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Tropical Storm BLANCA

Tropical Storm Blanca Discussion Number   5
NWS National Hurricane Center Miami FL       EP022021
300 PM MDT Mon May 31 2021
Thunderstorms activity has increased markedly since the previous 
advisory and convection now wraps almost 75 percent around the 
well-defined low-level center. A bullseye ASCAT-B and a partial 
ASCAT-A pass at 1717Z and 1602Z, respectively, depicted a few 
35-kt surface vectors just northwest of the tight low-level center 
along with a small radius of maximum winds (RMW) of about 15 nmi. 
Based on the continued increase in the convective organization since 
the ASCAT passes, the advisory intensity has been raised to 40 kt, 
which is a little below the consensus T3.0/45 kt satellite 
intensity classifications from TAFB and SAB, and objective intensity 
estimates of 46 kt and 47 kt from UW-CIMSS ADT and SATCON, 

Blanca is forecast to maintain a general west-northwestward to 
northwestward motion along the south side of a deep-layer 
subtropical ridge for the next 3 days or so. Thereafter, a gradual 
turn to the west-northwest is expected on day 4, followed by a 
westward motion on day 5 as the cyclone moves over cooler water and 
weakens, thus becoming more vertically shallow and steered by the 
low-level easterly trade wind flow. The new official NHC forecast 
track is similar to the previous advisory track and lies near the 
center of the tightly packed guidance envelope, which is close to 
an average of the consensus track models TVCE and HCCA.
Blanca is expected to remain in favorable environmental conditions 
of low vertical wind shear less than 10 kt, high oceanic heat 
content, and moist low- to mid-level air for the next 24 hours or 
so.  As a result, steady strengthening is forecast during that 
time, with a brief period of rapid intensification a distinct 
possibility owing to the cyclone's small RMW. Thereafter, the 
combination of increasing westerly wind shear, along with 
decreasing SSTs and mid-level humidity, should cause gradual 
weakening. The new NHC intensity forecast is a blend of the HWRF, 
HCCA, and Decay-SHIPS (DSHP) models, which is slightly above the 
previous intensity forecast for the first 24 hours, and then is 
very similar to the previous advisory thereafter.
INIT  31/2100Z 13.5N 108.9W   40 KT  45 MPH
 12H  01/0600Z 14.0N 109.9W   50 KT  60 MPH
 24H  01/1800Z 14.6N 111.0W   55 KT  65 MPH
 36H  02/0600Z 15.2N 112.1W   45 KT  50 MPH
 48H  02/1800Z 15.6N 113.0W   40 KT  45 MPH
 60H  03/0600Z 15.9N 113.7W   35 KT  40 MPH
 72H  03/1800Z 16.0N 114.4W   35 KT  40 MPH
 96H  04/1800Z 16.2N 116.2W   30 KT  35 MPH
120H  05/1800Z 16.2N 118.1W   25 KT  30 MPH
Forecaster Stewart