000 AXPZ20 KNHC 290917 TWDEP Tropical Weather Discussion NWS National Hurricane Center Miami FL 918 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 0600 UTC surface analysis and satellite imagery through 0900 UTC. ...SPECIAL FEATURES... Weak and disorganized low pressure embedded in the monsoon trough is located SW of Mexico near 16N105W moving W around 5 kt. Scattered moderate to strong convection is within 120 nm SW of the coast of Mexico, although it is unclear if this was purely diurnally driven convection that developed over SW Mexico before propagating offshore. Additional convection is to the W along a nearby tropical wave. It is not clear if there is a well defined center, and earlier scatterometer data showed another circulation more to the W along the tropical wave. Fresh to strong monsoonal winds and building seas are occurring on the S through SW portion and model guidance shows and expansion of these winds wrapping around the NE side as the low potentially develops into a tropical cyclone. In any case, fresh to near gale force winds at a minimum will occur, including SW of Mexico where funneling up along the coastline develops, and seas are forecast to build to greater than 12 ft through mid-week. The low is forecast to move NW to between 18N109W by early Wed, then 21N110W by early Thu, continuing NW offshore of the Baja California Peninsula thereafter. Increasing winds and seas will propagate toward and through the entrance to the Gulf of California as the low moves NW. ...TROPICAL WAVES... A tropical wave is analyzed N of 10N along 111W moving W at 15 kt. Scattered moderate and isolated strong convection from 11N to 18N between 106W and 113W. A tropical wave is analyzed from 11N to 20N along 119W moving W at around 10 kt. Associated convection is analyzed along the monsoon trough as described below. ..INTERTROPICAL CONVERGENCE ZONE/MONSOON TROUGH... The monsoon trough axis extends from 10N83W to 09N88W to 16N98W to low pressure near 16N105W to 15N115W to 12N130W to 10N140W. Scattered moderate and isolated strong convection is from 05N to 09N between 86W and 94W. Scattered moderate convection is from 11N to 15N between 114W and 122W. ...DISCUSSION... OFFSHORE WATERS WITHIN 250 NM OF MEXICO... Please refer to the special features section for developing low pressure SW of Mexico near 16N105W. Otherwise, a ridge axis extends toward the northern offshore waters just W of 120W supporting gentle to moderate NW flow across the open waters W of the Baja California Peninsula. Winds in the Gulf of California are light and variable with seas 2 ft or less, except 3 to 5 ft near the entrance. In the Gulf of Tehuantepec, light offshore nocturnal flow is expected this week into the upcoming weekend, with light to gentle onshore flow during the day. OFFSHORE WATERS WITHIN 250 NM OF CENTRAL AMERICA, COLOMBIA, AND WITHIN 750 NM OF ECUADOR... Weak and transient low pressure is near 10N89W. This low will move W of the area by mid-week. In the Gulf of Papagayo, gentle offshore nocturnal flow is expected this week into the upcoming weekend. Otherwise, light and variable flow is expected N of the monsoon trough through the week and into the upcoming weekend, 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 5 to 7 ft seas will gradually subside through mid-week. REMAINDER OF THE AREA... The remnant trough of Kenneth in the far NW corner is finally dissipating while high pressure ridging dominates the remainder of the waters W of 120W. The ridging will support moderate to locally fresh trades and 4 to 7 ft seas through the week and into the upcoming weekend. The pressure gradient will tighten offshore of central California later in the week which may build and send down fresh 8 ft seas into the area N of 26N between 122W and 133W. $$ Lewitsky