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Hurricane NORMAN


Hurricane Norman Discussion Number   8
NWS National Hurricane Center Miami FL       EP162018
200 AM PDT Thu Aug 30 2018

Norman is in the midst of a remarkable period of rapid
intensification.  An eye developed in infrared satellite imagery
around 0500 UTC and is completely surrounded by very cold cloud
tops quadrants.  A burst of lightning also began a couple of hours
ago in the southeastern quadrant, where cloud tops are as cold as
-84C.  Subjective Dvorak estimates rose quickly to T5.5/102 kt from
SAB and T5.0/90 kt from TAFB at 0600 UTC, and since the satellite
presentation has continued to improve, the initial intensity is set
near the top of that range at 100 kt, making Norman a major
hurricane.  Norman's intensity has increased by an estimated 45-50
kt over the past 24 hours.

Norman remains in a low-shear environment with good upper-level
outflow in all quadrants, and the hurricane is moving over very
warm waters of 29-30 degrees Celsius.  Barring any unforeseen
structural changes like an eyewall replacement, Norman is likely to
continue strengthening for the next 24 hours or so, and nearly all
of the intensity models depict the current rapid intensification
phase persisting for the next 12 hours.  The updated NHC intensity
forecast has been increased during the first 48 hours to account
for recent trends, and it closely matches an average of the HCCA
model, Florida State Superensemble, and ICON intensity consensus.
A very gradual weakening is expected after 48 hours as Norman
encounters some shear and cooler waters.

A strong subtropical ridge extending west of northern Mexico is
steering Norman westward, or 275/6 kt.  The depth and strength of
the ridge is expected to force Norman west-southwestward during the
next 24-48 hours, followed by a turn back toward the west and then
west-northwest on days 3-5.  The track models are in fairly good
agreement throughout the 5-day forecast period, although there are
some differences in exactly how much of an S-curve Norman will
make.  The ECMWF shows the most pronounced bend in the forecast
track, starting along the southern periphery of the guidance
envelope and then moving to the northern periphery by days 4 and 5.
Although the new NHC track forecast does not follow the ECMWF
exactly, it does show slightly more bend than the previous forecast.


INIT  30/0900Z 17.8N 117.4W  100 KT 115 MPH
 12H  30/1800Z 17.9N 118.5W  115 KT 130 MPH
 24H  31/0600Z 17.6N 120.1W  120 KT 140 MPH
 36H  31/1800Z 17.0N 121.6W  120 KT 140 MPH
 48H  01/0600Z 16.3N 123.3W  115 KT 130 MPH
 72H  02/0600Z 16.2N 127.1W  105 KT 120 MPH
 96H  03/0600Z 18.0N 132.0W   95 KT 110 MPH
120H  04/0600Z 20.0N 137.5W   75 KT  85 MPH

Forecaster Berg