Central Pacific Basin Tropical Cyclones

Tropical Depression Greg Forecast Discussion

WTPA43 PHFO 172046

Tropical Depression Greg Discussion Number  16
NWS Central Pacific Hurricane Center Honolulu HI   EP082023
1100 AM HST Thu Aug 17 2023

Greg has been able to produce relatively short-lived bursts of 
convection in its northern semicircle over the past 12 to
18 hours, but it has been occurring significantly far from the
increasingly ill-defined low-level circulation center. Shear is
analyzed to be relatively light, but satellite observations
indicate that even this morning's flare-up of thunderstorms 
have been unable to wrap around the cyclone's core. Subjective 
Dvorak intensity estimates are 1.5/2.5 from PHFO/PGTW, with SAB 
determining that Greg is too weak to classify. Automated intensity 
estimates from UW-CIMSS are all below tropical-storm-strength, and a 
blend of these estimates yields an initial intensity estimate of 
30 kt.

The initial motion vector for this advisory is 270/11 kt. Greg will
move generally toward the west (or just south of west) with the
trade wind flow in which it is embedded for the remainder of its
existence. The latest track forecast represents little change from
the previous, and lies close to TVCE and EMXI guidance. While SSTs
along the forecast track are sufficiently warm to sustain a tropical
cyclone, Greg is expected to gradually weaken over the next day
or two as increasing vertical wind shear prevents convection from 
persisting over the center. Greg will likely soon become post- 
tropical, then dissipate by Saturday, with the official intensity 
forecast placing the greatest weight on the dynamical guidance.


INIT  17/2100Z 12.2N 157.1W   30 KT  35 MPH
 12H  18/0600Z 12.1N 158.8W   30 KT  35 MPH...POST-TROPICAL
 24H  18/1800Z 11.8N 161.3W   25 KT  30 MPH...POST-TROPICAL
 36H  19/0600Z 11.4N 164.0W   25 KT  30 MPH...POST-TROPICAL
 48H  19/1800Z...DISSIPATED

Forecaster Birchard

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