[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 200514
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
105 AM EST SAT DEC 20 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...
ITCZ IS CENTERED ALONG 9N14W 7N21W 6N34W 4N42W TO THE EQUATOR AT
49W. SCATTERED MODERATE CONVECTION IS FROM 4N-8N BETWEEN
15W-25W. NUMEROUS MODERATE/ISOLATED STRONG CONVECTION IS FROM
1N-10N BETWEEN 27W-38W.

...DISCUSSION...

GULF OF MEXICO...
A 1023 MB SURFACE HIGH IS OVER THE W ATLC NEAR 28N73W...WITH
SURFACE ANTICYCLONIC FLOW OF 10 TO 20 KT AROUND THIS HIGH ACROSS
MUCH OF THE GULF REGION. SUBSIDENCE ASSOCIATED WITH THIS HIGH IS
RESULTING IN ATMOSPHERIC STABILITY AND FAIR WEATHER CONDITIONS
ACROSS MUCH OF THE GULF REGION. THIS STABILITY IS BEING ENHANCED
IN THE VICINITY OF A BROAD UPPER LEVEL RIDGE EXTENDING WESTWARD
ACROSS THE GULF REGION FROM AN UPPER HIGH CENTERED N OF CUBA
NEAR 24N78W. THIS UPPER RIDGE IS ASSOCIATED WITH RELATIVELY
LIGHT AND BROAD ANTICYCLONIC FLOW ALOFT...AND DEEP LAYER DRY
AIR...ACROSS MUCH OF THE GULF REGION. FARTHER TO THE N...A DEEP
LONGWAVE TROUGH AND ASSOCIATED STRONG UPPER LEVEL JET STREAM
OVER THE CENTRAL CONUS IS SUPPORTING A SURFACE FRONT EXTENDING
FROM THE MID-ATLANTIC STATES ACROSS THE SOUTHERN PLAINS AND INTO
THE SOUTHERN ROCKY MOUNTAIN REGION OF THE CONUS. THIS TROUGH IS
FORECAST TO MOVE EAST-SOUTHEASTWARD...WITH THE FRONT MOVING
SOUTHWARD ACROSS THE GULF ON SUNDAY AND MONDAY AS A COLD FRONT.
INCREASED NE TO E SURFACE WINDS ARE FORECAST IN THE WAKE OF THE
FRONT...WITH GALE FORCE WINDS EXPECTED SUNDAY AFTERNOON AND
EVENING OVER THE NW GULF N OF 25N W OF 95W.

CARIBBEAN SEA...
CONFLUENCE IN WESTERLY FLOW ALOFT IS GENERATING SUBSIDENCE AND
ATMOSPHERIC STABILITY ACROSS THE CARIBBEAN REGION...WHERE
GENERALLY DEEP LAYER DRY AIR IS PRESENT. THESE FACTORS ARE
RESULTING IN FAIR WEATHER CONDITIONS ACROSS MUCH THE CARIBBEAN
REGION. THE SOUTHERN PERIPHERY OF THE ANTICYCLONIC FLOW AROUND
THE AFOREMENTIONED 1023 MB SURFACE HIGH OVER THE W ATLC NEAR
28N73W IS BRINGING NE SURFACE WINDS OF 15 TO 20 KT TO THE
CARIBBEAN REGION...EXCEPT UP TO 25 KT NEAR THE COAST OF
COLOMBIA. UPPER LEVEL MOISTURE IS STREAMING NORTHWARD FROM SOUTH
AMERICA INTO THE S CARIBBEAN...WITH ISOLATED SHOWERS ACROSS THE
S CARIBBEAN S OF 15N E OF 76W. ALSO...A SURFACE TROUGH EXTENDS
FROM THE W ATLC NEAR 24N60W TO 20N64W TO THE NE CARIBBEAN NEAR
17N65W...WITH SATELLITE IMAGERY DEPICTING CYCLONIC MOTION OF
CLOUDS IN THE VICINITY OF THIS SURFACE TROUGH. LOW LEVEL
CONVERGENCE IS RESULTING IN ISOLATED SHOWERS WITHIN 60 NM EITHER
SIDE OF THIS SURFACE TROUGH.

