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000
AXPZ20 KNHC 220218
TWDEP

TROPICAL WEATHER DISCUSSION
NWS NATIONAL HURRICANE CENTER MIAMI FL
0405 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 0000 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH 0215 UTC.


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

THE ITCZ AXIS WAS ANALYZED FROM 08N93W TO 06N103W TO 09N114W. A TROUGH WAS ANALYZED FROM 12N117W TO LOW PRES NEAR 08N121W 1008 MB TO 02N124W. THE MONSOON TROUGH AXIS WAS ANALYZED FROM 06N124W TO 06N130W TO LOW PRES NEAR 08N137W 1009 MB. SCATTERED MODERATE TO STRONG CONVECTION WAS OBSERVED FROM 05N TO 13N BETWEEN 115W AND 127W.


...DISCUSSION...

N OF 15N E OF 120W...A PAIR OF UPPER SHORT WAVE TROUGHS WILL MOVE ACROSS SOUTHERN CALIFORNIA AND THE NORTHERN PORTION OF BAJA CALIFORNIA NORTE AND THE GULF OF CALIFORNIA THROUGH LATE FRI...SUPPORTING 1008 MB LOW PRESSURE CENTERED OVER THE CALIFORNIA/ARIZONA BORDER. THIS HAS BEEN THE IMPETUS FOR 20 KT SW WINDS OVER THE FAR NORTHERN GULF OF CALIFORNIA AS NOTED IN EARLIER SCATTEROMETER SATELLITE IMAGERY. WINDS TO 25 KT ARE LIKELY IN THIS AREA THROUGH TONIGHT...WITH WINDS DIMINISHING EARLY FRI AS THE LOW PRESSURE WEAKENS AND SHIFTS NE OF THE AREA. MEANWHILE THE SUBTROPICAL RIDGE WILL BUILD ACROSS THE EASTERN PACIFIC WATERS N OF 20N IN THE WAKE OF THE UPPER TROUGH. A 17 UTC SCATTEROMETER PASS INDICATED A SURFACE TROUGH RELATED TO THE UPPER SHORT WAVE TROUGHS DENTING THE RIDGE...REACHING FROM 27N120W TO 27N115W. THIS FEATURE WILL ALLOW FOR GENTLE TO MODERATE BREEZES FARTHER OFFSHORE OF THE BAJA COAST NORTH OF PUNTA EUGENIA THROUGH TONIGHT. THE TROUGH WILL DISSIPATE THROUGH LATE SAT...ALLOWING A SLIGHT INCREASE IN NORTHERLY WINDS ALONG THE BAJA COAST AS THE RIDGE BUILDS EASTWARD.

LOOKING AHEAD...GLOBAL MODELS ARE INDICATING 15 TO 20 KT NORTHERLY WINDS AND SEAS 6 TO 7 FT OFF THE LENGTH OF THE BAJA COAST LATE FRIDAY THROUGH SUNDAY.

S OF 15N E OF 110W...1010 MB LOW PRESSURE WAS EVIDENT IN A 15 UTC SCATTEROMETER SATELLITE PASS OFF THE COAST OF COSTA RICA NEAR 09N85W. THIS MAY BE RELATED TO 15 TO 20 KT PLUME OF GAP WINDS THROUGH THE GULF OF PAPAGAYO JUST TO THE NORTH...AND PERHAPS A WEAK TROPICAL WAVE PASSING WEST IN THE LOWER TO MID LEVELS OF THE ATMOSPHERE. SURROUNDING CONVECTION IS RELATED TO DIVERGENCE ALOFT BETWEEN UPPER RIDGING TO THE EAST AND AN UPPER TROUGH TO THE NW OFF THE GUATEMALAN COAST. THE FRESH GAP FLOW THROUGH PAPAGAYO HAS DIMINISHED FOR NOW BUT WILL LIKELY RETURN OVERNIGHT THE NEXT COUPLE OF NIGHTS. GLOBAL MODELS INITIALIZE WELL WITH THE LOW PRESSURE...AND SHOW IT WEAKENING TO A SURFACE TROUGH THROUGH FRI AS IT DRIFTS WEST. CONVECTION WILL BE ACTIVE OVERNIGHT ALONG THE COASTLINE AND FARTHER WEST TO 100W NEAR THE ITCZ ALONG ROUGHLY 07N TO 10N. PERSISTENT SUBSIDENT NORTHERLY FLOW ALOFT IS LIMITING CONVECTIVE DEVELOPMENT ALONG THE ITCZ BETWEEN 100W AND 110W.

VARIOUS WAVE MODELS CONTINUE TO INDICATE LONGER PERIOD SOUTHERLY SWELL WITH HEIGHTS OF 8 TO 9 FT CROSSING THE EQUATOR TONIGHT REACHING AS FAR NORTH AS 03N THROUGH FRIDAY WEST OF THE GALAPAGOS BEFORE DECAYING BELOW 8 FT SAT. SEAS OF 5 TO 7 FT WILL REACH THE CENTRAL AMERICAN AND SOUTHERN MEXICAN COASTS SATURDAY WITH THE POTENTIAL FOR LARGE AND DANGEROUS SURF CONDITIONS.

LOOKING AHEAD...GLOBAL MODELS ARE IN LOOSE AGREEMENT SHOWING A BROAD LOW BECOMING MORE ORGANIZED EARLY NEXT WEEK NEAR ROUGHLY 10N100W...ALTHOUGH THERE REMAINS MUCH DISAGREEMENT REGARDING POSITION...TIMING AND STRENGTH. THE MAIN IMPACTS WILL BE INCREASE EASTERLY FLOW FROM 10N TO 15N EAST OF 100W...SEAS TO AT LEAST 7 FT...AND INCREASED SHOWERS AND THUNDERSTORMS.

ELSEWHERE...CONVECTION REMAINS VERY ACTIVE ACROSS THE DEEP TROPICS SOUTH OF 12N WEST OF 110W...WITH AN ELONGATED TROUGH FROM 12N117W TO 02N123W AND BROAD 1009 MB LOW PRESSURE CENTERED NEAR 07N136W. THESE SYSTEMS REMAIN FAIRLY DISORGANIZED FOR NOW...BUT GLOBAL MODELS INDICATE SLOW DEVELOPMENT THROUGH 48 HOURS. FOR NOW THE MAIN MARINE CONCERN OUTSIDE THUNDERSTORM ACTIVITY IS INCREASED TRADE WIND FLOW BETWEEN THE DEVELOPING LOW PRESSURE AREAS AND THE SUBTROPICAL RIDGE BUILDING TO THE NORTH. VARIOUS SHIP AND BUOY OBSERVATIONS ALONG WITH RECENT SCATTEROMETER AND ALTIMETER SATELLITE DATA INDICATE AREAS OF TRADE WINDS 20 TO 25 KT WITH SEAS TO 8 FT...SLIGHTLY ABOVE GUIDANCE INITIALIZATIONS. THE MARINE FORECAST REMAINS SLIGHTLY ABOVE GUIDANCE ACCORDINGLY INTO FRIDAY...ALTHOUGH SHIFTS TO A MORE CONSERVATIVE SOLUTION FAVORING THE ECMWF OVER THE GFS INTO SATURDAY CONCERNING DEVELOPMENT OF LOW PRESSURE ALONG THE TROUGH NEAR 120W.

LOOKING AHEAD...TROPICAL CYCLONE DEVELOPMENT IS POSSIBLE AFTER 48 HOURS ESPECIALLY CONCERNING LOW PRESSURE FORMING ALONG THE TROUGH AS IT SHIFTS WESTWARD.

$$ CHRISTENSEN

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