000 AXPZ20 KNHC 280330 TWDEP Tropical Weather Discussion NWS National Hurricane Center Miami FL 330 UTC Fri Dec 28 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 0300 UTC. .INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH... A surface trough extends from Colombia near 05N77W to 06N105W. The ITCZ continues from 06N105W to 07N120W to beyond 07N140W. Scattered moderate convection is noted within 120 nm either side of ITCZ between 105W and 135W. ...DISCUSSION... OFFSHORE WATERS WITHIN 250 NM OF MEXICO... A tight gradient has set up between 1034 mb high pressure well west of the area near 39N132W, and 1010 mb low pressure over southern Arizona. This is supporting generally moderate to fresh NW winds off Baja California north of Punta Eugenia, with gentle to moderate breezes elsewhere off the Baja California coast. NW swell of 8 to 10 ft is accompanying the winds. The gradient will weaken through Fri allowing the winds to subside. However the NW swell of 8 to 9 ft will persist beyond 120 nm off the Baja California coast through Sat, before subsiding below 8 ft through Sun. Looking ahead, while there will be little change in the regional pattern, another group of NW swell to 8 ft will reach the waters around Guadalupe Island early next week. For the Gulf of California, this pattern is also supporting fresh to strong westerly gap winds along 30N into the northern Gulf of California through tonight. While the gap winds will diminish Fri morning, strong high pressure building well north of the area over the Great Basin through Fri will fresh northerly flow into the northern Gulf of California. This will become strong northerly flow by Fri night, reaching across the central Gulf of California by Sat night with seas building to 8 ft. The strong winds and associated seas will diminish through Sun as the high pressure weakens and shifts eastward. Looking ahead, this pattern repeats early in the week, with pulses of strong northerly winds returning to the northern Gulf of California late Mon and Tue. For the Gulf of Tehuantepec, overnight drainage flow will bring fresh northerly winds into the Gulf of Tehuantepec Sat night, followed by pulses of fresh to strong gap winds Sun night. Looking ahead, model guidance suggests another strong Tehunatepec gap wind event by mid week, possibly reaching strong gale or storm force by late in the week. OFFSHORE WATERS WITHIN 250 NM OF CENTRAL AMERICA, COLOMBIA, AND WITHIN 750 NM OF ECUADOR... Gulf of Papagayo: Fresh to strong NE to E winds are expected across the area through Tue. The winds will be greatest during the overnight and early morning hours, with the assistance of the nocturnal drainage flow, and some added enhancement from the easterly gradient flow from the SW Caribbean. Seas are forecast to build to 8-10 ft while winds peak near gale force mainly at night. Gulf of Panama: Moderate to fresh N winds are expected through Tue, with seas generally in the 4 to 6 ft range. Elsewhere, gentle to moderate NE winds will prevail N of 08N, while gentle to moderate southerly winds are expected S of 08N through Tue. REMAINDER OF THE AREA... A ridge extends from a 1034 mb high pressure system centered near 39N132W across the forecast waters to beyond the Revillagigedo Islands. Recent scatterometer passes indicated a broad area of fresh trade winds farther south in the tropics west of 110W, supported by the strong ridge. Trade wind convergence was assisting development of scattered moderate showers and a few thunderstorms along the ITCZ as well. Concurrent altimeter satellite data indicated seas of 8 to 10 ft over much of the area north of the ITCZ and west of 120W. Long period NW swell is responsible for most of this, although there is a secondary component of short period wave due to trade winds mainly south of 20N and west of 130W, where seas may be reaching 11 ft. The NW swell will decay slightly through early next week, but the trade winds and related seas will cover greater areal extent west of 130W as the ridge builds. Elsewhere, little change is expected. Looking ahead, the mid to upper pattern becomes more amplified north of 20N Fri and Sat. A sharp upper trough will reach from northern Baja California westward along 25N by late Sat. Global models indicate a strong cold-core upper disturbance will dig into the base of the mid/upper trough early next week, supporting development of a sharp surface trough or even weak low pressure, along the ITCZ near 120W by mid week. This will likely enhance the trade winds north of the ITCZ and west of 120W, with near gale conditions possible on the northern end of the surface trough from 10N to 15N between 115W and 120W. $$ Christensen