[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 171748
TWDAT

TROPICAL WEATHER DISCUSSION
NWS NATIONAL HURRICANE CENTER MIAMI FL
105 PM EST MON DEC 17 2012

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...WEATHER OBSERVATIONS...RADAR...AND METEOROLOGICAL
ANALYSIS.

BASED ON 1200 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY
THROUGH 1715 UTC.

...THE ITCZ/THE MONSOON TROUGH...

THE MONSOON TROUGH PASSES THROUGH SIERRA LEONE AND NORTHERN
LIBERIA NEAR 7N10W TO 7N14W. THE ITCZ CONTINUES FROM 7N15W TO
5N26W 3N40W TO JUST OFF THE COAST OF NORTHEASTERN BRAZIL.
SCATTERED MODERATE TO ISOLATED STRONG CONVECTION IS 220 NM S OF
THE ITCZ BETWEEN 9W AND 30W. SIMILAR CONVECTION SURROUNDS THE
ITCZ FROM THE EQUATOR TO 7N BETWEEN 30W AND 40W. A CLUSTER OF
ISOLATED MODERATED TO STRONG CONVECTION IS FROM 7N TO 9N BETWEEN
42W AND 46W. SCATTERED MODERATE CONVECTION IS OFF THE COAST FROM
THE BORDER OF VENEZUELA AND GUYANA FROM 8N TO 10N BETWEEN 56W
AND 62W.

...DISCUSSION...

THE GULF OF MEXICO...

BROAD MIDDLE TO UPPER LEVEL ANTICYCLONIC WIND FLOW COVERS THE
REGION. A DEEP LAYER TROUGH IS DIGGING THROUGH NORTHEASTERN
TEXAS SUPPORTING A SURFACE COLD FRONT THAT PASSES THROUGH WEST
CENTRAL LOUISIANA...27N95W...THE SOUTHERN TIP OF TEXAS INTO
MEXICO NEAR 24N98W. SCATTERED SHOWERS ARE WITHIN 60 NM OF THE
COLD FRONT. A PREFRONTAL TROUGH EXTENDS FROM SOUTHWESTERN COAST
OF ALABAMA NEAR 30N88W SOUTHWESTWARD TO 28N90W 26N93W PRODUCING
SCATTERED SHOWERS WITHIN 120 NM OFF THE COAST OF LOUISIANA AND
MISSISSIPPI. ANOTHER SURFACE TROUGH LIES IN THE SOUTHWEST GULF
WITH AXIS ALONG 95W. WITHIN 24 HOURS...PRECIPITATION IS EXPECTED
TO AFFECT THE GULF AS THE COLD FRONT KEEPS DISPLACING EASTWARD
TOWARD NW FLORIDA.

THE CARIBBEAN SEA...

THE BROAD MIDDLE TO UPPER LEVEL ANTICYCLONIC WIND FLOW THAT
COVERS THE GULF EXTENDS OVER THE CARIBBEAN WITH MODERATE TO
STRONG SUBSIDENCE. A SURFACE TROUGH IS IN THE WESTERN CARIBBEAN
S OF CENTRAL CUBA FROM 20N79W TO 16N80W. LIGHT SHOWERS COULD BE
POSSIBLE WITHIN 75 NM ALONG THE TROUGH. ELSEWHERE FAIR WEATHER
DOMINATES. WITHIN 24 HOURS...THE SURFACE TROUGH IS EXPECTED TO
DISSIPATE STEADILY AND TRADE WINDS OF 10 KT TO 20 KT WILL
PREDOMINATE THE ENTIRE REGION.

THE ATLANTIC OCEAN...

BROAD SURFACE RIDGING COVERS THE WESTERN ATLANTIC PROVIDING
MOSTLY FAIR CONDITIONS ACROSS THIS AREA. IN THE CENTRAL
ATLANTIC...A MIDDLE LEVEL TO UPPER LEVEL TROUGH AXIS EXTENDS
FROM 25N51W SOUTHWESTWARD TO E OF THE LESSER ANTILLES. THIS
TROUGH IS SUPPORTING THREE SURFACE TROUGHS. THE FIRST TROUGH
EXTENDS FROM 29N47W SOUTHWESTWARD TO 25N53W 24N61W. THE SECOND
SURFACE TROUGH IS A COLD FRONT PREFRONTAL TROUGH THAT ENTERS THE
REGION NEAR 30N40W AND EXTENDS TO 23N46W. THE THIRD TROUGH IS
FURTHER EAST AND EXTENDS FROM 25N39W SOUTHWESTWARD TO 15N48W.
SCATTERED SHOWERS ARE BOUNDED BY THE SECOND AND THIRD TROUGH
FROM 20N TO 30N BETWEEN 35W AND 45W. IN THE EASTERN ATLC SURFACE
RIDGING FROM A 1O27 MB HIGH NEAR 34N13W DOMINATES THE
REGION...AND WITH MIDDLE TO UPPER LEVEL DRY AIR SUBSIDENCE IS
PROVIDING FAIR WEATHER CONDITIONS N OF 17N E OF 33W.

FOR ADDITIONAL INFORMATION PLEASE VISIT
HTTP://WWW.HURRICANES.GOV/MARINE

$$
NAR/CW





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