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TROPICAL STORM LESTER DISCUSSION NUMBER  44
NWS CENTRAL PACIFIC HURRICANE CENTER HONOLULU HI   EP132016
500 AM HST SUN SEP 04 2016
 
A pocket of deep convection with tops to near 50 thousand feet
developed during the past few hours in the northern semicircle of
Lester. However, the partially exposed low-level center of the
tropical cyclone is also evident south of these thunderstorms,
which is not a sign of a healthy system. Southwesterly vertical
wind shear of near 25 kt is causing Lester to continue weakening
this morning. Earlier tonight, a 0710 UTC ASCAT pass over most
of Lester's circulation showed a large area of winds of 45 kt or
greater, with a maximum wind speed of 50 kt. The latest subjective
Dvorak satellite intensity estimates range from 2.5/35 kt from SAB
to 3.5/55 kt from PHFO and JTWC. The latest CIMSS ADT estimate is
2.1/31 kt. Based on the degraded appearance of Lester in satellite
imagery and these intensity estimates, we have initialized the
intensity at 50 kt for this advisory.
 
The initial motion for this advisory is 305/15 kt. The latest track
guidance remains tightly clustered, taking Lester along a
northwestward path through 36 hours, followed by gradual slowing and
a northward turn on day 2. Lester is then then accelerated
northeastward from days 3 to 5. Lester is currently being steered by
the subtropical ridge north of latitude 30N. However, a weakness in
this ridge due to an upper level trough northwest of the main
Hawaiian Islands has cause the tropical cyclone to move
northwestward. The latest forecast track closely follows the
previous one, except for slight nudging to the TVCN and GFEX
consensus guidance during the 36 to 72 hour time frame. The Ocean
Prediction Center coordinated the 4 and 5 day positions.
 
All intensity guidance shows slow, but steady weakening of Lester
through day 5 as this system passes over cooler water and the
current 15 to 20 kt of southwesterly shear increases. The global
models, notably GFS, keep Lester stronger through day 3 than HWRF or
GFDL. The latest forecast indicates slight weakening, followed by
nearly steady state through day 3, when Lester is forecast to
transition to an extra-tropical gale low over the North Pacific
Ocean. Lester will then gradually weaken on days 4 and 5. This
intensity forecast closely follows the latest SHIPS and the IVCN
consensus guidance.
 
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  04/1500Z 24.4N 159.1W   50 KT  60 MPH
 12H  05/0000Z 25.9N 160.9W   45 KT  50 MPH
 24H  05/1200Z 28.0N 163.0W   45 KT  50 MPH
 36H  06/0000Z 30.0N 164.7W   45 KT  50 MPH
 48H  06/1200Z 32.4N 165.3W   45 KT  50 MPH
 72H  07/1200Z 37.5N 164.0W   45 KT  50 MPH...POST-TROP/EXTRATROP
 96H  08/1200Z 45.0N 158.0W   40 KT  45 MPH...POST-TROP/EXTRATROP
120H  09/1200Z 51.1N 145.0W   30 KT  35 MPH...POST-TROP/EXTRATROP
 
$$
Forecaster Houston
 
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