000 AXPZ20 KNHC 071608 TWDEP Tropical Weather Discussion NWS National Hurricane Center Miami FL 1605 UTC Fri Apr 7 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 1200 UTC surface analysis and satellite imagery through 1545 UTC. ...SPECIAL FEATURE... GULF OF TEHUANTEPEC GALE WARNING... High pressure surging south along the Sierra Madre Oriental mountains of eastern Mexico has created a tight gradient over southeastern Mexico and just inland the Gulf of Tehuantepec region as it interacts with lower pressure south of the Gulf and over the northern part of Central America. This pattern has induced a gale event of north to northeast 30 to 35 kt winds over the Gulf of Tehuantepec, with seas up to 14 ft downstream of the Gulf waters near 14N95.5W. These winds will briefly diminish to just below gale force by early this afternoon, then increase again to minimal gale force this evening, and continue through the overnight hours diminishing to just below gale force by around 12Z on Saturday. Model guidance indicates that these winds diminish further to strong category by Saturday evening, and to fresh category by late Saturday night into Sunday. The resultant north to northeast swell, in the form of 8 to 9 ft seas will propagate SW mixing with long period cross-equatorial southwest swell, reaching as far south as 08N between 94W and 102W tonight before beginning to subside. Expect all associated seas to subside to less than 8 ft on Sat night. ...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH... A 1010 mb low is over NW Colombia near 09.5N76W with a trough extending southwest to a 1009 mb low at 05N78W and continues southwest to near 04N80W. Satellite imagery shows that a trough extends from 06N81W to 04N91W to 05N97W to 04N105W, where scatterometer winds and satellite imagery indicate that the ITCZ forms and continues to 04N115W to 03N124W to 04N131W to 01N140W. Scattered moderate/isolated strong convection is observed within 120 nm of the trough between 87W and 92W, and within 60 nm north of the trough between 103W and 105W. Scattered moderate convection is within 60 nm of the trough between 105W and 108W. ...DISCUSSION... OFFSHORE WATERS WITHIN 250 NM OF MEXICO... See special features above for on the ongoing Gulf of Tehuantepec gale force gap wind event. Broad weak high pressure is present over the offshore waters west of the Baja California Peninsula, with the associated gradient allowing for gentle to moderate northern continuing into Saturday afternoon. A dissipating cold front moving eastward over the northern waters to the west will move through the area, with high pressure behind the dying front to gradually tighten the pressure gradient beginning Saturday afternoon and through much of Sunday. This will increase northwest winds to the fresh to locally strong category across the waters west of the Baja California Peninsula through late on Sunday. Seas with these winds are expected to build to the 8 to 10 ft range. The gradient will begin to slowly relax late Sunday night through Monday, with moderate to locally fresh northwest winds expected early next week. Gulf of California: Light and variable winds are expected through early Saturday until the pressure gradient west of the peninsula tightens over weekend. This is expected to produce fresh to strong northwest to north winds over mainly the northern part of the Gulf on Sunday, and diminishing late Sunday night OFFSHORE WATERS WITHIN 250 NM OF CENTRAL AMERICA, COLOMBIA, AND WITHIN 750 NM OF ECUADOR... Gulf of Papagayo: Fresh to locally strong nocturnal drainage winds are expected through Saturday afternoon, with the resultant northeast swell propagating west-southwest to as far as 07N and between 89W and 92W. These winds briefly diminish to the fresh category on Saturday evening, then increase again to the fresh to locally strong range late Saturday night into Gulf of Panama: Moderate to fresh northerly nocturnal flow is expected during the overnight hours through the weekend. Light to gentle winds, and combined seas of 3 to 5 ft, are occurring elsewhere outside of the swells originating near the gap events. REMAINDER OF THE AREA... Moderate to locally fresh northeast trade winds are expected across the tropics from 05N to 15N w of 110W with the northeast wind waves resulting in an area of 6 to 9 ft combined seas forming across the tropics from 06N to 15N W of 122W over the upcoming weekend. A couple of weak cold fronts will dip across the northwest waters and sweep eastward across the northern waters through the weekend. The first of these cold front extends from near 32N131W to 28N140W. Strong northwest winds are northwest of this front. This front will dissipate from near 32N122W to 25N130W to 24N140W early on Saturday, with winds behind it diminishing to the fresh category. However, large post frontal northwest swell will produce combined seas of 8 to 10 ft to the north of a line from 30N118W to 23N126W to 21N131W to 24N136W to 25N140W. These seas will slowly subside through late in Sunday as the swell energy decays. $$ Aguirre