000
AXNT20 KNHC 272351
TWDAT 

TROPICAL WEATHER DISCUSSION 
NWS NATIONAL HURRICANE CENTER MIAMI FL 
805 PM EDT SAT APR 27 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 THE COAST OF SIERRA LEONE AT 
8N13W TO 4N20W. THE ITCZ BEGINS AT 4N20W AND CONTINUES ALONG 
3N30W EQ40W 3S50W. SCATTERED MODERATE CONVECTION IS FROM 4N-6N 
BETWEEN 16W-20W...AND FROM 3N-5N BETWEEN 31W-35W.

...DISCUSSION...

GULF OF MEXICO...    
BROAD UPPER RIDGING CONTINUES TO COVER THE GULF OF MEXICO 
SUPPORTING SURFACE RIDGING EXTENDING FROM A 1029 MB HIGH OFF THE 
COAST OF NEW JERSEY NEAR 39N74W. THIS PATTERN IS PROVIDING EAST 
TO SOUTHEAST SURFACE FLOW OF 10-15 KT. DRY AIR ALOFT IS HELPING 
CLEAR SKIES THROUGHOUT. HOWEVER...A BURST OF 
SHOWERS/THUNDERSTORMS HAS FORMED JUST INLAND OVER EASTERN TEXAS 
NEAR THE LOUISIANA BORDER. THIS ACTIVITY IS SE OF A FRONTAL 
BOUNDARY THROUGH CENTRAL TEXAS. THE FRONT WILL LIKELY STAY NORTH 
OF THE DISCUSSION AREA...BUT SHOWERS AND THUNDERSTORMS WILL BE 
POSSIBLE ALONG THE NORTHERN GULF COAST OVER THE NEXT COUPLE OF 
DAYS. 
 
CARIBBEAN SEA... 
THE BROAD UPPER RIDGE ACROSS THE GULF OF MEXICO CONTINUES INTO 
THE WESTERN CARIBBEAN WHILE BROAD UPPER TROUGHING COVERS THE 
REMAINDER OF THE BASIN WITH AXIS NEAR 75W. MOSTLY DRY AIR ALOFT 
IS PROVIDING FAIR SURFACE CONDITIONS WITH CLEAR SKIES EXCEPT FOR 
A FEW PATCHES OF CLOUDS AND POSSIBLE SHOWERS SOUTH OF PUERTO 
RICO AND HAITI. A FEW PATCHES OF CLOUDS ARE ALSO MOVING THROUGH 
THE NW CARIBBEAN AND INTO HONDURAS AND NICARAGUA. A LARGE AREA 
OF SHOWERS/THUNDERSTORMS REMAINS EAST OF WINDWARD ISLANDS. MODEL 
GUIDANCE CONTINUES TO SHOW A GRADUAL SHIFT WEST OF THIS MOISTURE 
BY EARLY NEXT WEEK...WHICH MAY BRING HEAVY SHOWERS AND 
THUNDERSTORMS TO THE SE CARIBBEAN. TRADEWIND FLOW OF 10-15 KT IS 
CURRENTLY PRESENT ACROSS THE MAJORITY OF THE BASIN WITH LITTLE 
CHANGE EXPECTED OVER THE NEXT 24 HOURS. 

ATLANTIC OCEAN...  
UPPER LEVEL RIDGING OVER THE SE CONUS SUPPORTS SURFACE RIDGING 
ACROSS THE WEST ATLC ANCHORED BY A 1029 MB HIGH OFF THE COAST OF 
NEW JERSEY NEAR 39N74W. A NARROW UPPER LEVEL TROUGH TO THE EAST 
ALONG 60W SUPPORTS A COLD FRONT NORTH OF THE AREA WHICH 
TRANSITIONS INTO A SURFACE TROUGH ALONG 31N64W 28N67W. A SECOND 
SURFACE TROUGH IS TO THE SE ALONG 30N59W TO 25N55W WITH POSSIBLE 
ISOLATED SHOWERS WITHIN 90 NM EAST OF THE AXIS. A WEAK THIRD 
SURFACE TROUGH IS FARTHER SOUTH ACROSS THE SE BAHAMAS AND 
HISPANIOLA ALONG 23N72W TO 18N69W WITH NO ASSOCIATED SHOWER 
ACTIVITY EXCEPT FOR A FEW POSSIBLE SHOWERS OVER HISPANIOLA. A 
LARGE AREA OF SHOWERS/POSSIBLE THUNDERSTORMS ARE EAST OF THE 
WINDWARD ISLANDS FROM 8N-13N BETWEEN 53W-61W. THE ACTIVITY IS 
LIKELY LINKED TO MOIST SOUTHWESTERLY FLOW ALOFT AROUND A BROAD 
UPPER TROUGH ACROSS THE CARIBBEAN. FARTHER NORTH...AN UPPER 
LEVEL LOW NEAR 36N38W CONTINUES TO SUPPORT 1007 MB SURFACE LOW 
NEAR 35N37W. A DISSIPATING COLD FRONT EXTENDS INTO THE 
DISCUSSION AREA ALONG 31N25W 24N28W 22N33W. POSSIBLE ISOLATED 
SHOWERS ARE ALONG THE AXIS. A BROAD UPPER RIDGE COVERS THE 
REMAINDER OF THE EASTERN TROPICAL ATLC PROVIDING MOSTLY FAIR 
CONDITIONS ACROSS THE AREA. 

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

$$ 
WALTON