000 AXPZ20 KNHC 290230 TWDEP Tropical Weather Discussion NWS National Hurricane Center Miami FL 0405 UTC Tue Aug 29 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 0000 UTC surface analysis and satellite imagery through 0230 UTC. ...SPECIAL FEATURE... The leading edge of a swath of fresh to locally strong southwesterly monsoon flow, and 7 to 11 ft seas, has reached along 15N between 99W and 108W. An elongated and disorganized tropical low appears to be developing near 16N104W, with an estimated pressure of 1006 mb. This low is forecast to reach near 17N106W early Tue, near 18.5N108W late Tue, and near 21N109W late Wed with very favorable environmental conditions for tropical cyclone formation. A band of strong easterly winds will develop within 150 nm over the NE quadrant on Tue as a band of strong to near gale force southwesterly flow, with building seas and banding TSTMS is forecast to develop over the entire SE semicircle. These conditions will shift N and W across the Mexican offshore waters between about 103W and 113W this week with the low center forecast to turn W just to the S of the southern tip of the Baja Peninsula on Wed night. Associated winds are forecast to increase to minimal gale force on Thu over the E semicircle, with a narrow band of gale force winds spreading N across the southern Gulf of California waters on Thu evening. Expect seas of 8 ft or greater across the Gulf of California to the S of 27N on Fri night. Plenty of uncertainty in this scenario, and changes to track and intensity are very likely. ...TROPICAL WAVES AND TROPICAL LOWS... A tropical wave is analyzed N of 08N along 79.5W and has been moving W at 15 kt across the SW Caribbean. Scattered moderate isolated strong convection is observed to the N of 06N between 80W and 83W, with TSTMS continuing to flare over western Panama. A tropical low is embedded in the monsoon trough at 09N85.5W and is estimated at 1009 mb. Scattered moderate isolated strong convection is noted within 240 nm over the SW quadrant of the low. A tropical low is embedded in the monsoon trough at 09N90W and is estimated at 1009 mb. Scattered moderate isolated strong convection is noted within 300 nm over the W semicircle of the low. A tropical wave is analyzed from 13N109.5W to 24N109W, and has moved W at 15 kt over the past 24 hours. Scattered moderate isolated strong convection is observed to the S of 21N within 120 nm either side of the wave axis. A tropical wave is analyzed from 12N119W to 20N119W, and has moved W at about 08 kt over the past 24 hours. Scattered moderate isolated strong convection is observed to the S of 15N within 240 nm of the wave axis. ..INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH... The monsoon trough extends W across Panama, the Gulf of Panama, and the southern tip of Costa Rica through embedded surface lows at 09N85.5W and 09N90W, then turns NW to 14.5N95W, then the monsoon trough turns W through a 1006 mb surface low embedded in the trough axis at 16N104W, with the monsoon trough continuing W through tropical waves at 16N.5109W and 14N119W, and then continues SW to beyond 10N140W. Scattered moderate isolated strong convection is observed elsewhere within 150 nm either side of a line from 07N81W to 09N92W, and within 240 nm either side of a line from 14N98W to 15N121W. ...DISCUSSION... OFFSHORE WATERS WITHIN 250 NM OF MEXICO... Refer to the special features paragraph. A NW to SE orientated ridge extends across EPAC waters well beyond 250 nm. The resultant pressure gradient will support a gentle to locally moderate NW breeze across the open waters W of the Baja California Peninsula through late Tue, then the pressure gradient will relax some N of 24N as the center of the tropical low, or possible tropical cyclone passes S of the Baja Peninsula and continues NW across the waters s of 27N and W of Baja through the upcoming weekend. Gulf of Tehuantepec: light offshore nocturnal flow expected this week, with light to gentle onshore flow during the day. OFFSHORE WATERS WITHIN 250 NM OF CENTRAL AMERICA, COLOMBIA, AND WITHIN 750 NM OF ECUADOR... Gulf of Papagayo: Gentle offshore nocturnal flow expected this week. Otherwise, light and variable flow is expected N of the monsoon trough through the middle of next week, while moderate to locally fresh southerly winds are expected S of the monsoon trough axis. Long period southerly cross-equatorial swell, in the form of 7 to 8 ft seas, currently across the waters from 03N to 06N between 82W and 88W, is forecast to subside to less than 8 ft by sunrise on Tue. REMAINDER OF THE AREA... A ridge extends from 32N135W to near 16N116W, and is accompanied by moderate anticyclonic winds and 4 to 7 ft seas. Fresh to locally strong southerly monsoonal winds, and seas of 7 to 10 ft are observed from 08N to 14N between 100W and 132W. The southwesterly flow will increase from 09N to 15N between 103W 120W this week as the tropical low described in the special feature paragraph strengthens. $$ Nelson