Central Pacific Basin Tropical Cyclones

Tropical Storm Greg Forecast Discussion

WTPA43 PHFO 150237

Tropical Storm Greg Discussion Number   5
NWS Central Pacific Hurricane Center Honolulu HI   EP082023
500 PM HST Mon Aug 14 2023

Greg's convection continues to pulse, and remains concentrated on 
the west side of the center due to southeasterly shear in the 
vicinity. Objective Dvorak intensities range from 34 to 42 
kt, and subjective intensities from PHFO, SAB and JTWC are between 
2.5 and 3.0. Using a blend of these estimates, maintaining the 
initial intensity at 40 kt.

The initial motion is 270/10 kt. Greg continues to move to the west
on the southern edge of the subtropical ridge to the north. Expect
little change in this over the next couple of days, with Greg 
heading in a west to slightly west-northwest direction. As the 
system reaches the western edge of the ridge, it is expected to 
weaken and slowly take a turn to the southwest. On this path, Greg 
will pass far south of the Hawaiian Islands Thursday and Friday, 
with no direct impacts to the state. The forecast track remains 
similar to the previous forecast, with some influence from the HCCA 
and TVCE. The track slows the forward progress a bit for hours 36 to 
60 based on the HCCA and TVCE, and is a touch further north around 
hour 60. 

Greg remains over very warm waters, with weakening southeasterly 
shear. Over the next 36 hours, the shear is expected to weaken, 
which will allow Greg to slowly strengthen. The forecast intensity 
is on the high end of the consensus models during this time, and 
then follows the gradual weakening trend in the guidance. Between 
hours 48 and 60, Greg will move over slightly cooler waters, with an 
increase in deep layer shear, and mid-level dry air beginning to 
feed into the system. These all contribute to the weakening of the 
system between days 2 and 3, with Greg becoming post-tropical on day 
4, and opening up into a trough and dissipating by day 5.


INIT  15/0300Z 11.3N 143.1W   40 KT  45 MPH
 12H  15/1200Z 11.5N 145.0W   45 KT  50 MPH
 24H  16/0000Z 11.7N 147.4W   45 KT  50 MPH
 36H  16/1200Z 12.1N 149.9W   45 KT  50 MPH
 48H  17/0000Z 12.7N 152.2W   40 KT  45 MPH
 60H  17/1200Z 12.8N 154.6W   40 KT  45 MPH
 72H  18/0000Z 12.6N 157.3W   35 KT  40 MPH
 96H  19/0000Z 11.8N 162.5W   30 KT  35 MPH...POST-TROP/REMNT LOW
120H  20/0000Z...DISSIPATED

Forecaster M Ballard

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