000 AXPZ20 KNHC 200908 TWDEP Tropical Weather Discussion NWS National Hurricane Center Miami FL 902 UTC Thu Jul 20 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 0900 UTC. ...SPECIAL FEATURES... Recently downgraded Tropical Storm Fernanda is centered near 18.2N 137.7W at 20/0900 UTC moving WNW at 8 kt. Estimated minimum central pressure is 992 mb. Maximum sustained winds are 60 kt with gusts to 75 kt. Scattered moderate to strong convection within 90 nm of center. Fernanda will continue to weaken as it moves west of 140W late Thu. Large swell will continue to expand and spread out ahead of Fernanda to the NW and W during the next few days. See latest NHC forecast/advisory under AWIPS/WMO headers MIATCMEP1/WTPZ21 for more details. Tropical Storm Greg is centered near 14.1N 114.7, or 585 nm SSW of the southern tip of the Baja Peninsula at 20/0900 UTC, moving W or 270 deg at 9 kt. Estimated minimum central pressure is 1006 mb. Maximum sustained winds are 35 kt with gusts to 45 kt. Scattered moderate to strong convection is noted within 120 nm of the center. Despite recently weakening Greg is expected to intensify and reach hurricane strength within 48 hours. See the latest NHC forecast/advisory under AWIPS/WMO headers MIATCMEP2/WTPZ22 for more details. Tropical Depression Eight-E is centered near 13.9N 122.2W, or about 1015 miles SW of the southern tip of the Baja Peninsula at 20/0300 UTC, moving W-SW or 245 deg at 5 kt. Estimated minimum central pressure is 1009 mb. Strong winds surround the center within about 75 nm. Scattered moderate isolated strong convection is noted within 30 nm E and within 90 nm W of the center. Eight-E is experiencing northerly shear and is not expected to reach tropical storm strength. See the latest NHC forecast/advisory under AWIPS/WMO headers MIATCMEP3/WTPZ23 for more details. A tropical wave is analyzed from 08N to 16N along 102W with scattered moderate isolated strong convection observed to the S of 15N within 150 nm either side of the wave axis. A surface low is forecast to develop along the wave near 11N106W on Thu, and possibly become a tropical cyclone as it moves westward to near 14N111W late Fri. ...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH... The monsoon trough extends from 08N78W to 08N88W TO 09N92W, then turns NW through the tropical wave at 11N102W to 13N109W where it loses identity in the cyclonic circulation associated with Tropical Strom Greg. The monsoon trough resumes S of Hurricane Fernanda at 12N134W and continues SW to beyond 09N140W. Except as previously mentioned, scattered moderate isolated strong convection is observed within 150 nm either side of a line from 06N82W to 11N100W, from 07N to 14N between 103W and 110W, within 60 nm of 11N117W and 10N124W, and within 45 nm either side of a line from 16N130W to 10N137W. ...DISCUSSION... OFFSHORE WATERS WITHIN 250 NM OF MEXICO... Please see the special features for information on Tropical Storm Greg southwest of Manzanillo, Mexico. A surface trough meandering E to W from the coast of southern California southward to off the coast of the Baja California Peninsula will continue to block the advance of the subtropical ridge maintaining gentle to moderate NW winds off the Baja California peninsula through Thu. Seas will remain 5 to 7 ft in a mix of long period north and southwesterly swell. Gentle southerly flow will persist in the Gulf of California, except for moderate southerly flow over the northern Gulf. Light to gentle variable winds will prevail across the Gulf of Tehuantepec through today, then fresh northerly gap winds will once again pulse to around 20 kt at night. Winds may increase to fresh to strong by the end of the week into the weekend. OFFSHORE WATERS WITHIN 250 NM OF CENTRAL AMERICA, COLOMBIA, AND WITHIN 750 NM OF ECUADOR... In the Gulf of Papagayo, moderate to fresh offshore winds will pulse to fresh each night with nocturnal drainage through the week, occasionally building max seas to 8 ft in a mix of east swell and longer period southwest swell. Gentle to moderate southerly winds are expected south of the monsoon trough axis. Long period cross-equatorial southerly swell and 6-7 ft seas will continue to propagate into the waters reaching the coast of Central America through the day. Another pulse of large southerly swell will move into the region today and raise seas to 6-8 ft through Thu. REMAINDER OF THE AREA... Please see the special features section for information on Hurricane Fernanda and Tropical Depression Eight-E. Weak ridging is producing moderate to fresh north to northeast winds north of 25N. The ridge will build modestly eastward through mid-week, tightening the gradient north of Fernanda as it moves west of 135W tonight, and produce fresh northeast winds across much of the area north of 25N, helping build seas to 8-10 ft in mixed northerly and southerly swell. $$ Christensen