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Hurricane Erick Discussion Number  15
NWS Central Pacific Hurricane Center Honolulu HI   EP062019
500 PM HST Tue Jul 30 2019
 
The rapid intensification of Erick has waned this afternoon, but 
it still remains a powerful category 4 hurricane. Satellite images 
show that the eye has become cloud-filled and elongated since the 
last advisory, with outflow somewhat restricted in the southwestern 
semicircle. On the other hand, outflow in the northeastern 
semicircle appears optimal, and the eyewall convection has been a 
prolific lightning producer through the day. Subjective Dvorak 
current intensity estimates range from 6.0/115 kt from SAB/PHFO to 
6.5/127 kt from PGTW, while ADT is also now near 6.0. The initial 
intensity estimate for this advisory has been held at 115 kt. 

A gradual turn toward the west-northwest has taken place today, and 
the initial motion estimate for this advisory is 290/13 kt. There
is not much change to the ongoing track forecast philosophy, and
only minor changes were made to the official forecast, despite
increasing model spread in the later forecast periods. A track
toward the west-northwest is expected over the next 24 hours or so,
with a subtle turn toward the west on days 2 and 3, before a turn
back to the west-northwest occurs on days 4 and 5. Initially, the
strong hurricane will be steered by the deep-layer flow, with
southwest winds in the upper levels helping Erick to gain latitude.
As these winds shear the cyclone, it is expected to become
increasingly shallow, steered by a low- to mid-level ridge to the
north, which will induce the westward track. As the weakened cyclone
reaches the western edge of the ridge on days 4 and 5, it is
expected to resume a motion toward the west-northwest, but forecast
models disagree as to the extent of the poleward motion. The
official forecast lies closest to HCCA guidance, with the 5 day
forecast point almost on top of the UKMET ensemble guidance. 

The window for further intensification appears to be closing, as 
increased vertical wind shear (20 kt increasing to 40 kt) lies
along the forecast track, especially after about 24 hours. Once
Erick encounters this southwesterly to westerly shear, associated
with a semi-permanent trough aloft northwest of Hawaii, significant
weakening is expected. In the meantime, Erick is expected to change
little, but it wouldn't be surprising to see the eye clear out again
overnight. The updated intensity forecast closely follows HCCA and
FSSE guidance. 

An 1845Z partial ASCAT pass was used to expand 34 kt wind radii, 
mainly in the northern semicircle. 

 
FORECAST POSITIONS AND MAX WINDS
 
INIT  31/0300Z 14.0N 145.4W  115 KT 130 MPH
 12H  31/1200Z 14.5N 147.0W  115 KT 130 MPH
 24H  01/0000Z 15.1N 149.2W  100 KT 115 MPH
 36H  01/1200Z 15.6N 151.7W   90 KT 105 MPH
 48H  02/0000Z 16.1N 154.0W   70 KT  80 MPH
 72H  03/0000Z 17.1N 158.9W   40 KT  45 MPH
 96H  04/0000Z 18.6N 163.1W   35 KT  40 MPH
120H  05/0000Z 20.0N 166.0W   35 KT  40 MPH
 
$$
Forecaster Birchard
 
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