[Tropical] Tropical Weather Discussion

EMWIN Server emwin at nashvilleweather.net
Wed Oct 22 05:50:20 CDT 2008


AXNT20 KNHC 221049
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
805 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 0600 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
1015 UTC.

...TROPICAL WAVES...
A TROPICAL WAVE IS ALONG 23W/24W S OF 15N MOVING W NEAR 10 KT.
DRY AIR EMBEDDED WITHIN THE BASE OF AN UPPER TROUGH IN THE E
ATLC N OF 10N E OF 37W 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 IS FROM 4N-10N BETWEEN 19W-27W...
LIKELY BEING ENHANCED BY LOW LEVEL CONVERGENCE NEAR THE ITCZ
AXIS.

A TROPICAL WAVE IS ALONG 51W/52W S OF 21N 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 29N50W TO 22N49W TO 19N48W. 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 15N-24N BETWEEN
45W-49W. ADDITIONALLY...ISOLATED MODERATE CONVECTION IS WITHIN
240 NM EITHER SIDE OF WAVE AXIS S OF 12N...LIKELY BEING ENHANCED
BY LOW LEVEL CONVERGENCE NEAR THE ITCZ AXIS.

A TROPICAL WAVE IS ALONG 77W 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. NUMEROUS MODERATE/ISOLATED STRONG
CONVECTION IS FROM 11N-16N BETWEEN 77W-82W...WHICH IS BEING
ENHANCED BY UPPER DIFFLUENCE SW OF AN UPPER HIGH IN THE CENTRAL
CARIBBEAN NEAR 17N76W.

...THE ITCZ...
ITCZ AXIS IS CENTERED ALONG 9N13W 9N20W 8N31W 9N48W 10N61W. IN
ADDITION TO CONVECTION ASSOCIATED WITH TROPICAL WAVES...ISOLATED
MODERATE CONVECTION IS WITHIN 150 NM EITHER SIDE OF AXIS BETWEEN
30W-48W. ISOLATED MODERATE CONVECTION IS WITHIN 180 NM N OF AXIS
BETWEEN 58W-61W.

...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 CENTRAL CARIBBEAN NEAR
17N76W. 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
1021 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...SCATTERED SHOWERS...AND ISOLATED THUNDERSTORMS TO
THE FAR SE GULF FROM 23N-25N BETWEEN 80W-85W...WHERE UPPER LEVEL
DIVERGENCE IS STRONGER. ALSO...SURFACE OBSERVATIONS AND
SATELLITE IMAGERY INDICATE THAT A SURFACE TROUGH EXTENDING FROM
26N94W TO 23N94W TO 20N93W 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...ESPECIALLY N OF
23N.

CARIBBEAN SEA...
A SURFACE TROUGH EXTENDS FROM THE NE YUCATAN PENINSULA NEAR
22N87W TO A 1011 MB SURFACE LOW OVER THE GULF OF HONDURAS NEAR
18N88W 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 CENTRAL CARIBBEAN NEAR 17N76W...IS RESULTING IN
SCATTERED MODERATE/ISOLATED STRONG CONVECTION FROM 17N-20N
BETWEEN 84W-89W. THIS INCLUDES PORTIONS OF THE NW CARIBBEAN SEA
AND NEARBY INLAND AREAS OF CENTRAL AMERICA AND SE MEXICO.
SIGNIFICANT DEVELOPMENT OF THIS SYSTEM APPEARS UNLIKELY DUE TO
ITS PROXIMITY TO 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...CLOUDINESS AND ISOLATED SHOWERS FROM
19N-21N BETWEEN 74W-80W ARE BEING ENHANCED BY LOW LEVEL
CONVERGENCE NEAR A SURFACE COLD FRONT THAT EXTENDS FROM THE W
ATLC TO E CUBA NEAR 20N77W. 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 CENTRAL ATLC...AND IS SUPPORTING
A SURFACE COLD FRONT THAT EXTENDS FROM 32N52W TO 23N60W TO E
CUBA NEAR 20N77W. ISOLATED SHOWERS ARE OCCURRING WITHIN 60 NM
EITHER SIDE OF THE COLD FRONT. TO THE W OF THE COLD FRONT...DEEP
CONVECTION IS BEING SUPPRESSED BY SUBSIDENCE IN W AND NW FLOW
ALOFT UPSTREAM OF THE DEEP LAYER TROUGH AXIS. THIS SUBSIDENCE IS
BEING FURTHER ENHANCED BY A 1021 MB SURFACE HIGH IN THE W ATLC
NEAR 30N74W. FARTHER TO THE E...A SHARP UPPER LEVEL TROUGH AXIS
EXTENDS FROM FROM 29N50W TO 22N49W TO 19N48W...WHICH IS
INTERACTING WITH THE TROPICAL WAVE ALONG 51W/52W S OF 21N TO
RESULT IN NUMEROUS MODERATE/ISOLATED STRONG CONVECTION FROM
15N-24N BETWEEN 45W-49W. THE AFOREMENTIONED DEEP LAYER TROUGH IS
BEGINNING TO MERGE WITH THE SHARP TROUGH...YIELDING INCREASED
UPPER LEVEL DIVERGENCE AND AN ENHANCEMENT TO THIS CONVECTION.
FARTHER TO THE E...AN UPPER RIDGE IS N OF 18N BETWEEN 37W-47W.
ALSO...AN UPPER TROUGH IS PRESENT OVER THE E ATLC N OF 10N E OF
37W...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 43N20W...AND A SURFACE
RIDGE EXTENDS FROM THIS SURFACE HIGH TO THE SW NEAR
15N38W...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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