Central Pacific Basin Tropical Cyclones

Tropical Storm Greg Forecast Discussion

WTPA43 PHFO 161434

Tropical Storm Greg Discussion Number  11
NWS Central Pacific Hurricane Center Honolulu HI   EP082023
500 AM HST Wed Aug 16 2023

Over the last several hours, the southeastern edge of the low 
level center has been apparent at times on the CIRA ProxyVis 
imagery. Convection has been pulsing as it is sheared to the 
northwest of the center. An 0430Z HY-2B scatterometer pass showed 40 
kt on the north side of the center. Subjective Dvorak intensities 
from PHFO, JTWC and SAB range from 2.5 to 3.5, while objective 
intensities range from 31 to 41 kt. Using a blend of these 
estimates, will hold the initial intensity at 45 kt. 

The initial motion is 280/12 kt, continuing a slightly north of west
path. Greg continues to move along the southern edge of a 
subtropical ridge to the north. As it continues to the west today, 
it will gain some latitude as it reaches the western end of the 
ridge. A building deep layer ridge to the north will then help to 
steer Greg to the west-southwest Thursday night and Friday. There 
is little change in  the forecast track, continuing to closely 
follow the HCCA and TVCA which remain near the middle of a 
relatively tightly clustered guidance envelope. Along this track, 
Greg will pass far south of Hawaii Thursday through Friday with no 
direct impacts to the islands. 

With the convection at times being displaced to the north of the 
center, Greg appears at times to be encountering some additional 
southerly shear, but remains over sufficiently warm waters. Little 
change is expected in the next 24 to 36 hours, however anticipate
additional bursts of shear, which will hinder strengthening. Beyond
36 hours, the system will move over slightly cooler waters, and 
begin to encounter stronger shear from the west. The intensity 
forecast has been held at 45 kt through 24 hours, which is on the
high end of the consensus models. Beyond that, the gradual 
weakening in the forecast follows the IVCN trend.


INIT  16/1500Z 11.8N 151.1W   45 KT  50 MPH
 12H  17/0000Z 12.1N 153.0W   45 KT  50 MPH
 24H  17/1200Z 12.2N 155.3W   45 KT  50 MPH
 36H  18/0000Z 12.1N 157.8W   40 KT  45 MPH
 48H  18/1200Z 11.8N 160.5W   35 KT  40 MPH
 60H  19/0000Z 11.4N 163.2W   35 KT  40 MPH
 72H  19/1200Z 11.1N 165.8W   30 KT  35 MPH
 96H  20/1200Z 10.1N 170.8W   25 KT  30 MPH...POST-TROP/REMNT LOW
120H  21/1200Z...DISSIPATED

Forecaster M Ballard

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