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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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