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Tropical Storm Fernanda Discussion Number  43
NWS Central Pacific Hurricane Center Honolulu HI   EP062017
500 AM HST Sat Jul 22 2017
 
The satellite presentation of Fernanda continues to indicate a 
strongly sheared system, with the low level circulation center 
(LLCC) devoid of deep convection for nearly 6 hours prior to a 
recent small burst of convective development to the north of the 
storm. The latest subjective Dvorak intensity estimates came in at 
25 knots from PHFO, too weak to classify from SAB, with the ADT 
intensity from UW-CIMSS also coming in at 25 knots. Despite the
lack of any significant convection overnight, we have kept
Fernanda, perhaps conservatively as a minimal Tropical Storm for
this advisory based on the 22/0640Z ASCAT pass which showed a small
area of 35 knot winds to the north of the LLCC.

The initial motion for this advisory is 280/8 kt, representing an 
increase in the west-northwestward motion since the previous 
advisory. The GFS continues to be the northern outlier solution, 
with the ECMWF solution the farthest to the south. Very hostile 
environmental conditions will remain over Fernanda over the next 
couple of days, keeping the system shallow with the track
influenced primarily by the low level trade wind flow. As a result,
the forecast track for this advisory will remain very close to that
of the previous advisory, keeping it to the south of the GFEX and
TVCN consensus aids that are likely too far north due to the
influence from the outlier GFS solution. A general motion toward the
west-northwest with an increase in forward speed is expected
through system dissipation.

Fernanda remains in an unfavorable environment with sea surface 
temperatures between 25 and 26C, very dry air aloft as evident in 
water vapor imagery, as well as strong southwesterly shear of
around 30 knots. Strong shear of 30 to 40 knots, very dry air aloft,
and unfavorable sea surface temperatures hovering between 25 and 26C
are expected to persist through the forecast period, and will
eventually lead to the dissipation of Fernanda. As a result, the
forecast will continue to show slow and steady weakening, with
Fernanda expected to become a Tropical Depression later today and a
remnant low tonight, with dissipation forecast after 36 hours.
 
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  22/1500Z 19.1N 146.4W   35 KT  40 MPH
 12H  23/0000Z 19.5N 148.0W   30 KT  35 MPH
 24H  23/1200Z 19.9N 150.2W   30 KT  35 MPH...POST-TROP/REMNT LOW
 36H  24/0000Z 20.2N 153.0W   25 KT  30 MPH...POST-TROP/REMNT LOW
 48H  24/1200Z...DISSIPATED
 
$$
Forecaster Jelsema
 
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