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Tropical Storm Blanca Discussion Number 10
NWS National Hurricane Center Miami FL EP022021
900 PM MDT Tue Jun 01 2021
A cirrus canopy associated with a resurgence of deep convection
is obscuring Blanca's center. However, the cirrus has a
sharp western edge in infrared satellite imagery, indicative of
continued southwesterly shear. Because Blanca's satellite
appearance is a little better than it was earlier today, the
initial intensity is being held at 45 kt, in best agreement with
a Dvorak classification of T3.0 from TAFB.
A 2030 UTC AMSR microwave pass and recent visible images suggest
that Blanca has turned slightly to the left and slowed down, with
the initial motion now estimated to be 295/6 kt. This slower
motion is the result of a mid- to upper-level low which has
developed near the northern Baja California peninsula and has
dissolved the subtropical ridge. With the steering flow
essentially collapsing, Blanca is forecast to drift westward in the
coming days, with its slowest forward speeds occurring from 24-48
hours. After 48 hours, there should be enough of a low-level ridge
to help a weakening Blanca move a little faster toward the west
within the trade wind flow. Overall, the NHC track forecast favors
a solution on the southern side of the guidance envelope, close to
the previous forecast and the HFIP Corrected Consensus (HCCA).
Several environmental factors are likely to contribute to Blanca's
weakening over the next few days. (1) Moderate southwesterly
vertical shear, caused by the aforementioned mid-/upper-level
trough, is expected to gradually increase over the next 2 to 3
days, (2) the upper-level environment is forecast to become more
subsident after 24 hours, and (3) Blanca will be heading toward
marginally warm waters of around 26 degrees Celsius. Gradual
weakening is therefore expected, and Blanca could become a tropical
depression within 48 hours and a remnant low by day 4. The
intensity models are in good agreement on a gradual weakening
trend, and the NHC official forecast closely follows the IVCN
intensity consensus and the HCCA model.
FORECAST POSITIONS AND MAX WINDS
INIT 02/0300Z 14.9N 111.6W 45 KT 50 MPH
12H 02/1200Z 15.1N 112.2W 40 KT 45 MPH
24H 03/0000Z 15.3N 112.8W 40 KT 45 MPH
36H 03/1200Z 15.5N 113.4W 35 KT 40 MPH
48H 04/0000Z 15.6N 114.1W 30 KT 35 MPH
60H 04/1200Z 15.6N 115.2W 30 KT 35 MPH
72H 05/0000Z 15.6N 116.3W 25 KT 30 MPH
96H 06/0000Z 15.7N 118.4W 25 KT 30 MPH...POST-TROP/REMNT LOW
120H 07/0000Z 16.0N 120.0W 25 KT 30 MPH...POST-TROP/REMNT LOW
$$
Forecaster Berg
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