000 AXPZ20 KNHC 142154 TWDEP TROPICAL WEATHER DISCUSSION NWS NATIONAL HURRICANE CENTER MIAMI FL 2205 UTC THU MAY 14 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 2015 UTC. ...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH... THE MONSOON TROUGH AXIS WAS ANALYZED FROM 10N84W TO 06N94W TO 11N115W. THE ITCZ AXIS WAS ANALYZED FROM TO 12N119W TO LOW PRES NEAR 10N123W 1010 MB TO LOW PRES NEAR 09N133W 1010 MB TO 06N140W. SCATTERED MODERATE TO STRONG CONVECTION WAS FROM 04N- 08N BETWEEN 84W-91W. SCATTERED MODERATE WITH ISOLATED STRONG CONVECTION WAS FROM 09N-14N BETWEEN 111W-122W. SCATTERED MODERATE CONVECTION WAS WITHIN 90 NM N AND 180 NM S OF THE AXIS BETWEEN 122W AND 128W...WITHIN 150 NM SE QUADRANT OF THE LOW PRES NEAR 09N133W AND BETWEEN 150 NM AND 330 NM S OF THE AXIS BETWEEN 127W-139W. ...DISCUSSION... A 1026 MB SUBTROPICAL HIGH CENTERED NW OF THE AREA NEAR 33N147W EXTENDS A RIDGE SE THROUGH 25N135W TO NEAR 19N107W. THE PRESSURE GRADIENT BETWEEN THIS RIDGE AND LOW PRES SYSTEMS EMBEDDED IN THE ITCZ NEAR 09N133W IS GENERATING FRESH TO STRONG NE TRADE WINDS THIS AFTERNOON. THE SURFACE RIDGE IS EXPECTED TO SHIFT SW THROUGH FRI AS A COLD FRONT APPROACHES THE HIGH FROM THE NW AND A SERIES OF IMPULSES ON THE W SIDE OF THE UPPER TROUGH CENTERED ALONG 125W N OF 20N DIP INTO THE NE PORTION OF THE AREA. THIS WILL KEEP THE PRESSURE GRADIENT STRONG ENOUGH TO SUPPORT FRESH TO STRONG TRADES DESPITE THE EXPECTED TRANSIENT NATURE LOW PRES ALONG THE ITCZ. THE SUBTROPICAL HIGH WILL SHIFT SOUTHWARD THROUGH FRI BEFORE MERGING INTO THE SE SIDE OF A NEW HIGH CENTERED N OF HAWAII SAT. TRADES ARE STILL EXPECTED TO BE A FRESH TO OCCASIONALLY STRONG BREEZE THROUGH SAT AFTERNOON. ONE OF THE IMPULSES IN THE AFOREMENTIONED UPPER TROUGH CENTERED NEAR 125W IS EXPECTED TO LIE OFF THE SOUTHERN CALIFORNIA COAST BY FRI MORNING. A STRONG SURFACE REFLECTION IS EXPECTED WITH THIS IMPULSE. NW SWELL ASSOCIATED WITH THE SYSTEM WILL BUILD SEAS TO 8 FT N OF 29N BETWEEN 126W AND 135W THIS EVENING. A COLD FRONT WILL MOVE INTO N WATERS EARLY FRI MORNING AND IS EXPECTED TO APPROACH THE COAST NEAR ENSENADA FRI AFTERNOON BEFORE MOVING INTO THE NORTHERN GULF OF CALIFORNIA. WINDS IN THE PACIFIC WILL REACH A FRESH TO STRONG BREEZE ON THE LEADING EDGE OF THE SYSTEM OVERNIGHT TONIGHT AND SEAS WILL BUILD AS HIGH AS 11 FT FRI. A VAST ANTICYCLONE ALOFT IS CENTERED NEAR 07N118W AND EXTENDS A RIDGE AXIS SW TO BEYOND 04N140W. THE ITCZ IS