WTPZ42 KNHC 271445

800 AM PDT THU AUG 27 2015

Ignacio continues to produce cloud tops colder than -80C near the center. A recent GPM over pass showed a 20-25 n mi wide eye forming under the overcast. However, the eye is ragged, and the deep convection in the eyewall is mainly southwest of the center. Satellite intensity estimates from TAFB and SAB are 90 kt and 77 kt, and the CIMSS Advanced Dvorak Technique is estimating 80 kt. Based on these data, the initial intensity is increased to 80 kt.

The initial motion is now 285/11. There is little change in the forecast philosophy since the previous advisory, with the subtropical ridge north of Ignacio expected to steer the cyclone generally west-northwestward through the forecast period with a gradual decrease in forward speed. Some spread in the track guidance develops by day 5, as the ECMWF turns a weaker Ignacio westward while the GFS turns a stronger Ignacio northwestward. Despite this, the consensus models and the center of the guidance envelope are near the previous forecast, and the new forecast is a slightly faster update of the previous forecast.

Ignacio should remain over warm sea surface temperatures and in an environment of light vertical wind shear for at least the next two days, which should allow continued strengthening to a major hurricane. After that time, the cyclone should encounter increasing westerly shear and move over slightly cooler water, which should start a gradual weakening. The new intensity forecast follows this scenario and is basically unchanged since the previous advisory. One note of uncertainty in the intensity forecast is that the GFS shear at day 5, which is used in the SHIPS and LGEM models, looks weaker than that forecast by the ECMWF and UKMET models. Should the latter models verify, Ignacio could weaken faster than currently forecast.

Ignacio is expected to move into the Central Pacific basin at about 1800Z. Therefore, this is the last advisory on this system by the National Hurricane Center. Subsequent advisories will be issued by the Central Pacific Hurricane Center in Honolulu, Hawaii.


INIT 27/1500Z 12.9N 139.5W 80 KT 90 MPH 12H 28/0000Z 13.6N 141.1W 90 KT 105 MPH 24H 28/1200Z 14.5N 143.1W 95 KT 110 MPH 36H 29/0000Z 15.4N 144.8W 100 KT 115 MPH 48H 29/1200Z 16.1N 146.1W 100 KT 115 MPH 72H 30/1200Z 17.5N 149.0W 95 KT 110 MPH 96H 31/1200Z 19.0N 151.5W 85 KT 100 MPH 120H 01/1200Z 20.5N 154.0W 75 KT 85 MPH

$$ Forecaster Beven