[Tropical] Tropical Cyclone Discussion

[EMWIN Server]

WTNT45 KNHC 312031
TCDAT5

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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