[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 220536
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
205 AM EDT WED OCT 22 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.

...TROPICAL WAVES...
A TROPICAL WAVE IS ALONG 22W/23W S OF 14N MOVING W NEAR 10 KT.
DRY AIR EMBEDDED WITHIN THE BASE OF AN UPPER TROUGH IN THE E
ATLC N OF 11N E OF 38W IS SUPPRESSING CONVECTIVE DEVELOPMENT
ACROSS N PORTIONS OF WAVE AXIS. NEVERTHELESS...CIMSS WAVETRAK
PRODUCT DEPICTS LOW LEVEL COUNTERCLOCKWISE CIRCULATION PRESENT
ALONG WAVE AXIS...AND DEEP LAYER MOISTURE IS MAXIMIZED ALONG
WAVE AXIS BASED ON TOTAL PRECIPITABLE WATER PRODUCT FROM CIMSS.
ISOLATED MODERATE CONVECTION FROM 3N-7N BETWEEN 15W-22W...LIKELY
BEING ENHANCED BY LOW LEVEL CONVERGENCE NEAR THE ITCZ.

A TROPICAL WAVE IS ALONG 50W/51W S OF 22N MOVING W 10-15 KT.
BOTH DEEP LAYER MOISTURE AND A BROAD INVERTED-V PATTERN IN CLOUD
COVERAGE BASED ON SATELLITE IMAGERY ARE BEING STRETCHED
NORTHWARD NEAR THE WAVE. THIS IS THE RESULT OF THE INTERACTION
BETWEEN THE WAVE AND A SHARP UPPER LEVEL TROUGH WITH AN AXIS
EXTENDING FROM 28N50W TO 16N49W. DEEP CONVECTION OVER THE N
PORTIONS OF THE WAVE AXIS IS BEING ENHANCED BY STRONG UPPER
LEVEL DIVERGENCE TO THE SE OF AN UPPER LEVEL WIND SPEED MAXIMUM
E OF THE UPPER TROUGH AXIS...WITH NUMEROUS MODERATE/ISOLATED
STRONG CONVECTION FROM 17N-26N BETWEEN 46W-51W. ADDITIONALLY...
ISOLATED MODERATE CONVECTION IS WITHIN 210 NM EITHER SIDE OF
WAVE AXIS S OF 13N...LIKELY BEING ENHANCED BY LOW LEVEL
CONVERGENCE NEAR THE ITCZ.

A TROPICAL WAVE IS ALONG 76W S OF 17N MOVING W 10-15 KT. DEEP
LAYER MOISTURE IS MAXIMIZED ALONG WAVE AXIS. WAVE ALSO COINCIDES
WITH A MAXIMUM IN LOW LEVEL COUNTERCLOCKWISE CIRCULATION BASED
ON CIMSS WAVETRAK PRODUCT. ISOLATED MODERATE CONVECTION IS
WITHIN 60 NM EITHER SIDE OF WAVE AXIS S OF 11N.

...THE ITCZ...
ITCZ AXIS IS CENTERED ALONG 9N13W 9N20W 8N30W 10N48W 9N61W. IN
ADDITION TO CONVECTION ASSOCIATED WITH TROPICAL WAVES...ISOLATED
MODERATE CONVECTION IS WITHIN 150 NM EITHER SIDE OF AXIS BETWEEN
31W-47W. ISOLATED MODERATE CONVECTION IS WITHIN 180 NM N OF AXIS
BETWEEN 54W-56W.

...DISCUSSION...

GULF OF MEXICO...
MUCH OF THE GULF IS GENERALLY COVERED BY WEST-SOUTHWESTERLY FLOW
ALOFT TO THE NW OF AN UPPER HIGH IN THE E CARIBBEAN NEAR 15N71W.
A VIGOROUS UPPER LEVEL TROUGH OVER THE SOUTHERN PLAINS OF THE
CONUS CONTINUES TO APPROACH THE FAR NW GULF...WHERE
SOUTHWESTERLY FLOW ALOFT IS INCREASING. NEVERTHELESS...DEEP
LAYER DRY AIR AND STABLE CONDITIONS ARE AFFECTING MUCH OF THE
GULF REGION...ESPECIALLY WITH A SURFACE RIDGE EXTENDING FROM A
1022 MB SURFACE HIGH IN THE W ATLC NEAR 30N74W INTO THE E GULF.
HOWEVER...GREATER DEEP MOISTURE ROTATING NORTHEASTWARD AROUND
THE AFOREMENTIONED UPPER LEVEL HIGH IS BRINGING INCREASED
CLOUDINESS AND ISOLATED SHOWERS TO THE FAR SE GULF FROM 22N-25N
BETWEEN 81W-85W. ALSO...SURFACE OBSERVATIONS AND SATELLITE
IMAGERY INDICATE THAT A SURFACE TROUGH EXTENDING FROM 27N93W TO
23N93W TO 20N91W IS MOVING WESTWARD OVER THE W GULF. DEEP
MOISTURE ORIGINATING IN THE CARIBBEAN IS INTERACTING WITH THIS
FEATURE TO RESULT IN CLOUDINESS AND ISOLATED SHOWERS WITHIN 150
NM EITHER SIDE OF THE SURFACE TROUGH AXIS.

