000 AXPZ20 KNHC 131525 TWDEP Tropical Weather Discussion NWS National Hurricane Center Miami FL 1310 UTC Thu Dec 13 2018 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 1445 UTC. ...SPECIAL FEATURES... Gulf of Tehuantepec Gale Warning: A cold front forecast to enter the NW Gulf of Mexico this afternoon will initiate gale to strong gale force winds across the Gulf of Tehuantepec by this evening. This long lived gale event will last until Mon afternoon. Peak winds will be 40 kt on Saturday as corresponding seas quickly building to between 16 and 18 ft. ...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH... The monsoon trough extends from 07N73W to 07N91W to 05N96W to 05N102W. The ITCZ continues from 05N102W to 10N119W to 09N133W, then resumes from 07N136W to beyond 07N140W. Numerous moderate and scattered strong convection is observed within 30 nm either side of a line from 05.5N77W to 01.5N81W. Scattered moderate and isolated strong convection is occurring within 30 nm either side of a line from 05.5N92W to 06N103W. ...DISCUSSION... OFFSHORE WATERS WITHIN 250 NM OF MEXICO... Over the open waters off Baja California, another pulse of NW swell is expected to reach Baja California Norte and Guadalupe Island tonight. This latest round of swell will sweep SE and cause seas to build to between 7 and 11 ft for the offshore waters along the length of the Baja Peninsula by Fri afternoon. A cold front approaching 30N140W late tonight will introduce more long period NW swell to Baja Waters by Sun morning and maintain sea heights. A much stronger cold front will reach Baja California Norte by Mon night. Strong winds associated with this front could brush 30N as the front crosses 30N140W. Long period NW swell as high as 18 ft could enter the waters adjacent to Baja California Norte during this time frame. Swell as high as this would present a hazard to mariners as well as cause dangerously high surf along the Pacific Beaches. Strong high pressure building over the Great Basin will support fresh to strong winds over the Gulf of California between 25N and 29N this afternoon through Fri morning. seas could approach 8 ft over the southern Gulf tonight. Winds and seas will subside through Sat as the high pressure shifts eastward. OFFSHORE WATERS WITHIN 250 NM OF CENTRAL AMERICA, COLOMBIA, AND WITHIN 750 NM OF ECUADOR... Gulf of Papagayo...Strong gap winds will taper off today but will return during the overnight and early morning hours Sat night, then persist through Mon night as high pressure builds north of the region. Seas are expected to top out around 10 ft on Sun. Gulf of Panama...Fresh northerly winds will pulse to around 20 kt this morning, then back to the NW and diminish through Sat. Elsewhere, gentle to moderate winds will persist on either side of the monsoon trough through the remainder of the week, with seas remaining in the 4-6 ft range. REMAINDER OF THE AREA... A large area of mixed seas persists over much of the north Pacific between 95W and 120W. This area consists of NE and E swell generated by gap winds, merging with longer period NW swell. Maximum combined sea heights in this area are 10 ft. This area of 8 ft seas will vanish by late tonight as these swell decay. Farther west, a persistent surface trough extends from 09N133W to 15N133W. The gradient between this trough and high pressure north of the region is supporting strong trade winds from 15N to 20N between 128W and 134W. Recent satellite-derived sea height data indicate seas as high as 11 ft. The high will weaken today ahead of an approaching cold front, allowing the trade winds to diminish by tomorrow morning. A cold front will reach from 30N135W to 28N140W by early Fri, and be accompanied by a new round of NW swell of 12 to 15 ft. The front will dissipate later on Fri, with the swell subsiding as well. Elsewhere NW swell in excess of 8 ft will more or less dominate the waters west of 110W through Sun. Very large NW swell, in excess of 20 ft, will enter the forecast area early Sun in conjunction with the arrival of a strong cold front. Seas of 12 ft or above could encompass almost all of the forecast waters N of 07N and W of 115W by Tue morning. $$ CAM