000
AXNT20 KNHC 212312
TWDAT 

TROPICAL WEATHER DISCUSSION
NWS NATIONAL HURRICANE CENTER MIAMI FL
805 PM EDT THU MAR 21 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 
2245 UTC.

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

THE MONSOON TROUGH EXTENDS FROM THE NORTHERN COAST OF GUINEA 
NEAR 11N15W INTO THE EASTERN TROPICAL ATLC ALONG 5N16W 3N25W. 
THE ITCZ BEGINS AT 3N25W AND CONTINUES ALONG 3N39W EQ47W. A 
LARGE CLUSTER OF NUMEROUS STRONG CONVECTION IS SOUTH OF THE 
MONSOON TROUGH FROM EQ-5N BETWEEN 12W-18W. ISOLATED MODERATE 
CONVECTION IS WITHIN 120 NM NORTH OF THE AXIS BETWEEN 24W-46W.
 
...DISCUSSION...

THE GULF OF MEXICO...

SURFACE RIDGING HAS BEGUN TO BUILD ACROSS THE GULF OF MEXICO 
AROUND A 1016 MB SURFACE HIGH CENTERED SOUTH OF THE FLORIDA 
PANHANDLE NEAR 29N86W...AS OF 2100 UTC. THE RIDGE IS SUPPORTED 
BY A BROAD UPPER RIDGE MOVING OVER MEXICO...TEXAS AND OTHER 
PORTIONS OF THE CENTRAL CONUS. ALSO AS OF 2100 UTC...THE PORTION 
OF THE FRONTAL BOUNDARY IN THE SOUTHERN GULF HAS BEGUN TO 
QUICKLY DISSIPATE. A DISSIPATING COLD FRONT NOW EXTENDS ACROSS 
MUCH OF CUBA FROM 23N80W TO 23N86W BECOMING A DISSIPATING 
STATIONARY FRONT TO 22N94W. SCATTERED SHOWERS/THUNDERSTORMS ARE 
ACROSS CUBA NEAR THE AXIS...AS WELL AS SOUTH OF THE AXIS ACROSS 
THE NE TIP OF THE YUCATAN PENINSULA. NO SHOWERS ARE ALONG THE 
REMAINDER OF THE AXIS. STRONG SURFACE FLOW IS ALSO NORTH OF THE 
AXIS AROUND THE RIDGE RANGING FROM 15-20 KT WITH LIGHTER WINDS 
NEAR THE HIGH CENTER. LIGHTER WINDS ALSO REMAIN SOUTH OF THE 
FRONT IN THE SW GULF. THE FRONT WILL CONTINUE TO DISSIPATE AND 
THE RIDGE IS EXPECTED TO SHIFT EAST ALLOWING FOR RETURN FLOW TO 
BUILD ACROSS THE WESTERN GULF. 

THE CARIBBEAN SEA...
                                                 
MOSTLY FAIR WEATHER IS ACROSS THE CARIBBEAN DUE TO DRY AIR ALOFT 
AROUND A BROAD UPPER LEVEL RIDGE COVERING THE BASIN. ONLY A FEW 
POSSIBLE ISOLATED SHOWERS ARE OVER THE NORTHEAST PORTION OF THE 
BASIN AND ACROSS CUBA NEAR THE DISSIPATING COLD FRONT. A LIGHT 
PRESSURE GRADIENT ACROSS THE AREA IS PRODUCING WEAK TRADEWINDS 
OF 5-10 KT THROUGHOUT WITH A SMALL AREA OF 15 KT WINDS IN THE 
FAR EASTERN CARIBBEAN. LITTLE CHANGE IS EXPECTED EXCEPT FOR A 
POSSIBLE INCREASE IN MOISTURE AND SHOWER ACTIVITY ACROSS THE 
NORTHEASTERN CARIBBEAN AS THE FRONTAL BOUNDARY IN THE WEST ATLC 
MOVES EAST. 

THE ATLANTIC OCEAN...
 
A DEEP LAYERED TROUGH IS IMPACTING THE WESTERN GULF WITH A LARGE 
UPPER LOW CENTERED NORTH OF NEW YORK STATE AND UPPER TROUGH 
AXIS EXTENDING DOWN 63W. THE UPPER LEVEL PATTERN SUPPORTS A COLD 
FRONT THAT ENTERS THE DISCUSSION AREA NEAR 32N67W AND CONTINUES 
TO THE SE BAHAMAS NEAR 23N73W AND BEGINS TO DISSIPATE INTO CUBA 
NEAR 22N77W. A SURFACE TROUGH IS EAST OF THE FRONT ALONG THE 
LINE OF HEAVY SHOWERS AND THUNDERSTORMS THE AXIS IS ALONG 31N63W 
TO 26N68W. THE LINE OF SHOWERS IS MOVING RAPIDLY EAST AND NOW IS 
EAST OF THE TROUGH AXIS WITHIN 230 NM. STRONG WINDS ARE ALSO 
ALONG THE FRONT AXIS. NO SHOWER ACTIVITY IS ALONG THE FRONTAL 
BOUNDARY. SURFACE RIDGING DOMINATES THE CENTRAL ATLC AROUND A 
1023 MB HIGH NEAR 30N43W. THE RIDGE IS SUPPORTED BY AN UPPER 
LEVEL RIDGE ALONG 49W. FAIR CONDITIONS ARE ACROSS THIS AREA. 
FARTHER EAST...A BROAD UPPER TROUGH WITH AXIS ALONG 18W SUPPORTS 
ANOTHER COLD FRONT THAT ENTERS THE AREA NEAR 32N16W AND 
CONTINUES ALONG 26N24W 23N34W AND BEGINS TO DISSIPATE TO 24N42W. 
POSSIBLE ISOLATED SHOWERS ARE ALONG THE AXIS. FAIR WEATHER 
REMAINS ACROSS THE REMAINDER OF THE EAST ATLC. 

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

$$
WALTON