDINESS AND MAYBE SOME
ISOLATED SHOWERS LIE E OF 76W MOVING CYCLONICALLY AROUND THE
UPPER LOW. SCATTERED SHOWERS ARE MAINLY TO THE E OF THE WINDWARD
ISLANDS AHEAD OF A TROPICAL WAVE ALONG 57W. LIGHT TO MODERATE
TRADES NEAR 10-20 KT ARE OBSERVED IN THE REGION...THESE WINDS
ARE LIKELY TO REMAIN THAT WAY OVER THE NEXT COUPLE OF DAYS. GFS
DOES SHOW SOME MOISTURE ASSOCIATED WITH THE TROPICAL WAVE JUST E
OF THE AREA MOVING OVER THE LESSER ANTILLES LATER TODAY.

THE ATLANTIC OCEAN...
A LARGE DEEP UPPER LEVEL TROUGH COVERS THE WRN ATLC AND THE
EASTERN CARIBBEAN. A TAIL SFC TROUGH EXTENDS FROM THE
EXTRATROPICAL STORM FLORENCE AND ENTERS THE AREA ALONG 32N60W
27N69W ACROSS THE W BAHAMAS NEAR 23N79W. THIS SFC TROUGH WAS
WELL DEFINED IN AN EARLIER QUIKSCAT PASS ALONG WITH SATELLITE
IMAGERY. A VERY WEAK LOW MIGHT BE FORMING ALONG THE BOUNDARY
NEAR 27N70W. SCATTERED SHOWERS ARE WITHIN 120 NM OF THE
BOUNDARY. A LARGE FETCH OF N/NE WINDS PERSISTS OFF THE MID ATLC
AND NE US COAST BETWEEN EXTRATROPICAL FLORENCE AND THE 1023MB
HIGH BUILDING INTO NEW ENGLAND. ASSOCIATED MODERATE TO STRONG NE
SWELL WILL CONTINUE TO PRODUCE DANGEROUS SURF CONDITIONS AT
BEACHES EXPOSED TO NE SWELL OVER THE NEXT COUPLE OF
DAYS...BEFORE SUBSIDING THROUGH THE WEEKEND. SEE STATEMENTS FROM
LOCAL WEATHER SERVICE OFFICES FOR MORE DETAILS. HURRICANE GORDON
IS MOVING NORTHWARD NEAR THE NW PERIPHERY OF A WEAK SUB-TROPICAL
RIDGE CENTERED NEAR 20N55W. THE MID TO UPPER LEVEL RIDGING HAS
BEEN SIGNIFICANTLY ERODED BY FLORENCE AND ALSO BY A LARGE UPPER
LEVEL LOW CENTERED NEAR 30N46W...WHICH IS MOVING NORTHWESTWARD.
SCATTERED SHOWERS ARE SPIRALING AROUND THE LOW FROM 27N-35N
BETWEEN 42W-48W. DUE TO THE LARGE BREAK IN THE SUBTROPICAL
RIDGE...GORDON IS EXPECTED TO STAY IN THE OPEN ATLANTIC. FARTHER
EAST...A MID TO UPPER HIGH IS OVER THE ERN ATLC OFF THE COAST OF
AFRICA NEAR 25N28W. THIS IS THE PRIMARY STEERING COMPONENT FOR
TROPICAL DEPRESSION EIGHT KEEPING THE SYSTEM ON A GENERAL
WESTWARD TRACK OVER THE NEXT COUPLE OF DAYS. AT THE SFC...A 1026
MB HIGH IS CENTERED SW OF THE AZORES NEAR 36N35W WITH RIDGING
DOMINATING THE E ATLC.

$$
CANGIALOSI




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