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Tropical Storm Douglas Discussion Number   5
NWS National Hurricane Center Miami FL       EP082020
500 AM HST Tue Jul 21 2020
 
A recent SSMIS microwave pass indicated that Douglas's low-level 
center is located very near the head of a broken band of convection 
which curls around the southern, western, and northern side of the 
circulation.  This center is also now embedded beneath a Central 
Dense overcast in infrared imagery, near an area of cold 
overshooting cloud tops.  TAFB and SAB Dvorak classifications have 
both risen to T3.5, and Douglas's initial intensity is therefore 
raised to 55 kt.
 
Douglas continues to dip west-southwestward, or 255/13 kt, due to 
strong mid-level ridging to its north.  A mid- to upper-level low 
located northeast of the Hawaiian Islands is forecast to retrograde 
westward over the next few days, which will allow the ridge to take 
on a more east-west orientation.  As a result, Douglas is expected 
to turn westward later today and then move west-northwestward 
beginning overnight Wednesday into the weekend.  The track guidance 
all agrees on this scenario, but there are some speed differences, 
bookended by slower GFS and HWRF solutions and a faster ECMWF 
solution.  Overall, however, the new NHC forecast remains very 
close to the multi-model consensus aids, and no significant changes 
were made compared to the previous forecast, except maybe a slight 
northward adjustment on days 4 and 5.

The low-shear, warm sea surface temperature environment within 
which Douglas is moving is a recipe for continued strengthening, 
potentially at a rapid rate, for the next 48 hours.  The intensity 
guidance has been trending higher, and the latest SHIPS Rapid 
Intensification (RI) indices are highlighting the increased chance 
of RI.  For example, there is currently a 50/50 shot that Douglas's 
winds will increase by 25 kt within the next 24 hours, and a 40-50 
percent chance of a 30-kt increase during that period.  Based on 
this guidance, the new HCCA and Florida State Superensemble 
solutions, and the intensity consensus, the NHC intensity forecast 
has been increased from the previous cycle and now shows Douglas 
becoming a hurricane later today with a higher peak occurring in 
about 2 days.  Since oceanic heat content falls to zero along 
Douglas's path by day 3, some gradual weakening is shown in the 
latter stages of the forecast.
 
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  21/1500Z 12.4N 124.2W   55 KT  65 MPH
 12H  22/0000Z 12.1N 126.0W   70 KT  80 MPH
 24H  22/1200Z 12.1N 128.5W   80 KT  90 MPH
 36H  23/0000Z 12.6N 131.0W   85 KT 100 MPH
 48H  23/1200Z 13.6N 133.7W   90 KT 105 MPH
 60H  24/0000Z 14.9N 136.5W   85 KT 100 MPH
 72H  24/1200Z 16.1N 139.4W   75 KT  85 MPH
 96H  25/1200Z 18.0N 145.5W   65 KT  75 MPH
120H  26/1200Z 18.5N 151.5W   55 KT  65 MPH
 
$$
Forecaster Berg
 
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