Tropical Storm Ignacio Discussion Number 4
NWS National Hurricane Center Miami FL EP102021
900 AM MDT Mon Aug 02 2021
A large burst of deep convection has developed near the center and
over most of the southwestern semicircle of the cyclone. Recent
subjective satellite intensity estimates are a consensus T2.5/35 kt
from TAFB and SAB, and objective estimates from UW-CIMSS ADT and
SATCON are 37 kt and 39 kt, respectively. Based on these data, the
intensity has been increased to 35 kt, making the system the ninth
tropical storm of the 2021 eastern North Pacific hurricane season.
Tropical Storm Ignacio has continued to move west-northwestward, and
the initial motion estimate is 295/08 kt. Both the track forecast
and synoptic reasoning remain unchanged for this advisory. Ignacio
is expected to maintain a west-northwestward motion, wedged between
a strong mid-/upper-level ridge to the north and Hurricane Hilda to
the southwest throughout the 48-hour forecast period. The new track
forecast is essentially just an update of the previous advisory
track, and lies down the middle of the tightly packed consensus
track models.
Ignacio is likely near its peak intensity given that northeasterly
vertical wind shear of 18-20 kt is expected to keep the strongest
convection displaced away from the strongest surface winds that are
likely occurring in the northeastern semicircle. By 24 hours or so,
Ignacio will be moving over sub-26C sea-surface temperatures and
into even stronger wind shear, which should induce steady weakening,
with dissipation expected by 60 hours. The new NHC intensity
forecast is similar to the previous advisory, and closely follows a
blend of the NOAA-HCCA and IVCN consensus intensity models.
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