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Eastern Pacific Tropical Weather Discussion



000
AXPZ20 KNHC 180923
TWDEP 

TROPICAL WEATHER DISCUSSION                                    
NWS NATIONAL HURRICANE CENTER MIAMI FL                         
1005 UTC THU DEC 18 2014

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 0600 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 
0900 UTC. 

...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH... 

THE MONSOON TROUGH EXTENDS W FROM THE PACIFIC COAST OF COLOMBIA  
NEAR 06N77W TO 07N90W WHERE IT TRANSITIONS TO AN ITCZ EXTENDING 
WESTWARD TO BEYOND 05N140W. MODERATE CONVECTION IS NOTED WITHIN 
60 NM S OF THE MONSOON TROUGH BETWEEN 90W AND 95W.

...DISCUSSION...                                                 

W OF 110W...
AN UPPER TROUGH FROM THE NORTHERN GULF OF CALIFORNIA 
TO 22N120W WILL SHIFT E TODAY AS MID/UPPER LEVEL SHORT WAVE 
ENERGY MOVES INTO SOUTHERN CALIFORNIA. DEEP LAYER RIDGING IS 
BUILDING OVER THE REGION W OF 120W. AN ASSOCIATED 1027 MB 
SURFACE HIGH IS CENTERED NEAR 28N148W WITH A RIDGE EXTENDING TO 
THE CENTRAL COAST OF THE BAJA CALIFORNIA PENINSULA. A 06 UTC 
ASCAT SATELLITE PASS INDICATES FRESH TO STRONG TRADE WINDS SOUTH 
OF THE RIDGE FROM THE ITCZ TO GENERALLY 20N. THE ASCAT PASS ALSO 
INDICATED A SHARP SURFACE TROUGH SOUTH OF 10N EMBEDDED IN THE 
ITCZ NEAR 138W. THIS FEATURE HAS BEEN MOVING ALONG THE ITCZ OVER 
THE PASS COUPLE OF DAYS...AND IS ENHANCING TRADE WIND FLOW TOWARD 
THE RIDGE AXIS TO THE NORTH. SEVERAL ALTIMETER SATELLITE PASSES 
OVER THE PAST 12 HOURS INDICATED SEAS OF 8 TO 10 FT IN THE AREA 
OF FRESH TO STRONG TRADE WINDS...LIKELY A COMBINATION OF 
LINGERING LONG PERIOD NW SWELL WITH SEAS GENERATE BY THE TRADE 
WINDS. ELSEWHERE LINGER NW SWELL IS MAINTAINING SEAS AT OR JUST 
BELOW 8 FT OVER MUCH OF THE AREA BETWEEN 110W AND 140W. 

DIVERGENCE ALOFT IN THE RIGHT REAR ENTRANCE REGION OF THE 
SUBTROPICAL JET ALOFT IS SUPPORTING A LARGE AREA OF MID/UPPER 
CLOUDINESS WITH A FEW EMBEDDED SHOWERS AND THUNDERSTORMS FROM 
12N TO 18N BETWEEN 115W AND 125W. 

THROUGH LATE FRI...A WEAK MID/UPPER IMPULSE WILL SWEEP EASTWARD 
N OF THE AREA INTO THE U.S. WEST COAST THROUGH LATE FRI. A 
BLOCKING RIDGE WILL DEVELOP IN THE WAKE OF THIS...REINFORCING 
THE SUBTROPICAL RIDGE AND ALLOWING THE AREA OF FRESH TO STRONG 
TRADE WINDS TO SPREAD EASTWARD TO 115W BY LATE FRI. THE EASTWARD 
SHIFT OF THE RIDGE WILL ALSO SUPPORT FRESH NW FLOW OFF THE 
PACIFIC COAST OF THE BAJA CALIFORNIA PENINSULA AND ALONG THE 
GULF OF CALIFORNIA. VARIOUS OPERATIONAL AND ENSEMBLE WAVE MODELS 
SUGGEST THAT A NEW SET OF LONG PERIOD NW SWELL WILL ENTER THE 
AREA FROM THE N CENTRAL PACIFIC WITH SEAS OF 12 TO 18 
FT...REACHING AS FAR AS W OF A LINE FROM SOUTHERN CALIFORNIA TO 
15N140W BY LATE FRI.

E OF 110W...AN AREA OF 7 TO 8 FT THAT IS THE REMNANT OF SHORT 
PERIOD NE SWELL FROM AN EARLIER GULF OF TEHUANTEPEC 
PULSE...MIXED WITH LONGER PERIOD NW SWELL...PERSISTS NEAR 
11N110W. THIS WILL DIMINISH BELOW 8 FT THROUGH TONIGHT. 

GULF OF PAPAGAYO...NE 15-20 KT NOCTURNAL PULSES EXPECTED THROUGH 
EARLY FRI.

GULF OF CALIFORNIA...LIGHT AND VARIABLE WINDS ARE EXPECTED TO 
BECOME NW AT 10-15 KT LATE THU...THEN GRADUALLY INCREASE TO 15-
20 KT BY EARLY FRI...THEN CONTINUING THROUGH THE WEEKEND. 

$$
CHRISTENSEN



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Page last modified: Thursday, 18-Dec-2014 09:24:08 UTC