000 AXPZ20 KNHC 122151 TWDEP TROPICAL WEATHER DISCUSSION NWS NATIONAL HURRICANE CENTER MIAMI FL 2205 UTC TUE MAY 12 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 2030 UTC. ...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH... THE ITCZ AXIS WAS ANALYZED FROM 07N90W TO 06N115W TO 06N122W TO 08N128W TO LOW PRES NEAR 07N130W 1010 MB TO 03N140W. SCATTERED MODERATE WITH ISOLATED STRONG CONVECTION WAS WITHIN 180 NM N OF THE AXIS BETWEEN 90W-95W. ISOLATED MODERATE TO STRONG CONVECTION WAS FROM 00N-06N BETWEEN 100W-127W. A TROUGH WAS ANALYZED N OF THE AXIS FROM 12N111W TO 06N115W. SCATTERED MODERATE WITH ISOLATED STRONG CONVECTION WAS WITHIN 210 NM EITHER SIDE OF THE TROUGH...EXCEPT 390 NM W OF TROUGH FROM 06N-09N. ...DISCUSSION... A 1034 MB SUBTROPICAL HIGH CENTERED NW OF THE AREA NEAR 39N151W EXTENDS A RIDGE SE TO NEAR 16N100W. THE PRESSURE GRADIENT BETWEEN THIS RIDGE AND TWO SLOW MOVING SURFACE TROUGHS EMBEDDED WITHIN THE ITCZ...ONE NEAR 113W AND ONE NEAR 129W...IS PRODUCING FRESH TRADES OVER THE WESTERN WATERS WITH SEAS TO 9 FT IN THE AREA FROM 07N-15N W OF 121W. THE SURFACE RIDGE IS EXPECTED TO WEAKEN AND SHIFT SW OVER THE NEXT TWO DAYS AS 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. THE AREA OF FRESH TRADES WILL SHRINK IN RESPONSE...WITH SEAS EXPECTED TO SUBSIDE BELOW 8 FT BY EARLY THU MORNING. THE EASTERN MOST OF THE AFOREMENTIONED SURFACE TROUGHS EMBEDDED IN THE ITCZ IS THE FOCUS OF SCATTERED MODERATE TO STRONG CONVECTION...WITH DEEP CONVECTION ALSO NOTED S OF THE ITCZ NEAR THE TROUGH. THIS CONVECTION IS DESCRIBED IN THE SECTION ABOVE. THE ABUNDANT CONVECTION IN THIS AREA IS ASSOCIATED WITH A KELVIN WAVE PROPAGATING INTO THE REGION. FORECAST GUIDANCE SUGGESTS THAT ITCZ WILL REMAIN PARTICULARLY CONVECTIVELY ACTIVE BETWEEN 110W-130W OVER THE NEXT DAY OR SO. THE PRESSURE GRADIENT BETWEEN THE SURFACE RIDGE AND LOW PRESSURE OVER THE SW UNITED STATES IS PRODUCING FRESH TO STRONG NW-N ALONG THE CENTRAL CALIFORNIA COAST AND S INTO FORECAST WATERS N OF 29N BETWEEN 119W AND 122W. SHIP PHSG AND AN UNKNOWN SHIP NEAR 30N121.5W AT 1800 UTC REPORTED FRESH TO STRONG N-NW WINDS AND SEAS OVER 8 FT IN THIS AREA. THESE WINDS AND SEAS AREA EXPECTED TO DIMINISH BY WED MORNING AS THE RIDGE WEAKENS AND THE SYSTEM OVER THE WESTERN UNITED STATES BEGINS TO SHIFT NE. LONG PERIOD CROSS EQUATORIAL SOUTHERLY SWELL AT 19-22 SECONDS WILL REACH THE ENTIRE MEXICAN AND CENTRAL AMERICAN COAST...EXCLUDING THE GULF OF CALIFORNIA...OVERNIGHT TONIGHT. THIS LONG PERIOD SWELL WILL LEAD TO HAZARDOUS SURF AND BEACH CONDITIONS ALONG THE MEXICAN AND CENTRAL AMERICAN COASTS THROUGH WED. SEA HEIGHTS OF 8 FT OR GREATER IN SW SWELL WILL PRIMARILY IMPACT THE AREA S OF 10N E OF 120W...EXCEPT IN THE LEE OF THE GALAPAGOS ISLANDS...THROUGH WED BEFORE SUBSIDING N OF THE EQUATOR BY THU MORNING. GULF OF CALIFORNIA...THE PRES GRADIENT BETWEEN THE SUBTROPICAL RIDGE AND TROUGHING OVER THE SW UNITED STATES IS FORECAST TO TIGHTEN THIS EVENING...WITH FRESH TO STRONG SOUTHERLY WINDS DEVELOPING N OF 30N OVERNIGHT TONIGHT. THE WINDS WILL DIMINISH BY SUNRISE WED THEN WILL RETURN EARLY THU MORNING AS A NEW IMPULSE LOWERS SURFACE PRESSURES IN THE SW UNITED STATES. THIS IMPULSE WILL MOVE NE...DIMINISHING THE WINDS BY THU AFTERNOON. GULF OF PAPAGAYO...THE PRESSURE GRADIENT BETWEEN RIDGING OVER THE NW CARIBBEAN AND TROUGHING NEAR THE ITCZ IS TIGHT ENOUGH TO SUPPORT A FRESH TO STRONG BREEZE THIS AFTERNOON...WITH SHIP VRBH6 REPORTING NE WINDS AT 22 KT WITH 10 FT SEAS AT 1800 UTC. WINDS ARE EXPECTED TO REACH 30 KT IN THE MORNING HOURS BEFORE SUNRISE WED WITH THE ASSISTANCE OF NOCTURNAL DRAINAGE FLOW. THE PRESSURE GRADIENT SHOULD SLACKEN SOME WED INTO THU...WITH WINDS EXPECTED TO DIMINISH BELOW A FRESH TO STRONG BREEZE BY THU AFTERNOON. GULF OF TEHUANTEPEC...A SURFACE TROUGH MOVING W OFF THE YUCATAN PENINSULA INTO THE BAY OF CAMPECHE WILL ABUT WITH RIDGING ALONG THE SW GULF COAST IN THE MORNING HOURS WED AND THU...ALLOWING N WINDS TO FUNNEL THROUGH CHIVELA PASS. THESE WINDS WILL PASS INTO THE GULF OF TEHUANTEPEC...REACHING NEAR GALE FORCE WED MORNING BEFORE DIMINISHING TO LESS THAN 20 KT IN THE AFTERNOON. THE PRESSURE GRADIENT SHOULD BE SLIGHTLY WEAKER THU MORNING...WITH A FRESH TO STRONG BREEZE EXPECTED WITH THE ASSISTANCE OF NOCTURNAL DRAINAGE FLOW JUST BEFORE SUNRISE BEFORE DIMINISHING AGAIN. $$ SCHAUER