000 AXPZ20 KNHC 140335 TWDEP Tropical Weather Discussion NWS National Hurricane Center Miami FL 0405 UTC Fri Dec 14 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 0000 UTC surface analysis and satellite imagery through 0230 UTC. ...SPECIAL FEATURES... Gulf of Tehuantepec Gale Warning: A cold front has entered the NW Gulf of Mexico early tonight and will move quickly southeastward through the Bay of Campeche Fri to initiate gale to strong gale force winds across the Gulf of Tehuantepec by late Fri afternoon. Computer model guidance suggests that these gales will continue through the weekend and will last until Mon afternoon. Peak winds are forecast to be around 40 kt on Sat as corresponding seas quickly building to near 18 ft. The first blast of strong northerly winds associated with this event is expected to start across the Gulf of Tehuantepec Fri afternoon. ...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH... The monsoon trough extends from 08N75W TO 10N86W TO 06N101W. The ITCZ continues from 06N101W TO 10N136W to beyond 08N140W. Scattered moderate isolated strong convection is observed from 01N to 08.5N to the east of 93W. An upper level trough across far NW portions of the area is creating a large area of overcast middle and high level clouds, and scattered light to moderate elevated convection from 16N to 26N between 122W and 134W. ...DISCUSSION... OFFSHORE WATERS WITHIN 250 NM OF MEXICO... Over the open waters off Baja California, gentle northerly winds and modest seas of 4-6 ft prevail early tonight. Another pulse of NW swell is expected to reach Baja California Norte and Guadalupe Island overnight 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 at 7-9 ft through Mon morning. Looking ahead, a much stronger cold front will reach Baja California Norte by Mon night. Strong winds associated with this front could brush along 30N as the front crosses 30N140W. Long period NW swell of 10-18 ft will enter the waters adjacent to Baja California Norte during this time frame. Swell of this size and period will present hazardous seas for mariners, as well as cause very powerful and dangerous surf along the Pacific reefs and beaches. Strong high pressure building over the Great Basin is supporting the development of fresh to strong winds over the Gulf of California between 25N and 29N early tonight, and will prevail across the Gulf through Fri morning. Seas will reach 7-8 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 tapered off this afternoon but will pulse to around 20 kt tonight and Fri night before returning to fresh to strong during the overnight and early morning hours Sat night. These conditions will then persist through Mon night as high pressure builds north of the region. Seas are expected to max out near 10 ft Sun morning. Gulf of Panama...Fresh northerly winds across and downstream of the Gulf have begun to back to the NW this evening and will slowly diminish through Sat, then become fresh from the north Sat night through Sun. 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 98W and 120W. This area consists of NE and E swell generated by recent Central American gap wind events, merging with longer period NW swell. Maximum combined sea heights in this area are now down to 9 ft, and will diminish by late tonight as these swell decay. Farther west, a persistent surface trough extends from 09N137W TO 18N132W. The gradient between this trough and high pressure north of the region is supporting strong trade winds from 15N to 20N between 125W and 140W. Recent satellite-derived wave height data indicate seas as high as 12 ft. The high will weaken tonight ahead of an approaching cold front, allowing the trade winds to diminish to around 20 kt by Fri morning. A cold front will reach from 30N135W to 28N140W by early Fri, and be accompanied by a new round of NW swell with seas of 12 to 15 ft. The front will dissipate late 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 NW portions of the forecast area early Sun in conjunction with the arrival of a strong cold front. Seas of 12 ft or higher could encompass almost all of the forecast waters N of 07N and W of 115W by Tue morning. $$ Stripling