ATLANTIC OCEAN...
ACROSS THE W ATLC...A 1023 MB SURFACE HIGH IS CENTERED NEAR
28N73W...WHICH IS BRINGING SUBSIDENCE AND FAIR WEATHER
CONDITIONS TO MUCH OF THE W ATLC. THIS SUBSIDENCE IS BEING
ENHANCED IN THE VICINITY OF THE UPPER HIGH N OF CUBA NEAR
24N78W. NORTHERLY UPPER LEVEL FLOW TO THE E OF THIS UPPER HIGH
IS ADVECTING UPPER LEVEL MOISTURE ACROSS PORTIONS OF THE W ATLC.
FARTHER TO THE E...A SURFACE TROUGH OVER THE CENTRAL ATLC
EXTENDS FROM 30N45W TO 26N49W TO 23N47W. LOW LEVEL CONVERGENCE
ASSOCIATED WITH THIS SURFACE TROUGH IS RESULTING IN NUMEROUS
SHOWERS FROM 23N-30N BETWEEN 40W-47W. THIS ACTIVITY IS BEING
ENHANCED BY ATMOSPHERIC INSTABILITY IN THE VICINITY OF AN UPPER
TROUGH WITH AN AXIS EXTENDING FROM 19N59W TO 27N51W TO 32N48W TO
N OF THE DISCUSSION AREA. ALSO...UPPER LEVEL DIVERGENCE IN THE
NE QUADRANT OF AN 80-90-KT UPPER LEVEL JET MAXIMUM E OF THIS
UPPER TROUGH AXIS IS SUPPORTING THIS ACTIVITY...ALONG WITH LOW
LEVEL CONVERGENCE ASSOCIATED WITH A SURFACE STATIONARY FRONT
EXTENDING FROM NW OF THE DISCUSSION AREA TO 32N59W TO 31N56W AND
A SURFACE COLD FRONT EXTENDING FROM 31N56W TO 32N59W TO NE OF
THE DISCUSSION AREA. ACROSS THE E ATLC...SUBSIDENCE ASSOCIATED
WITH A SURFACE RIDGE EXTENDING SOUTHWESTWARD FROM A 1036 MB
SURFACE HIGH NEAR 45N10W IS GENERALLY INHIBITING DEEP CONVECTION
N OF 18N E OF 34W. HOWEVER...ATMOSPHERIC INSTABILITY ASSOCIATED
WITH AN UPPER LOW NEAR 31N18W IS RESULTING IN SCATTERED SHOWERS
N OF 27N BETWEEN 16W-25W. FARTHER TO THE S...A SURFACE TROUGH
EXTENDS FROM 24N60W TO 20N64W TO THE NE CARIBBEAN NEAR
17N65W...WITH SATELLITE IMAGERY DEPICTING CYCLONIC MOTION OF
CLOUDS IN THE VICINITY OF THIS SURFACE TROUGH. LOW LEVEL
CONVERGENCE IS RESULTING IN ISOLATED SHOWERS WITHIN 60 NM EITHER
SIDE OF THIS SURFACE TROUGH. ALSO...AN UPPER RIDGE IS S OF 12N
BETWEEN 16W-51W. UPPER LEVEL DIFFLUENCE ASSOCIATED WITH THIS
UPPER RIDGE IS ENHANCING THE CONVECTION ASSOCIATED WITH THE
ITCZ. THIS UPPER LEVEL DIFFLUENCE IS ALSO SUPPORTING SCATTERED
SHOWERS AND ISOLATED THUNDERSTORMS FROM 7N-11N BETWEEN 46W-56W.

$$
COHEN




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