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Post-Tropical Cyclone Guillermo Forecast Discussion

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WTPZ42 KNHC 202034

Post-Tropical Cyclone Guillermo Discussion Number  14
NWS National Hurricane Center Miami FL       EP072021
200 PM PDT Tue Jul 20 2021

Guillermo's circulation consists of a tight swirl of low-level 
clouds, and the earlier brief convective flare up dissipated 
shortly after the release of the previous advisory.  Given that 
the system has been devoid of organized deep convection for most of 
the last 18 hours, the system is now considered a remnant low and 
this will be the last NHC advisory.   The initial intensity remains 
30 kt based on a recent ASCAT pass that showed an area of 25-30 kt 
winds north of the center.

The post-tropical cyclone will remain in an dry, stable airmass 
while moving over SSTs of 24-25C, which should result in a gradual 
spin down of the circulation. Global model fields indicate that the 
low will open up into a trough within 48-60 hours, and that is 
indicated in the official forecast. 

The remnant low is now moving a little south of due west, with an 
initial motion estimate of 265/15. The system is expected to move  
west-southwestward until dissipation under the influence of the 
expansive low-level ridge centered over the north-central Pacific. 
The new NHC track forecast is a little south of and faster than the 
previous one, trending toward the latest consensus aids. 


INIT  20/2100Z 18.7N 126.5W   30 KT  35 MPH...POST-TROP/REMNT LOW
 12H  21/0600Z 18.2N 128.9W   25 KT  30 MPH...POST-TROP/REMNT LOW
 24H  21/1800Z 17.5N 131.8W   25 KT  30 MPH...POST-TROP/REMNT LOW
 36H  22/0600Z 16.8N 134.5W   25 KT  30 MPH...POST-TROP/REMNT LOW
 48H  22/1800Z 16.1N 137.0W   20 KT  25 MPH...POST-TROP/REMNT LOW
 60H  23/0600Z...DISSIPATED

Forecaster Brennan/Cangialosi