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000
AXPZ20 KNHC 181552 RRA
TWDEP

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

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