[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 211056
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
805 AM EDT TUE OCT 21 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 21W/22W S OF 14N MOVING W 10-15 KT.
SATELLITE IMAGERY INDICATES THAT WAVE IS EMBEDDED WITHIN A BROAD
INVERTED-V CLOUD PATTERN...AND CIMSS WAVETRAK PRODUCT DEPICTS
LOW LEVEL COUNTERCLOCKWISE CIRCULATION PRESENT ALONG WAVE AXIS.
WESTWARD SURGE OF DEEP LAYER MOISTURE ALSO COINCIDES WITH WAVE
AXIS BASED ON TOTAL PRECIPITABLE WATER PRODUCT FROM CIMSS.
SCATTERED MODERATE CONVECTION IS FROM 5N-14N BETWEEN 16W-20W...
AND ISOLATED MODERATE CONVECTION IS FROM 8N-11N BETWEEN 22W-24W.

A TROPICAL WAVE IS ALONG 47W S OF 19N MOVING W NEAR 10 KT.
SATELLITE IMAGERY DEPICTS WELL-DEFINED INVERTED-V SIGNATURE IN
CLOUD COVERAGE ALONG WAVE AXIS. DEEP LAYER MOISTURE IN THE
VICINITY OF THE WAVE AXIS CONTINUES TO BE DRAWN NORTHWARD AROUND
AN UPPER LOW CENTERED NW OF THE WAVE NEAR 22N52W. THIS IS
RESULTING IN THE NORTH-TO-SOUTH ELONGATION OF THE DEEP LAYER
MOISTURE FIELD AROUND THE WAVE AXIS. ISOLATED MODERATE
CONVECTION IS FROM 12N-24N BETWEEN 36W-49W.

A LOW AMPLITUDE TROPICAL WAVE IS IN THE CENTRAL CARIBBEAN ALONG
73W S OF 16N MOVING W 10-15 KT. CIMSS WAVETRAK PRODUCT INDICATES
LOW LEVEL COUNTERCLOCKWISE CIRCULATION MAXIMIZED ALONG WAVE
AXIS. HOWEVER...DEEP LAYER DRY AIR AND SUBSIDENCE AROUND AN
UPPER HIGH IN THE E CARIBBEAN NEAR 15N70W ARE LIMITING DEEP
CONVECTION NEAR WAVE...WITH ISOLATED MODERATE CONVECTION WITHIN
150 NM EITHER SIDE OF WAVE AXIS S OF 12N.

...THE ITCZ...
ITCZ AXIS IS CENTERED ALONG 8N13W 6N24W 6N35W 9N49W 9N61W. IN
ADDITION TO CONVECTION ASSOCIATED WITH THE TROPICAL WAVES...
ISOLATED MODERATE CONVECTION IS WITHIN 150 NM EITHER SIDE OF
AXIS BETWEEN 25W-36W. ISOLATED MODERATE CONVECTION IS ALSO
WITHIN 210 NM N OF AXIS BETWEEN 53W-61W.

...DISCUSSION...

GULF OF MEXICO...
MUCH OF THE ENERGY WITH THE UPPER TROUGH PREVIOUSLY OVER THE
GULF IS NOW OVER THE W AND CENTRAL ATLC...WITH GENERALLY LIGHT
UPPER LEVEL WESTERLY FLOW COVERING THE GULF. A BROAD UPPER RIDGE
IS SLOWLY MOVING EASTWARD OVER THE SE CONUS AND N GULF. AS A
RESULT...STABLE ATMOSPHERIC CONDITIONS AND WIDESPREAD SUBSIDENCE
ARE BRINGING FAIR WEATHER CONDITIONS TO MUCH OF THE GULF
REGION...ESPECIALLY AS A SURFACE RIDGE LINGERS OVER THE N GULF.
INCREASED CLOUDINESS CAN BE FOUND OVER THE FAR SE GULF...WHERE
GREATER DEEP MOISTURE PERSISTS IN THE VICINITY OF A SURFACE COLD
FRONT AND STATIONARY FRONT DRAPED ACROSS THE W ATLC AND NW
CARIBBEAN...RESPECTIVELY.

