[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 280001
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
805 PM EDT WED SEP 27 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 1800 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
2345 UTC.

...SPECIAL FEATURE...
SATELLITE IMAGES INDICATE THAT THE NINTH TROPICAL DEPRESSION OF
THE 2006 HURRICANE SEASON HAS FORMED OVER THE CENTRAL ATLANTIC.
AT 500 PM EDT...2100 UTC...THE CENTER OF TROPICAL DEPRESSION
NINE WAS LOCATED NEAR LATITUDE 26.5 NORTH...LONGITUDE 53.1 WEST
OR ABOUT 700 NM EAST-SOUTHEAST OF BERMUDA. THE DEPRESSION IS
MOVING TOWARD THE NORTHWEST NEAR 12 KT. THIS GENERAL MOTION IS
EXPECTED TO CONTINUE DURING THE NEXT 24 HOURS. THE ESTIMATED
MINIMUM CENTRAL PRESSURE IS 1012 MB. MAXIMUM SUSTAINED WINDS ARE
NEAR 30 KT WITH GUSTS TO 40 KT. SOME SLOW STRENGTHENING IS
FORECAST...AND THE DEPRESSION COULD BECOME A TROPICAL STORM
DURING THE NEXT 24 HOURS. SEE THE LATEST NHC FORECAST/ADVISORY
UNDER AWIPS/WMO HEADERS MIATCMAT4/WTNT24 KNHC AND THE PUBLIC
ADVISORY UNDER MIATCPAT4/WTNT34 KNHC FOR MORE DETAILS. SCATTERED
TO NUMEROUS MODERATE CONVECTION IS FROM 22N-30N BETWEEN 48W-54W.

...TROPICAL WAVES...
AN EASTERN ATLANTIC OCEAN TROPICAL WAVE IS ALONG 20W/21W SOUTH
OF 18N MOVING WEST NEAR 10 KT.  A 1010 MB LOW PRESSURE CENTER IS
ALONG THE WAVE AXIS NEAR 12.5N. THE AVAILABLE SURFACE AND SHIP
OBSERVATIONS IN THE VICINITY SHOW CLEAR CYCLONIC CURVATURE ABOUT
THE WAVE AXIS. SCATTERED MODERATE/ISOLATED STRONG CONVECTION IS
FROM 9N-19N BETWEEN 19W-23W.

A LOW AMPLITUDE ATLANTIC OCEAN TROPICAL WAVE IS ALONG 42W/43W
SOUTH OF 15N MOVING WEST NEAR 15 KT.  THE WAVE IS SUBTLE WITH
THE PLACEMENT BASED ON CONTINUITY AND HOVMOLLER DIAGRAMS.
CONVECTION IS MINIMAL AND CONFINED MOSTLY NEAR THE ITCZ WITH
SCATTERED MODERATE FROM 9N-12N BETWEEN 40W-47W.

A TROPICAL WAVE IS APPROACHING THE LESSER ANTILLES ALONG 58W
SOUTH OF 20N MOVING WEST 10 TO 15 KT. SATELLITE IMAGERY AND THE
AVAILABLE SURFACE OBSERVATIONS SUGGEST A WEAK SURFACE LOW MAY BE
FORMING ALONG THE LOW NEAR 17N. HOWEVER...THE CONVECTION IN THIS
REGION A COUPLE HUNDRED MILES E OF THE LEEWARD ISLANDS HAS BEEN
DECREASING IN BOTH COVERAGE AND INTENSITY OVER THE LAST FEW
HOURS. ALTHOUGH SIGNIFICANT DEVELOPMENT OF THIS SYSTEM IS NOT
ANTICIPATED...IT COULD BRING SHOWERS AND GUSTY WINDS TO PORTIONS
OF THE LESSER ANTILLES DURING THE NEXT DAY OR SO.

A TROPICAL WAVE IS OVER THE WESTERN CARIBBEAN SEA ALONG 78W
MOVING WEST NEAR 15 KT. CONVECTION REMAINS LIMITED TO MOSTLY THE
NORTHERN PORTION OF THE WAVE WITH SCATTERED MODERATE FROM
16N-20N BETWEEN 76W-83W.

...THE ITCZ...
ITCZ AXIS IS CENTERED ALONG 13N16W 11N30W 9N40W 9N50W TO
TRINIDAD NEAR 10N61W.  OTHER THAN THE CONVECTION MENTIONED IN
THE TROPICAL WAVE SECTION...ISOLATED MODERATE CONVECTION IS FROM
8N-11N BETWEEN 46W-51W...AND ALSO NEAR NE TRINIDAD AND TOBAGO.

