000 AXPZ20 KNHC 092205 TWDEP Tropical Weather Discussion NWS National Hurricane Center Miami FL 2205 UTC Thu Nov 9 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 2145 UTC. ...SPECIAL FEATURES... A Gale Warning is in effect for the Gulf of Tehuantepec. High pressure surging southward behind a cold front moving across the western Gulf of Mexico is pushing a cooler air mass southward towards the eastern slopes of the Sierra Oriental mountains along eastern Mexico. This has significantly tighten the pressure gradient already in place across southeastern Mexico allowing for gale force northerly winds to push through the Isthmus of Tehuantepec and out across the Gulf where warm sea surface temperatures are present. These gale force are expected to increase to the range of 30-40 kt tonight along with seas building to the range of 10-15 ft. The gale force winds will only diminish slightly on Friday and through Saturday, however the resultant seas Will remain within the same range. Model guidance suggests that this event will last through early next week, with winds increasing again to 35-40 kt Sunday night through Monday night. During this time period, seas are forecast to build to 14-16 ft. ...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH... The monsoon trough axis extends from 10N84W to 09N92W to 09N101W to 09N111W to 08N118W to low pressure near 10N125W 1009 mb and to beyond 09N140W. Scattered moderate isolated strong convection is seen within 120 nm S of the axis between 108W-111W, and within 60 nm of the axis between 121W-125W. Scattered moderate convection is noted from 06N-08N between 80W-83W, and also within 60 nm of the axis between 105W-108W. ...DISCUSSION... OFFSHORE WATERS WITHIN 250 NM OF MEXICO... Please see the Special Features section for information on the ongoing Gulf of Tehuantepec Gale Warning. A ridge will dominate the waters W of Baja California through the rest of the week, while a trough will meander between the coast of NW Mexico and the Gulf of California. Moderate to locally fresh NW to N flow will prevail across the waters W of Baja California, increasing to fresh to locally strong offshore of the northern waters this evening through Friday as the pressure gradient slightly tightens between a high pressure center over the northern forecast waters and the aforementioned trough. A cold front is expected to weaken before reaching the area on Friday, but the associated long period NW swell inducing seas in the range of 8-10 ft will propagate southeastward across the waters N of 23N and to the W of Baja California on Friday, then spread southward through all of the waters W of Baja on Saturday while slowly subsiding. Looking beyond the 48 hour forecast period of the discussion, the pressure gradient W of Baja California will significantly tighten early next week allowing for strong NW winds to develop over those waters along with seas possibly building to around 9 ft N of about 25N. Gulf of California: A relatively tight pressure gradient is supporting moderate to fresh NW flow across the central and southern Gulf, with gentle to moderate NW flow to the N. Seas are 2 ft or less in the northern Gulf, and 3-4 ft elsewhere. The gradient will slacken on Friday allowing for winds to become generally light and variable and remain as such through Saturday, with seas subsiding to 2 ft or less, except for higher seas of 3-5 ft near the entrance of the gulf. Elsewhere, mainly gentle to moderate NW flow and 4 to 6 ft seas will prevail through Saturday. OFFSHORE WATERS WITHIN 250 NM OF CENTRAL AMERICA, COLOMBIA, AND WITHIN 750 NM OF ECUADOR... Gulf of Papagayo: Nocturnal drainage flow will support pulsing moderate to fresh winds during the overnight hours for the next several days, with seas occasionally building to 5 or 6 ft downstream of the Gulf near 11N87W. Light and variable winds and seas of 4-6 ft are expected elsewhere to the N of 09N, while moderate to locally fresh southerly winds and seas of 5-7 ft are forecast S of 09N through the next several days. REMAINDER OF THE AREA... The cold front that moved across the NW waters during the past couple of days is analyzed from near 32N126W to 28N135W and as a dissipating stationary front to beyond the area at 27N140W. A new set of long period NW swell follows the front, with seas in the range of 8-11 ft in NW swell, except for higher seas in the range of 10-13 ft N of 29N. This swell event will propagate southeastward through the area reaching the waters W of Baja California as previously mentioned. The front will weaken and become stationary from near 32N126W to 26N133W by Friday afternoon, and dissipate late Friday. Seas of 8 ft or greater will cover the waters N of 15N W of 115W by Friday evening, then begin to subside to near 8 ft throughout the waters by Sunday evening. A surface to low-level trough is near 137W from 15N-22N. Latest satellite imagery shows scattered moderate within 120 nm W of the trough from 19N-22N. A tight pressure gradient over the northern part of trough is producing NE-E winds of 20 kt from 19N-22.5N and between 136W-140W. A weak low pressure of 1009 mb as described above remains along the monsoon trough near 10N125W, and will continue to move westward through the upcoming weekend and into early next week. Model guidance indicates a tightening pressure gradient between the low and and building high pressure to the N during the weekend into early next week. This may allow for trades to increase to fresh to strong across the waters S of 20N and N of the monsoon trough/ITCZ, supporting fresh seas of 8 to 10 ft. $$ Aguirre