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Tropical Depression Fifteen-E Forecast Discussion Number 1
2021-09-07 22:41:22| National Hurricane Center (East Pacific)
Issued at 300 PM MDT Tue Sep 07 2021 000 WTPZ45 KNHC 072041 TCDEP5 Tropical Depression Fifteen-E Discussion Number 1 NWS National Hurricane Center Miami FL EP152021 300 PM MDT Tue Sep 07 2021 Over the past day or so, convection has gradually become better organized in association with the area of low pressure offshore of the coast of southwestern Mexico. There is now a large curved band to the east of the center, and outflow is increasing in all quadrants. Based on the improving convective organization, advisories are being initiated on Tropical Depression Fifteen-E. An ASCAT-B overpass a few hours ago indicated the peak winds associated with the depression were 26 kt, and assuming some undersampling, the initial advisory intensity is set at 30 kt. The depression has been moving slowly west-northwestward today, to the south of a weak mid-level ridge over northwestern Mexico. Another ridge is forecast to begin building from the southwestern United States to over northern Mexico tonight, which should turn the cyclone to the northwest. The system should then gradually accelerate through midweek as it gets caught in the flow between this ridge, and a mid- to upper-level trough to its west. By late in the forecast period, a turn to the west is expected as the cyclone weakens and becomes steered by the low-level flow. The model guidance is generally in good agreement on this scenario, and the NHC track forecast is close to the various model consensus solutions. It should be noted that based on this track forecast, the center of the cyclone would approach within 120 n mi of the southern tip of the Baja California peninsula on Thursday. Therefore, any deviation in the track to the right would increase the chance for impacts to that area. There are very favorable environmental conditions around the depression that should allow for strengthening over the next couple of days. The only inhibiting factor for quick strengthening in the short term appears to be the lack of a tight circulation and inner-core convection. Because of this, the NHC intensity forecast is on the lower end of the guidance through the first 24 hours, nearest to the LGEM, as it appears the HWRF/HMON are a bit too aggressive in intensifying the cyclone during that time. By 24 hours, it is assumed that the inner-core will become better established, and faster strengthening is indicated from 24 to 48 hours. By 72 hours, the system is forecast to begin moving over much cooler waters and into a dry, stable atmospheric environment, which should cause weakening. By this weekend, the cyclone is expected to degenerate into a remnant low. The NHC intensity forecast beyond 24 hours is very near the IVCN consensus. FORECAST POSITIONS AND MAX WINDS INIT 07/2100Z 18.2N 107.9W 30 KT 35 MPH 12H 08/0600Z 18.4N 108.1W 35 KT 40 MPH 24H 08/1800Z 19.0N 108.6W 45 KT 50 MPH 36H 09/0600Z 20.0N 109.3W 55 KT 65 MPH 48H 09/1800Z 21.1N 110.5W 65 KT 75 MPH 60H 10/0600Z 22.4N 112.0W 65 KT 75 MPH 72H 10/1800Z 23.4N 113.7W 55 KT 65 MPH 96H 11/1800Z 24.5N 116.5W 40 KT 45 MPH 120H 12/1800Z 24.5N 118.9W 30 KT 35 MPH...POST-TROP/REMNT LOW $$ Forecaster Latto
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