000 AXPZ20 KNHC 200227 TWDEP Tropical Weather Discussion NWS National Hurricane Center Miami FL 227 UTC Thu Apr 20 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 0000 UTC surface analysis and satellite imagery through 0215 UTC. ...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH... A surface trough axis extends from 10N86W to 04N91W to 05N100W. The intertropical convergence zone axis extends from 05N112W to 05N130W to 03N140W. Scattered moderate and isolated strong convection is within 360 nm southeast of the trough east of 89W. ...DISCUSSION... OFFSHORE WATERS WITHIN 250 NM OF MEXICO... A surface ridge extends from 1026 mb high pressure centered near 32N128W to across the Revillagigedo Islands to 18N107W. Fresh to strong NW winds over the offshore waters west of Baja California Norte where the pressure gradient is locally tight. These winds are generating NW swell and causing seas up to 8 ft. The fresh to strong winds will spread southward over the offshore waters W-SW of the Baja California Peninsula through Thursday evening to 23.5N as new and stronger high pressure builds SE from N of the area. As a result, combined seas will build to 8-11 ft through early Friday. The pressure gradient will then slacken on Friday and Saturday and allow winds and seas to diminish as a cold front weakens the ridge to the west. Another round of NW swell generated to the lee of the cold front will cause seas to build to between 8 and 10 ft west of Baja California Norte Sunday night through Tuesday. In the Gulf of California south of 29N, moderate to fresh NW winds will prevail through Saturday with late afternoon heating leading to local enhancement of winds. Winds will be light to gentle north of 29N as surface troughing developing over far northern Baja weakens the pressure gradient. Seas will generally be 2-4 ft, except up to 5 ft near the entrance to the Gulf. In the Gulf of Tehuantepec, an earlier scatterometer pass showed a brief and local surge of fresh to strong northerly winds in the immediate Gulf. Model guidance shows a similar surge late tonight into early Thursday in the immediate Gulf. Moderate to occasionally fresh northerly drainage flow is then expected Thursday night into Friday morning. Gentle to light southerly winds will ensue thereafter until early Sunday. The next significant northerly gap wind event is expected to begin Sunday evening as a relatively strong cold front for this time of year pushes south along the Sierra Madre Oriental. Model guidance continues to suggest strong to minimal gale force winds Sunday night through Monday morning. High pressure following behind the front will shift eastward by Tuesday, allowing winds and seas to diminish and subside. OFFSHORE WATERS WITHIN 250 NM OF CENTRAL AMERICA, COLOMBIA, AND WITHIN 750 NM OF ECUADOR... Light to gentle winds, onshore during the day and offshore at night, 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 1026 mb surface high centered near 32N128W will strengthen through tonight with ridging extending SE to near the Revillagigedo Islands. During the past few days the high and associated middle atmospheric ridging has blocked the eastward progress of cold fronts that have stalled and dissipated over the NW waters. Even so, NW swell generated to the W of the fronts is still propagating SE into the discussion waters. Seas of 8 and 12 ft are affecting the NW waters. This set of NW swell with seas of 8 ft or greater will continue propagating SE and eventually envelop almost all of the waters N of the ITCZ and W of 110W by early Friday. A new set of NW swell will arrive behind a cold front that will decay over the waters just to the west of Baja California Norte this weekend. Southerly winds ahead of the front could become strong over the far NW corner of the discussion area late Thursday night into early Friday. This large area of reinforced swell will decay on Saturday and Sunday with seas subsiding to less than 8 ft N of 18N W of 127W by Monday night. Otherwise, moderate to fresh trades will prevail SW of the ridging over the W central waters N of the ITCZ and W of 120W through the next several days with little change. Trade wind seas in this area will help support seas up to 8 ft from roughly 07N to 12N between 114W and 131W. This area of 8 ft seas will combine by Thursday afternoon with the area currently over the NW portion of the discussion area that is spreading SE. $$ LEWITSKY