000
FZPN03 KNHC 181508 RRA
HSFEP2

TROPICAL WEATHER DISCUSSION                                    
NWS NATIONAL HURRICANE CENTER MIAMI FL                         
1605 UTC SAT APR 18 2015

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 
1515 UTC. 
 
...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH...              

ITCZ AXIS EXTENDS FROM 05N100W TO 02N110W TO 05N135W. SCATTERED 
MODERATE TO ISOLATED STRONG CONVECTION IS OBSERVED FROM 03N TO 
11N BETWEEN 130W AND 138W. ALSO...TRADE WIND CONVERGENCE IS 
PRODUCING MODERATE CONVECTION WITHIN 90 NM EITHER SIDE OF A LINE 
FROM 13N115W TO 11N125W.

A TROUGH EXTENDS FROM 07N85W TO 06N100W. SCATTERED 
MODERATE CONVECTION IS WITHIN 180 NM S OF THE TROUGH BETWEEN 
85W AND 95W.

CONVERGENCE OF 15 TO 20 KT SOUTHERLY FLOW ACROSS THE EQUATOR IS 
PRODUCING SCATTERED MODERATE TO ISOLATED STRONG CONVECTION 
WITHIN 120 NM EITHER SIDE OF A LINE FROM 00N97W AND 00N105W. 

...DISCUSSION... 

E OF 120W...
A WEAK PRESSURE PATTERN CONTINUES ACROSS THE REGION. RECENT BUOY 
AND SHIP OBSERVATIONS ALONG WITH SCATTEROMETER SATELLITE DATA 
INDICATE MAINLY LIGHT TO GENTLE BREEZES. RECENT ALTIMETER 
SATELLITE DATA INDICATED NW SWELL WITH WAVE HEIGHTS 8 TO 9 FT 
PROPAGATING E OF 120W TO NEAR 117W TO THE NORTH OF 13N. FARTHER 
SOUTH ALTIMETER DATA IS SHOWING WAVE HEIGHTS TO 7 FT W OF THE 
GALAPAGOS ISLANDS...PRIMARILY DUE TO SOUTHERLY SWELL. VARIOUS 
WAVE GUIDANCE INDICATES THE SOUTHERLY SWELL WILL PERSIST W OF 
110W THROUGH SUNDAY. ELSEWHERE SEAS ARE GENERALLY 3 TO 5 
FT...MAYBE SLIGHTLY HIGHER NEAR THE GULF OF PAPAGAYO WHERE 15 TO 
20 KT WINDS WERE LIKELY EARLIER THIS MORNING. WEAK DIVERGENCE 
ALOFT ON THE SOUTHERN PERIPHERY OF AN UPPER ANTICYCLONE CENTERED 
NEAR 07N90W IS ENHANCING MODEST CONVECTION ALONG A TROUGH 
EXTENDING FROM 07N85W TO 06N100W. OVERNIGHT SCATTEROMETER DATA 
SHOWED 15 TO 20 KT SOUTHERLY FLOW CROSSING THE EQUATOR AND  
CONVERGING INTO NEARLY CALM WINDS TO PRODUCE A LINE OF SHOWERS 
AND THUNDERSTORMS WITHIN 120 NM EITHER SIDE OF A LINE FROM 
00N97W AND 00N105W.

W OF 120W...
A LARGE AREA OF SHOWERS AND THUNDERSTORMS REMAINS ACTIVE FROM 
03N TO 11N W OF 130W. THIS IS DUE TO LOW LEVEL TRADE WIND 
CONVERGENCE INTERACTING WITH PERSISTENT DIVERGENCE ALOFT BETWEEN 
A SHARP UPPER TROUGH NW OF AREA AND A BROAD UPPER RIDGE CENTERED 
NEAR 10N120W. AN ASSOCIATED SURFACE TROUGH REMAINS STATIONARY 
AMID THE CONVECTION ALONG ROUGHLY 140W BETWEEN 03N AND 13N. THE 
FRESH TRADE WINDS PERSIST IN THE REGION BETWEEN THE TROUGH AND 
THE MODERATELY STRONG SUBTROPICAL RIDGE...REACHING FROM 30N140W 
TO SOUTH OF THE BAJA CALIFORNIA PENINSULA. LONG PERIOD NW SWELL 
CONTINUES TO PROPAGATE INTO THE REGION. ALTIMETER DATA SHOW SEAS 
8 TO 10 FT OVER MUCH OF THE AREA N OF 12N. THE OFFICIAL FORECAST 
FOLLOWS THE ECWAVE GUIDANCE FOR THIS SWELL THAT IS MORE 
INDICATIVE OF ENSEMBLE MEANS INDICATING THE SWELL 8 FT OR 
GREATER WILL PERSIST INTO EARLY MON...OVER THE MWW3 WHICH DECAYS 
MOST OF THE SWELL TO LESS THAN 8 FT THROUGH LATE TODAY.

$$
CHRISTENSEN