Pacific Hurricane and Tropical Cyclone Track Updates

Tropical Depression Seventeen-E Forecast Discussion

WTPZ42 KNHC 221457

Tropical Depression Seventeen-E Discussion Number   1
NWS National Hurricane Center Miami FL       EP172021
1000 AM CDT Fri Oct 22 2021

Over the past 24 h, the convective organization has steadily 
increased in association with the area of low pressure to the 
southwest of southern Mexico. Overnight, an ASCAT overpass showed 
that the system still lacked a well-defined low-level center. 
However, since that time visible satellite imagery reveals that the 
disturbance has become much better organized and that a tropical 
cyclone has formed. The most recent subjective Dvorak intensity 
estimates from both TAFB and SAB were T-2.0/30 kt, and therefore 
30 kt is the initial advisory intensity.

The tropical depression is moving 280/9 kt to the south of a 
mid-tropospheric ridge. A deep-layer trough is forecast to dig 
southeastward toward the western United States this weekend and 
early next week, which should create a weakness in the ridge to the 
north of the cyclone. This would cause the depression to slow its 
forward motion and turn northwest or north-northwest towards this 
weakness. There is a fair amount of spread in the model guidance 
beyond 24 h, as the various models have different solutions as to 
how abrupt of a turn to the right the cyclone will make in response 
to the change in the steering flow. The NHC track forecast is near 
the HFIP corrected consensus, HCCA, and the TVCE guidance. Based on 
the current NHC forecast track, the cyclone would be nearing the 
coast of southwestern Mexico in 72 h, and inland by 96 h. However, 
due to the larger-than-normal model spread beyond 24 h, that 
portion of the forecast track is not particularly of high 

The cyclone is expected to be within an ideal environment for 
strengthening over the next couple of days, with very little 
vertical wind shear, a moist airmass, and sea surface temperatures 
near 30 degrees C. Therefore, steady intensification is indicated by 
all of the model guidance through 60 h. There is some weakening 
indicated by the models at 72 h, around the time the system would be 
nearing the coast of Mexico,  which could be due to some dry air 
entraining into the cyclone's circulation. The NHC intensity 
forecast is near the IVCN consensus solution through 72 h but below 
HCCA. Beyond landfall, the intensity forecast is near the 
Decay-SHIPS prediction. It should be noted that the SHIPS Rapid 
Intensification guidance indicates a greater than 60 percent chance 
of a 55-kt increase in strength over the next 60 h and 65 kt over 
the next 72 h. 

Based on the forecast track, intensity, and wind radii, Tropical 
Storm or Hurricane Watches may be issued for a portion of the 
southwestern Mexico coast as early as tonight. 


INIT  22/1500Z 12.7N 100.5W   30 KT  35 MPH
 12H  23/0000Z 13.0N 101.3W   40 KT  45 MPH
 24H  23/1200Z 13.9N 101.9W   50 KT  60 MPH
 36H  24/0000Z 14.6N 102.3W   65 KT  75 MPH
 48H  24/1200Z 15.3N 102.7W   75 KT  85 MPH
 60H  25/0000Z 16.2N 103.1W   80 KT  90 MPH
 72H  25/1200Z 17.3N 103.5W   75 KT  85 MPH
 96H  26/1200Z 19.8N 104.0W   35 KT  40 MPH...INLAND
120H  27/1200Z 22.0N 104.3W   20 KT  25 MPH...POST-TROP/INLAND

Forecaster Latto

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