Central Pacific Basin Tropical Cyclones

Tropical Storm Greg Forecast Discussion

WTPA43 PHFO 142034

Tropical Storm Greg Discussion Number   4
NWS Central Pacific Hurricane Center Honolulu HI   EP082023
1100 AM HST Mon Aug 14 2023

Greg has demonstrated pulsing convection over the last several hours
on the western side of the low level center, due to southeasterly 
shear in the vicinity. Subjective Dvorak intensities from PHFO, 
JTWC and SAB ranged from 2.5 to 3.0, and objective intensities 
ranged from 35 to 41 kt. Using a blend of the subjective and 
objective estimates, the initial intensity has been raised to 40 

The initial motion is 270/10 kt, and Greg is expected to continue
to move to the west today, along the southern edge of the
subtropical ridge to the north. Little change is expected in this
steering flow over the next couple of days, so expect Greg to
continue to move to the west in the short term, and then turn to
the west-southwest as it reaches the western edge of the ridge. As
the system weakens beyond that, the system is expected is expected
to shift slowly southward. On this path, Greg will pass far south of
the Hawaiian Islands on Thursday and Friday, with no direct impacts
in the state. The forecast track remains similar to the previous
forecast, splitting the difference between the HCCA and TVCE
particularly starting from day 3 onwards.

Although Greg will remain over very warm waters throughout the
forecast period, the southeasterly shear is expected to
prevent significant strengthening in the short term. The shear is
expected to weaken a little over the 12 to 36 hour period which
would allow Greg to strengthen some. Beyond that, guidance suggests
the shear will once again increase, with some of the models also
indicating drier air being ingested into the system. This would
contribute further to a weakening trend beyond hour 60, with Greg
weakening to a depression on day 4, and becoming post-tropical on
day 5.


INIT  14/2100Z 11.3N 141.7W   40 KT  45 MPH
 12H  15/0600Z 11.4N 143.4W   40 KT  45 MPH
 24H  15/1800Z 11.7N 145.7W   40 KT  45 MPH
 36H  16/0600Z 12.0N 148.3W   45 KT  50 MPH
 48H  16/1800Z 12.4N 150.9W   45 KT  50 MPH
 60H  17/0600Z 12.7N 153.4W   40 KT  45 MPH
 72H  17/1800Z 12.6N 155.9W   40 KT  45 MPH
 96H  18/1800Z 12.0N 161.0W   30 KT  35 MPH
120H  19/1800Z 11.4N 166.2W   25 KT  30 MPH...POST-TROP/REMNT LOW

Forecaster M Ballard

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