[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 240554
TWDAT

TROPICAL WEATHER DISCUSSION
NWS NATIONAL HURRICANE CENTER MIAMI FL
205 AM EDT SAT SEP 24 2011

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 0000 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
0445 UTC.

...SPECIAL FEATURES...

TROPICAL STORM OPHELIA IS CENTERED NEAR 16.0N 54.5W AT 24/0300
UTC OR ABOUT 425 NM E OF THE LEEWARD ISLANDS MOVING WNW AT 12
KT. ESTIMATED MINIMUM CENTRAL PRESSURE IS 1006 MB. MAXIMUM
SUSTAINED WIND SPEED IS 45 KT WITH GUSTS TO 55 KT. PLEASE SEE
LATEST NHC FORECAST/ADVISORY UNDER AWIPS/WMO HEADERS MIATCMAT1/
WTNT21 KNHC FOR MORE DETAILS. OPHELIA IS IN A WEAKENING TREND AS
IT IS BEING SHEARED. SCATTERED MODERATE/STRONG CONVECTION IS
WELL REMOVED FROM THE LOW LEVEL CENTER WITHIN A 45 NM RADIUS OF
18N53W WITH SCATTERED MODERATE/ISOLATED STRONG CONVECTION
COVERING THE REMAINDER OF THE AREA FROM 15N-20N BETWEEN 48W-55W.

A 1008 MB LOW IS S OF THE CAPE VERDE ISLANDS NEAR 10N23W
EMBEDDED WITHIN THE MONSOON TROUGH. SCATTERED MODERATE/ISOLATED
STRONG CONVECTION IS FROM 9N-11N BETWEEN 23W-26W. THIS SYSTEM
CONTINUES TO BECOME BETTER ORGANIZED. ENVIRONMENTAL CONDITIONS
ARE CONDUCIVE FOR A TROPICAL DEPRESSION TO FORM LATER TODAY AND
THIS SYSTEM HAS A HIGH CHANCE OF BECOMING A TROPICAL CYCLONE
DURING THE NEXT 48 HOURS AS IT MOVES WEST-NORTHWESTWARD AT ABOUT
8 KT.

...TROPICAL WAVES...

TROPICAL WAVE IS ANALYZED FROM 19N35W 12N37W TO 6N38W MOVING W
AT 10-15 KT. WAVE IS WELL DEFINED IN THE UPPER LEVEL SATELLITE
WINDS AND IN THE LOW CLOUDS ON SATELLITE IMAGERY. WAVE REMAINS
EMBEDDED WITHIN DEEP LAYER MOISTURE AS SEEN ON THE TOTAL
PRECIPITABLE WATER IMAGERY. SCATTERED SHOWERS ARE WITHIN 75 NM
EITHER SIDE OF THE WAVE AXIS.

...ITCZ/MONSOON TROUGH...

THE MONSOON TROUGH EXTENDS ACROSS AFRICA TO THE COAST NEAR
20N16W THEN RESUMES NEAR 12N17W THROUGH THE 1008 MB LOW IN THE
SPECIAL FEATURES TO 8N32W. SMALL CLUSTERS OF SCATTERED MODERATE/
ISOLATED STRONG CONVECTION ARE FROM 5N-10N BETWEEN 29W-32W WITH
LARGER CLUSTERS S OF OPHELIA FROM 10N-16N BETWEEN 46W-58W.

...DISCUSSION...

