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Tropical Depression Kate Discussion Number  17
NWS National Hurricane Center Miami FL       AL102021
500 AM AST Wed Sep 01 2021
 
After the earlier convective hiatus, a concentrated area of
thunderstorm activity containing numerous lightning strikes has
developed over and to the east of the low-level center. In
addition, upper-level outflow has been expanding to the west, an
indication that the hostile shear conditions that have been
plaguing the cyclone the past few days has finally waned. ASCAT
data around 0000-0100Z showed peak winds near 25 kt; however, the
recent sharp increase in deep convection along with a consensus
Dvorak subjective intensity of T2.0/30 kt supports increasing the
intensity to 30 kt. The 30-kt advisory intensity is also supported
by UW-CIMSS objective intensity estimates of T2.1/31 kt from ADT
and 39 kt from SATCON.
 
The initial motion estimate is 340/08 kt. Kate is moving 
north-northwestward between a small mid- to upper-level low to the 
south of the cyclone and deep-layer ridge located to the north and 
east of the system. A gradual turn toward the northwest is expected 
later today, followed by a turn back toward the north on Thursday as 
Kate rounds the western periphery of the ridge. By Friday, 
recurvature toward the north-northeast and northeast into the 
mid-latitude westerlies is forecast when the cyclone will be lifted 
out by an eastward-moving deep-layer trough currently crossing the 
western Atlantic.  The new NHC track forecast is similar to but a 
little to the left of the previous advisory track, and closely 
follows the tightly packed consensus track forecast models TVCA and 
NOAA-HCCA.
 
A 0505 UTC AMSR-2 microwave pass revealed that Kate's compact 
circulation had tightened up considerably since the earlier 0100 UTC 
ASCAT wind data, which shows a broad and elongated inner-core wind 
field. Also, Kate is currently passing between two small upper-level 
lows to the north and south of the cyclone, which is aiding the 
upper-level divergence across the system, albeit somewhat 
constrained due to the short distance of only about 300 nmi between 
the two upper lows. Given the locally enhanced outflow and the 
recent increase in deep convection, it s not out of the question 
that Kate could restrengthen back into a low-end tropical storm 
during the next 24 hours or so. However, the entrainment of dry 
mid-level air with humidity values less than 50 percent should 
prevent any significant or rapid restrengthening from occuring. by 
48 hours, moderate northerly shear and even drier mid-level air 
should cause convection weaken, resulting in a gradual spin down of 
the circulation and eventual dissipation by 72 hours. The new NHC 
intensity forecast is similar to but slightly lower than the 
consensus intensity models IVCN and HCCA, and the Decay-SHIPS 
statistical-dynamical intensity model.
 
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  01/0900Z 25.7N  51.7W   30 KT  35 MPH
 12H  01/1800Z 26.9N  52.5W   30 KT  35 MPH
 24H  02/0600Z 28.5N  53.2W   30 KT  35 MPH
 36H  02/1800Z 30.3N  53.7W   25 KT  30 MPH
 48H  03/0600Z 31.9N  53.5W   25 KT  30 MPH...POST-TROP/REMNT LOW
 60H  03/1800Z 33.5N  53.1W   25 KT  30 MPH...POST-TROP/REMNT LOW
 72H  04/0600Z...DISSIPATED
 
$$
Forecaster Stewart
 
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