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Tropical Storm Douglas Discussion Number   7
NWS National Hurricane Center Miami FL       EP082020
500 PM HST Tue Jul 21 2020
 
This afternoon's satellite presentation reveals a tropical
cyclone that's struggling with the inhibiting factors from
mid-level dry air intrusion.  Cloud tops near the center of
circulation have warmed considerably during the past few hours, and
the primary convective band in the east semicircle has become a bit
fragmented. A blend of an earlier SATCON of 52 kt, an ADT objective
estimate of 51 kt and a Dvorak satellite classification of T3.5
from both TAFB and SAB supports holding the initial intensity at 55
kt, although the aforementioned recent changes in the cloud
pattern may consider this as a bit generous.
 
The better performing HFIP HCCA and IVCN multi-model intensity
guidance still show Douglas shaking off the dry air invasion and
strengthening into a hurricane in 12 hours, and the official
forecast reflects this.  The consensus intensity models and the
FV3/GFS SHIPS show the cyclone reaching a peak intensity in around
two days.  Afterward, Douglas will be moving over 25-deg-C oceanic
temperatures and into stable air mass.  These negative
contributions should, therefore, induce a slow weakening trend
through day 5.
 
The initial motion is estimated to be westward, or 270/12 kt within
the mid-tropospheric easterly steering flow provided by a
subtropical ridge anchored to the north of Douglas.  This ridge is
forecast to gradually build westward in response to a retreating
large cut-off low near the Hawaiian Islands.  As a result, Douglas
should progressively turn West-northwestward by late Wednesday.
and this general motion is forecast to continue for the remainder
of the 5-day forecast period.  The official NHC forecast is quite
similar to the previous one with only a slight adjustment to the
right beyond 72 hours through 120 hours in order to conform to
the various consensus models.
 
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  22/0300Z 12.1N 126.7W   55 KT  65 MPH
 12H  22/1200Z 12.1N 128.5W   70 KT  80 MPH
 24H  23/0000Z 12.6N 130.8W   80 KT  90 MPH
 36H  23/1200Z 13.6N 133.2W   85 KT 100 MPH
 48H  24/0000Z 15.1N 136.0W   90 KT 105 MPH
 60H  24/1200Z 16.4N 138.8W   80 KT  90 MPH
 72H  25/0000Z 17.5N 141.7W   70 KT  80 MPH
 96H  26/0000Z 18.8N 147.3W   60 KT  70 MPH
120H  27/0000Z 19.4N 153.1W   50 KT  60 MPH
 
$$
Forecaster Roberts
 
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