000 AXPZ20 KNHC 022210 TWDEP Tropical Weather Discussion NWS National Hurricane Center Miami FL 2205 UTC Sat Dec 2 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 2100 UTC. ...SPECIAL FEATURES... Gulf of Tehuantepec Gale Warning: Gale force N to NE winds across the Tehuantepec region for the past few days diminished below gale force late this morning and are assumed to have lessened further to the 20 to near 30 kt range. Seas are slowly subsiding to 7-10 ft this afternoon. NE swell induced by the long duration of this event is mixing with longer period NW swell well downstream from the Gulf of Tehuantepec, producing seas of 8-9 ft elsewhere from 08N TO 11N between 105W AND 111W. Model guidance indicates that the northerly winds will gradually diminish to 20 kt or less and seas to less than 8 ft by early Monday afternoon as high pressure N of the area weakens and shifts eastward. Computer models indicate that another gale event is expected to develop late on Wednesday as a strong cold front moves into the Gulf of Mexico and across southern Mexico. INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH... The Monsoon Trough extends from 09.5N75W to low pres near 06N78W to 08N85W TO low pres near 08N108W TO 08N113W, where it transitions to ITCZ, and continues on to 09.5N122W TO 11N137W TO beyond 10.5N140W. Scattered to locally numerous moderate to strong convection is occurring from 07N to 11N between 104W and 114W. Scattered moderate isolated strong convection is from 08N to 16.5N between 118W and 128W. ...DISCUSSION... OFFSHORE WATERS WITHIN 250 NM OF MEXICO... An upper level disturbance moving slowly across Baja California Norte this morning has shifted across the northern Gulf of California and western Sonora, Mexico this afternoon, and will continue eastward across northern Mexico this evening and tonight. Isolated showers are noted over central portions of the Gulf of California. Weak ridging over the region will support gentle to moderate northerly winds across the offshore waters into early next week. Long period NW swell propagating across the waters offshore of Baja California during the past couple of days has reached to near 105W, and is resulting in seas of the range between 8-10 ft across the offshore waters of northern and central Baja California. Seas in this range are also present from Baja California Sur to south of Manzanillo and the Revillagigedo Islands. The swell will slowly decay through Monday allowing for seas to lower to 8 ft, and then to below 8 ft by Tuesday afternoon, except for seas remaining at the 6-8 ft range over the offshore waters of northern Baja California. High pressure building in the wake of a cold front moving across the SW U.S. Sunday night through Monday night will induce strong NW winds through the entire length of the Gulf of California Monday and Tuesday. Looking ahead, the high pressure will strengthen through Wednesday, possibly increasing these winds to gale force over the northern Gulf of California late Wednesday, or on Thursday with seas building to 8-10 ft, possibly higher, across the north through central gulf. Please see Special Features section for details about the gale warning in the Gulf of Tehuantepec. OFFSHORE WATERS WITHIN 250 NM OF CENTRAL AMERICA, COLOMBIA, AND WITHIN 750 NM OF ECUADOR... Gulf of Papagayo: Fresh to strong offshore gap winds across the Papagayo region will peak to 25 kt during the late night and early morning hours through Monday. Seas downstream from the gulf will build to 6-8 ft during the time of peak winds, subsiding slightly each afternoon and evening. Elsewhere, light to gentle N to NE winds are expected north of the monsoon trough and mainly moderate S to SW winds are expected to the south of the monsoon trough. Seas are in the 4-6 ft, but are expected to build to 5-7 ft in a SW swell to the south of the monsoon trough beginning on Sunday afternoon and into Monday. REMAINDER OF THE AREA... A large area of long period NW swell producing seas of 8-12 ft will continue to propagate across the region west of 100W. The swell will decay to less than 8 ft south of 20N through next week, but persist at 8 ft and greater north of 20N due to reinforcing NW swell entering the region. Very Active convection is occurring near the monsoon trough between 104W and 114W, where a 1010 mb low pressure center was depicted by afternoon scatterometer data along 08N108W. 20-30 kt E winds across the N portions of the low are kicking up wind waves that are combining with the NW swell moving through the regional waters to produce seas of 10-14 ft as sampled by an afternoon altimeter pass. A rather strong jet stream branch extends in a SW to NE fashion from 25N140W to NE of the area at 35N123W. The associated dynamics is helping to initiate scattered showers and possible isolated elevated thunderstorms within 180 nm to the SE of the jet stream. A cold front NW has moved into the NW corner of the area from 30N139W TO 28N140W this afternoon, and is connected to a 1012 surface low near 31N140.5. This low will deepen tonight and drift generally southwestward, staying to the west of 140W with associated gale force winds. Another mid to upper level disturbance will support the development of a trough near a position from 20N135W to 22N132W by Sunday afternoon. The gradient between the trough and high pressure to the north of the area will result in fresh to strong easterly winds from 20N and 30N between 130W-140W with seas building to 8-11 ft through early next week as the trough slowly moves westward. $$ Stripling