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Tropical Storm Greg Discussion Number   2
NWS National Hurricane Center Miami FL       EP082023
1100 PM HST Sun Aug 13 2023
 
After the release of the previous advisory a burst of deep
convection developed closer to the center of the cyclone.  However, 
easterly shear has caused the area of convection to propagate 
westward away from the center, leaving it exposed.  Recently 
arriving ASCAT overpasses show that the depression has 
strengthened into a tropical storm. Both ASCAT-B and ASCAT-C 
revealed peak winds of 34-35 kt to the north-northwest of the 
center. 
 
Greg is moving westward or 275 degrees at 11 kt. A narrow
mid-level ridge to the north of the cyclone should continue to
steer it westward to west-northwestward during the next 2 to 3 days.
After that time, the tropical storm is forecast to gradually 
weaken and come under the influence of the low-level trade wind 
flow.  That should cause the cyclone to turn westward or 
west-southwestward late in the period.  The track model envelope 
shifted southward this cycle so the NHC forecast was adjusted 
accordingly.  The new forecast track is near the HFIP corrected 
consensus aid, but it is not as far south as the typically reliable 
GFS and ECMWF models.
 
The tropical storm is located over SSTs of around 28 degrees 
Celsius, but within an area of light to moderate easterly shear. 
These conditions are expected to allow for some modest 
strengthening during the next couple of days.   After that time, 
slightly cool waters, the continuation of easterly shear, and a 
drier mid-level air mass are likely to cause gradual weakening.  
Much of the intensity guidance predict a lower peak intensity 
this cycle, and the official forecast has been adjusted 
slightly downward.  It should be noted that the ECMWF and GFS show 
the system degenerating into a trough of low pressure by day 5.  
This scenario is certainly possible, but not reflected in the 
latest official forecast.
 
The depression will cross into the central Pacific basin by 1200
UTC today.  Therefore, the next advisory on this system will be
issued by the Central Pacific Hurricane Center at 1500 UTC or
500 AM HST.  Information about this system will continue to be
available on the web at hurricanes.gov
 
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  14/0900Z 11.3N 139.8W   35 KT  40 MPH
 12H  14/1800Z 11.4N 141.5W   40 KT  45 MPH
 24H  15/0600Z 11.5N 143.9W   45 KT  50 MPH
 36H  15/1800Z 11.7N 146.2W   45 KT  50 MPH
 48H  16/0600Z 12.1N 148.6W   45 KT  50 MPH
 60H  16/1800Z 12.5N 151.1W   45 KT  50 MPH
 72H  17/0600Z 12.8N 153.6W   40 KT  45 MPH
 96H  18/0600Z 12.7N 158.7W   35 KT  40 MPH
120H  19/0600Z 12.1N 163.9W   30 KT  35 MPH
 
$$
Forecaster Brown
 
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