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TROPICAL STORM LESTER DISCUSSION NUMBER  53
NWS CENTRAL PACIFIC HURRICANE CENTER HONOLULU HI   EP132016
1100 AM HST TUE SEP 06 2016
 
While Lester is over relatively cool 25C water this morning, the
system continues to exhibit tropical characteristics in an
environment characterized by light northwesterly shear. Latest
geostationary satellite images, however, show waning deep
convection, with visible imagery helping to determine that the
low-level center is partially exposed on the northwestern edge of
diminishing mid-and high-level clouds. The initial intensity for
this advisory will be maintained at 50 kt, partially based on global
model analyses that depict a strong gradient in the eastern
semicircle. Meanwhile, subjective Dvorak intensity estimates
indicate a much weaker system, ranging from too weak to classify
from SAB, to 1.5/25 kt from GTW using a subtropical technique, to a
current intensity of 2.5/35 kt from PHFO.
 
Lester is tracking toward the north between a deep-layer ridge to
the east, and an approaching mid-latitude trough to the northwest,
with an initial motion vector estimate of 360/09 kt. Lester is
forecast to turn toward the northeast over the next 24 hours, with
an increase in forward speed until dissipation occurs by day 3. This
will occur as Lester rounds the western edge of the ridge, and
becomes embedded in an increasingly strong and deep southwesterly
flow ahead of the approaching trough. The updated official track
forecast parallels the previous but moves Lester at a faster forward
speed on day 2, in line with a blend of the latest GFS, ECMwF and
UKMET guidance, and with input from the Ocean Prediction Center
(OPC).
 
Also in collaboration with OPC, the transition to an extratropical
low is expected to take place in about 24 hours, and will likely be
complete in about 36 hours. Although the wind field will be
undergoing some changes as this occurs, little change in intensity
is expected. Lester's existence as an extratropical low will be
brief, as dissipation is forecast by day 3, when Lester is forecast
to become absorbed by a larger developing low that moves into the
Gulf of Alaska. The intensity forecast is largely being driven by
global model guidance, but is also supported by the latest SHIPS
guidance.
 
A 1223Z JASON-2 pass detected maximum seas near 22 feet, which
matched well with Wave Watch III guidance, with this data and
OPC guidance helping to outline the area of 12 foot seas.
  
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  06/2100Z 34.1N 166.4W   50 KT  60 MPH
 12H  07/0600Z 35.8N 166.1W   50 KT  60 MPH
 24H  07/1800Z 38.7N 164.6W   50 KT  60 MPH
 36H  08/0600Z 42.4N 161.4W   50 KT  60 MPH...POST-TROP/EXTRATROP
 48H  08/1800Z 48.0N 154.0W   45 KT  50 MPH...POST-TROP/EXTRATROP
 72H  09/1800Z...DISSIPATED
 
$$
Forecaster Birchard
 
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