661 AXPZ20 KNHC 262154 TWDEP Tropical Weather Discussion NWS National Hurricane Center Miami FL 2154 UTC Sun Aug 26 2018 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 2100 UTC. ...SPECIAL FEATURES... Tropical Storm Miriam centered near 13.6N 126.6W at 26/2100 UTC or 1100 nm WSW of The Southern Tip Of Baja California moving W at 12 kt. Estimated minimum central pressure is 1004 mb. Maximum sustained wind speed is 40 kt with gusts to 50 kt. Miriam is becoming better organized this afternoon, with a prominent band developing on the west side of the storm, and numerous moderate to strong convection within 90 nm of the center. Miriam is expected to intensify to hurricane strength by late Mon as it moves westward. See latest NHC forecast/advisory under AWIPS/WMO headers MIATCPEP5/WTPZ35 KNHC for more details. A band of strong convection is observed north of 1009 mb low pressure centered near 12N106W. The low pressure is embedded along a tropical wave reaching from 04N106W to 17N106W. The showers and thunderstorms are active within 240 nm in the NE semicircle of the center of the low. There is a medium chance that this area of low pressure will develop into a tropical cyclone within the next 48 hours. Please refer to the latest eastern north Pacific Tropical Weather Outlook for more information. ...TROPICAL WAVES... A tropical wave axis is near 94W N of 05N, moving W at 15 kt. Associated convection is described in the Monsoon Trough section below. A tropical wave axis is near 106W from 04N to 17N, moving W at 15 kt. Please see above in special features section for more on developing low pressure and the possibility of tropical cyclone development in association to this feature. ...INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH... The monsoon trough extends from 09N79W to low pressure near 12N106W to 14N120W. Scattered moderate convection is evident within 180 nm south of the monsoon trough axis between 85W and 90W, and within 210 nm north of the monsoon trough axis between 102W and 108W. ...DISCUSSION... OFFSHORE WATERS WITHIN 250 NM OF MEXICO... A ridge extends southeast from 1039 mb high pressure near 45N148W through the Revillagigedo Islands. The associated pressure gradient between the high and a persistent trough across the Baja California Peninsula will continue to support moderate NW winds funneling along the coast of Baja through the next several days, with seas generally 4 to 6 ft. Low pressure will deepen over the southwest United States and along a trough extending across the Gulf of California early next week enhancing winds offshore of Baja California Norte Mon night through Wed. Seas over this area will then gradually build to 6 to 8 ft. Meanwhile, gentle to moderate southerly flow will persist over the Gulf of California this weekend, occasionally pulsing to fresh across north portions. Winds are expected to diminish early next week across south portion of the Gulf leading to variable winds. In the Gulf of Tehuantepec, nocturnal drainage flow and a high pressure building in the wake of a passing tropical wave will support fresh to strong gap winds Sun night into early Mon. OFFSHORE WATERS WITHIN 250 NM OF CENTRAL AMERICA, COLOMBIA, AND WITHIN 750 NM OF ECUADOR... The monsoon trough will linger along 09N/10N during the next few days. Winds on both sides of the trough axis will generally be light to moderate. The main exception to this will be over the Gulf of Papagayo where nocturnal offshore gap winds will pulse to fresh to strong during starting Sun night. REMAINDER OF THE AREA... Please see special features section above for more on recently named T.S. Miriam, and for possible tropical cyclone development of broad low pressure associated with a tropical wave near 105W. Elsewhere, the pressure gradient between ridging across the waters north of 20N and the monsoon trough will support moderate to locally fresh trades and 4 to 7 ft seas in mixed swell north of the monsoon trough and west of 120W through the remainder of the weekend. Southerly swell to 5 to 8 ft will continue to cross the Equator into the area south of the monsoon trough into Mon then subside. $$ Christensen