Tropical Weather Discussion
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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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