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Tropical Storm Douglas Discussion Number   4
NWS National Hurricane Center Miami FL       EP082020
1100 PM HST Mon Jul 20 2020
 
Conventional and scatterometer satellite data indicate that Douglas 
has continued to strengthen, although cloud tops have recently begun 
to warm. A well-defined CDO, along with a curved convective band in 
the western semicircle, has developed, and an earlier SSMI/S 
overpass suggested that a primitive eye feature may be developing. 
The initial intensity of 50 kt is based on a 0506Z ASCAT-A pass that 
showed a small area of winds to 45 kt located less than 15 nmi 
northeast of the center. This intensity is supported by a consensus 
T3.0/45-kt estimate from TAFB and SAB, and an upward-trending 
UW-CIMSS ADT intensity estimate of T3.2/49 kt. The symmetrical 34-kt 
wind radii are based on the aforementioned ASCAT data.
 
The initial motion estimate remains west-southwestward or 255/12 kt. 
A ridge located between TD-07E to the north and Douglas to the south 
is expected to keep the latter cyclone moving west-southwestward 
into Tuesday morning. After that time, the global and regional 
models are forecasting the ridge to weaken and retreat eastward 
faster than originally expected, resulting in Douglas turning 
west-northwestward in 36-48 h. As a result of this more poleward 
motion, the new NHC official track forecast was shifted north of 
the previous advisory track, but not as far north as the some of 
the consensus models and the ECMWF model, which is the northernmost 
track in the NHC model guidance suite.
 
Although Douglas should remain in a favorable low-shear-high-SST 
environment for the next 72 h, which would typically favor rapid 
intensification, the small cyclone will be battling occasional 
intrusions of dry mid-level air. Such an intrusion appears to be 
occurring now based on the recent cloud-top warming that has been 
observed. Thus, only gradual strengthening, with brief periods of 
arrested development, is expected for the next 3 days. On days 4 and 
5, the cyclone will be moving over 25-deg-C SSTs and into an even 
drier airmass, a negative combination that is expected to induce a 
slow weakening trend. The new official intensity forecast is 
similar to the previous advisory, and lies between the consensus 
models IVCN and NOAA-HCCA.


FORECAST POSITIONS AND MAX WINDS
 
INIT  21/0900Z 13.0N 122.8W   50 KT  60 MPH
 12H  21/1800Z 12.5N 124.5W   55 KT  65 MPH
 24H  22/0600Z 12.2N 127.0W   65 KT  75 MPH
 36H  22/1800Z 12.3N 129.7W   75 KT  85 MPH
 48H  23/0600Z 13.0N 132.2W   80 KT  90 MPH
 60H  23/1800Z 14.2N 134.9W   80 KT  90 MPH
 72H  24/0600Z 15.4N 137.6W   75 KT  85 MPH
 96H  25/0600Z 17.0N 143.2W   65 KT  75 MPH
120H  26/0600Z 17.8N 148.9W   50 KT  60 MPH
 
$$
Forecaster Stewart
 
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