...DISCUSSION...
THE GULF OF MEXICO...
A QUASI-STATIONARY FRONTAL BOUNDARY EXTENDS FROM S FLORIDA TO
THE BAY OF CAMPECHE ALONG 27N82W 24N90W 18N94W. THE FRONT SEEMS
TO BE PROGRESSING SE MORE THAN IT WAS AT 1800 UTC...SO HAVE
OPTED TO MAKE IT A PROGRESSIVE COLD FRONT ON THE 2100 UTC MAP
OVER FL AND ERN GULF. CONVECTION OVER THE GULF ASSOCIATED WITH
THE FRONT REMAINS ISOLATED AT BEST WITHIN 100NM OF THE FRONT.
THE STRONGEST SHOWERS/TSTMS HAVE BEEN MOVING THROUGH SE FLORIDA
AND NOW INTO THE ADJACENT ATLC WATERS. THERE IS A SWATH OF MID
TO UPPER LEVEL MOISTURE WITH A FEW SHOWERS IN THE W GULF FROM
20N-27N BETWEEN 90W-98W...BUT THIS SEEMS MORE ASSOCIATED WITH
UPPER DIFFLUENCE BETWEEN AN UPPER RIDGE EXTENDING E FROM JUST S
OF CABO SAN LUCAS AND TROUGHING OVER THE CENTRAL/ERN US. THERE
IS A 1020MB SURFACE HIGH JUST S OF THE WRN LOUISIANA COAST. THIS
HIGH IS EXPECTED TO DRIFT SLOWLY W WHILE WEAKENING OVER THE NEXT
24HRS WHILE THE NEXT COLD FRONT APPROACHES FROM THE NW. THE
FRONT EXTENDING THROUGH S FLORIDA WILL CONTINUE DRIFTING SLOWLY
SE WHILE WEAKENING.

THE CARIBBEAN SEA...
WELL DEFINED MID TO UPPER LEVEL HIGH IS DOMINATING THE WRN HALF
OF THE CARIBBEAN THIS EVENING WITH AN ESTIMATED CENTER FROM WV
IMAGERY AND GOES WINDS NEAR 13N79W. THERE MAY ALSO BE A WEAKER
EMBEDDED UPPER HIGH CENTER NEAR 16N84W OR JUST OFF THE COAST OF
HONDURAS. UPPER DIFFLUENCE BETWEEN THIS SMALLER HIGH AND THE
LARGER/BROAD HIGH SEEMS TO BE ASSISTING IN THE CONVECTION
MENTIONED WITH THE TROPICAL WAVE ALONG 78W...BETWEEN HONDURAS
AND CUBA. THE ONLY OTHER MID TO UPPER LEVEL MOISTURE WITH
ISOLATED SHOWERS SEEN IS BETWEEN HISPANIOLA AND VENEZUELA. THIS
IS A MORE OBVIOUS REGION OF UPPER DIFFLUENCE BETWEEN THE UPPER
HIGH NEAR 13N79W AND UPPER TROUGHING N OF HISPANIOLA/PUERTO
RICO. 10 TO 20 KT TRADES PERSIST THIS EVENING WITH SW PORTION OF
THE ATLC HIGH INTERACTING WITH LOWER PRESSURE NEAR THE COLOMBIAN
COAST.

THE ATLANTIC OCEAN...
A QUASI-STATIONARY FRONT IS OVER THE W ATLANTIC ALONG 31N74W
27N80W.  THE FRONT IS NOW DRIFTING SLOWLY SE AS A COLD FRONT.
ISOLATED MODERATE CONVECTION MOSTLY AHEAD OF THE FRONT IS FROM
23N-30N BETWEEN 68W-80W...ALSO BEING SUPPORTED BY UPPER
DIFFLUENCE BETWEEN AN UPPER RIDGE EXTENDING ENE THROUGH THE
BAHAMAS AND THE UPPER SW FLOW OFF THE SE US COAST. THERE IS AN
UPPER LOW JUST W OF TROPICAL DEPRESSION 9 NEAR 28N59W AND A
UPPER HIGH TO THE EAST OF THE DEPRESSION NEAR 26N48W. A WELL
DEFINED UPPER LOW IS NEAR 25N28W IN THE ERN ATLC BUT IS NOT
GENERATING MUCH SHOWER ACTIVITY IN THE IMMEDIATE VICINITY. THERE
IS A CLUSTER OF MODERATE CONVECTION JUST WSW OF THE CANARY
ISLANDS THAT IS ASSOCIATED WITH UPPER DIFFLUENCE BETWEEN THE
UPPER LOW TO THE W AND AN UPPER HIGH OVER WRN AFRICA. ELSEWHERE
AT THE SURFACE...A 1026MB HIGH IS AFFECTING MUCH OF THE REGION
FROM ITS CENTER IN THE CENTRAL ATLANTIC NEAR 34N45W.

$$
WILLIS


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