000
AXNT20 KNHC 182335
TWDAT 

TROPICAL WEATHER DISCUSSION  
NWS NATIONAL HURRICANE CENTER MIAMI FL 
805 PM EDT THU APR 18 2013

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 
2315 UTC.

...ITCZ/MONSOON TROUGH... 

THE MONSOON TROUGH EXTENDS ACROSS AFRICA INTO THE E TROPICAL 
ATLC NEAR 13N16W THEN ALONG 8N18W TO 5N21W WHERE THE ITCZ BEGINS 
AND CONTINUES ALONG 5N28W 3N37W TO S OF THE EQUATOR NEAR 43W. 
SMALL CLUSTERS OF SCATTERED MODERATE CONVECTION ARE WITHIN 180 
NM ALONG THE COAST OF SW AFRICA S OF 6N W OF 4W AND WITHIN 240 
NM N OF THE ITCZ BETWEEN 33W-43W. 

...DISCUSSION...

GULF OF MEXICO...                                               
A BROAD UPPER RIDGE DOMINATES THE GULF WITH THE AXIS EXTENDING 
ACROSS S MEXICO INTO THE GULF NEAR VERACRUZ ALONG 26N90W THEN N 
TO OVER THE SE CONUS NEAR MOBILE ALABAMA. A LARGE UPPER TROUGH 
IS MOVING FROM THE PLAIN STATES TOWARD THE MISSISSIPPI VALLEY 
SUPPORTING A COLD FRONT THAT AT 18/2100 UTC EMERGED INTO THE 
GULF ENTERING NEAR PORT ARTHUR TEXAS TO A 1005 MB LOW NEAR 
28N96W CONTINUING TO INLAND OVER MEXICO AT THE TEXAS/MEXICO 
BORDER. SCATTERED SHOWERS AND POSSIBLE ISOLATED THUNDERSTORMS 
ARE WITHIN 90/120 NM W OF THE FRONT. A WEAK SURFACE RIDGE 
EXTENDS FROM THE W ATLC OVER THE N GULF COAST TO SE LOUISIANA. 
SOUTHERLY SURFACE FLOW AND MOSTLY CLEAR SKIES COVER THE 
REMAINDER OF THE GULF. THE COLD FRONT WILL EXTEND FROM MOBILE 
BAY TO VERACRUZ MEXICO FRI WEAKEN AND STALL FROM SW FLORIDA TO 
THE CENTRAL BAY OF CAMPECHE SAT THEN DISSIPATE SUN. GALE FORCE 
WINDS AND RAPIDLY BUILDING SEAS ARE EXPECTED W OF THE FRONT IN 
THE W AND SW GULF STARTING LATER TONIGHT THROUGH FRI NIGHT. 

CARIBBEAN SEA...                                               
THE UPPER RIDGE OVER THE GULF OF MEXICO COVERS THE FAR NW 
CARIBBEAN. A SECOND UPPER RIDGE ANCHORED IN THE TROPICAL ATLC 
COVERS MOST OF THE REMAINDER OF THE CARIBBEAN. BETWEEN THE TWO 
UPPER RIDGES IS AN INDUCED UPPER TROUGH THAT EXTENDS FROM E CUBA 
ACROSS THE CAYMAN ISLANDS TO OVER HONDURAS. THE TROPICAL ATLC 
UPPER RIDGE IS ADVECTING UPPER LEVEL MOISTURE OVER THE S 
CARIBBEAN WITH SCATTERED SHOWERS INLAND AND WITHIN 75 NM ALONG 
THE COAST OF COLOMBIA AND VENEZUELA BETWEEN 67W-75W. ISOLATED 
SHOWERS DOT THE N CARIBBEAN WITHIN 90/120 NM OF LINE FROM OVER 
HISPANIOLA NEAR 19N70W TO 20N83W INCLUDING PORTIONS OF CUBA AND 
JAMAICA. THIS IS LEAVING THE REMAINDER OF THE CARIBBEAN UNDER 
MOSTLY CLEAR SKIES THIS EVENING. WEAK SURFACE RIDGE ACROSS THE W 
AND CENTRAL ATLC WILL MAINTAIN MODERATE TO FRESH TRADE WINDS 
ACROSS THE CARIBBEAN THROUGH FRI WITH FRESH TO STRONG WINDS IN 
THE CENTRAL CARIBBEAN AND GULF OF HONDURAS. STRONG HIGH PRESSURE 
IN THE NW ATLC WILL BUILD S ACROSS THE W ATLC TONIGHT AND FRI TO 
STRENGTHEN WINDS FRI THROUGH SUN. 

ATLANTIC OCEAN...                                               
A BENIGN UPPER LEVEL PATTERN COVERS THE W ATLC THIS EVENING WHILE 
A SURFACE RIDGE BUILDS S OVER THE W AND CENTRAL ATLC ANCHORED BY 
A 1033 MB HIGH OFF THE CANADIAN MARITIMES. AN UPPER TROUGH IS IN 
THE CENTRAL ATLC EXTENDING THROUGH 32N42W ALONG 26N50W TO 22N58W 
SUPPORTING A COLD FRONT THAT EXTENDS THROUGH 32N39W TO 30N41W. 
SCATTERED SHOWERS AND POSSIBLE ISOLATED THUNDERSTORMS ARE WITHIN 
75 NM E OF THE FRONT. THE REMAINDER OF THE ATLC IS UNDER THE 
INFLUENCE OF WEAK SURFACE RIDGING. STRONG HIGH PRESSURE BUILDING 
S FROM THE NW ATLC WILL PERSIST THROUGH FRI. A COLD FRONT WILL 
ENTER THE W ATLC EARLY SAT MORNING STALLING LATE SAT/EARLY SUN 
FROM 32N74W TO CENTRAL FLORIDA THEN DISSIPATING THE FIRST OF 
NEXT WEEK. 

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

$$
PAW