ZCZC MIATCDEP5 ALL
TTAA00 KNHC DDHHMM
 
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
 
NNNN