[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 121719
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
205 PM EST THU NOV 12 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 8N12W 7N22W 7N31W 5N41W 6N58W.
SCATTERED MODERATE/ISOLATED STRONG CONVECTION IS FROM 6N-10N
BETWEEN 17W-21W. A SECONDARY BOUNDARY...ANALYZED AS A SURFACE
TROUGH...LIES TO THE N ALONG 15N13W 11N18W 11N25W. SCATTERED
MODERATE ISOLATED STRONG CONVECTION IS WITHIN 200 NM N OF THIS
BOUNDARY. SIMILAR CONVECTION IS FROM 5N-11N BETWEEN 26W-35W NEAR
AN EMBEDDED SURFACE TROUGH ALONG 11N30W 7N33W. SIMILAR ACTIVITY
IS ALSO FROM 4N-8N BETWEEN 36W-44W.

...DISCUSSION...

GULF OF MEXICO...
MAINLY NLY SURFACE FLOW PREVAILS ACROSS THE GULF OF MEXICO
BEHIND THE PASSAGE OF A PAIR OF COLD FRONTS NOW IN THE WRN ATLC.
STRONGEST SURFACE WINDS ARE OVER THE ERN BASIN REACHING UP TO 25
KT ACCOMPANIED BY A LARGE AREA OF STRATOCUMULUS CLOUDS EXTENDING
ACROSS THE MAJORITY OF THE BASIN. ALOFT...UPPER LEVEL WLY FLOW
DOMINATES S OF THE BASE OF A SHORTWAVE UPPER LEVEL TROUGH
CENTERED OVER NORTH CAROLINA...ALONG WITH SIGNIFICANT DRY AIR
AND SUBSIDENCE ACROSS THE GULF NOTED ON WATER VAPOR IMAGERY.
EXPECT WINDS TO DIMINISH ACROSS THE BASIN AS HIGH PRESSURE
BUILDS ACROSS THE AREA. SE RETURN FLOW IS EXPECTED ACROSS THE
WRN GULF TOMORROW AHEAD OF A COLD FRONT FORECAST TO MOVE OFF THE
TEXAS COAST MONDAY.

CARIBBEAN SEA...
AS OF 1500 UTC...A COLD FRONT EXTENDS ACROSS WRN CUBA TO THE
YUCATAN PENINSULA ALONG 23N81W 21N84W 21N88W. A LAYER OF
STRATOCUMULUS CLOUDS EXTENDS TO THE NW BEHIND THE FRONT. NO
SHOWER ACTIVITY IS CURRENTLY ASSOCIATED WITH THIS FRONT. A
SECOND COLD FRONT EXTENDS FROM ERN CUBA TO NE NICARAGUA ALONG
21N77W 18N79W 15N83W. SCATTERED SHOWERS/ISOLATED THUNDERSTORMS
ARE WITHIN 90 NM EITHER SIDE OF THE FRONT WITH THE MOST
CONCENTRATED SHOWER ACTIVITY S OF CUBA AND W OF JAMAICA. BOTH OF
THESE FRONTS EXTEND NWD ACROSS THE W ATLC TO A 992 MB SURFACE
LOW OFF THE VIRGINIA COAST...AND ARE SUPPORTED BY A SHORTWAVE
UPPER TROUGH CENTERED OVER NORTH CAROLINA. SCATTERED
SHOWERS/THUNDERSTORMS HAVE FORMED OVER THE SW CARIBBEAN S OF 11N
BETWEEN 76W-82W DUE TO SURFACE CONVERGENCE NEAR THE E PACIFIC
ITCZ. IN THE UPPER LEVELS...AN UPPER LEVEL RIDGE COVERS THE
MAJORITY OF THE BASIN W OF 67W PROVIDING GENERALLY FAIR WEATHER
ACROSS THE CENTRAL CARIBBEAN. AN UPPER LEVEL TROUGH E OF 67W
SUPPORTS SCATTERED SHOWERS/THUNDERSTORMS ACROSS THE LEEWARD
ISLANDS N OF 16N BETWEEN 62W-65W...AND ISOLATED
SHOWERS/THUNDERSTORMS BETWEEN 65W-69W.

ATLANTIC OCEAN...
A PAIR OF COLD FRONTS EXTEND ACROSS THE WRN ATLC FROM A 992 MB
LOW OFF THE COAST OF VIRGINIA NEAR 34N77W. AS OF 1500 UTC...ONE
FRONT ENTERS THE DISCUSSION AREA NEAR 32N75W TO THE NE BAHAMAS
NEAR 27N78W TO WRN CUBA NEAR 23N81W. NO SHOWER ACTIVITY IS
ASSOCIATED WITH THIS FRONT. HOWEVER...A LARGE AREA OF
STRATOCUMULUS CLOUDS TRAIL BEHIND THE FRONT. THE SECOND FRONT
ENTERS THE DISCUSSION AREA NEAR 32N74W TO THE CENTRAL BAHAMAS
NEAR 24N75W TO ERN CUBA NEAR 21N77W. SCATTERED SHOWERS/ISOLATED
THUNDERSTORMS ARE E OF THE FRONT N OF 29N BETWEEN 71W-73W.
ISOLATED SHOWERS/THUNDERSTORMS ARE ALSO ALONG THE FRONT AXIS
ACROSS THE CENTRAL BAHAMAS. A 1005 MB LOW IS CENTERED NEAR
31N64W. ISOLATED SHOWERS/THUNDERSTORMS ARE WITHIN 200 NM OF THE
CENTER IN THE NE AND SE QUADRANTS. THE LOW IS SUPPORTED BY AN
UPPER LEVEL TROUGH ALONG 30N64W 19N59W 11N60W. THE UPPER LEVEL
TROUGH IS ALSO SUPPORTING SCATTERED SHOWERS/ISOLATED
THUNDERSTORMS FROM 18N-24N BETWEEN 60W-64W...AND N OF 26N
BETWEEN 50W-55W. A BROAD SURFACE RIDGE DOMINATES THE REMAINDER
OF THE ERN ATLC ANCHORED BY A 1019 MB HIGH NEAR 33N28W. AN UPPER
LEVEL TROUGH OVER THE ERN ATLC WITH AXIS FROM THE CANARY ISLANDS
NEAR 29N16W TO THE CENTRAL TROPICAL ATLC NEAR 11N33W IS SHEARING
MOISTURE FROM THE ITCZ TO THE NE SUPPORTING SHOWER ACTIVITY NEAR
AND N OF THE ITCZ.

$$
WALTON






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