[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 180543
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
205 AM EDT SAT OCT 18 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 0000 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
0515 UTC.

...SPECIAL FEATURES...
OMAR HAS BEEN DOWNGRADED TO A TROPICAL STORM AT 18/0300 UTC.
TROPICAL STORM OMAR CENTERED NEAR 31.5N 52.8W OR ABOUT 615 NM
E OF BERMUDA AND ABOUT 1325 NM W OF THE AZORES AT 18/0300 UTC.
ESTIMATED MINIMUM CENTRAL PRESSURE IS 989 MB. MAXIMUM SUSTAINED
WIND SPEED IS 55 KT WITH GUSTS TO 65 KT. PLEASE SEE LATEST NHC
PUBLIC ADVISORY UNDER AWIPS/WMO HEADERS MIATCPAT5/WTNT35 KNHC
AND THE FULL FORECAST/ADVISORY UNDER AWIPS/WMO HEADERS
MIATCMAT5/WTNT25 KNHC FOR MORE DETAILS ON TROPICAL STORM OMAR.
TROPICAL STORM FORCE WINDS EXTEND OUTWARD UP TO 90 NM FROM THE
CENTER. ISOLATED MODERATE CONVECTION IS FROM 24N-31N BETWEEN
47W-52W. TROPICAL STORM OMAR IS MOVING OVER COLDER WATERS...AND
ADDITIONAL WEAKENING IS EXPECTED DURING THE NEXT COUPLE DAYS.

...TROPICAL WAVES...
A TROPICAL WAVE IS ALONG 33W/34W S OF 16N MOVING W 10-15 KT.
THIS WAVE COINCIDES WITH BROAD WESTWARD-MOVING DEEP LAYER
MOISTURE SURGE BASED ON TOTAL PRECIPITABLE WATER PRODUCT FROM
CIMSS. COMPUTER MODEL GUIDANCE AND CIMSS WAVETRAK PRODUCT SHOW A
DISTINCT MAXIMUM IN LOW LEVEL COUNTERCLOCKWISE CIRCULATION
AROUND WAVE AXIS. SCATTERED MODERATE CONVECTION IS WITHIN 180 NM
EITHER SIDE OF WAVE AXIS.

A TROPICAL WAVE IS ALONG 52W/53W S OF 16N MOVING W NEAR 10 KT.
THIS WAVE COINCIDES WITH A NORTH-TO-SOUTH DEEP LAYER MOISTURE
MAXIMUM. SATELLITE IMAGERY DEPICTS BROAD INVERTED-V PATTERN IN
CLOUD FIELD AROUND WAVE AXIS. ISOLATED MODERATE CONVECTION IS
WITHIN 120 NM W OF WAVE AXIS S OF 11N...WHICH IS BEING ENHANCED
BY THE ITCZ.

...THE ITCZ...
ITCZ AXIS IS CENTERED ALONG 8N13W 9N30W 8N46W 10N61W 10N82W. IN
ADDITION TO CONVECTION ASSOCIATED WITH THE TROPICAL WAVES...
SCATTERED MODERATE/ISOLATED STRONG CONVECTION IS WITHIN 180 NM
EITHER SIDE OF AXIS BETWEEN 21W-29W. ISOLATED MODERATE
CONVECTION IS WITHIN 90 NM EITHER SIDE OF AXIS BETWEEN 40W-49W.
ISOLATED MODERATE CONVECTION IS WITHIN 120 NM EITHER SIDE OF
AXIS BETWEEN 55W-60W. SCATTERED MODERATE CONVECTION IS FROM
6N-9N BETWEEN 75W-78W...AFFECTING NW COLOMBIA AND NW VENEZUELA.

...DISCUSSION...

