[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 280925 CCA
TWDAT

TROPICAL WEATHER DISCUSSION...CORRECTED
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
105 AM EST FRI NOV 28 2008

...CORRECTED TO INCLUDE MENTION OF SURFACE TROUGH IN TROPICAL
NORTH ATLANTIC...

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
0445 UTC.

...THE ITCZ...
THE ITCZ AXIS IS ANALYZED ALONG 8N12W 5N22W 6N33W 8N44W 6N58W. A
SURFACE TROUGH...EXTENDING FROM 11N48W TO 9N48W TO 7N49W...IS
EMBEDDED WITHIN THE ITCZ. SCATTERED MODERATE CONVECTION IS
OCCURRING WITHIN 180 NM EITHER SIDE OF THIS SURFACE TROUGH N OF
10N. ELSEWHERE...SCATTERED MODERATE CONVECTION IS FROM 4N-8N
BETWEEN 19W-27W. SCATTERED MODERATE/ISOLATED STRONG CONVECTION
IS FROM 4N-9N BETWEEN 28W-39W.

...DISCUSSION...

GULF OF MEXICO...
AN UPPER LEVEL RIDGE COVERS THE GULF REGION...WITH STRONG UPPER
LEVEL WINDS ACROSS THE NORTHERN PERIPHERY OF THE RIDGE OVER THE
SE CONUS AND N GULF. UPPER LEVEL MOISTURE CONTINUES STREAMING
ACROSS THE N GULF...WHILE DEEP LAYER DRY AIR IS PRESENT OVER THE
S GULF. DEEP LAYER SUBSIDENCE AND STABLE ATMOSPHERIC CONDITIONS
ARE RESULTING IN FAIR WEATHER CONDITIONS ACROSS MUCH OF THE GULF
REGION. THIS DEEP LAYER SUBSIDENCE IS BEING ENHANCED ACROSS E
PORTIONS OF THE GULF REGION...WHERE UPPER LEVEL CONVERGENCE IN
THE NW QUADRANT OF A 120-130 KT UPPER LEVEL JET MAXIMUM ENTERING
THE W ATLC IS SUPPORTING A 1021 MB SURFACE HIGH OVER THE NE GULF
NEAR 28N83W. FARTHER NW...A DEEP TROUGH OVER THE GREAT BASIN OF
THE W CONUS IS SUPPORTING A SURFACE FRONT THAT EXTENDS FROM THE
UPPER MIDWEST TO THE SOUTHERN PLAINS AND EXTENDS ACROSS THE
CENTRAL AND NORTHERN ROCKIES OF THE CONUS. AS THE DEEP TROUGH
MOVES EASTWARD...THE SURFACE FRONT WILL MOVE SOUTHWARD ACROSS
THE N GULF THIS WEEKEND AS A COLD FRONT...WITH SOUTHERLY FLOW
INCREASING AHEAD OF THE FRONT. THE FRONT IS ALSO FORECAST BE
ACCOMPANIED BY SCATTERED SHOWERS AND THUNDERSTORMS. IN THE WAKE
OF THE COLD FRONT...INCREASED NORTHERLY AND NORTHWESTERLY
SURFACE WINDS ARE EXPECTED...ALONG WITH RELATIVELY COOLER AND
DRIER CONDITIONS.

CARIBBEAN SEA...
IN THE SW CARIBBEAN...A 1011 MB SURFACE LOW IS CENTERED N OF
PANAMA NEAR 10N78W. LOW LEVEL CONVERGENCE NEAR THIS SURFACE LOW
IS SUPPORTING SCATTERED SHOWERS AND ISOLATED THUNDERSTORMS S OF
11N W OF 75W...INCLUDING PANAMA AND S COSTA RICA. THIS ACTIVITY
IS BEING ENHANCED BY UPPER LEVEL DIFFLUENCE IN THE VICINITY OF
AN UPPER RIDGE PRESENT OVER THE W CARIBBEAN...WITH THE AXIS OF
THIS UPPER RIDGE EXTENDING FROM N COLOMBIA NEAR 11N74W TO 13N83W
TO SE MEXICO NEAR 18N92W INTO THE W GULF REGION. OVER THE N
CARIBBEAN...DEEP LAYER SUBSIDENCE IS IN PLACE RESULTING IN FAIR
WEATHER CONDITIONS...WHERE STRONG WESTERLY CONFLUENT FLOW ALOFT
IS PRESENT. RELATIVELY DRY CONDITIONS PREVAIL ACROSS PORTIONS OF
THE N CARIBBEAN...WITH DEWPOINTS IN THE UPPER 50S AND LOWER 60S
ACROSS CUBA. THIS DRIER AIR IS A RESULT OF N TO NE SURFACE WINDS
AROUND THE 1021 MB SURFACE HIGH IN THE NE GULF NEAR 28N83W
ADVECTING THE STRONGLY MODIFIED CONTINENTAL POLAR AIRMASS ACROSS
THE N CARIBBEAN REGION. THIS AIRMASS IS IN THE WAKE OF A COLD
FRONT THAT IS E OF THE BAHAMAS. OUTSIDE OF SHOWER AND
THUNDERSTORM ACTIVITY...FRESH TRADEWINDS PREVAIL ACROSS THE
CARIBBEAN.

