[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 272355
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
805 PM EDT SAT SEP 27 2008

TROPICAL WEATHER DISCUSSION FOR NORTH AMERICA...CENTRAL
AMERICA...GULF OF MEXICO...CARIBBEAN SEA...NORTHERN SECTIONS
OF SOUTH AMERICA...AND 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 1800 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
2315 UTC.

...SPECIAL FEATURES...
AT 27/2100 UTC...T.S. KYLE IS UPGRADED TO HURRICANE STRENGTH.
THREE HOURS LATER...AT 28/0000 UTC THE CENTER OF KYLE IS NEAR
35.4N 69.7W OR ABOUT 350 NM SOUTH OF NANTUCKET MASSACHUSETTS AND
ABOUT 535 NM SOUTH-SOUTHWEST OF YARMOUTH NOVA SCOTIA MOVING
TOWARD THE N AT 21 KT. THE ESTIMATED MINIMUM CENTRAL PRESSURE IS
995 MB. THE MAXIMUM SUSTAINED WIND SPEEDS ARE 65 KT WITH HIGHER
GUSTS. A LITTLE ADDITIONAL STRENGTHENING IS POSSIBLE DURING THE
NEXT 24 HOURS.  HOWEVER...WEAKENING IS EXPECTED TO BEGIN LATE
SUNDAY OR MONDAY. PLEASE READ THE LATEST NHC PUBLIC ADVISORY
UNDER AWIPS/WMO HEADERS MIATCPAT1/ WTNT31 KNHC AND THE FULL
FORECAST/ADVISORY UNDER AWIPS/WMO HEADERS MIATCMAT1/WTNT21 KNHC
FOR MORE DETAILS. THE OVERALL ORGANIZATION OF THE CYCLONE
APPEARS TO HAVE CHANGED LITTLE DURING THE DAY...WITH THE CENTER
REMAINING NEAR THE SOUTHERN EDGE OF THE CONVECTION. SATELLITE
IMAGERY SHOWS AN AREA OF MODERATE TO ISOLATED STRONG CONVECTION
WITHIN 235 NM N OF KYLE'S CENTER. A RAINBAND OF MODERATE
CONVECTION IS NOTED WITHIN 220 NM SE SEMICIRCLE. INTERESTS IN
NEW ENGLAND AND THE CANADIAN MARITIMES SHOULD MONITOR THE
PROGRESS OF KYLE.

...TROPICAL WAVES...
A TROPICAL WAVE IS ADDED TO THE 1800 UTC ANALYSIS/SURFACE MAP
ALONG 18W SOUTH OF 17N BASED ON VIS SATELLITE IMAGERY AND SFC
OBSERVATIONS. IN ADDITION...THE SSMI-DERIVED TPW INDICATES A
NORTH-SOUTH MOISTURE MAXIMUM BETWEEN THE CAPE VERDE ISLANDS AND
THE WEST COAST OF AFRICA WHERE AN 850 MB VORTICITY MAXIMUM IS
ALSO SEEN. SCATTERED SHOWERS ARE MAINLY AHEAD OF THE WAVE
AXIS.

A TROPICAL WAVE IS ALONG 39W SOUTH OF 18N MOVING WNW NEAR 10
KT. THIS WAVE IS PRODUCING DISORGANIZED SHOWERS AND TSTMS WITH A
CLUSTER OF MODERATE TO ISOLATED STRONG CONVECTION WITHIN 100 NM
WEST OF THE WAVE AXIS FROM 15N-17N. UPPER-LEVEL WINDS ARE
EXPECTED TO REMAIN UNFAVORABLE FOR DEVELOPMENT AS THE SYSTEM
CONTINUES TO MOVE SLOWLY WEST-NORTHWESTWARD.

A TROPICAL WAVE IS ALONG 49W/50W SOUTH OF 15N MOVING WEST 10-15
KT. SOME INVERTED-V SIGNATURE IS NOTED ON SATELLITE IMAGERY. A
SWIRL OF LOW LEVEL CLOUDS IS AHEAD OF THE WAVE AXIS NEAR 12N53W.
THE WAVE IS GENERATING SCATTERED MODERATE CONVECTION FROM
10N-14.5N BETWEEN 46W-53W.

A TROPICAL WAVE IS OVER THE SW CARIBBEAN ALONG 79W/80W SOUTH OF
14N MOVING WEST 10-15 KT. A SMALL HINT OF CYCLONIC CIRCULATION
IS OBSERVED ON SFC OBSERVATIONS WITH A SHIP REPORTING SW WINDS
NEAR 10N79W. AN AREA OF MODERATE TO ISOLATED STRONG CONVECTION
IS OVER THE SW CARIBBEAN S OF 13N BETWEEN 80W-83W.

...THE ITCZ...
THE ITCZ AXIS IS CENTERED ALONG 11N15W 8N25W 13N38W 9N45W
10N62W. OUTSIDE FOR THE CONVECTION ASSOCIATED WITH THE TROPICAL
WAVES...A LARGE CLUSTER OF MODERATE TO STRONG CONVECTION IS OVER
SIERRA LEONE. SCATTERED MODERATE CONVECTION IS FROM 4N-7N
BETWEEN 19W-28W. SIMILAR CONVECTION IS WITHIN 70 NM NE OF LINE
FROM 5N30W TO 9N34W.

...DISCUSSION...

