000 AXPZ20 KNHC 271000 TWDEP Tropical Weather Discussion NWS National Hurricane Center Miami FL 704 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 0600 UTC surface analysis and satellite imagery through 0930 UTC. ...SPECIAL FEATURES... Newly formed Tropical Storm Selma is centered about 180 nm S of San Salvador El Salvador near 10.7N89.4W 1005 mb at 0900 UTC Oct 27 moving NW or 315 deg at 04 kt. Numerous moderate isolated strong convection is observed in the SW quadrant within 240 nm. Scattered moderate and isolated strong convection is seen elsewhere from 05N to 12N between 88W and 94W. Selma is forecast to move slowly, turn toward the N and intensify through tonight, then make landfall in El Salvador during the day on Saturday. Selma will weaken quickly once it moves inland and dissipate by Sunday morning. Monsoonal winds to the southeast of Selma will produce heavy rainfall across Costa Rica, Nicaragua, Honduras, and Guatemala as well as El Salvador during the next few 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 20 kt or less. 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 12N between 85W and 115W. Seas in this area range between 8 and 11 ft. These seas should subside to a max of 9 ft by sunrise Sun. Strong N winds will resume over the Gulf of Tehuantepec tonight, then increase to minimal gale force by mid morning on Sat. Gale conditions will then persist through Sun morning. 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 on Sun night. Refractive swell of 15 to 17 seconds will wrap around the southern tip of Baja and enter the southern Gulf of California on Sun. Large breaking waves may produce dangerous near shore conditions including rip currents and beach erosion. INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH... The monsoon trough extends from the Pacific coast of Costa Rica at 09N84W through Tropical Storm Selma at 11N89W to 12N115W to 11N126W. The ITCZ continues from 11N126W to beyond 10N140W. Scattered moderate and isolated strong convection is observed within 180 nm either side of the monsoon trough axis between 94W and 120W and between 131W and 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 a strong 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... Newly formed Tropical Storm Selma: please refer to the special features section above for information on a tropical low near 10N88W. Otherwise, moderate southerly winds, and 4 to 6 ft seas, are expected S of 08N through the upcoming weekend. REMAINDER OF THE AREA... A broad ridge dominates the EPAC 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 Fri. A new batch of long-period NW swell, in the form of 8 ft seas, will arrive at 32N140W this morning. Expect seas of 8 to 13 ft W of a line from 32N123W to 13N140W by midday on Sat. 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 a 110W by sunrise on Monday. $$ CAM