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Tropical Storm Douglas Discussion Number   6
NWS National Hurricane Center Miami FL       EP082020
1100 AM HST Tue Jul 21 2020
 
Douglas appears to have been trying to scour out a little bit of 
dry air on its western side during the day, although recent visible 
images suggest that deep convection is attempting to wrap entirely 
around the center.  Because the convective pattern didn't change 
much from earlier, Dvorak classifications from TAFB and SAB remain 
T3.5/55 kt, so the initial intensity is held steady on this 
advisory.

Strong ridging to the north of Douglas continues to impart a 
west-southwestward motion of the cyclone, or 255/13 kt.  As 
mentioned this morning, the ridge is likely to take on a more 
east-west orientation as a mid-/upper-level low northeast of the 
Hawaiian Islands retrogrades westward, and this pattern evolution 
will allow Douglas to turn westward by tonight and then 
west-northwestward by late Wednesday.  That general motion is 
forecast to continue for the remainder of the 5-day forecast 
period.  The track guidance still showcases a faster ECMWF and 
slower GFS and HWRF solutions, and the overall envelope and 
model consensus aids have again nudged northward.  The updated 
track forecast is therefore a little north of the previous one, 
mainly after 48 hours through day 5.

Once deep convection can isolate Douglas's center from the 
ambient environment, low shear and warm sea surface temperatures of 
28-29 degrees Celsius should allow intensification to resume.  
Despite this morning's hiatus in strengthening, the SHIPS Rapid 
Intensification (RI) guidance continues to key in on a significant 
chance of RI during the next day or two.  Therefore, the intensity 
forecast from this morning has been left unchanged, and it still 
generally lies between the HCCA and Florida State Superensemble, 
closer to the higher end of the guidance envelope.  Douglas should 
reach its peak intensity in about 48 hours, after which time 
oceanic heat content values drop to zero, which should cause some 
gradual weakening.

Based on a partial ASCAT-A pass, Douglas's tropical-storm-force 
wind radii were increased on the northern side.
 
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  21/2100Z 12.1N 125.4W   55 KT  65 MPH
 12H  22/0600Z 11.9N 127.1W   70 KT  80 MPH
 24H  22/1800Z 12.1N 129.5W   80 KT  90 MPH
 36H  23/0600Z 13.0N 131.9W   85 KT 100 MPH
 48H  23/1800Z 14.4N 134.5W   90 KT 105 MPH
 60H  24/0600Z 15.7N 137.3W   85 KT 100 MPH
 72H  24/1800Z 16.9N 140.2W   75 KT  85 MPH
 96H  25/1800Z 18.5N 146.0W   65 KT  75 MPH
120H  26/1800Z 19.0N 151.5W   55 KT  65 MPH
 
$$
Forecaster Berg
 
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