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Tropical Storm Lowell Discussion Number   9
NWS National Hurricane Center Miami FL       EP172020
200 PM PDT Tue Sep 22 2020
 
Lowell has been undergoing a bursting pattern today, with the
original mass dissipating and a new one developing in its place.
This is typical of sheared tropical cyclones. Just in the past
couple of hours, visible satellite imagery has shown a low-level
swirl ejecting to the northwest from the deep convection. Based on
the center position from an ASCAT overpass around 1700 UTC, the
exposed swirl may indeed be the primary center of the cyclone. This
same ASCAT overpass showed peak winds of 37 kt, and based on the
evolution of the cyclone's structure in the past couple of hours,
the initial intensity is being lowered to 40 kt. The northeasterly
shear causing the developmental issues for Lowell may abate somewhat
in a day or so. This may provide the cyclone with an opportunity for
some strengthening before it reaches cooler waters in a couple of
days. After 72 h, Lowell is forecast to begin moving over waters of
24-25 degrees C, and enter an increasingly hostile environment with
strong westerly shear and mid-level relative humidity values around
30 percent by the end of the forecast period. These conditions
should cause the cyclone to weaken starting late this week. There is
a possibility that the cyclone could lose its deep convection late
in the forecast period, and although the latest advisory does not
indicate it, Lowell could degenerate into a remnant low by day 5.
The latest NHC intensity forecast is near the various intensity
consensus values.
 
The initial motion of the cyclone is 295/12 kt, but this is
uncertain due to the recent northwestern motion of the low-level
center. A general west-northwest motion is expected through
Wednesday as Lowell moves south of a subtropical ridge. A turn to
the west is expected Wednesday night as the ridge changes its
orientation slightly.  The latest NHC track forecast is little
changed from the previous one and is near the tightly clustered
track guidance.
 
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  22/2100Z 19.2N 117.9W   40 KT  45 MPH
 12H  23/0600Z 19.7N 119.6W   40 KT  45 MPH
 24H  23/1800Z 20.0N 121.2W   40 KT  45 MPH
 36H  24/0600Z 20.4N 122.9W   45 KT  50 MPH
 48H  24/1800Z 20.6N 124.6W   50 KT  60 MPH
 60H  25/0600Z 20.7N 126.4W   50 KT  60 MPH
 72H  25/1800Z 20.7N 128.2W   50 KT  60 MPH
 96H  26/1800Z 20.7N 132.3W   40 KT  45 MPH
120H  27/1800Z 20.7N 136.2W   35 KT  40 MPH
 
$$
Forecaster Latto
 
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