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.
Hurricane Erick Discussion Number 13
NWS Central Pacific Hurricane Center Honolulu HI EP062019
500 AM HST Tue Jul 30 2019
The eye of hurricane became much more distinct in infrared
satellite imagery overnight, which indicates that rapid
intensification has occurred. The latest intensity estimates
from the satellite agencies are 5.0 (90 kt) from SAB, 5.5 (102 kt)
from HFO, and 6.0 (115 kt) from JTWC. The CIMSS ADT estimate using
the raw T number suggests the intensity is close to 100 kt. For this
advisory, we are intensifying Erick to 100 kt, so it is now a major
hurricane. Note that the initial wind radii for this advisory were
adjusted based on a 0633Z ASCAT pass, which covered nearly the
entire circulation of Erick.
The hurricane's initial motion is 280/15 kt for this advisory. The
mid-level ridge to the north is still forecast to weaken later
today, which is expected to cause a slower forward motion toward the
west-northwest. The track guidance now appears to have somewhat less
spread. The latest ECMWF and its ensemble mean continue to be
slightly faster than the rest of the models. For this advisory, we
are more closely following the latest NOAA corrected consensus
(HCCA) output. As a result, the track has been nudged slightly to
the right of the previous forecast during the 12-48 hour time frame.
After that, the latest track forecast follows the previous forecast
during days 3-5.
The latest estimates for wind shear in the vicinity of Erick appear
to be less than 10 kt from the west. In addition, sea surface
temperatures remain close to 28C along the track for the next couple
of days, and the CIRA Ocean Heat Content values show sufficient warm
water at depth along the forecast track. Therefore, the environment
around Erick will likely remain conducive for additional
intensification during the next 12-24 hours. The current forecast
closely follows the HCCA, as well as the consensus intensity
forecast output, IVCN. Some gradual weakening is forecast to begin
starting around 36 hours, and continuing through 48 hours. After
that time, the circulation around a broad upper-level trough in the
vicinity of the Hawaiian Islands will likely cause a significant
increase in shear (at least 25 kt from the west) as Erick continues
to move toward the west-northwest. Therefore, this advisory
continues to show rapid weakening during the 2-3 day time frame.
This weakening trend will likely persist during days 4 and 5.
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