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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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