[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 021147
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
705 AM EST SUN NOV 02 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
1115 UTC.

...THE ITCZ...
ITCZ AXIS IS ANALYZED ALONG 11N15W 7N25W 5N37W 6N50W 7N59W.
SCATTERED MODERATE CONVECTION IS WITHIN 150 NM EITHER SIDE OF
ITCZ AXIS BETWEEN 15W-33W...WHICH IS BEING ENHANCED BY UPPER
LEVEL DIVERGENCE. ISOLATED MODERATE CONVECTION IS FROM 2N-4N
BETWEEN 22W-30W...WHICH IS BEING ENHANCED BY UPPER LEVEL
DIVERGENCE.

...DISCUSSION...

GULF OF MEXICO...
AN UPPER LEVEL LOW IS OVER THE W FLORIDA PANHANDLE NEAR
31N87W...WITH INSTABILITY AND UPPER LEVEL MOISTURE NEAR THIS LOW
RESULTING IN ISOLATED SHOWERS AND THUNDERSTORMS N OF 27N E OF
87W. THIS LOW IS EMBEDDED WITHIN A BROAD UPPER LEVEL TROUGH THAT
COVERS MUCH OF THE GULF...WITH DEEP LAYER DRY AIR ROTATING
CYCLONICALLY AROUND THE BASE OF THIS TROUGH ACROSS THE S AND W
GULF...WHERE FAIR WEATHER CONDITIONS ARE PRESENT. COMPUTER MODEL
GUIDANCE INDICATES THAT THE UPPER LOW IS EXPECTED TO MOVE
EASTWARD ALONG THE GULF COAST OVER THE NEXT DAY...REACHING THE N
FLORIDA PENINSULA WITHIN 24 HOURS. MEANWHILE...A SURFACE RIDGE
OF HIGH PRESSURE IS AFFECTING MUCH OF THE GULF REGION. THIS
SURFACE RIDGE IS ANCHORED BY A 1027 MB SURFACE HIGH OVER THE SE
CONUS. ADDITIONALLY...STRONG N TO NE SURFACE WINDS ARE BLOWING
THROUGH THE ISTHMUS OF TEHUANTEPEC RESULTING IN GALE FORCE WINDS
IN THE E PACIFIC REGION.

CARIBBEAN SEA...
AN UPPER RIDGE AXIS EXTENDS FROM THE NE CARIBBEAN NEAR 16N62W TO
NW VENEZUELA NEAR 11N69W...WITH ANTICYCLONIC FLOW AROUND THE
RIDGE COVERING MUCH OF THE CARIBBEAN. DEEP MOISTURE AND UPPER
LEVEL DIVERGENCE W OF THE UPPER RIDGE ARE SUPPORTING SCATTERED
MODERATE/ISOLATED STRONG CONVECTION FROM 11N-19N BETWEEN
75W-83W. THIS CONVECTION IS BEING ENHANCED BY LOW LEVEL
CONVERGENCE IN THE VICINITY OF A SURFACE TROUGH OVER THE SW
CARIBBEAN THAT EXTENDS FROM 16N82W TO A 1010 MB SURFACE LOW AT
11N79W TO 9N77W. THIS SURFACE LOW HAS RECENTLY DEVELOPED BASED
ON LOW LEVEL CYCLONIC CIRCULATION EVIDENT IN SATELLITE IMAGERY
AND A RECENT QUIKSCAT PASS. SURFACE PRESSURE FALLS HAVE BEEN
NOTED IN THE VICINITY OF THIS LOW...ALONG WITH CYCLONIC
CURVATURE IN THE WIND FIELD FROM SURFACE OBSERVATIONS. DEEP
LAYER DRY AIR E OF THE UPPER RIDGE IS RESULTING IN MAINLY FAIR
WEATHER ACROSS THE E CARIBBEAN CONDITIONS. ALSO...DEEP LAYER DRY
AIR IN THE BASE OF THE UPPER TROUGH OVER THE GULF OF MEXICO IS
MOVING INTO THE FAR NW CARIBBEAN.

