000
WTPZ43 KNHC 241433
TCDEP3
 
Tropical Depression Marty Discussion Number   6
NWS National Hurricane Center Miami FL       EP132021
800 AM PDT Tue Aug 24 2021
 
There has been no significant deep convection within 100 nmi of 
Marty's center since about 0600 UTC. The cyclone's cloud pattern now 
consists of some mid-level clouds and mostly low-level cold-air 
stratocumulus clouds. The current intensity of 30 kt is based on a 
unanimous Dvorak satellite classification of T1.5/2.5 (25 kt/35 kt) 
from TAFB and SAB, which has resulted in Marty being downgraded to 
a tropical depression. Due to the cyclone's future track remaining 
over sub-26C sea-surface temperatures, coupled with additional 
entrainment of stable low clouds, Marty is now forecast to 
degenerate to a post-tropical remnant low later today. The new 
NHC intensity forecast closely follows the trends of the intensity 
consensus models IVCN and NOAA-HCCA.
 
The initial motion remains westward, or 270/10 kt. The strong 
deep-layer ridge to the north of the weakening shallow cyclone is 
expected to keep Marty on a generally westward track over the next 
36 hours or so, followed by a west-southwestward motion thereafter 
until the cyclone dissipates.  The new official forecast track lies 
near the extreme southern edge of the model guidance envelope, owing 
to the models' slight poleward bias noted over the past 36 hours.


FORECAST POSITIONS AND MAX WINDS
 
INIT  24/1500Z 20.6N 118.1W   30 KT  35 MPH
 12H  25/0000Z 20.6N 119.9W   25 KT  30 MPH...POST-TROP/REMNT LOW
 24H  25/1200Z 20.6N 121.9W   25 KT  30 MPH...POST-TROP/REMNT LOW
 36H  26/0000Z 20.6N 124.0W   20 KT  25 MPH...POST-TROP/REMNT LOW
 48H  26/1200Z 20.5N 126.1W   20 KT  25 MPH...POST-TROP/REMNT LOW
 60H  27/0000Z 20.2N 128.4W   20 KT  25 MPH...POST-TROP/REMNT LOW
 72H  27/1200Z 19.6N 130.9W   20 KT  25 MPH...POST-TROP/REMNT LOW
 96H  28/1200Z...POST-TROP/REMNT LOW
 
$$
Forecaster Stewart