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Post-Tropical Cyclone Marty Forecast Discussion


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738 
WTPZ43 KNHC 242041
TCDEP3

Post-Tropical Cyclone Marty Discussion Number   7
NWS National Hurricane Center Miami FL       EP132021
200 PM PDT Tue Aug 24 2021

There has been no significant deep convection within 100 nmi of 
Marty's center for more than 12 hours. As a result, Marty has 
degenerated into a remnant low. The initial intensity has been 
maintained at 30 kt based on ASCAT-B/-A passes between 1700-1800 
UTC that still showed a significant fetch of 25-kt winds over much 
of the northern quadrant, including a few embedded 28-kt vectors. 
Since Marty is forecast to remain over sub-26C sea-surface 
temperatures and within a large field of cold-air stratocumulus 
clouds, gradual spin down of the vortex and weakening of the 
cyclone's peak winds are expected until dissipation occurs in about 
72 hours. The new NHC intensity forecast is similar to the previous 
advisory, and closely follows a blend of the IVCN and NOAA-HCCA 
intensity consensus models.

The initial motion estimate remains westward, or 270/10 kt.  For 
the next 36 hours or so, the remnant low is forecast to move 
westward along the southern periphery of a sprawling deep-layer 
ridge located northwest through northeast of Marty. Thereafter, a 
motion toward the west-southwest is expected until the cyclone 
dissipates. The new NHC forecast track is essentially just an 
extension of the previous advisory track, and lies down the middle 
of the tightly packed consensus models, which have shifted a little 
to the south on this forecast cycle.

This is the last advisory being issued on Marty.  For additional 
information on the remnant low, please see High Seas Forecasts 
issued by the National Weather Service under AWIPS header NFDHSFEPI 
and WMO header FZPN02 KWBC.


FORECAST POSITIONS AND MAX WINDS

INIT  24/2100Z 20.5N 119.2W   30 KT  35 MPH...POST-TROP/REMNT LOW
 12H  25/0600Z 20.5N 120.8W   25 KT  30 MPH...POST-TROP/REMNT LOW
 24H  25/1800Z 20.5N 122.9W   25 KT  30 MPH...POST-TROP/REMNT LOW
 36H  26/0600Z 20.4N 125.0W   20 KT  25 MPH...POST-TROP/REMNT LOW
 48H  26/1800Z 20.2N 127.2W   20 KT  25 MPH...POST-TROP/REMNT LOW
 60H  27/0600Z 19.8N 129.6W   20 KT  25 MPH...POST-TROP/REMNT LOW
 72H  27/1800Z...DISSIPATED

$$
Forecaster Stewart