000 AXPZ20 KNHC 072150 TWDEP Tropical Weather Discussion NWS National Hurricane Center Miami FL 2205 UTC Thu Dec 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 1800 UTC surface analysis and satellite imagery through 2145 UTC. ...SPECIAL FEATURES... Gulf of California Gale... Sprawling 1050 mb high pressure is centered well north of the area over the Great Basin, along with 1035 mb high pressure over northern Texas. A tight gradient between these high pressure systems and troughing over Baja California and northwest Mexico is supporting minimal gale force winds over the northern Gulf of California with a 1710 UTC ASCAT pass indicating 30-35 KT winds N of 29N. This gale is forecast to continue through late Friday morning with seas to 11-12 ft. Gale force winds will spread through the central Gulf tonight at the same time that strong NW winds enter the southern Gulf, with seas building to 9 ft. The strong high pressure over west Texas will shift southward into north central Mexico tonight, while low pressure remains over the entrance to the Gulf of California. This will allow the strong to gale force winds to veer from the NW to the NE and E. This will limit the fetch and allow seas to subside. The winds will diminish Fri into Sat as the low pressure weakens. Fresh to strong NW winds will persist over the northern Gulf into Sun then diminish below 20 kt. Gulf of Tehuantepec Gale... Gulf of Tehuantepec: N to NE winds of 20-25 kt are funneling into the Gulf with maximum wave heights up to 9 ft, as a frontal system stalls over the western Gulf of Mexico waters before receiving a push of cold air and transition back to a strong cold front moving off the SE Gulf Friday night into Saturday morning. The tight pressure gradient over southeastern Mexico will keep this winds in the 20 to locally 30 kt range through Friday evening, with maximum wave heights building to around 11 ft. Gale force winds are expected to begin Fri night and increase further to 45 kt Sat and Sat night, likely reaching storm force early Sun in what looks like an extended gap wind event well into next week. Baja California Norte Gale... The NW winds to gale force over the Gulf of California will veer more N and NE late today and tonight. NE gales will funnel through lower lying areas over Baja California Norte into the Bay of Sebastian Vizcaino, roughly between Santa Rosalita and Puerto Canoas tonight through Friday morning. ...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH... The monsoon trough extends from 11N86W to 08N100W where it transitions to the intertropical convergence zone and continues to 10N120W to 11N131W, then from 10N135W to 09N140W. Scattered moderate convection was noted from 06N to 09N between 83W and 87W and within 180 nm either side of the ITCZ between 107W and 127W. ...DISCUSSION... OFFSHORE WATERS WITHIN 250 NM OF MEXICO... Along with winds to gale force near the coast listed above, the main issue in the near term will be strong to near gale force NE winds late today and tonight emerging off the coast of Baja California south of 30N, reaching nearly 400 nm into the Pacific open waters with seas of 8 to 12 ft by early Fri. The winds will diminish by early Saturday morning, with seas subsiding below 8 ft off the coast of Baja California through late Sat. Elsewhere gentle to moderate winds and 4 to 6 ft seas will persist through into next week. OFFSHORE WATERS WITHIN 250 NM OF CENTRAL AMERICA, COLOMBIA, AND WITHIN 750 NM OF ECUADOR... Gulf of Papagayo: Gentle to moderate gap winds will occasionally pulse to fresh gap winds through the Gulf of Papagayo though tonight. Strong high pressure building north of the area behind a cold front penetrating into the western Caribbean will allow strong gap winds by Sat night, reaching near gale by Sun morning and again Mon morning with seas building to 11-12 ft downstream. Elsewhere, light to gentle N to NE winds are expected N of the monsoon trough, and mainly gentle to moderate S to SW winds are expected to the S of the monsoon trough. Seas are in the 5 to 7 ft range in SW swell this evening to the S of the monsoon trough, and will subside to 4-6 ft through mid week. Large NW swell with wave heights of 8-10 ft from the upcoming Tehuantepec gap wind event will spread across the offshore waters of Guatemala late this week and over the weekend. Localized gap wind pulses of 20 to 25 kt are possible off the coast of El Salvador and Guatemala starting Sat night. REMAINDER OF THE AREA... A stationary front extends from 30N135W to 23N137W. Associated long period NW swell will continue to propagate into the region, encompassing the area north of 12N and west of 125W tonight, and most of the region west of 120W by Fri night. The longer period NW swell will mix with shorter period NE swell and wind waves by Fri night over the area north of 20N and east of 125W. A surface trough from 19N129W to 11N133W is drifting westward. A tight pressure gradient will develop N and NE of this trough between it and strong high that shifts eastward over the central and NE waters. This will lead to a brief period of NE to E 20 to 25 kt winds from 18N to 21N between 129W and 132W this evening with induced wave heights up to 9 ft. The area of seas merges with long period NW swell noted above on Fri. $$ Cobb