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Tropical Storm Greg Discussion Number 15
NWS Central Pacific Hurricane Center Honolulu HI EP082023
500 AM HST Thu Aug 17 2023
Greg has quickly become disorganized overnight, with convection
becoming further displaced to the north, and then rapidly weakening.
As the convection became displaced, the exposed low level center
began moving south of due west. The subjective and objective
estimates range from 25 to 45 kt. A blend of these lead to
lowering the initial intensity to 35 kt, but that may be too
generous. It is possible that Greg could be declared post-tropical
later today.
The initial motion is 270/11 kt. As the convection weakened, the
exposed low level center took a short jog to the west-southwest,
but is now back on its expected westward path. This westward motion
is expected to continue today as Greg follows the southern edge of
a ridge to the north. This path will have Greg passing well south
of Hawaii today, before turning to the west-southwest as it
weakens. The forecast track closely follows the previous package
leaning towards the TVCA which remains in the middle of the
relatively tightly clustered guidance.
The intensity forecast is a bit more challenging. Limited convection
has become significantly sheared to the north of the low level
center. Statistical guidance shows Greg remaining in a low sheared
environment for the next 24 hours. However the satellite depiction
would suggest that Greg was under the influence of stronger shear
overnight. While it is possible for convection to redevelop near
the center should shear remain low, there is good agreement in the
guidance that shear will increase from the west to northwest
beyond 24 hours. This leaves a limited window for any development
of the system. Have held the intensity at 35 kt for the first 12
hours, and then followed the gradual weakening trend of the
dynamical guidance.
FORECAST POSITIONS AND MAX WINDS
INIT 17/1500Z 11.9N 155.6W 35 KT 40 MPH
12H 18/0000Z 12.0N 157.4W 35 KT 40 MPH
24H 18/1200Z 11.9N 159.9W 30 KT 35 MPH
36H 19/0000Z 11.5N 162.5W 30 KT 35 MPH
48H 19/1200Z 11.1N 165.1W 30 KT 35 MPH...POST-TROP/REMNT LOW
60H 20/0000Z 10.6N 167.6W 25 KT 30 MPH...POST-TROP/REMNT LOW
72H 20/1200Z...DISSIPATED
$$
Forecaster M Ballard
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