000
AXPZ20 KNHC 201527
TWDEP 

TROPICAL WEATHER DISCUSSION                                      
NWS NATIONAL HURRICANE CENTER MIAMI FL                        
1605 UTC SAT APR 20 2013

TROPICAL WEATHER DISCUSSION FOR THE EASTERN PACIFIC OCEAN FROM 
THE EQUATOR TO 32N...EAST OF 140W. THE FOLLOWING INFORMATION IS 
BASED ON SATELLITE IMAGERY...WEATHER OBSERVATIONS...RADAR...AND 
METEOROLOGICAL ANALYSIS.

BASED ON 1200 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 
1500 UTC.

...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH...              
MONSOON TROUGH AXIS FROM 04N77W TO 08N90W TO 08N105W. ITCZ AXIS 
FROM 08N105W TO 06N115W TO 07N125W TO 04N140W. CLUSTER OF 
MODERATE TO ISOLATED STRONG FROM 03N TO 05N E OF 80W TO THE 
COAST OF COLOMBIA. SIMILAR CONVECTION IS NOTED S OF TROUGH 
BETWEEN 97W AND 100W...AND FROM 05N TO 07N BETWEEN 106W AND 
109W. SCATTERED MODERATE TO ISOLATED FROM 04N TO 07N BETWEEN 
130W AND 138W.

...DISCUSSION...                                                
GULF OF TEHUANTEPEC...AN EARLIER ASCAT PASS SHOWED MINIMAL GALE 
FORCE WINDS IN THE GULF OF TEHUANTEPEC. THESE WINDS ARE 
ASSOCIATED WITH A MODERATE SURFACE RIDGE OVER THE WESTERN GULF 
OF MEXICO IN THE WAKE OF A COLD FRONT CURRENTLY REACHING THE 
YUCATAN PENINSULA. GALE CONDITIONS ARE EXPECTED TO BE BRIEF... 
DIMINISHING BY THIS AFTERNOON AS THE HIGH PRESSURE BEHIND THE 
FRONT QUICKLY SHIFTS NORTHEASTWARD AWAY FROM THE SW GULF. WINDS 
ARE FORECAST TO BE BELOW 20-25 KT TONIGHT. NE SWELL FROM 
TEHUANTEPEC WILL MERGE WITH CROSS-EQUATORIAL 16-18 SECOND PERIOD 
SW SWELL LATER TODAY...WITH SEAS SUBSIDING TO 8 FT LATE TONIGHT. 
 
GULF OF CALIFORNIA...THE MOST RECENT ASCAT PASS SHOWED MAINLY 
FRESH NW WINDS IN THE CENTRAL GULF OF CALIFORNIA AND MODERATE NW 
WINDS IN THE SOUTHERN PART. WINDS WILL CONTINUE TO DIMINISH 
BELOW 20 KT IN THE CENTRAL PART TODAY AS THE PRESSURE GRADIENT 
OVER NW MEXICO SLACKENS. 

ALOFT...A VAST ANTICYCLONE CENTERED NEAR 14N108W EXTENDS A RIDGE 
AXIS NORTHWESTWARD TO BEYOND 30N126W AS WELL AS EASTWARD ACROSS 
SE MEXICO AND NORTHERN CENTRAL AMERICA INTO THE NW CARIBBEAN. 
UPPER LEVEL DIFFLUENCE ASSOCIATED WITH THE RIDGE AXIS IS 
ENHANCING SOME SHOWER ACTIVITY N OF 11N TO THE COASTS OF EL 
SALVADOR AND GUATEMALA. THE ANTICYCLONE IS EXPECTED TO WEAKEN 
OVER THE NEXT COUPLE OF DAYS. AN UPPER LOW THAT IS CURRENTLY 
NEAR 28N142W WILL CLIP THE N WATERS DURING THE FORECAST 
PERIOD...REACHING NEAR 31N129W BY MON EVENING. MODERATE TO 
STRONG UPPER LEVEL SUBSIDENCE AND IMPLIED DRY AIR MASS IS NOTED  
N OF 10N W OF 130W AND N OF 10N E OF 116W. IN BETWEEN... 
SOUTHERLY FLOW IS TRANSPORTING ABUNDANT MID TO UPPER LEVEL 
MOISTURE FROM THE TROPICS.  

AT THE SURFACE...THE 1033 MB SUBTROPICAL HIGH LOCATED NEAR 
39N137W EXTENDS A RIDGE AXIS SOUTHEASTWARD TO NEAR SOCORRO 
ISLAND. MODERATE TO FRESH NE TRADE WINDS CAN BE FOUND BETWEEN  
THE RIDGE AXIS AND THE ITCZ OVER WESTERN WATERS. WINDS HERE ARE 
EXPECTED TO DIMINISH TO A GENTLE TO MODERATE BREEZE BY SUN 
NIGHT...WITH SEAS THAT ARE CURRENTLY AROUND 9 FT UNDER NE SWELL 
GRADUALLY SUBSIDING BELOW 8 FT. 

$$
GR