[Tropical] Tropical Weather Discussion

[EMWIN Server]

AXNT20 KNHC 121158
TWDAT

TROPICAL WEATHER DISCUSSION
NWS NATIONAL HURRICANE CENTER MIAMI FL
805 AM EDT WED SEP 12 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 0600 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
1015 UTC.

...SPECIAL FEATURES...
TROPICAL STORM NADINE IS CENTERED NEAR 18.6N 46.6W 12/0900 UTC
OR ABOUT 865 NM ENE OF THE LESSER ANTILLES MOVING WNW AT 15 KT.
ESTIMATED MINIMUM CENTRAL PRESSURE IS 1001 MB. MAXIMUM SUSTAINED
WIND SPEED IS 40 KT WITH GUSTS TO 50 KT. SEE LATEST NHC
FORECAST/ADVISORY UNDER AWIPS/WMO HEADERS MIATCMAT4/WTNT24 KNHC
FOR MORE DETAILS. SCATTERED MODERATE TO STRONG CONVECTION IS
FROM 15N-22N BETWEEN 43W-49W. CLUSTER OF SCATTERED MODERATE/
ISOLATED STRONG CONVECTION ARE 13N-15N BETWEEN 44W-49W AND FROM
22N-25N BETWEEN 44W-49W.

...TROPICAL WAVES...

TROPICAL WAVE IS SW OF THE CAPE VERDE ISLANDS EXTENDING FROM
14N31W TO 5N25W MOVING W NEAR 20 KT. WAVE IS ALONG THE LEADING
EDGE OF AN AREA OF DEEP MOISTURE WITH A SWATH OF DRIER AIR
UNDERCUTTING THE WAVE NEAR 8N AS DEPICTED ON THE TOTAL
PRECIPITABLE WATER IMAGERY. SCATTERED SHOWERS/ISOLATED
THUNDERSTORMS ARE WITHIN 60/75 NM EITHER SIDE OF THE WAVE N OF
8N.

...ITCZ/MONSOON TROUGH...

THE MONSOON TROUGH EXTENDS ACROSS AFRICA INTO THE E TROPICAL
ATLC NEAR 15N17W TO 16N19W BEING DISRUPTED BY THE PRESENCE OF
TROPICAL STORM NADINE. THE ITCZ EXTENDS FROM 10N52W TO SOUTH
AMERICA NEAR 8N60W. CLUSTERS OF SCATTERED MODERATE/ISOLATED
STRONG CONVECTION ARE FROM 10-16N E OF 20W TO INLAND OVER W
AFRICA.

...DISCUSSION...

GULF OF MEXICO...
THE CUTOFF UPPER LOW REMAINS OVER THE LOWER MISSISSIPPI VALLEY
WITH THE UPPER TROUGH EXTENDING S OVER THE NW GULF OF MEXICO. AN
UPPER TROUGH COVERS THE FAR E U.S. INTO THE NW ATLC SUPPORTING A
COLD FRONT IN THE W ATLC AND ENTERING THE GULF OF MEXICO AT
12/0900 UTC OVER THE UPPER FLORIDA KEYS AS A WEAKENING
STATIONARY FRONT ALONG 26N87W TO INLAND ALONG THE COAST OF
LOUISIANA NEAR ATCHAFALAYA BAY. SCATTERED SHOWERS/ISOLATED
THUNDERSTORMS ARE N OF 26N BETWEEN 87W-95W. AN UPPER RIDGE
ANCHORED OVER SW MEXICO EXTENDS OVER THE SW GULF IS ENHANCING
CLUSTERS OF SCATTERED SHOWERS/ISOLATED THUNDERSTORMS WITHIN 90
NM ALONG THE COAST OF MEXICO S OF 23N W OF 93W TO INLAND OVER
MEXICO. THE REMAINDER OF THE GULF IS UNDER FAIR WEATHER THIS
MORNING. THE WEAKENING FRONTAL BOUNDARY WILL GRADUALLY DISSIPATE
THROUGH THU E OF 85W AND CONTINUE TO LIFT NORTHWARD INLAND W OF
85W. HIGH PRESSURE WILL BUILD IN FROM THE NE THROUGH THU NIGHT.
A WEAK COLD FRONT IS EXPECTED TO ENTER THE FAR NW GULF SAT AND
SUN.

