High Seas Forecast
Issued by NWS

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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



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