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Tropical Depression Fifteen-E Forecast Discussion Number 1
2018-08-26 10:42:24| National Hurricane Center (East Pacific)
Issued at 200 AM PDT Sun Aug 26 2018 276 WTPZ45 KNHC 260842 TCDEP5 Tropical Depression Fifteen-E Discussion Number 1 NWS National Hurricane Center Miami FL EP152018 200 AM PDT Sun Aug 26 2018 Various satellite data over the past several hours, including recent ASCAT scatterometer surface-wind data, indicate that the well-defined low pressure area located about 1000 nmi southwest of the southern tip of the Baja California peninsula has become much better organized, and has developed into a tropical depression. A small CDO-like feature has formed over the well-defined center depicted in the ASCAT data, and a recent burst of cold cloud tops of -80C have also developed just west of the center. The initial intensity of 30 kt is based on 0458Z and 0558Z ASCAT wind data, which indicated winds of 28-30 kt were located 35-40 nmi west and southwest of the low-level center. The initial motion estimate is 280/10 kt. The depression is expected to remain south of a strong deep-layer subtropical ridge for the next 96 hours, resulting in a general westward motion at a slightly faster forward speed. By day 5, the cyclone is forecast to move into a break in the ridge created by a broad mid-/upper-level trough that is forecast to dig southward out of the northern Pacific between 140W-145W longitude. The forecast track lies essentially down the middle of the guidance envelope, which is just north of the consensus model TVCE and the GFS model, but south of the ECMWF and UKMET models. The HRWF and HMON models were not being available for the TVCE consensus on this cycle, so some significant adjustments to the track in the next advisory may be required. The cyclone has a radius of maximum winds (RMW) of 35-40 nmi based on the recent ASCAT data. The combination of the modest RMW, low vertical wind shear of less than 10 kt, a very moist mid-level environment, and sea-surface temperatures above 28 deg C, favors steady intensification and even the possibility of rapid strengthening. Since this is the first forecast, however, the intensity forecast is on the conservative side and calls for a climatological increase of one T-number or 20 kt every 24 h for the next 48 hours, which is above all of the intensity guidance except for the Navy COAMPS (CTCI) model. By 96-120 hours, the intensity is leveled off due to possible entrainment of drier air and an increase in southwesterly vertical wind shear. FORECAST POSITIONS AND MAX WINDS INIT 26/0900Z 13.3N 124.1W 30 KT 35 MPH 12H 26/1800Z 13.5N 126.0W 40 KT 45 MPH 24H 27/0600Z 13.7N 128.4W 50 KT 60 MPH 36H 27/1800Z 13.9N 130.6W 60 KT 70 MPH 48H 28/0600Z 14.1N 132.6W 70 KT 80 MPH 72H 29/0600Z 14.3N 136.6W 80 KT 90 MPH 96H 30/0600Z 14.9N 140.1W 90 KT 105 MPH 120H 31/0600Z 17.4N 141.9W 90 KT 105 MPH $$ Forecaster Stewart
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