000 WTPZ41 KNHC 100858 TCDEP1 Tropical Depression Sixteen-E Discussion Number 1 NWS National Hurricane Center Miami FL EP162021 400 AM CDT Sun Oct 10 2021 The system we have been monitoring over the last several days off the southern coast of Mexico has been gradually improving in organization. An earlier ASCAT-A pass at 0257 UTC indicated that a closed surface vortex was developing, especially after investigating the ambiguity wind solutions from the instrument. In addition, the 0600 UTC subjective Dvorak from TAFB was at T2.0/30 kt, which is in good agreement with the peak winds (29 kt) from the earlier scatterometer data. Since that time, convection near the estimated center has only increased in coverage and intensity. Therefore, advisories are being initiated on TD16-E, the first tropical cyclone in the East Pacific basin in nearly a month. The initial intensity has been set at 30 kt in agreement with the scatterometer and satellite intensity estimate. The current motion of the depression is estimated at 290/15 kt, though some uncertainty exists given the system is in its formative stages. At present, the cyclone is situated on the equatorward side of an expensive mid-level ridge centered over Mexico that stretches westward into the East Pacific. This ridge should continue to steer the tropical cyclone to the west-northwest over then next day or so. Thereafter, a strong shortwave trough is forecast to dig into the western United States, creating a pronounced weakness in the mid-level ridge steering the system. The net result of this synoptic pattern change is that the tropical cyclone will likely bend sharply right as the ridge becomes oriented to its east, leading to a turn north to then northeastward in the 48-72 hour forecast. This track evolution would likely steer the system to the mainland Mexican coast in around 96 hours. The latest track guidance is in pretty good agreement on the general track, though investigating the GFS and ECMWF ensembles solutions reveals significant uncertainty in the along-track spread of the current forecast track. The initial NHC track forecast has been chosen to lie near the consensus aids, splitting the difference between the TVCA and HCCA solutions. The environment over the depression appears quite favorable for intensification, with low shear (around 10 kt) high mid-level moisture (around 70 percent) and warm sea-surface temperatures (29-30 C) expected to persist for the next three days. It may take 12-24 hours for an inner core to become established, but after this structural change occurs, the system appears poised for substantial intensification. In fact, the latest GFS-SHIPS guidance indicates a 44 percent chance of a 65 knot increase in intensity over the next 72 hours. The first NHC intensity forecast follows suit, showing a peak intensity of 95 kt in 72 hours. It is worth noting that this intensity forecast is less than some of the more bullish guidance, including the latest HFIP corrected consensus approach (HCCA) and this initial forecast could be conservative. FORECAST POSITIONS AND MAX WINDS INIT 10/0900Z 14.3N 102.9W 30 KT 35 MPH 12H 10/1800Z 15.1N 105.0W 35 KT 40 MPH 24H 11/0600Z 15.8N 107.2W 45 KT 50 MPH 36H 11/1800Z 16.6N 108.6W 60 KT 70 MPH 48H 12/0600Z 17.8N 109.6W 75 KT 85 MPH 60H 12/1800Z 19.0N 109.8W 85 KT 100 MPH 72H 13/0600Z 20.7N 109.4W 95 KT 110 MPH 96H 14/0600Z 25.2N 106.4W 75 KT 85 MPH...INLAND 120H 15/0600Z...DISSIPATED $$ Forecaster Papin