[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 181139
TWDAT

TROPICAL WEATHER DISCUSSION
NWS NATIONAL HURRICANE CENTER MIAMI FL
805 AM EDT THU OCT 18 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.

...TROPICAL WAVES...

WEAK TROPICAL WAVE IS ANALYZED FROM 18N42W TO 1N44W MOVING W
NEAR 10 KT. WAVE REMAINS DIFFICULT TO TRACK AS IT IS ALONG THE
EASTERN EDGE OF AN UPPER TROUGH. NO ASSOCIATED DEEP CONVECTION.

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

THE MONSOON TROUGH IS ANALYZED ACROSS W AFRICA INTO THE E
TROPICAL ATLC NEAR 13N16W ALONG 9N20W TO 7N30W WHERE THE ITCZ
BEGINS AND CONTINUES ALONG 11N49W TO 9N61W. A WEAK SURFACE
TROUGH IS BETWEEN BARBADOS AND THE REMAINING WINDWARD ISLANDS
EXTENDING FROM MARTINIQUE TO 20N60W. CLUSTERS OF SCATTERED
MODERATE/ISOLATED STRONG CONVECTION ARE WITHIN 90 NM ALONG THE
COAST OF LIBERIA AND SIERRA LEONE...FROM 6N-11N BETWEEN
20W-30W...AND WITHIN 75/90 NM OF LINE FROM 15N43W TO 11N53W.
CLUSTERS OF SCATTERED MODERATE CONVECTION ARE FROM 10N-13N
BETWEEN 36W-40W AND FROM 7N-10N BETWEEN 42W-55W.

...DISCUSSION...

GULF OF MEXICO...
A STRONG UPPER TROUGH IS DIGGING S FROM AN UPPER LOW OVER IOWA
ACROSS THE CENTRAL MISSISSIPPI VALLEY TO THE MISSISSIPPI COAST
SUPPORTING A COLD FRONT THAT AT 18/0900 EXTENDS ACROSS S
LOUISIANA NEAR LAKE CHARLES CLIPPING THE FAR NW GULF TO INLAND
OVER TEXAS JUST S OF GALVESTON. SCATTERED SHOWERS/ISOLATED
THUNDERSTORMS ARE ACROSS S LOUISIANA AND WILL BE MOVING INTO THE
NW GULF WATERS OVER THE NEXT FEW HOURS. A BROAD UPPER RIDGE
DOMINATES THE REMAINDER OF THE GULF WATERS WITH THE AXIS
EXTENDING FROM AN UPPER HIGH NEAR MEXICO CITY ACROSS THE BAY OF
CAMPECHE AND THE YUCATAN PENINSULA INTO THE FAR NW CARIBBEAN. A
SURFACE TROUGH EXTENDS FROM THE NW CARIBBEAN THROUGH THE YUCATAN
CHANNEL NEAR THE W TIP OF CUBA ALONG 23N85W TO 26N84W WITH
SCATTERED SHOWERS/ISOLATED THUNDERSTORMS S OF 26N E OF THE
TROUGH THROUGH THE STRAITS OF FLORIDA INCLUDING THE FLORIDA
KEYS. THIS IS LEAVING THE REMAINDER OF THE GULF UNDER MOSTLY
CLEAR SKIES THIS MORNING. THE COLD FRONT WILL MOVE FULLY OFF THE
TEXAS COAST THIS MORNING THEN WILL MOVE QUICKLY ACROSS THE GULF
REACHING FROM NEAR TAMPA FLORIDA TO CORPUS CHRISTI TEXAS BY FRI
EVENING THEN DISSIPATE FROM THE UPPER FLORIDA KEYS W TO THE
CENTRAL GULF BY SAT EVENING. WEAK HIGH PRESSURE WILL BUILD
ACROSS THE AREA SAT AND SUN.

