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Tropical Depression Kate Discussion Number  18
NWS National Hurricane Center Miami FL       AL102021
1100 AM AST Wed Sep 01 2021
 
It has been difficult to pinpoint where the low-level circulation of 
Kate is this morning. After last night's diurnal convective maximum, 
the remaining convection has taken on a very disorganized structure, 
with a mid-level vortex being left behind to the south, while 
deeper, but more outflow driven convection is racing off to the 
north, ahead of the estimated low-level center position. A recently 
received 1211 UTC ASCAT-A pass indicated that Kate's low-level 
circulation is still closed, but just barely. The scatterometer wind 
data supports maintaining the current intensity at 30-kt, which also 
agrees with the latest subjective and objective Dvorak estimates.
 
The estimated motion is continuing off to the north-northwest, at 
340/9 kt. Kate appears to now be primarily steered by the low-level 
flow around a subtropical ridge located to its east. A general 
north-northwest motion is expected to continue today, followed by a 
turn to the north and north-northeast around the periphery of this 
ridge. The latest NHC track guidance has been adjusted a bit right 
of the previous track, shifting towards the latest consensus 
guidance (TVCN) that can still track the cyclone beyond 24 hours.
 
A 0958 UTC SSMIS microwave pass suggested that the better organized 
structure observed last night has decayed, with the low- and 
mid-level centers quite misaligned. Vertical wind shear diagnosed by 
SHIPS is now between 15-20 kt out of the north. This shear is likely 
contributing to the vortex tilt, while also helping to import very 
dry mid-level air, preventing Kate's convective activity from 
organizing.  The bulk of the intensity guidance is in agreement that 
gradual spin down of the low-level circulation will occur over the 
next several days, with the deterministic ECMWF model suggesting 
Kate could open up to a trough as soon as tomorrow. The latest NHC 
intensity forecast makes Kate a remnant low in 36 hours, with 
dissipation after 48 hours. However, given the current structure, 
this could occur sooner than forecast.
 
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  01/1500Z 26.8N  52.3W   30 KT  35 MPH
 12H  02/0000Z 27.9N  52.7W   25 KT  30 MPH
 24H  02/1200Z 29.6N  53.1W   25 KT  30 MPH
 36H  03/0000Z 31.1N  53.2W   20 KT  25 MPH...POST-TROP/REMNT LOW
 48H  03/1200Z 32.4N  52.5W   20 KT  25 MPH...POST-TROP/REMNT LOW
 60H  04/0000Z...DISSIPATED
 
$$
Forecaster Papin
 
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