GULF OF MEXICO...
AN UPPER TROUGH OVER THE E CONUS EXTENDS INTO THE CENTRAL AND W
GULF...WITH SW TO W FLOW ALOFT COVERING MUCH OF THE GULF. THIS
TROUGH IS SUPPORTING A COLD FRONT THAT IS DRAPED ACROSS THE N
AND W GULF...EXTENDING FROM THE W FLORIDA PANHANDLE NEAR 31N86W
TO 26N92W TO THE BAY OF CAMPECHE NEAR 19N96W. MID/UPPER-LEVEL
MOISTURE EMBEDDED WITHIN THE FLOW ALOFT IS SUPPORTING ISOLATED
SHOWERS WITHIN 90 NM EITHER SIDE OF FRONT N OF 25N. OVER THE SE
GULF...DRY AIR EMBEDDED WITHIN WEAK DEEP LAYER FLOW IS RESULTING
IN MAINLY FAIR WEATHER. GENERALLY STABLE ATMOSPHERIC CONDITIONS
COVER THE BAY OF CAMPECHE UNDER AN UPPER HIGH CENTERED NEAR
19N93W. HOWEVER...WEAK UPPER DIFFLUENCE SE OF THE HIGH IS
RESULTING IN SCATTERED MODERATE CONVECTION OVER THE SW YUCATAN
PENINSULA...WHICH IS IMPACTING THE NEARBY WATERS OF THE BAY OF
CAMPECHE.

CARIBBEAN SEA...
AN UPPER RIDGE EXTENDS FROM AN UPPER HIGH NEAR 20N56W TO
N VENEZUELA...AND A WEAK UPPER TROUGH IS PRESENT OVER THE
NW CARIBBEAN. DRY AIR IN CONFLUENT UPPER FLOW BETWEEN THESE
FEATURES IS LIMITING CONVECTION OVER A LARGE PART OF THE
CARIBBEAN. HOWEVER...A SURFACE TROUGH EXTENDS FROM N HONDURAS
NEAR 15N87W TO A 1009 MB SURFACE LOW NEAR 17N87W TO 18N83W TO A
1010 MB SURFACE LOW NEAR 16N74W TO THE E CARIBBEAN NEAR 18N84W.
SCATTERED MODERATE/ISOLATED STRONG CONVECTION IS OCCURRING FROM
16N-18N BETWEEN 73W-75W IN RESPONSE TO LOW LEVEL CONVERGENCE
NEAR THE 1010 MB LOW NEAR 16N74W. ALSO...ISOLATED MODERATE
CONVECTION IN RESPONSE TO LOW LEVEL CONVERGENCE IS OCCURRING
WITHIN 120 NM EITHER SIDE OF THE SURFACE TROUGH BETWEEN
78W-88W...INCLUDING E PORTIONS OF THE YUCATAN PENINSULA AND E
BELIZE. SCATTERED MODERATE/ISOLATED STRONG CONVECTION OVER THE
HIGHER TERRAIN NW VENEZUELA AND N COLOMBIA IS IMPACTING THE
NEARBY CARIBBEAN WATERS.

ATLANTIC OCEAN...
PLEASE SEE SPECIAL FEATURES SECTION ABOVE FOR INFORMATION ON
TROPICAL STORM OMAR. AN UPPER TROUGH OVER THE E CONUS IS
BRINGING SW FLOW ALOFT TO THE W ATLC. HOWEVER...DRY AIR EMBEDDED
WITHIN THE FLOW...COMBINED WITH STABLE CONDITIONS AROUND A
1020 MB SURFACE HIGH NEAR 29N75W...IS LIMITING CONVECTION OVER
THE W ATLC. FURTHER TO THE E...AN UPPER HIGH IS CENTERED NEAR
21N56W...WITH MAINLY DRY AND STABLE CONDITIONS AROUND THIS HIGH.
TO THE NE OF THIS HIGH...THE UPPER LOW ASSOCIATED WITH TROPICAL
STORM OMAR IS LOCATED NEAR 31N40W. FURTHER TO THE E...A 1027 MB
SURFACE HIGH IS CENTERED NEAR 32N28W....AND A SURFACE RIDGE
EXTENDS FROM THIS HIGH TO THE SW NEAR 18N51W...WHERE SUBSIDENCE
AND STABLE CONDITIONS PREDOMINATE. WEAK INSTABILITY IN
ASSOCIATION WITH AN UPPER TROUGH OVER THE E ATLC N OF 24N AND
E OF 24W IS SUPPORTING ISOLATED SHOWERS WITHIN 120 NM OF 28N15W.
OVER THE TROPICAL ATLC...AN UPPER RIDGE EXTENDS ALONG 13N
BETWEEN W AFRICA AND 38W. TO THE W...A NE-TO-SW-TILTED UPPER
TROUGH EXTENDS FROM 22N35W TO AN UPPER LOW NEAR 16N41W TO
11N45W...WITH DEEP LAYER DRY AIR EMBEDDED WITHIN THESE FEATURES
PREVENTING ANY CONVECTIVE DEVELOPMENT.

$$
COHEN

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