ZCZC MIATCDEP2 ALL
TTAA00 KNHC DDHHMM

Hurricane Olivia Discussion Number  31
NWS National Hurricane Center Miami FL       EP172018
200 AM PDT Sat Sep 08 2018

The satellite presentation of Olivia has continued to degrade
overnight with the surrounding ring of deep convection warming
and the eye becoming less distinct.  Dvorak T-numbers have decreased
and a blend of current intensity (CI) numbers from TAFB and SAB, and
ADT and SATCON estimates from UW/CIMSS yields an initial wind speed
of 80 kt.  Although the vertical wind shear is expected to remain
low over Olivia, the hurricane will be moving over marginal sea
surface temperatures of 25-26C, and into a dry mid-level
environment. These factors are expected to cause gradual weakening
over the next 24 hours.  After that time, slightly warmer SSTs along
the forecast track should slow or halt the weakening process, and
little change in strength is expected between 24 and 72 hours.
Increasing southwesterly shear by day 3 is likely to result in
additional weakening later in the forecast period.  The NHC
intensity forecast is similar to the previous advisory and is
between the HFIP corrected consensus model and the IVCN consensus
aid.

Olivia is moving west-northwestward or 285/13 kt.  A strong
deep-layer ridge that is building westward across the central
Pacific should steer Olivia generally westward over the next 2-3
days.  After that time, most of the track guidance takes Olivia
west-southwestward as it comes under the influence of the
northeasterly trade wind flow.  Although the track models are fairly
unanimous in taking Olivia west-southwestward, there is large
cross-track spread in the guidance at 72 hours and beyond.  The HWRF
and ECMWF are along the northern side of the guidance envelope while
the GFS and UKMET bracket the southern side.  Given the large amount
of spread, the official forecast is again near the TVCN and HFIP
consensus models at 72-120 h.  On the forecast track, Olivia is
expected to cross into the central Pacific basin later today and
approach the Hawaiian Islands early next week.


KEY MESSAGES

1. Olivia is forecast to approach the main Hawaiian Islands from
the east early next week, but it is too soon to determine the exact
location and magnitude of any impacts.  Interests in Hawaii should
monitor the progress of Olivia this weekend and use this time to
enact your hurricane action plan.

2.  Do not focus on the exact track or intensity forecast, or any
specific landfall location, as errors can be large at extended time
ranges.  Tropical storm or hurricane conditions could be felt
anywhere in the islands as significant impacts could extend well
away from the center.


FORECAST POSITIONS AND MAX WINDS

INIT  08/0900Z 21.2N 136.6W   80 KT  90 MPH
 12H  08/1800Z 21.5N 138.7W   70 KT  80 MPH
 24H  09/0600Z 21.7N 141.5W   65 KT  75 MPH
 36H  09/1800Z 21.8N 144.0W   65 KT  75 MPH
 48H  10/0600Z 21.8N 146.2W   65 KT  75 MPH
 72H  11/0600Z 21.5N 150.0W   65 KT  75 MPH
 96H  12/0600Z 20.5N 154.0W   55 KT  65 MPH
120H  13/0600Z 19.2N 159.0W   45 KT  50 MPH

$$
Forecaster Brown

NNNN