[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 061749
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
105 PM EST SUN DEC 06 2009

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 1200 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
1645 UTC.

...ITCZ...

THE ITCZ AXIS IS CENTERED ALONG 7N11W 7N22W 4N35W EQ51W. SCATTERED
MODERATE/ISOLATED STRONG CONVECTION IS FROM 4N-8N BETWEEN 12W-32W.

...DISCUSSION...

GULF OF MEXICO...
A WEAK SURFACE RIDGE IS ACROSS THE GULF OF MEXICO EXTENDING FROM A
1030 MB HIGH OVER THE ERN OHIO VALLEY. ANTI-CYCLONIC SURFACE FLOW OF
10-15 KT IS AROUND THE RIDGE REACHING 20 KT IN THE WRN GULF. IN THE
UPPER LEVELS...SWLY FLOW ALOFT COVERS THE BASIN BETWEEN A BROAD
UPPER LEVEL TROUGH OVER THE WRN CONUS AND AN UPPER LEVEL RIDGE
EXTENDING FROM THE E PACIFIC ACROSS THE NW CARIBBEAN. THIS SW FLOW
IS DRAWING MID/UPPER LEVEL MOISTURE ACROSS MUCH OF THE BASIN NOTED
IN WATER VAPOR IMAGERY. INCREASING SLY RETURN FLOW ACROSS THE NW
GULF IS ALSO DRAWING TROPICAL MOISTURE NWD IN THE LOWER ATMOSPHERE.
THIS ABUNDANCE OF MOISTURE IS SUPPORTING MULTI-LAYER CLOUDS ACROSS
THE AREA...AS WELL AS ISOLATED SHOWERS ACROSS SE TEXAS AND THE NW
GULF N OF 20N W OF 93W. EXPECT RETURN FLOW OVER THE WRN GULF TO
INCREASE WITH CONTINUED MOISTURE ACROSS THE AREA. SHOWER ACTIVITY
WILL CONTINUE OVER THE NW GULF AND PUSH EWD AS LOW PRESSURE
CURRENTLY OVER NRN TEXAS SHIFTS E BRINGING A WEAK COLD FRONT TO THE
NW GULF BY MON.

CARIBBEAN SEA...
A STATIONARY FRONT DRAPES ACROSS THE NW CARIBBEAN FROM CENTRAL CUBA
NEAR 22N80W TO BELIZE NEAR 17N88W. NE WINDS UP TO 15 KT ARE NW OF
THE FRONT. ISOLATED SHOWERS ARE POSSIBLE ALONG THE FRONT AXIS.
BESIDES MODERATE MOISTURE ASSOCIATED WITH THE FRONT...THE REMAINDER
OF THE CARIBBEAN IS UNDER THE INFLUENCE OF DRY AIR AND STRONG
SUBSIDENCE ALOFT SUPPORTING GENERALLY FAIR WEATHER ACROSS THE AREA.
AN UPPER LEVEL RIDGE COVERS THE WRN CARIBBEAN EXTENDING FROM THE E
PACIFIC ACROSS NRN CENTRAL AMERICA TO THE CENTRAL BAHAMAS. AN UPPER
LEVEL TROUGH EXTENDS OVER THE ERN CARIBBEAN FROM THE LEEWARD ISLANDS
TO NRN COLOMBIA...BUT CONTINUES TO LACK MOISTURE. FRESH TO STRONG
TRADEWINDS ARE ACROSS THE BASIN WITH STRONGER WINDS NEAR THE COAST
OF COLOMBIA. EXPECT THE STATIONARY BOUNDARY IN THE NW CARIBBEAN TO
DISSIPATE TONIGHT.

ATLANTIC OCEAN...
AS OF 1500 UTC...A COLD FRONT EXTENDS ACROSS THE SW N ATLC JUST E OF
BERMUDA ENTERING THE DISCUSSION AREA NEAR 31N66W ALONG 28N71W
BECOMING STATIONARY NEAR THE CENTRAL BAHAMAS AT 26N76W. SCATTERED
SHOWERS/POSSIBLE THUNDERSTORMS ARE WITHIN 100 NM AHEAD OF THE FRONT
N OF 30N. A SHORTWAVE UPPER LEVEL TROUGH EXTENDING FROM THE
NORTHEAST UNITED STATES TO NEAR 28N67W SUPPORTS THE FRONT. DIFFLUENT
FLOW ALOFT BETWEEN THIS TROUGH AND AN UPPER LEVEL RIDGE EXTENDING NE
FROM HISPANIOLA TO NEAR THE AZORES ISLANDS IS ENHANCING THE SHOWER
ACTIVITY NEAR THE FRONT. THE UPPER LEVEL RIDGE IS ALSO SUPPORTING A
WEAK SURFACE RIDGE ACROSS THE REMAINDER OF THE W ATLC ANCHORED BY A
1025 MB HIGH NEAR 30N46W. IN THE CENTRAL ATLC...A COLD FRONT CLIPS
THE DISCUSSION AREA ALONG 32N28W 30N36W 32N42W. A PRE-FRONTAL
SURFACE TROUGH IS ANALYZED AHEAD OF THE FRONT ALONG 30N27W 27N34W
26N42W. ISOLATED SHOWERS ARE POSSIBLE ALONG BOTH BOUNDARIES. A
NARROW UPPER LEVEL TROUGH EXTENDING FROM W OF THE CANARY ISLANDS SW
TO 19N40W TO E OF THE LEEWARD ISLANDS SUPPORTS THE FRONTAL SYSTEM.
AN UPPER LEVEL WLY JET TO THE S OF THE UPPER TROUGH AXIS IS
ENHANCING CONVECTION ALONG THE ITCZ.

$$
WALTON



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