000
AXNT20 KNHC 181042
TWDAT 

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

...ITCZ/MONSOON TROUGH... 

THE MONSOON TROUGH EXTENDS FROM THE AFRICAN COAST NEAR 12N16W TO 
03N21W. THE INTERTROPICAL CONVERGENCE ZONE AXIS EXTENDS FROM 
03N21W TO 01N25W TO THE EQUATOR NEAR 36W. ISOLATED MODERATE 
CONVECTION IS FROM 01N-05N BETWEEN 10W-42W.

...DISCUSSION...

GULF OF MEXICO...                                               
WATER VAPOR IMAGERY INDICATES UPPER LEVEL RIDGING CONTINUES TO 
BUILD IN OVER PORTIONS OF THE WESTERN GULF WITH NORTH-
NORTHWESTERLY FLOW ALOFT DOMINATING W OF 83W. THIS UPPER LEVEL 
REGIME IS SUPPORTIVE OF THE SOUTHWESTERN PERIPHERY OF A SURFACE 
RIDGE ANCHORED OVER THE SE CONUS. EAST-SOUTHEASTERLY WINDS IN 
THE RANGE OF 15 TO 25 KT ARE NOTED ON SHIP OBSERVATIONS... 
BUOYS...AND OFFSHORE OIL PLATFORMS WITH THE STRONGEST WINDS 
PRIMARILY OCCURRING W OF 90W THIS MORNING AS AN AREA OF LOW 
PRESSURE CONTINUES TO DEVELOP AND PRODUCE ACTIVE WEATHER FROM 
THE GREAT LAKES REGION TO THE RIO GRANDE RIVER VALLEY. THE 
ASSOCIATED COLD FRONT WITH THIS LOW IS EXPECTED TO EMERGE OFF 
THE TEXAS AND LOUISIANA COAST LATE THURSDAY INTO EARLY FRIDAY. 
NORTH-NORTHEASTERLY WINDS WILL THEN SWEEP ACROSS THE GULF DURING 
THE WEEKEND AS THE FRONT MOVES EAST OF THE BASIN BY LATE 
SATURDAY.

CARIBBEAN SEA...                                               
AN UPPER LEVEL TROUGH AXIS EXTENDS FROM OVER THE NW CARIBBEAN 
NEAR 21N83W TO 14N88W. EAST OF THE TROUGH AXIS DRY AND SUBSIDENT 
WEST-NORTHWESTERLY FLOW CONTINUES TO PROVIDE OVERALL TRANQUIL 
CONDITIONS FOR THE A MAJORITY OF THE BASIN THIS MORNING WITH THE 
EXCEPTION OF AN AREA OF ISOLATED SHOWERS OCCURRING IN THE 
VICINITY OF THE LESSER ANTILLES FROM 14N-18N BETWEEN 56W-63W. 
OTHERWISE...TRADES PERSIST IN THE RANGE OF 15 TO 25 KT WITH THE 
HIGHEST WINDS ANTICIPATED S OF 14N BETWEEN 68W-78W...AND IN 
CLOSE PROXIMITY TO THE COAST OF COLOMBIA. THIS OVERALL SYNOPTIC 
PATTERN IS EXPECTED TO CONTINUE THROUGH THE UPCOMING WEEKEND.

ATLANTIC OCEAN...                                               
DRY AND SUBSIDENT NW FLOW ALOFT DOMINATES OVER THE SW NORTH 
ATLC...HOWEVER AT THE SURFACE...AN ELONGATED SURFACE TROUGH 
SNAKES FROM WEST OF BERMUDA NEAR 34N67W TO 28N71W PROVIDING 
FOCUS FOR ISOLATED LOW-TOPPED SHOWERS GENERALLY N OF 30N BETWEEN 
62W-74W. FARTHER EAST...A MIDDLE TO UPPER LEVEL TROUGH IS NOTED 
ON WATER VAPOR IMAGERY WITH AXIS EXTENDING FROM 34N43W TO A BASE 
NEAR 21N58W. THIS TROUGHING SUPPORTS A DISSIPATING COLD FRONT 
ANALYZED FROM 32N39W SW TO 25N54W WITH ISOLATED SHOWERS 
OCCURRING WITHIN 120 NM EITHER SIDE OF THE BOUNDARY. 
OTHERWISE...THE REMAINDER OF THE EASTERN ATLC IS UNDER THE 
INFLUENCE OF WEAK SURFACE RIDGING WITH NORTHEASTERLY TRADES IN 
THE RANGE OF 10 TO 20 KT.

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

$$
HUFFMAN