[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 210559
TWDAT

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

...TROPICAL WAVES...
A TROPICAL WAVE IS ALONG 20W/21W S OF 14N MOVING W 10-15 KT.
SATELLITE IMAGERY AND COMPUTER MODEL GUIDANCE DEPICT 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 WITHIN 210 NM E OF WAVE AXIS N OF 12N.

A TROPICAL WAVE IS ALONG 46W S OF 20N 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 22N51W. THIS IS
RESULTING IN THE NORTH-TO-SOUTH ELONGATION OF THE DEEP LAYER
MOISTURE FIELD AROUND THE WAVE AXIS. ISOLATED MODERATE
CONVECTION IS FROM 9N-26N BETWEEN 35W-46W...AND SCATTERED
MODERATE CONVECTION IS FROM 11N-14N BETWEEN 49W-58W.

A LOW AMPLITUDE TROPICAL WAVE IS IN THE CENTRAL CARIBBEAN ALONG
72W 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 16N71W ARE LIMITING DEEP
CONVECTION NEAR WAVE...WITH ISOLATED SHOWERS WITHIN 60 NM EITHER
SIDE OF WAVE AXIS S OF 13N.

...THE ITCZ...
ITCZ AXIS IS CENTERED ALONG 8N12W 8N23W 6N33W 10N49W 9N61W. IN
ADDITION TO CONVECTION ASSOCIATED WITH TROPICAL WAVES...
SCATTERED MODERATE CONVECTION IS FROM 4N-8N BETWEEN 13W-17W.
ISOLATED MODERATE CONVECTION IS WITHIN 150 NM EITHER SIDE OF
AXIS BETWEEN 24W-34W.

...DISCUSSION...

GULF OF MEXICO...
MUCH OF THE ENERGY WITH THE UPPER TROUGH PREVIOUSLY OVER THE
GULF IS NOW OVER THE W ATLC...WITH A SECONDARY UPPER TROUGH
TRAILING SOUTHWESTWARD FROM THE W ATLC ACROSS THE SE GULF INTO
THE BAY OF CAMPECHE. TO THE NW OF THESE UPPER TROUGHS...A BROAD
UPPER RIDGE IS PRESENT OVER THE SE CONUS. STABLE ATMOSPHERIC
CONDITIONS AND WIDESPREAD SUBSIDENCE ARE RESULTING IN FAIR
WEATHER CONDITIONS OVER MUCH OF THE GULF REGION...ESPECIALLY
WITH A SURFACE RIDGE COVERING MUCH OF THE CENTRAL AND W GULF.
INCREASED CLOUDINESS CAN BE FOUND OVER THE SE GULF...WHERE
GREATER DEEP MOISTURE PERSISTS IN THE VICINITY OF A SURFACE COLD
FRONT DRAPED ACROSS THE NW CARIBBEAN AND W ATLC.

CARIBBEAN SEA...
A 1010 MB SURFACE LOW REMAINS IS OVER THE GULF OF HONDURAS NEAR
16N87W. 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 FROM 15N-19N
BETWEEN 83W-88W...INCLUDING 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 COLD FRONT EXTENDS FROM E CUBA NEAR 21N77W
TO 21N83W TO THE N YUCATAN PENINSULA NEAR 21N87W. 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. FARTHER TO THE E...CONVECTIVE
COVERAGE IS LIMITED AS A RESULT OF SUBSIDENCE AND DRY AIR AROUND
AN UPPER HIGH NEAR 16N71W. HOWEVER...ISOLATED MODERATE
CONVECTION IS OCCURRING ACROSS THE SE CARIBBEAN IN THE VICINITY
OF THE TROPICAL WAVE ALONG 72W. ALSO...SCATTERED
MODERATE/ISOLATED STRONG CONVECTION OVER N VENEZUELA IS
IMPACTING THE NEARBY S CARIBBEAN WATERS. THIS CONVECTION IS
BEING ENHANCED BY GREATER INSTABILITY OVER HIGHER TERRAIN.

ATLANTIC OCEAN...
A DEEP LAYER TROUGH IS OVER THE W ATLC...AND IS SUPPORTING A
SURFACE COLD FRONT THAT EXTENDS FROM 32N60W TO 25N67W TO E CUBA
NEAR 21N77W. ATMOSPHERIC LIFT IN MOIST SOUTHWESTERLY FLOW ALOFT
IS SUPPORTING ISOLATED SHOWERS WITHIN 120 NM EITHER SIDE OF THE
COLD FRONT. TO THE NW...DEEP CONVECTION IS BEING SUPPRESSED BY
SUBSIDENCE IN NW FLOW ALOFT UPSTREAM OF THE UPPER TROUGH AXIS.
FARTHER TO THE E...A COMPACT UPPER LOW IS CENTERED NEAR
22N51W...AND AN UPPER RIDGE AXIS EXTENDS FROM 32N43W TO 13N39W.
DEEP LAYER SOUTHERLY FLOW BETWEEN THESE FEATURES IS DRAWING DEEP
LAYER MOISTURE NORTHWARD FROM THE TROPICAL WAVE ALONG 46W...
RESULTING IN ISOLATED MODERATE CONVECTION FROM 9N-26N BETWEEN
35W-46W...AND SCATTERED MODERATE CONVECTION FROM 11N-14N BETWEEN
49W-58W. FARTHER TO THE E...A 1026 MB SURFACE HIGH IS CENTERED
NEAR 33N38W...AND A SURFACE RIDGE EXTENDS FROM THIS HIGH TO THE
S NEAR 16N31W...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
19N AND E OF 23W...WITH DEEP LAYER DRY AIR EMBEDDED WITHIN THE
TROUGH PREVENTING DEEP CONVECTION NEAR THIS FEATURE.

$$
COHEN

WWWW
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