ZCZC HFOTCDCP3 ALL
TTAA00 PHFO DDHHMM
Tropical Storm Greg Discussion Number 13
NWS Central Pacific Hurricane Center Honolulu HI EP082023
500 PM HST Wed Aug 16 2023
Deep convection surrounding Greg continues to pulse under the
influence of southeasterly vertical wind shear. This has displaced
much of the convection to the north of a partially exposed
low-level circulation center. Dvorak current intensity estimates
range from 2.0/30 kt by SAB, to 3.5/35 kt out of JTWC, to 3.0/45 kt
at HFO. Since a 2343 UTC CIMSS SATCON came in at 43 kt and CIMSS ADT
was recently holding as high as 37 kt, a blend of the inputs
supports keeping the official intensity at 40 kt for this advisory,
though that may be generous.
Greg remains on a relatively steady forward motion that is slightly
north of due west, 280/11 kt. A low- to mid-level ridge far to the
north will keep the tropical cyclone moving along a general
westward track through Thursday night, causing Greg to pass well
south of Hawaii. A turn toward the west-southwest is forecast on
Friday as the weakening tropical cyclone is steered by a deepening
ridge to the north. The official forecast track was altered little
from the prior advisory and lies near TVCE in the middle of a
tightly clustered guidance envelope.
Relatively light, southerly vertical wind shear will likely produce
only slow weakening of Greg over the next day or so. Beyond 24
hours, the dynamical guidance suggests steady weakening, likely due
to a gradual increase in northerly vertical wind shear produced by
a strengthening ridge aloft to the north. Conversely, the
statistical guidance shows little short term change in Greg,
followed by some strengthening. Given the tropical cyclone's
inability to strengthen within the current shear environment and
sufficiently warm SST, the official forecast follows the steady
weakening trend of the dynamical guidance beyond 24 hours, and Greg
is expected to become a post-tropical remnant low by late Friday or
Saturday.
FORECAST POSITIONS AND MAX WINDS
INIT 17/0300Z 12.1N 153.5W 40 KT 45 MPH
12H 17/1200Z 12.2N 155.2W 40 KT 45 MPH
24H 18/0000Z 12.3N 157.6W 35 KT 40 MPH
36H 18/1200Z 12.1N 160.3W 35 KT 40 MPH
48H 19/0000Z 11.7N 163.0W 30 KT 35 MPH
60H 19/1200Z 11.3N 165.5W 30 KT 35 MPH...POST-TROP/REMNT LOW
72H 20/0000Z 10.8N 168.0W 25 KT 30 MPH...POST-TROP/REMNT LOW
96H 21/0000Z...DISSIPATED
$$
Forecaster Wroe
NNNN