000 AXPZ20 KNHC 050343 TWDEP Tropical Weather Discussion NWS National Hurricane Center Miami FL 0405 UTC Mon Dec 4 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 0000 UTC surface analysis and satellite imagery through 0200 UTC. ...SPECIAL FEATURES... Gulf of California: Strong high pressure is currently building from the U.S. Great Basin and northern Rockies southward towards the desert SW of the U.S., and has begun to support the development of fresh to strong NW flow in the far northern Gulf N of 29.5N. Winds will increase to minimal gales Tue morning in the northern Gulf as the pressure gradient continues to tighten, then will diminish below gale by Tue evening as it slackens slightly. Meanwhile, the fresh to strong winds will spill southward across the entire Gulf by mid-week. Another area of strong high pressure will build across the region Wed night through Thu and is expected to initiate another round of gales across N and N central portions Thu. Seas are expected to build up to 9 ft across the northern part of the basin by late Tue and to 6 to 9 ft across the remainder of the basin Wed through Thu. Also, as the strong winds develop across the Gulf, strong northeasterly gap winds will bleed through gaps in the mountain peaks across the northern peninsula and spill across the Bay of San Sebastian. ...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH... The monsoon trough axis extends from low pressure near 06.5N78W to 10N86W to 07N93W, then transitions to ITCZ, extending on to 10N125W to 10N136W. Very active convection along and well N of the ITCZ is described below. ...DISCUSSION... OFFSHORE WATERS WITHIN 250 NM OF MEXICO... Gulf of Tehuantepec: Southerly return flow continues across the W half of the Gulf of Mexico this evening and is acting to limit the northerly drainage flow across and downstream of the Gulf of Tehuantepec. Winds across Tehuantepec continue at 10-20 kt this evening with seas of 4 to 6 ft. Associated seas are 5 to 8 ft in shorter period swell generated from the strong gap winds reaching 200 to 300 nm downstream of the Gulf of Tehuantepec, mixed with longer period NW swell. Moderate to fresh northerly winds will continue across Tehuantepec through Tue, with peak winds pulsing at night, then increase to fresh to strong at night through Thu morning, possibly increasing to gale force by late Wed night as a cold front pushes across the western Gulf of Mexico and through southern Mexico. Looking ahead, strong high pressure building N of the area behind the Gulf of Mexico cold front will supporting a persistent strong gale event across the Gulf of Tehuantepec through late in the week. Elsewhere off the Pacific coast of Mexico, weak high pressure is maintaining gentle to moderate breezes across the region. Long period NW swell is producing seas of 6 to 9 ft swell propagating across all open waters, except within 100 to 200 nm off the coast south of Los Cabos and the central Mexican coast, where seas are 5-7 ft. The swell will gradually decay to less than 8 ft across all offshore waters by Tue. OFFSHORE WATERS WITHIN 250 NM OF CENTRAL AMERICA, COLOMBIA, AND WITHIN 750 NM OF ECUADOR... Gulf of Papagayo: Fresh NE winds across the Papagayo region this evening will pulse to strong again tonight with seas downstream building to 6 to 8 ft. Winds and seas will diminish through late week as strong trades winds over the southwest Caribbean diminish and veer SE. Looking ahead, strong high pressure will build N of the region, allowing strong gap winds and building seas to reappear by Sun. Winds may even approach minimal gale force late Sun night through early Mon. Elsewhere, light to gentle N to NE winds are expected N of the monsoon trough, and mainly 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 to 6 ft through mid week. REMAINDER OF THE AREA... A surface trough embedded in the tradewind belt extends from near 09.5N126W to 17N118W, and is racing near 20 kt along the ITCZ. Strong trad winds just ahead and behind the trough continue to initiate scattered moderate isolated strong convection from 07.5N to 16N between 115W and the trough, and is being enhanced by upper level divergence. The trough will move W and gradually become absorbed in a deep layered low pressure area along 132W by Wed night. A sharp and deep layered trough is moving very slowly into W portions of the area, where a pair of low pressure centers and a stalled front have developed at the surface. Recent analysis suggests a 1011 mb low pressure center near 27N138W with a trough extending to a second 1011 mb low near 24.5N136W then a stationary front to 22N135.5W to beyond 19N140W. Strong E to SE winds N of 21-22N between these surface features and 126W are initiating scattered moderate convection, while scattered moderate to strong convection is occurring from 08.5N TO 22N, W of 125W. Upper level divergence E of the upper level trough there is sustaining the convection across this area and will maintain unstable conditions there into early Wednesday. The pressure gradient between a strong ridge across the NE pacific and the two low centers is supporting these strong winds E of the lows and fronts to about 129W. The lows will lift N and drag a new front into the area from the W by Wednesday afternoon to produce persistent strong SE to S winds across NW portions. Seas will remain at 8-11 ft in NW swell, or higher, during this time. Elsewhere, NW swell greater than 8 ft covers almost the entire discussion waters beyond 250 nm offshore of Central and South America. These seas will gradually decay through the early part of the week. $$ Stripling