GULF OF MEXICO...
THE TAIL END OF A WEAKENING COLD FRONT EXTENDS INTO THE GULF
ACROSS THE FLORIDA PANHANDLE NEAR PENSACOLA ALONG 28N87W TO
27N90W SUPPORTED BY AN UPPER TROUGH THAT COVERS THE MISSISSIPPI
VALLEY AND THE E CONUS INTO THE GULF N OF 23N. HOWEVER...THE N
GULF IS DOMINATED BY STRONG SUBSIDENCE AND DRY STABLE AIR THUS
THE FRONT IS CURRENTLY PRODUCING ONLY WIDELY ISOLATED SHOWERS.
AN UPPER RIDGE EXTENDS FROM THE E PACIFIC REGION ACROSS MEXICO
COVERING THE SW GULF AND THE BAY OF CAMPECHE. A SURFACE TROUGH
EXTENDS FROM THE E GULF NEAR 27N84W TO OVER THE YUCATAN
PENINSULA NEAR 21N89W TO THE N BORDER OF GUATEMALA GENERATING
SCATTERED SHOWERS AND POSSIBLE ISOLATED THUNDERSTORMS S OF 26N
BETWEEN 83W-91W TO OVER THE YUCATAN PENINSULA AND INTO THE E BAY
OF CAMPECHE. THE NW GULF IS UNDER REMARKABLY CLEAR SKIES
TONIGHT. THE WEAK COLD FRONT WILL REACH FROM THE FLORIDA BIG
BEND REGION TO THE CENTRAL GULF LATER THIS MORNING THEN STALL
AND DISSIPATING THROUGH MON. HIGH PRESSURE WILL BUILD IN THE
WAKE OF THE FRONT SUN THROUGH TUE AND SHIFT N WED.

CARIBBEAN SEA...
AN UPPER RIDGE COVERS THE SW CARIBBEAN S OF 18N W OF 70W WHILE
AN UPPER TROUGH FROM THE CENTRAL ATLC COVERS THE E CARIBBEAN.
EASTERLY WINDS COMBINED WITH THE DIFFLUENT ENVIRONMENT ALOFT
OVER THE CENTRAL CARIBBEAN ARE GENERATING CLUSTERS OF SCATTERED
SHOWERS/ISOLATED THUNDERSTORMS MAINLY FROM 12N-18N W OF 73W TO
OVER CENTRAL AMERICA AND IN THE GULF OF HONDURAS. THE MONSOON
TROUGH EXTENDS ACROSS THE SW CARIBBEAN FROM COLOMBIA NEAR 9N76W
ALONG 10N80W ACROSS COSTA RICA INTO THE E PACIFIC REGION NEAR
10N84W GENERATING SCATTERED SHOWERS/ISOLATED THUNDERSTORMS S OF
12N BETWEEN 7W-84W. THIS IS LEAVING THE E CARIBBEAN UNDER CLEAR
SKIES TONIGHT. TROPICAL STORM OPHELIA WILL CONTINUE TO MOVE NE
OF THE LEEWARD ISLANDS SAT NIGHT THROUGH MON.

ATLANTIC OCEAN...
A SMALL UPPER RIDGE IS ANCHORED OVER THE FAR W ATLC NEAR THE
CENTRAL BAHAMAS PROVIDING A DIFFLUENT ENVIRONMENT ALOFT WHILE A
SURFACE TROUGH EXTENDS FROM 29N77W ACROSS GRAND BAHAMA ISLANDS
TO THE N COAST OF CUBA NEAR 23N80W. HEAVY SHOWERS AND
THUNDERSTORMS COVER THE S BAHAMA ISLANDS FROM 24N TO OVER CUBA
BETWEEN 73W-77W WHILE SCATTERED SHOWERS/ISOLATED THUNDERSTORMS
COVER THE REMAINDER OF THE AREA S OF 30N BETWEEN 70W-81W. A
BROAD UPPER RIDGE DOMINATES THE W ATLC ANCHORED ABOUT 150 NM NW
OF BERMUDA PROVIDING DRY STABLE AIR OVER THE AREA N OF 25N
BETWEEN 40W-70W. AN UPPER TROUGH EXTENDS FROM THE CENTRAL ATLC
NEAR 23N63W OVER THE E CARIBBEAN BUT DUE TO THE DRY STABLE AIR
IS NOT PRODUCING ANY SHOWER ACTIVITY. A BROAD SURFACE RIDGE
DOMINATES THE REMAINDER OF THE ATLC N OF 20N ANCHORED BY A
SERIES OF HIGHS N OF THE DISCUSSION AREA. THE SURFACE TROUGH
WILL REMAIN NEARLY STATIONARY AND GRADUALLY DISSIPATE THROUGH
SAT NIGHT. TROPICAL STORM OPHELIA WILL CONTINUE TO MOVE NE OF
THE LEEWARD ISLANDS SAT NIGHT BEING N OF THE VIRGIN ISLANDS MON
NIGHT BEFORE TURNING MORE NORTHWARD.

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

$$
PAW





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