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Tropical Depression Kate Discussion Number  15
NWS National Hurricane Center Miami FL       AL102021
500 PM AST Tue Aug 31 2021
 
Kate continues to produce small, sporadic bursts of convection near 
and to the east of its partially exposed low-level center this 
afternoon. The cyclone has moved north of the subtropical jet stream 
that it has been centered under for the past couple of days, so the 
mid- to upper-level vertical wind shear is beginning to diminish. 
Unfortunately, all three ASCAT passes this morning missed Kate's 
small circulation. The current intensity Dvorak estimates from TAFB 
and SAB support maintaining the initial intensity at 30 kt for this 
advisory.
 
The cyclone is moving a little faster to the north, or 360/6 kt. The 
track forecast reasoning is largely unchanged. Kate is expected to 
begin moving north-northwestward tonight as a mid-level ridge builds 
to the east and northeast of the cyclone. This general motion should 
continue through early Thursday, before an approaching mid- to 
upper-level trough begins steering Kate more northward through 
Friday. The official NHC track forecast is essentially an update of 
the previous one and lies near the center of the guidance envelope, 
remaining close to the multi-model consensus aids.

The intensity forecast is a bit more challenging, with mixed signals 
noted from the various intensity models. On the one hand, satellite 
imagery indicates the vertical wind shear is obviously diminishing 
over Kate, and the cyclone is forecast to move over SSTs of around 
28.5 deg C for the next couple of days. However, the cyclone remains 
embedded within a dry mid-level environment that is clearly making 
it difficult for Kate to produce organized convection. The official 
NHC intensity forecast still shows no explicit intensity change and 
remains closest to the HFIP corrected consensus approach (HCCA) and 
IVDR aids. However, some short-term intensity fluctuations are 
certainly possible, which is notable since Kate's intensity is 
hovering around the tropical depression/storm threshold. By 
Thursday, Kate will be moving into an even drier, more subsident 
environment that will make it even more difficult to sustain deep 
convection. Thus, the NHC forecast shows Kate becoming a remnant low 
completely devoid of convection by Friday, with dissipation shortly 
thereafter ahead of an approaching frontal system.
 
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  31/2100Z 24.6N  50.9W   30 KT  35 MPH
 12H  01/0600Z 25.5N  51.5W   30 KT  35 MPH
 24H  01/1800Z 26.9N  52.6W   30 KT  35 MPH
 36H  02/0600Z 28.6N  53.5W   30 KT  35 MPH
 48H  02/1800Z 30.3N  54.2W   30 KT  35 MPH
 60H  03/0600Z 32.0N  54.2W   30 KT  35 MPH
 72H  03/1800Z 33.7N  53.8W   30 KT  35 MPH...POST-TROP/REMNT LOW
 96H  04/1800Z...DISSIPATED
 
$$
Forecaster Reinhart
 
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