Central Pacific Basin Tropical Cyclones

Tropical Storm Greg Forecast Discussion

WTPA43 PHFO 160834

Tropical Storm Greg Discussion Number  10
NWS Central Pacific Hurricane Center Honolulu HI   EP082023
1100 PM HST Tue Aug 15 2023

Satellite continues to show Greg's convection sheared to the west
and northwest of the low level circulation. Subjective Dvorak 
intensities ranged from 2.5/35 kt to 3.5/55 kt, and objective 
intensities ranged from 33 to 48 kt. Using a blend of these 
estimates initial intensity held at 45 kt. 

The initial motion is 280/12 kt as Greg takes on a slightly north 
of west track. Greg continues to move along the southern edge of the
subtropical ridge to the north. There remains little change in the 
guidance through the forecast period and as such, the forecast 
remains very close to the previous track. This closely follows 
the HCCA and TVCA guidance which remains near the middle of the 
relatively tightly clustered guidance envelope. Along this track, 
Greg is expected to move a little north of west overnight, and then 
to the west through Thursday, before turning to the west-southwest 
Thursday night and Friday in response to a deep ridge to the north. 
Along this track, Greg will pass far south of Hawaii Thursday 
through Friday with no direct impacts to the islands expected. 

The environmental conditions will remain relatively unchanged in 
the short term, with light south to southeast shear, and SSTs around
27-28C. It is during this time that the system has the greatest 
chance for any strengthening. Between hours 36 and 48, the system 
will move over slightly cooler waters, and encountering some 
additional deep layer shear. This is expected to contribute to a 
weakening of the system. The latest intensity guidance has shown an 
overall weakening trend, but given the small window of possible 
development, have maintained the slight strengthening for the first 
24 hours. Beyond that, the intensity forecast follows the weakening 
trend of most of the guidance, loosely following the IVCN. Greg 
looks to weaken to a post tropical system by hour 96.


INIT  16/0900Z 11.8N 149.6W   45 KT  50 MPH
 12H  16/1800Z 12.2N 151.5W   50 KT  60 MPH
 24H  17/0600Z 12.6N 153.9W   50 KT  60 MPH
 36H  17/1800Z 12.5N 156.4W   45 KT  50 MPH
 48H  18/0600Z 12.3N 159.0W   40 KT  45 MPH
 60H  18/1800Z 12.0N 161.6W   35 KT  40 MPH
 72H  19/0600Z 11.6N 164.2W   30 KT  35 MPH
 96H  20/0600Z 10.7N 169.3W   25 KT  30 MPH...POST-TROP/REMNT LOW
120H  21/0600Z...DISSIPATED

Forecaster M Ballard

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