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Post-Tropical Cyclone Greg Forecast Discussion

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WTPA43 PHFO 180240

Post-Tropical Cyclone Greg Discussion Number  17
NWS Central Pacific Hurricane Center Honolulu HI   EP082023
500 PM HST Thu Aug 17 2023

A burst of convection that developed in Greg's northern semicircle 
this morning was unable to wrap around the cyclone's core, 
apparently due to moderate vertical wind shear. A 2058Z ASCAT pass 
found a couple 35 kt wind barbs in association with this convection, 
while also indicating that a closed low-level circulation center 
(LLCC) may no longer exist. Since then, disorganized convection has 
once again developed north of the center, while visible satellite 
imagery shows a fully exposed and elongated LLCC. Given the 
cyclone's inability to sustain deep convection over the increasingly 
ill-defined center for a prolonged period of time, Greg is deemed 
to be post-tropical with this advisory. Maximum sustained winds in 
the northern semicircle are estimated to be near 30 kt. 

The initial motion vector is a somewhat uncertain 265/15 kt, as the 
elongated LLCC appeared to relocate westward in response to this 
morning's convection. The remnant low will move generally toward the 
west (or just south of west) within the trade wind flow supplied by 
a surface high far to the north as it weakens to a trough on Friday. 
The updated track and intensity forecasts are strongly guided by 
regional and global dynamical model guidance.

This is the last advisory issued by the Central Pacific Hurricane 
Center on this system. Additional information on this system can be 
found in High Seas Forecasts issued by the National Weather Service 
in Honolulu, under AWIPS header HFOHSFNP, WMO header FZPN40 PHFO, 
and online at 


INIT  18/0300Z 12.0N 158.5W   30 KT  35 MPH...POST-TROP/REMNT LOW
 12H  18/1200Z 11.9N 160.5W   30 KT  35 MPH...POST-TROP/REMNT LOW
 24H  19/0000Z...DISSIPATED

Forecaster Birchard