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Tropical Storm Greg Discussion Number   3
NWS Central Pacific Hurricane Center Honolulu HI   EP082023
500 AM HST Mon Aug 14 2023
 
Deep convection associated with Greg continues to develop near and 
west of the low-level circulation this morning, which has become 
partially exposed due to southeasterly shear estimated to be near 
10 to 15 kt. An ASCAT pass from several hours ago, however, 
revealed the system has a well-defined circulation, with 35 kt 
winds depicted north of the center. Based on the ASCAT data and 
subjective Dvorak intensity estimates ranging from T2.0 to T3.0 
between PHFO, SAB, AND JTWC, the initial intensity is held at 35 kt.

The initial motion for this advisory is 270/11 kt, as Greg 
continues to move south of the subtropical ridge. No significant 
change in this steering is expected over the next couple of days. 
Thereafter, a gradual turn to the west-southwest is forecast as the 
weakening system becomes steered by low- to mid-level flow. Similar 
to the previous advisory, the track guidance continues to shift 
slowly southward, with Greg passing far south of the Hawaiian 
Islands later this week. This forecast track reflects that and lies 
near a combination of the previous forecast, HCCA, and TVCE.  

Despite the tropical storm being located over very warm waters and 
within a relatively moist environment, the aforementioned 
southeasterly shear will continue to inhibit strengthening 
initially. Guidance shows this shear persisting over the next 12 to 
18 h before trending down. Therefore, the intensity is held steady 
for the first 12 h, then followed by some modest strengthening 
between 24 and 48 h. Beyond that, drier mid-level air along with 
increasing shear and slightly cooler waters should result in a 
gradual weakening trend, with Greg becoming post-tropical by day 5.
 
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  14/1500Z 11.3N 140.9W   35 KT  40 MPH
 12H  15/0000Z 11.4N 142.6W   35 KT  40 MPH
 24H  15/1200Z 11.6N 144.9W   40 KT  45 MPH
 36H  16/0000Z 11.8N 147.3W   45 KT  50 MPH
 48H  16/1200Z 12.2N 149.7W   45 KT  50 MPH
 60H  17/0000Z 12.6N 152.2W   45 KT  50 MPH
 72H  17/1200Z 12.7N 154.7W   40 KT  45 MPH
 96H  18/1200Z 12.3N 159.8W   35 KT  40 MPH
120H  19/1200Z 11.7N 164.9W   30 KT  35 MPH...POST-TROP/REMNT LOW
 
$$
Forecaster Gibbs/Birchard
 
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