PARTICULARLY CONVECTIVELY ACTIVE BETWEEN 110W AND 140W IN THE VICINITY OF THIS ANTICYCLONE AND THIS RIDGE WHERE UPPER LEVEL DIVERGENCE IS ENHANCING LIFT OF THE MOIST LOW-LEVELS AROUND THE ITCZ. THIS CONVECTION IS DESCRIBED IN THE SECTION ABOVE. THE ABUNDANT CONVECTION IN THIS AREA IS ASSOCIATED WITH A KELVIN WAVE PROPAGATING THROUGH THE REGION. FORECAST GUIDANCE SUGGESTS THAT THE ANTICYCLONE WILL SHIFT SLIGHTLY NW TO NEAR 13N121W THROUGH SAT EVENING...WITH PRECIPITATION WANING A BIT DURING THAT PERIOD. 16-18 SECOND PERIOD CROSS-EQUATORIAL S-SW SWELL IS SUBSIDING ALONG THE MEXICAN AND CENTRAL AMERICAN COAST...EXCLUDING THE GULF OF CALIFORNIA. SURF CONDITIONS SHOULD BE IMPROVING IN THESE AREAS. SEA HEIGHTS OF 8 FT OR GREATER IN SW SWELL ARE NOW CONFINED TO THE SE WATERS PRIMARILY S-SW FROM THE GULF OF PANAMA. SHIP A8PC6 REPORTED 9 FT SEAS NEAR 6.7N79.6W AT 1800 UTC. THESE SEAS SHOULD SUBSIDE OVERNIGHT TONIGHT. GAP WINDS... GULF OF CALIFORNIA...THE PRES GRADIENT BETWEEN THE SUBTROPICAL RIDGE AND TROUGHING OVER THE SW UNITED STATES SUPPORTS FRESH TO STRONG S-SW WINDS IN THE GULF OF CALIFORNIA N OF 29.5N...WITH WINDS FUNNELING THROUGH MOUNTAIN PASSES LIKELY REACHING NEAR GALE FORCE. SEAS ARE BELIEVED TO BE AS HIGH AS 8 FT. WINDS SHOULD DIMINISH AROUND SUNRISE FRI AS THE SURFACE SYSTEM MOVES EASTWARD...BUT WILL RESUME AHEAD OF THE COLD FRONT MOVING INTO THE NORTHERN GULF OF CALIFORNIA LATE FRI. THE COLD FRONT WILL WEAKEN QUICKLY...WITH WINDS AND SEAS EXPECTED TO DIMINISH AROUND SUNRISE SAT. GULF OF PAPAGAYO...THE PRESSURE GRADIENT BETWEEN RIDGING OVER THE NW CARIBBEAN AND TROUGHING NEAR THE ITCZ IS SUPPORTING A FRESH TO STRONG BREEZE IN THE GULF OF PAPAGAYO ACCORDING TO THE 1808 UTC RAPIDSCAT PASS. THESE WINDS WILL DIMINISH AT THE DIURNAL MINIMUM THIS EVENING AND RETURN IN THE EARLY MORNING HOURS FRI WITH THE ASSISTANCE OF NOCTURNAL DRAINAGE FLOW BEFORE DIMINISHING AGAIN AFTER SUNRISE. THE PRESSURE GRADIENT WILL SLACKEN ENOUGH BY FRI EVENING TO PREVENT WINDS FROM REACHING A FRESH TO STRONG BREEZE ON SAT. SEAS ARE AS HIGH AS 10 FT IN MIXED NE AND SW SWELL...AND THEY WILL GENERALLY SUBSIDE FROM FRI MORNING THROUGH SAT MORNING. GULF OF TEHUANTEPEC...THE 1628 UTC ASCAT PASS SHOWED N WINDS IN THE GULF OF TEHUANTEPEC HAVE DIMINISHED BELOW A FRESH TO STRONG BREEZE. SEAS REMAIN AS HIGH AS 9 FT IN MIXED N-NE AND SW SWELL FROM THE COAST AS FAR S AS 12N...BUT THEY ARE EXPECTED TO SUBSIDE BELOW 8 FT OVERNIGHT. $$ SCHAUER