CARIBBEAN SEA...
A 1011 MB SURFACE LOW IS OVER THE GULF OF HONDURAS NEAR 16N88W.
BROAD LOW LEVEL CONVERGENCE AROUND THIS LOW...COMBINED WITH
UPPER LEVEL DIVERGENCE TO THE SE OF AN UPPER LEVEL WIND SPEED
MAXIMUM IN MOIST SOUTHWESTERLY FLOW ALOFT...IS SUPPORTING
SCATTERED MODERATE/ISOLATED STRONG CONVECTION PARTICULARLY NE OF
THE SURFACE LOW FROM 16N-20N BETWEEN 83W-89W. THIS INCLUDES
PORTIONS OF THE NW CARIBBEAN SEA AND ADJACENT INLAND AREAS OF SE
MEXICO AND CENTRAL AMERICA. SIGNIFICANT DEVELOPMENT OF THIS
SYSTEM IS NOT EXPECTED DUE TO ITS PROXIMITY TO LAND.
HOWEVER...LOCALLY HEAVY RAINS ARE POSSIBLE OVER PORTIONS OF
HONDURAS...GUATEMALA...BELIZE...AND THE YUCATAN PENINSULA DURING
THE NEXT COUPLE OF DAYS. FARTHER TO THE NE...A WEAKENING
STATIONARY FRONT EXTENDS FROM E CUBA NEAR 21N77W TO 21N82W TO
THE N YUCATAN PENINSULA NEAR 20N87W. ATMOSPHERIC LIFT IN MOIST
SOUTHWESTERLY FLOW ALOFT NEAR THIS FRONT IS SUPPORTING SCATTERED
MODERATE CONVECTION WITHIN 60 NM EITHER SIDE OF THE FRONT
BETWEEN 76W-82W...AND COULD BE ENHANCING THE CONVECTION
ASSOCIATED WITH THE AFOREMENTIONED SURFACE LOW. FARTHER TO THE
E...CONVECTIVE COVERAGE IS LIMITED AS A RESULT OF SUBSIDENCE AND
DRY AIR AROUND AN UPPER HIGH NEAR 15N70W. HOWEVER...SCATTERED
MODERATE/ISOLATED STRONG CONVECTION IS OVER THE SW CARIBBEAN S
OF 14N W OF 76W...WHERE UPPER DIFFLUENCE EXISTS SW OF THE UPPER
HIGH.

ATLANTIC OCEAN...
A DEEP LAYER TROUGH IS OVER THE W AND CENTRAL ATLC...AND IS
SUPPORTING A SURFACE COLD FRONT THAT EXTENDS FROM 32N57W TO
26N64W TO E CUBA NEAR 21N77W. ATMOSPHERIC LIFT IN MOIST
SOUTHWESTERLY FLOW ALOFT IS SUPPORTING ISOLATED SHOWERS WITHIN
150 NM EITHER SIDE OF THE COLD FRONT...PARTICULARLY N OF 25N
WHERE STRONGER UPPER LEVEL DIVERGENCE IS PRESENT. TO THE NW OF
THE COLD FRONT...DEEP CONVECTION IS BEING SUPPRESSED BY
SUBSIDENCE IN NW FLOW ALOFT UPSTREAM OF THE DEEP LAYER TROUGH
AXIS. FARTHER TO THE E...A COMPACT UPPER LOW IS CENTERED NEAR
22N52W...AND AN UPPER RIDGE AXIS EXTENDS FROM 32N43W TO 13N37W.
DEEP LAYER SOUTHERLY FLOW BETWEEN THESE FEATURES IS DRAWING DEEP
LAYER MOISTURE NORTHWARD FROM THE TROPICAL WAVE ALONG 47W...
RESULTING IN ISOLATED MODERATE CONVECTION FROM 12N-24N BETWEEN
36W-49W. FARTHER TO THE E...A 1026 MB SURFACE HIGH IS CENTERED
NEAR 33N37W...AND A SURFACE RIDGE EXTENDS FROM THIS HIGH TO THE
S NEAR 15N31W...WITH SUBSIDENCE AND STABLE CONDITIONS AROUND THE
SURFACE HIGH AND SURFACE RIDGE PREDOMINATING OVER MUCH OF THE E
ATLC. ALSO...AN UPPER TROUGH IS PRESENT OVER THE NE ATLC N OF
17N AND E OF 22W...WITH DEEP LAYER DRY AIR EMBEDDED WITHIN THE
TROUGH PREVENTING DEEP CONVECTION NEAR THIS FEATURE.

$$
COHEN



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