CARIBBEAN SEA...
A BROAD UPPER RIDGE OVER THE W ATLC DOMINATES THE N CARIBBEAN
WHILE A SECOND UPPER RIDGE DOMINATES THE SW WATERS. CLUSTERS OF
ISOLATED SHOWERS/THUNDERSTORMS DOT THE NW CARIBBEAN N OF 15N W
OF 76W. THE MONSOON TROUGH EXTENDS FROM COLOMBIA ALONG 10N
ACROSS COSTA RICA INTO THE E PACIFIC REGION GENERATING SCATTERED
SHOWERS/ISOLATED THUNDERSTORMS S OF 10N BETWEEN 79W-84W. A
CUTOFF UPPER LOW IS CENTERED NE OF THE VIRGIN ISLANDS EXTENDING
AN UPPER TROUGH OVER THE E CARIBBEAN E OF 70W. MODERATE TO FRESH
TRADE WINDS ARE ACROSS THE S CENTRAL CARIBBEAN WATERS WITH LIGHT
TO MODERATE TRADE WINDS ELSEWHERE. THESE TRADE WINDS ARE
USHERING IN SCATTERED SHOWERS/ISOLATED THUNDERSTORMS ACROSS THE
E CARIBBEAN N OF 14N E OF 70W AND S OF 13N E OF 66W. OTHERWISE
THE REMAINDER OF THE CARIBBEAN IS UNDER FAIR WEATHER THIS
MORNING. HIGH PRESSURE N OF THE AREA WILL MAINTAIN THE TRADE
WINDS ACROSS THE CARIBBEAN THROUGH THU.

ATLANTIC OCEAN...
THE PRIMARY CONCERN THIS MORNING IS TROPICAL STORM NADINE IN THE
CENTRAL TROPICAL ATLC. SEE SPECIAL FEATURES ABOVE. AN UPPER
TROUGH COVERS THE FAR E U.S. INTO THE NW ATLC SUPPORTING A COLD
FRONT THAT EXTENDS INTO THE CENTRAL ATLC NEAR 32N56W EXTENDING
ALONG 27N61W TO 25N65W WHERE IT BECOMES A WEAKENING STATIONARY
FRONT THROUGH THE N BAHAMA ISLANDS INTO THE GULF OF MEXICO OVER
THE UPPER FLORIDA KEYS. SCATTERED SHOWERS/ISOLATED THUNDERSTORMS
ARE WITHIN 120 NM W OF THE COLD FRONT WITH CLUSTERS OF SIMILAR
ACTIVITY WITHIN 60 NM S AND WITHIN 120/150 NM N OF THE
STATIONARY FRONT. A SURFACE RIDGE CONTINUES TO BUILD S OVER
THE W ATLC W OF THE ABOVE FRONTAL BOUNDARY ANCHORED BY A 1026 MB
HIGH OFF THE NEW ENGLAND COAST. A CUTOFF UPPER LOW IS CENTERED
IN THE W TROPICAL ATLC NE OF THE VIRGIN ISLANDS NEAR 20N61W
EXTENDING AN UPPER TROUGH OVER THE E CARIBBEAN AND NNE TO NEAR
26N56W PRECEDING TROPICAL STORM NADINE. BROAD UPPER LOW IS OVER
THE NE ATLC SUPPORTING A COLD FRONT THAT ENTERS THE E ATLC NEAR
32N20W EXTENDING ALONG 20N27W TO 31N35W GENERATING SCATTERED
SHOWERS/ISOLATED THUNDERSTORMS WITHIN 60 NM S OF THE FRONT.
SATELLITE IMAGES INDICATES SAHARAN DUST COVERS THE E TROPICAL
ATLC FROM 14N-26N E OF 40W AND TO THE NORTH OF TROPICAL STORM
NADINE. WEAKENING COLD FRONT WILL GRADUALLY DISSIPATE THROUGH
THU. HIGH PRESSURE WILL CONTINUE TO BUILD IN ACROSS THE AREA
BEHIND THE FRONT. TROPICAL STORM NADINE IN THE CENTRAL TROPICAL
ATLC IS FORECAST TO MOVE IN A GENERAL NW DIRECTION THROUGH THU
AS IT SLOWLY INTENSIFIES INTO A HURRICANE BEFORE IT TURNS IN A
NE DIRECTION.

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

$$
PAW






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