CARIBBEAN SEA...
A SURFACE TROUGH EXTENDS FROM THE NE YUCATAN PENINSULA NEAR
21N87W TO A 1011 MB SURFACE LOW OVER THE GULF OF HONDURAS NEAR
17N88W TO 16N88W. OVER THE W CARIBBEAN...BROAD LOW LEVEL
CONVERGENCE AROUND THESE FEATURES...COMBINED WITH AMPLE DEEP
LAYER MOISTURE AND UPPER LEVEL DIVERGENCE TO THE W OF THE UPPER
HIGH IN THE E CARIBBEAN NEAR 15N71W...IS RESULTING IN SCATTERED
MODERATE/ISOLATED STRONG CONVECTION FROM 11N-17N BETWEEN
79W-88W. THIS INCLUDES PORTIONS OF THE W CARIBBEAN SEA AND
NEARBY INLAND AREAS OF CENTRAL AMERICA AND SE MEXICO.
SIGNIFICANT DEVELOPMENT OF THIS SYSTEM APPEARS UNLIKELY DUE TO
PROXIMITY OF LAND. HOWEVER...LOCALLY HEAVY RAINS ARE POSSIBLE
OVER PORTIONS OF HONDURAS...GUATEMALA...BELIZE...AND THE YUCATAN
PENINSULA AS THE SYSTEM DRIFTS WESTWARD DURING THE NEXT DAY OR
SO. ALSO...MODERATE CONVECTION IS OVER THE NW CARIBBEAN FROM
19N-22N BETWEEN 79W-84W...WHICH IS BEING ENHANCED BY LOW LEVEL
CONVERGENCE NEAR A SURFACE COLD FRONT THAT EXTENDS FROM THE W
ATLC TO S OF CUBA NEAR 20N78W. TO THE E OF THE AFOREMENTIONED
UPPER HIGH...DEEP LAYER DRY AIR AND STABLE ATMOSPHERIC
CONDITIONS ARE INHIBITING DEEP CONVECTION OVER THE E CARIBBEAN.

ATLANTIC OCEAN...
A DEEP LAYER TROUGH IS OVER THE W AND CENTRAL ATLC...AND IS
SUPPORTING A SURFACE COLD FRONT THAT EXTENDS FROM 32N53W TO
23N61W TO S OF CUBA NEAR 20N78W. ATMOSPHERIC LIFT IN MOIST
SOUTHWESTERLY FLOW ALOFT IS SUPPORTING ISOLATED SHOWERS WITHIN
60 NM EITHER SIDE OF THE COLD FRONT. TO THE W OF THE COLD
FRONT...DEEP CONVECTION IS BEING SUPPRESSED BY SUBSIDENCE IN NW
FLOW ALOFT UPSTREAM OF THE DEEP LAYER TROUGH AXIS. THIS
SUBSIDENCE IS BEING ENHANCED BY A 1022 MB SURFACE HIGH IN THE
W ATLC NEAR 30N74W. FARTHER TO THE E...A SHARP UPPER LEVEL
TROUGH AXIS EXTENDS FROM 28N50W TO 16N49W...WHICH IS INTERACTING
WITH THE TROPICAL WAVE ALONG 50W/51W S OF 22N TO RESULT IN
NUMEROUS MODERATE/ISOLATED STRONG CONVECTION FROM 17N-26N
BETWEEN 46W-51W. FARTHER TO THE E...AN UPPER RIDGE IS N OF 15N
BETWEEN 37W-44W. ALSO...AN UPPER TROUGH IS PRESENT OVER THE E
ATLC N OF 11N E OF 38W...WITH DEEP LAYER DRY AIR EMBEDDED WITHIN
THE UPPER TROUGH PREVENTING DEEP CONVECTION NEAR THIS FEATURE.
ADDITIONALLY...A 1034 MB SURFACE HIGH IS CENTERED NEAR 44N22W...
AND A SURFACE RIDGE EXTENDS FROM THIS SURFACE HIGH TO THE
SW NEAR 17N38W...WITH SUBSIDENCE AND STABLE CONDITIONS AROUND
THESE FEATURES RESULTING IN GENERALLY FAIR WEATHER CONDITIONS
ACROSS MUCH OF THE E ATLC.

$$
COHEN

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