[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 290512
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
105 AM EST SAT NOV 29 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
0445 UTC.

...THE ITCZ...
THE ITCZ AXIS IS ANALYZED ALONG 8N11W 5N22W 5N33W 8N45W 8N60W.
SCATTERED MODERATE CONVECTION IS FROM 3N-5N BETWEEN 10W-13W.
SCATTERED MODERATE CONVECTION IS ALSO WITHIN 90 NM S OF THE ITCZ
AXIS BETWEEN 16W-20W. SCATTERED MODERATE/ISOLATED STRONG
CONVECTION IS FROM 2N-7N BETWEEN 21W-33W.

...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 AND W GULF...WHILE DEEP LAYER DRY AIR IS PRESENT
OVER THE SE GULF. DEEP LAYER SUBSIDENCE AND STABLE ATMOSPHERIC
CONDITIONS ARE RESULTING IN FAIR WEATHER ACROSS MUCH OF THE GULF
REGION. THIS DEEP LAYER SUBSIDENCE IS BEING ENHANCED IN THE
VICINITY OF A SURFACE RIDGE ACROSS THE E GULF THAT ORIGINATES
FROM THE 1018 MB SURFACE HIGH IN THE W ATLC NEAR 27N72W. FARTHER
N...A DEEP TROUGH OVER THE PLAINS OF THE CONUS IS SUPPORTING A
SURFACE FRONT THAT IS DRAPED ACROSS THE SE CONUS INTO SE TEXAS
AND FARTHER S INTO NE MEXICO. TWO SURFACE LOWS ARE PRESENT ALONG
THE FRONT...ONE OVER E TEXAS NEAR 31N94W...AND ANOTHER NEAR
28N98W. UPPER LEVEL DIVERGENCE IN THE SW QUADRANT OF A
100-110 KT UPPER LEVEL JET MAXIMUM OVER THE SE CONUS IS
INTERACTING WITH LOW LEVEL CONVERGENCE NEAR THE SURFACE LOWS AND
FRONT TO RESULT IN SCATTERED SHOWERS AND THUNDERSTORMS OVER
PORTIONS OF SE TEXAS. AS SOUTHERLY RETURN FLOW AROUND THE
1018 MB SURFACE HIGH IN THE W ATLC DRAWS GREATER MOISTURE AND
INSTABILITY OVER THE GULF REGION...THE THREAT FOR STRONG
THUNDERSTORMS WILL EXIST ACROSS THE GULF REGION ALONG AND AHEAD
OF THE FRONT AS IT MOVES SOUTHWARD AS A SURFACE COLD FRONT THIS
WEEKEND...ESPECIALLY GIVEN THE PRESENCE OF STRONG VERTICAL
SHEAR. IN THE WAKE OF THE COLD FRONT...RELATIVELY COOLER AND
DRIER CONDITIONS ARE EXPECTED.

CARIBBEAN SEA...
IN THE SW CARIBBEAN...A 1010 MB SURFACE LOW IS CENTERED N OF
PANAMA NEAR 9N79W. LOW LEVEL CONVERGENCE NEAR THIS SURFACE LOW
IS SUPPORTING SCATTERED SHOWERS AND ISOLATED THUNDERSTORMS S OF
10N W OF 75W...INCLUDING PORTIONS OF PANAMA. 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 8N76W TO 17N87W TO
SE MEXICO NEAR 18N91W TO THE W GULF. OVER THE N CARIBBEAN...
DEEP LAYER SUBSIDENCE IS IN PLACE RESULTING IN FAIR
WEATHER...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 E AND NE SURFACE WINDS
ADVECTING A STRONGLY MODIFIED CONTINENTAL POLAR AIRMASS ACROSS
THE N CARIBBEAN REGION. THIS AIRMASS ORIGINATES FROM THE 1018 MB
SURFACE HIGH OVER THE W ATLC NEAR 27N72W.

ATLANTIC OCEAN...
STRONG WESTERLY FLOW ALOFT COVERS MUCH OF THE W AND CENTRAL
ATLC. A SURFACE RIDGE EXTENDS ACROSS THE W ATLC FROM A 1018 MB
SURFACE HIGH NEAR 27N72W...WITH SUBSIDENCE AND FAIR WEATHER IN
THE VICINITY OF THIS RIDGE. TO THE E...A SURFACE TROUGH EXTENDS
FROM 31N53W TO 28N55W TO 26N59W...WITH LOW LEVEL CONVERGENCE
RESULTING IN SCATTERED SHOWERS WITHIN 60 NM EITHER SIDE OF THIS
FEATURE. THIS ACTIVITY IS BEING ENHANCED BY ATMOSPHERIC LIFT IN
MOIST SOUTHWESTERLY FLOW ALOFT E OF AN UPPER TROUGH AXIS
EXTENDING FROM 25N58W TO 32N58W TO N OF THE DISCUSSION AREA.
FARTHER TO THE E...A SURFACE TROUGH EXTENDS FROM 29N31W TO
32N33W TO NW OF THE DISCUSSION AREA...WITH LOW LEVEL CONFLUENCE
SUPPORTING SCATTERED SHOWERS AND THUNDERSTORMS WITHIN 120 NM
EITHER SIDE OF THIS SURFACE TROUGH. ALSO...STRONG UPPER LEVEL
DIVERGENCE IN THE NE QUADRANT OF A 100-110 KT UPPER LEVEL JET
MAXIMUM OVER THE E ATLC IS SUPPORTING SCATTERED SHOWERS AND
THUNDERSTORMS FROM 25N-31N BETWEEN 21W-28W. FARTHER TO THE S...
A SURFACE TROUGH EXTENDS FROM 23N33W TO 16N46W TO 10N59W...WITH
LOW LEVEL CONFLUENCE SUPPORTING SCATTERED SHOWERS AND
THUNDERSTORMS WITHIN 90 NM EITHER SIDE OF THIS SURFACE TROUGH.
ADDITIONALLY...AN UPPER RIDGE IS PRESENT S OF 9N W OF 18W...
WITH ASSOCIATED UPPER LEVEL DIFFLUENCE ENHANCING THE CONVECTION
IN THE VICINITY OF THE ITCZ W OF 18W. BY LATE THIS WEEKEND...A
SURFACE COLD FRONT WILL BEGIN TO MOVE ACROSS PORTIONS OF THE W
ATLC...WITH SCATTERED SHOWERS AND THUNDERSTORMS ACCOMPANYING THE
FRONT. THE THREAT FOR STRONG THUNDERSTORMS WILL EXIST ACROSS THE
W ATLC ALONG AND AHEAD OF THE FRONT AS IT MOVES SOUTHEASTWARD
LATE THIS WEEKEND AND MONDAY...ESPECIALLY GIVEN THE PRESENCE OF
STRONG VERTICAL SHEAR. ADDITIONALLY...STRONG WINDS ARE EXPECTED
WITH THE FRONT...WITH GALE CONDITIONS EXPECTED LATE SUNDAY INTO
MONDAY FOR THE SW N ATLC FROM 29N-31N BETWEEN 71W-77W. IN THE
WAKE OF THE COLD FRONT...RELATIVELY COOLER AND DRIER CONDITIONS
ARE EXPECTED.

$$
COHEN




This weather bulletin was brought to you by:
www.nashvilleweather.net