000 AXPZ20 KNHC 200931 TWDEP Tropical Weather Discussion NWS National Hurricane Center Miami FL 623 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 0600 UTC surface analysis and satellite imagery through 0900 UTC. ...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH... The axis of a surface trough curves from 09N84W to 06N90W to 04N97W. The intertropical convergence zone axis extends from 06N114W to 03N131W to beyond 03N140W. Scattered moderate and isolated strong convection is found within an area bounded by 08N79W to 02N83W to 04N94W to 09N84W to 08N79W. ...DISCUSSION... OFFSHORE WATERS WITHIN 250 NM OF MEXICO... A surface ridge extends SE from 1026 mb high pressure centered near 32N128W to near the Revillagigedo Islands at 18N114W. Fresh to strong NW winds are occurring N of 23.5N and E of 119W 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 to rise to 9 ft. The fresh to strong winds will continue to affect the offshore waters W-SW of the Baja California Peninsula through this evening as new and stronger high pressure builds SE from N of the area. As a result, combined seas in this area will build to 8-11 ft by dawn on 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 late 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 through Friday as surface troughing developing over far northern Baja weakens the pressure gradient. Surface troughing developing over the length of the baja Peninsula will cause winds to become light to moderate SW over the Gulf of California Sunday and Monday. Seas will generally be 2-4 ft through Saturday, then 2 ft or less on Sunday and Monday. The exception will be up to 5 ft near the entrance to the Gulf. Model guidance suggests the pressure gradient east of the surface trough could become strong enough to generate fresh to locally strong winds over the Gulf N of 29N Monday through Wednesday. In the Gulf of Tehuantepec, fresh to strong N winds are surging into the immediate Gulf as a result of earlier convection over the Bay of Campeche. Model guidance shows a similar surge this morning in the immediate Gulf. Moderate to occasionally fresh northerly drainage flow is then expected tonight and Friday morning. Gentle to light southerly winds will ensue thereafter until early Sunday. The next significant N 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, courtesy of a broad area of low pressure residing over the region. REMAINDER OF THE AREA... A 1026 mb surface high centered near 31N128W is ridging 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 11 ft are affecting the waters N of a line from 30N120W to 17N130W to 13N140W. This round of NW swell with seas of 8 ft or greater will continue propagating SE and envelop almost all of the waters N of the ITCZ and W of 112W by early Friday. A new set of NW swell will arrive behind a cold front that will dissipate over the waters just to the west of Baja California Norte on Sunday and Sunday night. Southerly winds ahead of the front are expected to become strong over the far NW corner of the discussion area late Thursday night and Friday morning. The area of 8 ft seas associated with the new round of NW swell will merge with the area already covering the NW portion of the discussion area. This large area of reinforced swell will decay on Sunday and Sunday night, leaving only the area associated with the tight pressure gradient just W of Baja to the N of 23N and E of 125W by Tuesday morning. Otherwise, moderate to fresh trades will prevail SW of the ridging over the waters N of the ITCZ and W of 120W through the beginning of next week with little change. Trade wind waves in this area will help maintain seas above 8 ft through Saturday night. The area of 8 ft seas will retreat to the west of a line from 22N126W to 07N136W by Sunday afternoon, and to west of 140W on Tuesday as NW swell passing through this area disperse. $$ cam