000 AXPZ20 KNHC 182117 TWDEP Tropical Weather Discussion NWS National Hurricane Center Miami FL 2117 UTC Tue Apr 18 2017 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. ...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH... A surface trough extends from 08N84W to 06N90W to 03N100W. The intertropical convergence zone axis extends from 09N110W to 05N120W to 03N136W. Widely scattered moderate convection is within 240 nm southeast of the trough east of 94W. ...DISCUSSION... OFFSHORE WATERS WITHIN 250 NM OF MEXICO... A weakening surface ridge extends from 1021 mb high pressure near 27N127W to beyond the Revillagigedo Islands to near 12N104W. NW winds are increasing to fresh to strong offshore of Baja California Norte where the pressure gradient is tight. These winds are supporting seas to 8 ft in NW swell. The fresh to strong winds will gradually spread southward across the offshore waters W-SW of the Baja California Peninsula through Thursday afternoon as new and strong high pressure builds down from NW-N of the area, and as more pronounced surface troughing develops from near Point Conception California to along and inland across the Baja California Peninsula. Fresh seas will be reinforced by longer period NW swell building combined seas to 8-11 ft through early Friday. The pressure gradient will then slacken through the upcoming weekend allowing for winds and subsequent seas to diminish and subside. In the Gulf of California, gentle to locally moderate NW flow is expected through tonight. A moderate to fresh nw breeze will follow Wednesday through Saturday with late afternoon heating leading to local enhancement of winds. Light to gentle variable winds are then expected on Sunday. Seas will be mainly 2 ft or less tonight, then will build to 2-4 ft with the freshening of the winds. In the Gulf of Tehuantepec, moderate to occasionally fresh northerly drainage flow is expected through Friday morning, with gentle to light southerly flow thereafter into early Sunday. The next significant northerly gap wind event is expected to begin Sunday afternoon. Model guidance suggests strong to minimal gale force winds will occur Sunday night through Monday morning. OFFSHORE WATERS WITHIN 250 NM OF CENTRAL AMERICA, COLOMBIA, AND WITHIN 750 NM OF ECUADOR... In the Gulf of Papagayo, mainly moderate nocturnal drainage winds are expected from the evening hours through late morning each of the next few days, with no significant gap wind events anticipated through the upcoming weekend. In the Gulf of Panama, mainly light and variable winds are expected this week into the upcoming weekend with periods of southerly wind flow to prevail as low pressure dominates NW Colombia and the adjacent Caribbean. Elsewhere, light to gentle winds and combined seas of 3 to 6 ft in mixing SW and NW swell will prevail through the next several days. REMAINDER OF THE AREA... A 1021 mb surface high centered near 27N127W will shift and merge with high pressure NW-N of the area through Wednesday night. The high and associated middle atmospheric ridging continues to block the eastward progress of cold fronts that continue to stall and dissipate over the NW waters. Even so, NW swell generated to the W of the fronts will still manage to propagate SE into the discussion waters building seas to between 8 and 12 ft across the NW waters tonight into early Wednesday. This set of NW swell will manage to propagate across the majority of the waters N of the ITCZ and W of 110W through the end of the week, then decaying into the upcoming weekend as another set of NW swell arrives and breaches the waters SE of 30N140W. The new set of NW swell arrive behind one of the decaying cold fronts this weekend. Southerly winds ahead of that front may manage to increase to fresh to strong in the far NW corner Thursday night into early Friday. Otherwise, moderate to fresh trades will prevail SE of the ridging across the W central waters N of the ITCZ and W of 120W through the next several days with little change. $$ LEWITSKY