ATLANTIC OCEAN...
STRONG WEST-SOUTHWESTERLY FLOW ALOFT COVERS MUCH OF THE W ATLC.
UPPER LEVEL DIVERGENCE SW OF A MAXIMUM IN MID/UPPER-LEVEL WIND
SPEED OVER THE W ATLC IS INDUCING ATMOSPHERIC ASCENT AND SURFACE
PRESSURE FALLS OVER A LARGE PORTION OF THE W ATLC. AS A
RESULT...A PORTION OF THE LOW LEVEL BOUNDARY THAT WAS PREVIOUSLY
STATIONARY OVER THE W ATLC IS NOW MOVING N AS A WARM FRONT
EXTENDING FROM E CUBA NEAR 21N76W TO 25N68W TO 27N61W. TO THE
NE...THIS BOUNDARY REMAINS A STATIONARY FRONT EXTENDING FROM
27N61W TO 29N56W TO 32N51W. DEEP MOISTURE MOVING NORTHEASTWARD
FROM THE W CARIBBEAN IS RESULTING IN SCATTERED SHOWERS WITHIN
120 NM EITHER SIDE OF THE STATIONARY FRONT AND WARM FRONT. OVER
THE COUPLE DAYS...COMPUTER MODEL GUIDANCE INDICATES THAT
ATMOSPHERIC LIFT OVER THESE BOUNDARIES WILL INCREASE AS THE
UPPER LOW OVER THE W FLORIDA PANHANDLE NEAR 31N87W APPROACHES
THE W ATLC. ACCORDINGLY...THE GUIDANCE INDICATES THAT THE WARM
FRONT WILL BECOME THE DOMINANT BOUNDARY OVER THE NEXT COUPLE
DAYS AS IT MOVES NORTHWARD OVER THE W ATLC...AIDED BY THE
DEVELOPMENT OF A SURFACE LOW ALONG THE FRONT 150 NM TO 200 NM E
OF THE FLORIDA COAST. THIS SURFACE LOW IS ALSO FORECAST TO BE
ACCOMPANIED BY A NORTH-TO-SOUTH SURFACE TROUGH...WITH INCREASED
NORTHERLY WINDS TO THE W OF THE SURFACE TROUGH. FARTHER TO THE
E...AN UPPER LEVEL TROUGH IS PRESENT WITH AN AXIS THAT EXTENDS
FROM AN UPPER LOW NEAR 30N35W TO 21N44W TO 9N50W. NEAR THIS
UPPER LEVEL TROUGH...SATELLITE IMAGERY INDICATES THAT TWO
SURFACE TROUGHS ARE PRESENT. ONE SURFACE TROUGH EXTENDS FROM
23N58W TO 18N57W TO 12N55W. THE OTHER SURFACE TROUGH EXTENDS
FROM 15N46W TO A 1011 MB SURFACE LOW AT 12N46W TO 9N46W...WITH
ISOLATED MODERATE CONVECTION FROM 11N-14N BETWEEN 42W-45W.
FARTHER TO THE E...A DEEP LAYER TROUGH IS N OF 26N E OF 27W...
WHICH IS SUPPORTING A SURFACE COLD FRONT THAT EXTENDS FROM THE W
COAST OF AFRICA NEAR 23N16W TO 26N27W TO 31N34W. ISOLATED
SHOWERS ARE OCCURRING WITHIN 60 NM EITHER SIDE OF THE COLD FRONT
W OF 19W. OVER THE TROPICAL ATLC...AN EAST-TO-WEST UPPER RIDGE
IS ALONG 14N BETWEEN THE AFRICAN COAST AND 36W. UPPER LEVEL
DIVERGENCE NEAR THIS RIDGE IS ENHANCING ISOLATED MODERATE
CONVECTION FROM 12N-16N BETWEEN 26W-32W.

$$
COHEN



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