ATLANTIC OCEAN...
STRONG WESTERLY FLOW ALOFT COVERS MUCH OF THE W AND CENTRAL
ATLC. A SURFACE RIDGE EXTENDS INTO THE W ATLC FROM A 1021 MB
SURFACE HIGH OVER THE NE GULF NEAR 28N83W...WITH SUBSIDENCE AND
FAIR WEATHER IN THE VICINITY OF THIS RIDGE. TO THE E OF THE
BAHAMAS...A SURFACE COLD FRONT EXTENDS FROM 24N69W TO 28N62W TO
32N57W TO N OF THE DISCUSSION AREA. LOW LEVEL CONVERGENCE IS
RESULTING IN SCATTERED SHOWERS WITHIN 90 NM EITHER SIDE OF THIS
COLD FRONT. FARTHER TO THE E...UPPER LEVEL DIVERGENCE IN THE NE
QUADRANT OF A 100-110 KT UPPER LEVEL JET MAXIMUM IS SUPPORTING A
1003 MB SURFACE LOW IN THE CENTRAL ATLC NEAR 30N42W...WITH AN
ASSOCIATED SURFACE TROUGH EXTENDING FROM 31N43W TO 33N35W TO
28N31W TO 23N32W. LOW LEVEL CONVERGENCE NEAR THESE FEATURES IS
SUPPORTING SCATTERED SHOWERS AND THUNDERSTORMS N OF 19N BETWEEN
26W-35W...WITH SCATTERED SHOWERS N OF 28N BETWEEN 37W-42W.
ALSO...A NEW 1007 MB SURFACE LOW HAS FORMED NEAR 32N50W...AND AN
ATTENDANT SURFACE TROUGH EXTENDS FROM THIS SURFACE LOW TO 30N49W
TO 28N46W...WITH LOW LEVEL CONVERGENCE SUPPORTING SCATTERED
SHOWERS N OF 29N BETWEEN 46W-50W. AN UPPER TROUGH AXIS IS TILTED
FROM 27N30W TO 32N36W TO AN UPPER LOW NEAR 36N46W...WITH UPPER
DIFFLUENCE E OF THE UPPER TROUGH AXIS ENHANCING THE SHOWER AND
THUNDERSTORM ACTIVITY N OF 26N BETWEEN 26W-35W. ACROSS THE E
ATLC...A SURFACE RIDGE IS N OF 17N E OF 28W...WHERE SUBSIDENCE
IS RESULTING IN FAIR WEATHER CONDITIONS. OVER THE TROPICAL
ATLC...AN UPPER RIDGE IS PRESENT S OF 10N W OF 21W...WITH
ASSOCIATED UPPER LEVEL DIFFLUENCE ENHANCING THE CONVECTION IN
THE VICINITY OF THE ITCZ. ADDITIONALLY...A SURFACE TROUGH IN THE
TROPICAL NORTH ATLC EXTENDS FROM 16N45W TO 11N51W TO 8N59W. LOW
LEVEL CONFLUENCE IN THE VICINITY OF THIS TROUGH IS RESULTING IN
SCATTERED SHOWERS AND THUNDERSTORMS WITHIN 120 NM EITHER SIDE OF
THIS FEATURE. ALSO...A SURFACE TROUGH...EXTENDING FROM 11N48W TO
9N48W TO 7N49W...IS EMBEDDED WITHIN THE ITCZ...WITH SCATTERED
MODERATE CONVECTION OCCURRING WITHIN 180 NM EITHER SIDE OF THIS
SURFACE TROUGH N OF 10N.

$$
COHEN




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