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.
