000
AXPZ20 KNHC 171526
TWDEP 

TROPICAL WEATHER DISCUSSION                                    
NWS NATIONAL HURRICANE CENTER MIAMI FL                         
1605 UTC FRI APR 17 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 
1500 UTC. 
 
...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH...              

THE ITCZ AXIS EXTENDS FROM 05N100W TO 04N120W TO 03N130W TO 
06N137W. SCATTERED MODERATE CONVECTION IS OBSERVED WITHIN 120 NM 
S OF THE AXIS BETWEEN 105W AND 115W...AND ALSO S OF THE AXIS 
BETWEEN 120W AND 125W.

A TROUGH EXTENDS FROM 08N90W TO 06N95W TO 05N100W. SCATTERED 
MODERATE CONVECTION IS OBSERVED WITHIN 60 NM EITHER SIDE THE 
TROUGH BETWEEN 93W AND 100W.

AN AREA OF SCATTERED MODERATE CONVECTION IS OBSERVED FROM 02N TO 
07N E OF 90W UNDER AN AREA OF UPPER LEVEL DIVERGENCE.

AN AREA OF SCATTERED MODERATE TO ISOLATED STRONG CONVECTION IS 
NOTED FROM 08N TO 12N W OF 132W.

...DISCUSSION... 

E OF 120W... 
A MID TO UPPER LEVEL TROUGH IS MOVING EASTWARD 
ACROSS BAJA CALIFORNIA SUR THIS MORNING. INSTABILITY ASSOCIATED 
WITH UPPER JET DYNAMICS AHEAD OF THE TROUGH IS SUPPORTING A 
BROAD AREA OF HIGH CLOUDINESS ACROSS THE SOUTHERN BAJA PENINSULA 
AND GULF OF CALIFORNIA. LOCAL OBSERVATIONS SUGGEST THERE IS WITH 
LITTLE IMPACT ON SURFACE CONDITIONS. RIDGING BUILDING BEHIND THE 
TROUGH IS SUPPORTING 15 TO 20 KT NORTHERLY WINDS OFF THE BAJA 
COAST AS NOTED BY A FEW SHIP OBSERVATIONS THIS MORNING. SEAS OFF 
THE BAJA COAST ARE CURRENTLY 4 TO 6 FT. AN ALTIMETER SATELLITE 
PASS ALONG 122W EARLIER THIS MORNING OBSERVED 8 TO 10 FT SEAS N 
OF 25N. THIS IS EVIDENCE OF LONGER PERIOD NW SWELL INITIALIZED 
IN WAVE MODEL GUIDANCE THAT SHOW SEAS OFF THE BAJA COAST E TO 
120W BUILDING TO 5 TO 8 FT THROUGH TONIGHT BEFORE SUBSIDING 
THROUGH SATURDAY. 

A WEAK PRESSURE PATTERN CONTINUES OVER THE TROPICAL WATERS E OF 
120W WITH BUOY OBSERVATIONS AND SCATTEROMETER SATELLITE DATA 
SHOWING GENERALLY LIGHT TO GENTLE TRADE WIND FLOW. UPPER 
DIVERGENCE ON THE SOUTHERN PERIPHERY OF AN UPPER ANTICYCLONE 
SITUATED OVER 12N90W IS SUPPORTING CLUSTERS OF SHOWERS AND 
THUNDERSTORMS FROM 02N TO 07N E OF 90W. MODEST TRADE WIND 
CONFLUENCE IS SUPPORTING A FEW SHOWERS AND THUNDERSTORMS ALONG 
THE ITCZ BETWEEN 105W AND 115W. OVERNIGHT LOCAL DRAINAGE EFFECTS 
WILL ALLOW WINDS OF 15 TO 20 KT TONIGHT IN THE GULF OF 
PAPAGAYO...WITH SEAS OF 5 TO 7 FT. OTHERWISE SEAS ARE GENERALLY 
3 TO 5 FT IN MOST AREAS...WITH UP TO 6 FT IN SOUTHERLY SWELL W 
OF THE GALAPAGOS. LITTLE CHANGE IS EXPECTED THROUGH 48 HOURS.

W OF 120W...
AREAS OF MODERATE TO STRONG CONVECTION IS NOTED ON SATELLITE 
IMAGERY FROM 08N TO 12N W OF 132W...ON THE NORTH SIDE OF A 
SURFACE TROUGH NEAR 140W S OF 10N. THE TROUGH AND ATTENDANT 
CONVECTION IS ASSOCIATED WITH UPPER DIVERGENCE AHEAD OF A SHARP 
UPPER TROUGH NW OF THE AREA. FRESH TRADE WINDS ARE NOTED BETWEEN 
THE SURFACE TROUGH AND THE SUBTROPICAL RIDGE N OF THE AREA...AS 
NOTED BY AN EARLIER SCATTEROMETER SATELLITE PASS AND REPORTS 
FROM GERMAN RV SONNE ON STATION NEAR 14N130W. THE TROUGH WILL 
SHIFT W OF THE AREA LATE TODAY. THE FRESH TRADE WINDS WILL 
PERSIST FROM 10N TO 15N W OF 130W INTO EARLY SUNDAY. RECENT DATA 
FROM A PAIR OF ALTIMETER SATELLITE PASSES INDICATE SEAS OF 8 TO 
10 FT OVER MUCH OF THE AREA NW OF A LINE FROM 30N120W TO 11N140W 
DUE MAINLY TO LONG PERIOD NW SWELL. THE MWW3 SHOWS MUCH OF THIS 
SWELL DECAYING BELOW 8 FT THROUGH SATURDAY...BUT THIS MAY BE 
AFFECTED BY A LOW BIAS WRT TO SWELL AND IS AN OUTLIER COMPARED 
TO ALL OTHER GUIDANCE. THE OFFICIAL FORECAST FAVORS THE 
ECMWF/UKWAVE/GWES SHOWING 8 FT SEAS LINGERING OVER A LARGER AREA 
THROUGH 48 HOURS FROM 08N TO 15N W OF 115W...DECAYING TO BELOW 8 
FT IN MOST AREAS THROUGH LATE SUNDAY.

$$
CHRISTENSEN