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Hurricane Fernanda Discussion Number  30
NWS National Hurricane Center Miami FL       EP062017
200 AM PDT Wed Jul 19 2017

Fernanda's convective cloud pattern has continued to wither, and
has been accompanied by a general warming of the cloud tops. The eye
is no longer evident in infrared imagery and a 0640Z AMSU overpass
indicated that the eye had become open in the southern semicircle.
Intensity estimates are a consensus T4.5/77 kt from TAFB and SAB,
along with a recent CIRA-AMSU estimate of 82 kt. A blend of these
values supports lowering the advisory intensity to 80 kt.

The initial motion estimate remains 310/08 kt. Fernanda is forecast
to move northwestward today and turn toward the west-northwest by
tonight or Thursday. A continuation of that general motion is
expected through the end of the forecast period due to a strong
subtropical ridge remaining entrenched to the north and northeast of
the Hawaiian Islands.  The new NHC forecast track is almost on top
of the previous advisory track, and lies close to the HFIP Corrected
Consensus (HCCA) and TVCN consensus models.

Fernanda is expected to steadily weaken throughout the forecast
period. The first 36-48 hours of weakening will primarily be due to
the cyclone moving over sub-25C SSTs. Following that will be a
sharp increase in southwesterly vertical wind shear to 25-30 kt,
causing Fernanda to degenerate into a post-tropical cyclone by 72
hours. The official intensity forecast follows the downward trend of
the previous advisory and is similar to the ICON and IVCN consensus
models.

FORECAST POSITIONS AND MAX WINDS

INIT  19/0900Z 17.0N 135.0W   80 KT  90 MPH
 12H  19/1800Z 17.5N 135.9W   70 KT  80 MPH
 24H  20/0600Z 18.1N 137.2W   60 KT  70 MPH
 36H  20/1800Z 18.6N 138.8W   50 KT  60 MPH
 48H  21/0600Z 19.1N 140.6W   40 KT  45 MPH
 72H  22/0600Z 20.1N 143.9W   35 KT  40 MPH...POST-TROPICAL
 96H  23/0600Z 21.1N 147.8W   30 KT  35 MPH...POST-TROP/REMNT LOW
120H  24/0600Z 22.0N 152.1W   25 KT  30 MPH...POST-TROP/REMNT LOW

$$
Forecaster Stewart

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