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Eastern Pacific Tropical Weather Discussion



000
AXPZ20 KNHC 222129
TWDEP 

TROPICAL WEATHER DISCUSSION                                     
NWS NATIONAL HURRICANE CENTER MIAMI FL                         
2205 UTC FRI MAY 22 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 1800 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY  
THROUGH 2100 UTC. 

...SPECIAL FEATURES... 
A PAIR OF LOW PRESSURE SYSTEMS CONTINUE TO BECOME BETTER 
ORGANIZED THIS AFTERNOON OVER THE DEEP TROPICS W OF 120W. A 
TROUGH REACHES FROM 11N123W TO 1009 MB LOW PRES NEAR 05N126W. 
NUMEROUS MODERATE TO ISOLATED STRONG CONVECTION IS EVIDENT 
WITHIN 120 NM EITHER SIDE OF THE TROUGH AXIS. SCATTEROMETER AND 
ALTIMETER SATELLITE DATA INDICATE 20 TO 25 KT TRADE WINDS AND 
SEAS TO 8 FT BETWEEN THE TROUGH AND A BUILDING SUBTROPICAL RIDGE 
TO THE NORTH...SPECIFICALLY FROM 11N TO 16N BETWEEN 120W AND 
128W. THE SECOND LOW PRES IS FARTHER WEST NEAR 05N135W WITH AN 
ESTIMATED MSLP OF 1008 MB. THIS SYSTEM IS BETTER ORGANIZED FOR 
NOW ALTHOUGH CONVECTION IS DIMINISHING. GLOBAL MODELS ARE IN 
GOOD AGREEMENT SHOWING THE EASTERNMOST SYSTEM DEVELOPING AT THE 
EXPENSE OF THE WESTERNMOST LOW...AND SHIFTING NW TOWARD 12N130W 
IN 24 HOURS...AND 13N133W BY 48 HOURS. EITHER SYSTEM MAY DEVELOP 
INTO A TROPICAL CYCLONE WITHIN THE NEXT 48 HOURS...BUT THE LOW 
PRES NEAR 05N135W HAS MUCH NARROWER TIME WINDOW TO 
DEVELOP...AFTER WHICH IT WILL BECOME WEAKER. THE OFFICIAL 
FORECAST REFLECTS THIS SHOWING A MORE DOMINANT EASTERN LOW WITH 
WINDS REACHING 25 TO 30 KT THROUGH 48 HOURS NEAR THE LOW 
CENTER AND SEAS BUILDING 12 FT.

...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH...             
THE ITCZ AXIS WAS ANALYZED FROM 08N88W TO 07N95W TO 12N119W. 
SCATTERED MODERATE TO ISOLATED STRONG CONVECTION WAS OBSERVED 
WITHIN 180 NM N AND 240 NM S OF THE AXIS BETWEEN 88W AND 105W. 
SCATTERED MODERATE TO ISOLATED STRONG CONVECTION WAS EVIDENT 
WITHIN 180 NM N OF THE AXIS BETWEEN 105W AND 120W.

...DISCUSSION...

N OF 15N E OF 120W...
A DEEP LAYER TROUGH CONTINUES TO SLOWLY MOVE EASTWARD ACROSS THE 
BAJA PENINSULA AND THE GULF OF CALIFORNIA...SHIFTING EAST OF THE 
AREA SATURDAY. RIDGING WILL BUILD WEST OF THE AREA IN THE WAKE 
OF THE TROUGH. THE SURFACE RIDGE WILL EXTEND FROM WEST OF THE 
AREA THROUGH THE REVILLAGIGEDO ISLANDS...AND WILL ALLOW FOR A 
SLIGHT INCREASE IN NORTHERLY FLOW ALONG THE COAST OF BAJA 
CALIFORNIA THROUGH SUNDAY WITH SEAS 5 TO 7 FT. FRESH WESTERLY 
WINDS OVER THE FAR NORTHERN GULF OF CALIFORNIA WILL DIMINISH 
INTO SATURDAY AS THE TROUGH SHIFTS EAST.

S OF 15N E OF 110W...
AN UPPER TROUGH REMAINS ANCHORED FROM SOUTHERN MEXICO NEAR 
TEHUANTEPEC SOUTHWARD TO THE GALAPAGOS ISLANDS. DIVERGENCE AND 
INSTABILITY ASSOCIATED WITH THE UPPER TROUGH INTERACTED WITH 
COASTAL MORNING THUNDERSTORMS OFF GUATEMALA TO CREATE A SQUALL 
LINE THAT MOVED RAPIDLY WESTWARD INTO THE GULF OF TEHUANTEPEC 
BEFORE DISSIPATING THIS AFTERNOON. AN EARLIER SCATTEROMETER 
SATELLITE PASS INDICATED FRESH GAP WINDS THROUGH THE GULF OF 
PAPAGAYO. A CONCURRENT ALTIMETER SATELLITE PASS INDICATED SEAS 
TO 7 FT IN THE GAP WIND PLUME. THIS HAS DIMINISHED BY WILL 
LIKELY RETURN TONIGHT...POSSIBLY WITH WINDS BRIEFLY REACHING 25 
KT AND SEAS BUILDING TO 8 FT. AN UPPER RIDGE IS BUILDING 
WESTWARD ALONG ROUGHLY 08N-10N DISPLACING AND WEAKENING THE 
UPPER TROUGH. DIVERGENCE ALOFT ON THE SOUTHERN EDGE OF THE UPPER 
RIDGE IS ALREADY STARTING TO ENHANCE CONVECTION ALONG THE ITCZ. 

LONG PERIOD SOUTH-SOUTHWESTERLY SWELL PRODUCING WAVE HEIGHTS TO 
10 FT AND PERIODS OF 17-19 SECONDS WILL BEGIN TO SUBSIDE 
TONIGHT...WITH SEAS OVER 8 FT SLIPPING S OF THE EQUATOR BY SUN 
MORNING. 4 TO 6 FT OF SWELL WILL REACH THE COASTLINES OF CENTRAL 
AMERICA AND SOUTHERN MEXICO LATE TONIGHT AND SAT. THESE LONG 
PERIOD SWELLS WILL GENERATE LARGE AND DANGEROUS SURF CONDITIONS 
ALONG THESE COASTLINES THROUGH THE UPCOMING WEEKEND.

ELSEWHERE... 
A COLD FRONT APPROACHING THE HAWAIIAN ISLANDS IS 
EXPECTED TO TO MOVE JUST W OF THE FORECAST AREA OVER THE 
WEEKEND. SE WINDS WILL INCREASE AHEAD OF THE FRONT TO 20-25 KT 
BY SAT NIGHT WITH SEAS BUILDING TO 8-10 FT BY SUN MORNING IN THE 
AREA FROM 22N-29N W OF 137W. SHOWERS AND ISOLATED THUNDERSTORMS 
WILL ALSO MOVE IN AHEAD OF THE FRONT.

$$ 
CHRISTENSEN


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Page last modified: Friday, 22-May-2015 21:29:25 UTC