000 AXPZ20 KNHC 130242 TWDEP TROPICAL WEATHER DISCUSSION NWS NATIONAL HURRICANE CENTER MIAMI FL 0405 UTC WED MAY 13 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 0130 UTC. ...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH... THE ITCZ AXIS WAS ANALYZED FROM 07N90W TO 04N105W TO 06N115W TO 04N123W TO LOW PRES NEAR 08N130W 1007 MB TO 04N140W. SCATTERED MODERATE WITH ISOLATED STRONG CONVECTION WAS WITHIN 120 NM EITHER SIDE OF THE AXIS BETWEEN 90W-95W. SCATTERED MODERATE WITH ISOLATED STRONG CONVECTION WAS WITHIN 180 NM EITHER SIDE OF THE AXIS BETWEEN 103W-113W AS WELL AS WITHIN 300 NM EITHER SIDE OF THE AXIS BETWEEN 113W-127W. A TROUGH IS EMBEDDED IN THE ITCZ FROM 13N112W TO 06N116W. SCATTERED MODERATE TO STRONG CONVECTION WAS WITHIN 210 NM E OF THE TROUGH FROM 10N-13N. ...DISCUSSION... A 1033 MB SUBTROPICAL HIGH CENTERED NW OF THE AREA NEAR 39N152W EXTENDS A RIDGE SE TO NEAR 17N100W. THE PRESSURE GRADIENT BETWEEN THIS RIDGE AND TWO SLOW MOVING SURFACE TROUGHS EMBEDDED WITHIN THE ITCZ...ONE NEAR 114W AND ONE NEAR 129W...IS PRODUCING FRESH TRADES OVER THE WESTERN WATERS WITH SEAS TO 9 FT IN THE AREA FROM 07N-16N W OF 116W. 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...BUT NUMERICAL GUIDANCE SUGGESTS A WEAK...QUASI-STATIONARY AREA OF LOW PRES DEVELOPING NEAR 10N123W BY WED EVENING WILL CREATE A TIGHT ENOUGH PRESSURE GRADIENT TO ITS N BY THU EVENING TO ALLOW FRESH TO STRONG NE TRADES TO RETURN. 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 ON EITHER SIDE 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 WINDS 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 EARLY 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 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 TIGHTENING THIS EVENING...WITH FRESH TO STRONG SOUTHERLY WINDS BELIEVED TO BE N OF 30N. 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 TURN THE UPPER TROUGH NEGATIVE TILT AND STRENGTHEN THE SURFACE TROUGHING. SW WINDS IN THE NORTHERN GULF OF CALIFORNIA ARE EXPECTED TO INCREASE TO NEAR GALE FORCE THU EVENING. GULF OF PAPAGAYO...THE PRESSURE GRADIENT BETWEEN RIDGING OVER THE NW CARIBBEAN AND TROUGHING NEAR THE ITCZ WILL BE TIGHT ENOUGH TO SUPPORT WINDS TO 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 ONLY REACH A FRESH TO STRONG BREEZE THU MORNING BEFORE DIMINISHING AFTER SUNRISE. 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