CARIBBEAN SEA...
A BROAD UPPER RIDGE EXTENDS AN AXIS FROM ACROSS THE YUCATAN
PENINSULA NEAR 18N89W TO OVER THE NW CARIBBEAN TO NEAR 17N83W. A
NARROW UPPER TROUGH EXTENDS FROM THE W ATLC INTO THE N/CENTRAL
CARIBBEAN THROUGH THE WINDWARD PASSAGE TO 16N79W. A SURFACE
TROUGH EXTENDS FROM 17N84W THROUGH THE YUCATAN CHANNEL NEAR THE
W TIP OF CUBA INTO THE GULF OF MEXICO. A SECOND BROAD UPPER
RIDGE COVERS THE REMAINDER OF THE CARIBBEAN ANCHORED NEAR
14N71W. THE MONSOON TROUGH EXTENDS FROM COLOMBIA NEAR 11N75W
ALONG 12N78W 11N82W ACROSS CENTRAL AMERICA INTO THE E PACIFIC
REGION...THE SURFACE LOW IS NO LONGER DISCERNIBLE. SCATTERED
SHOWERS/ISOLATED THUNDERSTORMS ARE N OF 15N E OF 65W TO ACROSS
THE LESSER ANTILLES/E PUERTO RICO AND S OF 16N BETWEEN 68W-83W.
THE SURFACE TROUGH NEAR THE WINDWARD ISLANDS WILL MOVE W INTO
THE SE CARIBBEAN THROUGH TONIGHT THEN REACH 70W BY FRI EVENING.

ATLANTIC OCEAN...
A STRONG SHORTWAVE UPPER TROUGH EXTENDS FROM MASSACHUSETTS
THROUGH 32N74W TO CUBA NEAR 23N80W GENERATING SCATTERED SHOWERS/
ISOLATED THUNDERSTORMS N OF 24N W OF 70W TO THE COAST OF
FLORIDA. A NARROW UPPER TROUGHS EXTENDS FROM OFF THE CANADIAN
MARITIMES INTO THE W ATLC E OF BERMUDA CONTINUING INTO THE
N/CENTRAL CARIBBEAN THROUGH THE WINDWARD PASSAGE GENERATING
SCATTERED SHOWERS/ISOLATED THUNDERSTORMS FROM 21N-24N BETWEEN
66W-71W. THIS UPPER TROUGH IS SUPPORTING SURFACE TROUGH THAT
EXTENDS FROM 31N55W TO 24N63W WITH SCATTERED SHOWERS AND
POSSIBLE ISOLATED THUNDERSTORMS WITHIN 90/120 NM OF LINE FROM
22N59W TO BEYOND 32N53W. AN UPPER RIDGE EXTENDS FROM THE E
CARIBBEAN OVER PUERTO RICO/VIRGIN ISLANDS NEAR 18N64W ALONG
26N57W TO BEYOND 32N52W PROVIDING DIFFLUENCE ALOFT TO GENERATE
SCATTERED SHOWERS/ISOLATED THUNDERSTORMS FROM 10N-22N BETWEEN
56W-65W. AN UPPER LOW IN THE E/CENTRAL ATLC NEAR 21N48W HAS
BECOME CUT OFF FROM THE UPPER TROUGH OVER THE E ATLC. THIS UPPER
LOW IS MASKING THE TROPICAL WAVE MAKING IT DIFFICULT TO LOCATE.
THE E ATLC UPPER TROUGH EXTENDS IS N OF THE CANARY ISLANDS E OF
30W. THE CENTRAL AND E ATLC IS DOMINATED BY A SURFACE RIDGE
ANCHORED WELL N OF THE DISCUSSION AREA. A COLD FRONT WILL MOVE
INTO THE NW WATERS LATE FRI AND EXTEND FROM 32N73W TO EXTREME S
FLORIDA BY SAT EVENING THEN FROM NEAR BERMUDA THROUGH STRAITS OF
FLORIDA SUN EVENING BEFORE GRADUALLY DISSIPATING FROM THE
N/CENTRAL ATLC THROUGH THE STRAITS OF FLORIDA LATE MON. HIGH
PRESSURE WILL BUILD NW OF FRONT LATE SUN THROUGH MON.

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

$$
PAW






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