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Tropical Storm Lowell Discussion Number  12
NWS National Hurricane Center Miami FL       EP172020
500 AM HST Wed Sep 23 2020
 
Convective banding has improved a little bit since the previous 
advisory, but not enough to increase the various satellite intensity 
estimates. Lowell's low-level center remains near or just inside the 
northern edge of the deepest convection, with the strongest and 
most organized thunderstorm activity confined to the eastern and 
southern portions of Lowell's circulation. The initial intensity of 
45 kt is based on consensus Dvorak classifications of T3.0/45 kt 
from TAFB and SAB, and a UW-CIMSS SATCON estimate of 43 kt. These 
data are consistent with an overnight ASCAT-A pass of about 45 kt.

The initial motion estimate is now 285/08 kt. Lowell lies along the 
southern periphery of a large, deep-layer subtropical ridge, and 
this is the dominant synoptic-scale steering feature for the next 5 
days. As a result, the cyclone is expected to move 
west-northwestward today, followed by a turn toward the west on 
Thursday, with that motion continuing through the weekend and into 
early next week. The latest NHC model guidance is tightly packed 
around the previous forecast track, thus requiring no significant 
changes to the previous advisory track.

Low-to-moderate northwesterly to northerly vertical wind shear is 
forecast to affect Lowell for the next 60 hours or so while the 
cyclone hugs the 25- to 26-deg-C sea-surface temperature (SST) 
gradient. As a result, little change in intensity is forecast during 
that time. Thereafter, the combination of cooler SSTs and increasing 
wind shear from the west is expected to induce slow but steady 
weakening, with Lowell degenerating into a remnant low by 96 hours. 
The latest NHC intensity forecast is essentially just an update of 
the previous advisory, and closely follows a blend of the NOAA-HCCA, 
FSSE and IVCN intensity consensus models.
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  23/1500Z 20.0N 120.6W   45 KT  50 MPH
 12H  24/0000Z 20.4N 122.0W   45 KT  50 MPH
 24H  24/1200Z 20.8N 123.9W   45 KT  50 MPH
 36H  25/0000Z 21.0N 125.8W   45 KT  50 MPH
 48H  25/1200Z 21.1N 127.9W   45 KT  50 MPH
 60H  26/0000Z 21.2N 130.2W   40 KT  45 MPH
 72H  26/1200Z 21.1N 132.4W   35 KT  40 MPH
 96H  27/1200Z 21.0N 137.0W   30 KT  35 MPH...POST-TROP/REMNT LOW
120H  28/1200Z 21.2N 141.6W   25 KT  30 MPH...POST-TROP/REMNT LOW
 
$$
Forecaster Stewart
 
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