000 AXPZ20 KNHC 271604 TWDEP Tropical Weather Discussion NWS National Hurricane Center Miami FL 1605 UTC Fri Oct 27 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 1200 UTC surface analysis and satellite imagery through 1545 UTC. ...SPECIAL FEATURES... Tropical Storm Selma centered near 11.1N 89.5W 1005 mb or about 155 nm S of San Salvador El Salvador at 27/1500 UTC moving NW or 320 degrees with maximum sustained winds 35 kt gusts to 45 kt. First visible satellite imagery shows that the cyclone is sheared with the center exposed to N of the deep convective activity. The imagery shows scattered moderate to strong convection within 90 nm of the center in the SE quadrant, and within 120 nm of the center in the SW quadrant. Scattered moderate to isolated strong convection is elsewhere from 05N to 10N between 90W-94W. Selma is forecast to continue to slowly move NW through tonight while strengthening slightly, then turn towards the N early on Saturday. Selma is forecast to move inland while and intensify through tonight, then make landfall in El Salvador on Saturday afternoon and dissipate by early on Sunday. Selma will weaken quickly once it moves inland and dissipate by Sunday morning. Monsoonal winds to the southeast of Selma will produce heavy rainfall over El Salvador, southern Guatemala, southern Honduras and far western Nicaragua over the next couple of days. Gulf of Tehuantepec Gale Warning: The high pressure ridge over the gulf of mexico has shifted eastward away from the Bay of Campeche. This has lessened the pressure gradient over the Isthmus of Tehuantepec, and allowed the strong northerly winds over the gulf waters to diminish to 15-20 kt. However, the large NE swell that were generated continue to propagate S and mix with long period cross-equatorial southerly swell, as well as long-period NW swell. The resultant plume of seas has merged with a much larger area of mixed swell generally from 03.4S to 13N between 86W and 116W. Seas in this area range between 8-10 ft. These seas should subside to a maximum of 9 ft by early Sunday evening. A new area of strong high pressure is forecast to surge southward along the Sierra Madre Oriental mountains of Mexico beginning on Saturday resulting in a tightening of the pressure gradient over southeastern Mexico. This will produce a another gap wind event for the Gulf of Tehuantepec region, with northerly winds becoming strong on Saturday morning, reaching to near gale force near daybreak and to minimal gale force winds by early on Saturday afternoon. These gale conditions will continue into Sunday afternoon before diminishing to below gale force Sunday evening. Heavy Surf Conditions: Long period swell with a 20 to 24 second wave period, are forecast to reach the Pacific coast of the Baja Peninsula in the form of 8 to 9 ft seas on Sat night. The swell will propagate SE and reach the Pacific coast of Mexico as far S as 17N by Sunday night. Refractive swell of 15 to 17 seconds will wrap around the southern tip of Baja and enter the southern Gulf of California on Sunday. Large breaking waves may produce dangerous near shore conditions including rip currents and beach erosion. INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH... The monsoon trough axis extends from along the coast of NW Colombia to 09N79W to 10N89W, where it briefly ends. It resumes at 09N92W to 11N103W to 10N109W to 10N120W to 11N126W to 10N140W. Scattered moderate and isolated strong convection is seen within 120 nm S of the axis between 78W-79W. Scattered moderate convection is within 240 nm of the axis between 130W-134W, and within 60 nm S of the axis between 134W-138W. ...DISCUSSION... OFFSHORE WATERS WITHIN 250 NM OF MEXICO... Heavy Surf Conditions: please refer to the special features section above for information on heavy seas arriving this upcoming weekend. Gulf of Tehuantepec: please refer to the special features section above for information on an upcoming gale event. Gulf of California: Light and variable winds are expected through late Fri, then a moderate NW breeze is forecast through Sat night. Light and variable winds expected on Sun becoming a moderate S breeze on Mon. A surface ridge extends E across the waters W of the Baja Peninsula, with light to gentle anticyclonic winds, except becoming a moderate NW breeze within 180 nm W of the Central and Southern Baja Peninsula on Fri evening. OFFSHORE WATERS WITHIN 250 NM OF CENTRAL AMERICA, COLOMBIA, AND WITHIN 750 NM OF ECUADOR... Please refer to the special features section above for information on a Tropical Storm Selma. Otherwise, moderate southerly winds, and 4 to 6 ft seas, are expected S of 08N through Sunday. REMAINDER OF THE AREA... A broad ridge dominates the waters N of 12N W of 115W accompanied by gentle to moderate anticyclonic flow, and combined seas of 5 to 7 ft to the S of 30N, while moderate to fresh NE winds are observed N of 30N W of 128W. The pressure gradient will relax on Friday. A new set of long-period NW swell, in the form of 8 ft seas, will arrive into the area to the NW of a line from 32N136W to 28N140W by early this afternoon inducing seas in the range of about 8-12 ft. This swell will continue to propagate southeastward through Sunday reaching to the NW of a line from 32N114W to 15N122W to 10N130W to 04N140W at that time. Seas will then begin to subside but the area of seas 8 ft or higher will continue to expand SE to encompass almost all of the waters west of about 110W by early on Monday. $$ Aguirre