[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 172328
TWDAT

TROPICAL WEATHER DISCUSSION
NWS NATIONAL HURRICANE CENTER MIAMI FL
705 PM EST SAT NOV 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 1800 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
2245 UTC.

...ITCZ/MONSOON TROUGH...
THE MONSOON TROUGH EXTENDS ACROSS WEST AFRICA TO THE COAST OF
GUINEA AT 10N14W TO 7N17W. THE ITCZ BEGINS AT 7N17W AND
CONTINUES ALONG 6N28W 8N40W THEN RESUMES NEAR 12N45W TO 11N52W
8N59W. SCATTERED MODERATE CONVECTION IS FROM 7N-9N BETWEEN
25W-27W. AN UPPER LEVEL TROUGH OVER THE EASTERN ATLC CONTINUES
TO PROVIDE A LARGE AREA OF DIFFLUENCE ALOFT NORTH OF THE ITCZ
REGION AND CONCENTRATED NEAR A SURFACE TROUGH ALONG 19N35W TO
13N45W. ISOLATED MODERATE CONVECTION IS FROM 9N-14N BETWEEN
40W-45W. THE REMAINDER OF THE ACTIVITY IS FARTHER NORTH AND WILL
BE DESCRIBED IN THE ATLC DISCUSSION SECTION.

...DISCUSSION...

GULF OF MEXICO...
MAINLY NORTHWESTERLY FLOW ALOFT COVERS THE GULF OF MEXICO
BETWEEN AN UPPER LEVEL RIDGE EXTENDING THROUGH MEXICO INTO
TEXAS...AND AN UPPER LEVEL LOW CENTERED OVER SOUTH CAROLINA WITH
TROUGH AXIS EXTENDING SOUTHWARD ALONG 83W. WATER VAPOR IMAGERY
INDICATES MOSTLY DRY AIR IS WRAPPING AROUND THE WEST SIDE OF THE
UPPER TROUGH HELPING PROVIDE FAIR CONDITIONS ACROSS THE MAJORITY
OF THE GULF. AT THE SURFACE...NORTHEAST TO EAST WINDS OF 10-15
KT SPREAD ACROSS THE BASIN AROUND THE BASE OF A SURFACE RIDGE
COVERING THE EASTERN CONUS. SOME STRONGER WINDS UP TO 20 KT ARE
PRESENT IN THE CENTRAL GULF AND THROUGH THE FLORIDA STRAITS.
ISOLATED SHOWERS ARE PRESENT IN THE FAR SW GULF NEAR A SURFACE
TROUGH PARALLEL TO THE MEXICO COAST ALONG 24N97W TO 19N95W. A
FEW ISOLATED SHOWERS/POSSIBLE THUNDERSTORMS ARE ALSO ACROSS
FLORIDA AND THE FAR SE GULF NORTH OF CUBA. SURFACE RIDGING IT
EXPECTED TO REMAIN ACROSS THE EASTERN CONUS AND GULF OF MEXICO
FOR THE NEXT COUPLE OF DAYS. ISOLATED SHOWERS WILL REMAIN OVER
THE FAR SW AND SE GULF.

CARIBBEAN SEA...
THE UPPER LEVEL TROUGH OVER THE SE CONUS AND EASTERN GULF
CONTINUES SOUTH INTO THE NW CARIBBEAN ACCOMPANIED BY DRY AIR
ALOFT...WHICH IS PROVIDING FAIR CONDITIONS ACROSS THIS PORTION
OF THE BASIN. HOWEVER...DIFFLUENCE ALOFT BETWEEN THE UPPER
TROUGH AND AN UPPER LEVEL RIDGE OVER THE EASTERN CARIBBEAN ALONG
63W IS GENERATING SHOWERS AND ISOLATED THUNDERSTORMS FROM THE SW
CARIBBEAN TO HISPANIOLA AND COVERING MUCH OF THE CENTRAL
CARIBBEAN. THIS ACTIVITY IS ALSO BEING GENERATED BY SURFACE
CONVERGENCE BETWEEN TRADEWIND FLOW COMING FROM THE EAST AND
NORTHERLY FLOW PRESENT OVER THE WESTERN CARIBBEAN. THIS
CONVERGENCE BECOMES CONCENTRATED AROUND A WEAK 1010 MB SURFACE
LOW IN THE FAR SW GULF NEAR 11N77W AT THE END OF THE MONSOON
TROUGH AXIS WHICH EXTENDS ACROSS NORTHERN PANAMA TO THE LOW
CENTER. OVER THE EASTERN CARIBBEAN...FAIR CONDITIONS ARE PRESENT
AS DRY AIR ALOFT IS PRESENT NEAR THE UPPER RIDGE AXIS. LITTLE
CHANGE IS EXPECTED OVER THE NEXT COUPLE OF DAYS.

ATLANTIC OCEAN...
AN UPPER LEVEL LOW OVER SOUTH CAROLINA CONTINUES TO SUPPORT A
STATIONARY FRONT ALONG 32N76W 30N78W 26N80W. SCATTERED SHOWERS
AND THUNDERSTORMS ARE NEAR THE NORTHERN PORTIONS OF THE FRONT N
OF 29N BETWEEN 76W-81W. HOWEVER...MOIST SOUTHWESTERLY FLOW ALOFT
BETWEEN THE UPPER LOW/TROUGH AND AN UPPER LEVEL RIDGE EXTENDING
FROM THE EASTERN CARIBBEAN INTO THE ATLC TO NEAR 35N55W IS
HELPING SUPPORT A LARGE AREA OF OVERCAST SKIES BETWEEN 60W-75W
WITH SCATTERED SHOWERS AND ISOLATED THUNDERSTORMS FROM 21N-28N
BETWEEN 65W-71W WITH ISOLATED ACTIVITY ELSEWHERE. MORE SCATTERED
ACTIVITY IS ALSO NEAR A SURFACE TROUGH IN THE MIDDLE ALONG
32N63W TO 25N66W. THE UPPER LEVEL RIDGE IN THE CENTRAL ATLC
FEEDS INTO A BROAD UPPER RIDGE OVER THE NE ATLC SUPPORTING A
BROAD SURFACE RIDGE ANCHORED BY A 1028 MB HIGH NEAR
34N34W...WHICH CONTINUES INTO THE TROPICAL ATLC. HOWEVER...AN
UPPER LEVEL TROUGH SOUTH OF THE RIDGE ALONG 28N33W TO 9N50W IS
SUPPORTING A SURFACE TROUGH ALONG 19N35W TO 13N44W. SURFACE
CONVERGENCE ALONG WITH DIFFLUENCE ALOFT IS GENERATING SCATTERED
SHOWERS/POSSIBLE THUNDERSTORMS FROM 14N-23N BETWEEN 28W-41W.

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

$$
WALTON





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