THE GULF OF MEXICO...
A MIDDLE/UPPER LEVEL TROUGH EXTENDS FROM THE SE CONUS TO THE
WESTERN PART OF THE BAY OF CAMPECHE. DRY AIR/SUBSIDENCE IS SEEN
BEHIND THE TROUGH AXIS WHILE A BAND OF CLOUDINESS WITH EMBEDDED
SHOWERS IS NOTED AHEAD OF THE TROUGH AXIS COVERING THE EASTERN
PORTION OF THE BAY OF CAMPECHE...THE YUCATAN PENINSULA...THE SE
PORTION OF THE GULF INCLUDING THE FLORIDA KEYS AND SOUTH
FLORIDA. THIS UPPER FEATURE SUPPORTS A SFC TROUGH THAT RUNS FROM
THE YUCATAN PENINSULA ALL THE WAY NE TO N FLORIDA NEAR TO
29N82W. SFC DATA AND AN EARLIER ASCAT PASS CLEARLY SHOW THE WIND
SHIFT ASSOCIATED WITH THIS SFC TROUGH. PRES GRADIENT BETWEEN
RELATIVE LOW PRESSURE OVER THE YUCATAN PENINSULA AND CENTRAL
AMERICA AND HIGH PRESSURE BUILDING OVER THE WESTERN GULF IS
PRODUCING NLY WINDS OF 15-20 KT OVER THE SW PORTION OF THE  GULF
INCLUDING THE BAY OF CAMPECHE. WINDS ARE EXPECTED TO INCREASE
OVER THE SOUTH-CENTRAL GULF AT LEAST SUN THROUGH MON AS A LOW
PRES CENTER CURRENTLY IN THE VICINITY OF BELIZE MOVES NW ACROSS
THE YUCATAN PENINSULA.

THE CARIBBEAN SEA...
WIDESPREAD CLOUDINESS AND SHOWERS CONTINUE NEAR A BROAD AREA OF
LOW PRESSURE LOCATED IN THE VICINITY OF BELIZE NEAR 18N87.5W
THIS EVENING. ALTHOUGH SURFACE PRESSURES ARE NOT CURRENTLY
FALLING...SOME SLOW DEVELOPMENT IS POSSIBLE DURING THE NEXT DAY
OR TWO AS THE SYSTEM DRIFTS NORTHWARD AWAY FROM YUCATAN. HEAVY
RAINS AND LOCALIZED FLOODING ARE POSSIBLE OVER PORTIONS OF
SOUTHERN MEXICO...THE YUCATAN PENINSULA...BELIZE AND GUATEMALA
DURING THE NEXT COUPLE OF DAYS. CURRENTLY...CONVECTION HAS
FLARED UP OVER NORTHERN CENTRAL AMERICA AND ALSO OVER PARTS OF
CUBA. A DIFFLUENT PATTERN ALOFT BETWEEN THE AFOREMENTIONED
MID/UPPER LEVEL TROUGH AND AN UPPER- LEVEL HIGH SITUATED OVER
BELIZE IS HELPING TO INDUCE THIS ACTIVITY. UPPER NELY FLOW
COVERS MOST OF THE BASIN. THESE WINDS ARE ADVECTING MID/UPPER
LEVEL MOISTURE ACROSS THE EASTERN CARIBBEAN WHERE A FEW SHOWERS
ARE NOTED. THE SAN JUAN DOPPLER RADAR DEPICTS SCATTERED SHOWERS
OVER THE UK/US VIRGIN ISLANDS...PUERTO RICO AND THE CARIBBEAN
WATERS ASSOCIATED WITH PATCHES OF LOW LEVEL MOISTURE IN THE
TRADE WINDS. THIS SHOWER ACTIVITY IS ALSO REACHING THE MONA
PASSAGE AND DOMINICAN REPUBLIC.

THE ATLANTIC OCEAN...
THE MAIN FEATURE OF INTEREST ACROSS THE ATLC IS KYLE...THE SIXTH
HURRICANE SO FAR THIS TROPICAL SEASON. KYLE IS CROSSING WELL
EAST OF THE COAST OF NORTH CAROLINA...AND WILL THREATEN EASTERN
NEW ENGLAND AND THE CANADIAN MARITIMES. SEE SPECIAL FEATURES FOR
DETAILS. SWLY FLOW AHEAD OF THE ABOVE MENTIONED UPPER-LEVEL
TROUGH OVER THE GULF OF MEXICO IS TRANSPORTING ABUNDANT
UPPER-LEVEL MOISTURE THROUGH SOUTH-CENTRAL FLORIDA INTO THE W
ATLC. A BROAD UPPER-LEVEL LOW IS OVER THE CENTRAL ATLC NEAR
22N47W. THE CYCLONIC FLOW REACHES THE LESSER ANTILLES. THIS LOW
IS PRODUCING STRONG SWLY FLOW OVER THE TROPICAL WAVES LOCATED
NEAR 39W AND 49W/50W. FURTHER EAST...A BROAD UPPER-LEVEL RIDGE
CENTERED OVER WEST AFRICA DOMINATES THE REMAINDER OF THE ATLC.
THIS RIDGE IS ENHANCING CONVECTION SOUTH OF THE ITCZ AXIS. AT
THE SFC...A COLD FRONT ENTERS THE AREA NEAR 31N33W THEN
CONTINUES SW TO NEAR 24N41W. A SFC RIDGE ENTERS THE DISCUSSION
AREA BETWEEN KYLE AND THIS COLD FRONT COVERING PART OF THE WEST
AND CENTRAL ATLC. A WEAK 1011 SURFACE LOW IS NE OF THE MADEIRA
ISLANDS.

$$
GR






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