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Hurricane Lane Discussion Number  25...Corrected
NWS Central Pacific Hurricane Center Honolulu HI   EP142018
500 PM HST Mon Aug 20 2018
 
Visible satellite imagery this afternoon shows an impressive,
distinct eye on Hurricane Lane, though the convection surrounding
the core looks more ragged on the last few infrared images. A 2258Z
AMSR2 pass indicated that Lane had a concentric eyewall structure.
Satellite intensity estimates ranged from 5.5 from SAB and JTWC to
6.0 from PHFO. CIMSS ADT had 5.5 at 0000Z but has since risen to
6.0. Based on these estimates and the earlier reconnaisance data,
we have maintained a 115 kt intensity for this advisory. Another
aircraft reconnaisance mission will investigate Lane this evening.
 
The initial motion estimate continues to be 280/10. A subtropical
ridge to the north of Lane continues to steer the system westward.
However, changes in the steering pattern are expected relatively
soon, as the ridge weakens ane leaves a weakness to the north of
Lane. This will allow the tropical cyclone to begin gaining
latitude a little more quickly by 48 hours. 

The models are struggling with a couple of factors that make the
track forecast beyond 48 hours very challenging. One is the
evolution of a new ridge which develops to the east and southeast of
Lane, and the other is the effect of gradually increasing shear. The
ECMWF is stronger with the ridge, and starts shearing the system
sooner, so the track is on the left side of the guidance envelope.
The GFS and NAVGEM are quite a bit weaker with the ridge, and keep
Lane away from the westerly shear longer. There do not appear to be
any clear signals at this point to suggest which track to favor,
and so we continue to follow the consensus guidance which is down
the middle of an uncomfortably large guidance envelope. A turn more
toward the west is expected toward the end of the period as Lane is
expected to be decoupled and move as a shallower system in the
trades. The rather large uncertainty in the track forecast
necessitates close attention by interests in the Hawaiian Islands
over the next couple of days. It is important to not focus your
attention on the exact forecast track, and be prepared for changes
to the forecast. 

Weak to moderate southwesterly shear and sea surface temperatures
near 28C are sufficient to allow Lane to maintain intensity for the
next 24 hours or so. Some fluctuations in intensity are possible
due to difficult to forecast eyewall replacement cycles. As
mentioned before, increasing shear will lead to a gradual weakening
trend at first, with more rapid weakening expected beyond 72 hours
as Lane approaches stronger winds aloft from a subtropical jet
stream.
 
The larger than normal uncertainty in the future track of Lane
necessitates close attention by interests in the Hawaiian Islands
over the next few days as Lane approaches the islands. It is
important not to focus on the exact forecast track, and be prepared
for changes to the forecast. 
 
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  21/0300Z 13.8N 150.3W  115 KT 130 MPH
 12H  21/1200Z 14.0N 151.7W  115 KT 130 MPH
 24H  22/0000Z 14.3N 153.3W  115 KT 130 MPH
 36H  22/1200Z 14.8N 154.7W  110 KT 125 MPH
 48H  23/0000Z 15.7N 155.9W  105 KT 120 MPH
 72H  24/0000Z 17.9N 157.6W   95 KT 110 MPH
 96H  25/0000Z 20.0N 159.0W   75 KT  85 MPH
120H  26/0000Z 20.8N 161.0W   55 KT  65 MPH
 
$$
Forecaster R Ballard
 
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