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Tropical Depression TERRY

Tropical Depression Terry Discussion Number  20
NWS National Hurricane Center Miami FL       EP182021
200 AM MST Tue Nov 09 2021
Terry has been undergoing a convective bursting pattern since the 
previous advisory, with thunderstorms containing cloud tops of -75C 
to -80C persisting near and west of the well-defined low-level 
circulation center. ASCAT-B scatterometer data around 0534Z depicted 
the low-level circulation quite well and there were some 26-kt wind 
vectors on the edge of the path swath, which were just east of the 
coldest convective cloud tops. Assuming that some stronger wind 
speeds existed west of those scatterometer-derived winds, the 
initial intensity has been maintained at 30 kt for this advisory. It 
should be noted that this intensity estimate is lower than the 45-kt 
and 35-kt subjective Dvorak satellite intensity estimates provided 
by TAFB and SAB, respectively.
Terry's motion remains a little north of due west, or 280/12 kt. A 
general westward motion is expected for the next several days as 
Terry moves along the southern periphery of a strong subtropical 
ridge that extends westward across most of the eastern North Pacific 
basin. The latest NHC model guidance is tightly clustered around the 
previous forecast track, so only minor tweaks were made, with the 
new official forecast track lying down the middle of the track model 
guidance envelope.
While mid-level dry air intrusions had been inhibiting convective 
development during the previous 18 h or so, the more recent cluster 
of vigorous thunderstorms persisting near Terry's center might be a 
signal that the cyclone is mixing out at least some of the dry air 
from the inner-core region. Moreover, the latest GFS- and 
ECMWF-based SHIPS intensity guidance now indicates that moderate 
mid-level wind shear that had been hindering development has abated 
and is expected to remain near zero while the deep-layer shear is 
forecast to remain low at less than 10 kt for the next couple of 
days. This change in the environmental wind flow affecting the 
cyclone would argue for at least some modest strengthening to occur. 
For now, the new NHC intensity forecast has simply pulled back the 
rate of weakening through the next 48 hours, keeping Terry as a 
30-kt depression during that time. However, if the aforementioned 
favorable environmental conditions persist in subsequent models 
runs, then a change to a strengthening trend would be warranted, as 
indicated by the bulk of the latest intensity guidance.
INIT  09/0900Z 11.1N 110.4W   30 KT  35 MPH
 12H  09/1800Z 11.5N 112.2W   30 KT  35 MPH
 24H  10/0600Z 11.7N 114.6W   30 KT  35 MPH
 36H  10/1800Z 11.8N 117.2W   30 KT  35 MPH
 48H  11/0600Z 11.7N 119.6W   30 KT  35 MPH
 60H  11/1800Z 11.5N 122.2W   25 KT  30 MPH
 72H  12/0600Z 11.0N 124.7W   20 KT  25 MPH...POST-TROP/REMNT LOW
 96H  13/0600Z...DISSIPATED
Forecaster Stewart