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Post-Tropical Cyclone Irwin Discussion Number  12
NWS National Hurricane Center Miami FL       EP102023
1100 AM HST Tue Aug 29 2023
 
Irwin has failed to produce any convection near its center during 
the last 15-18 h. Since it no longer satisfies the criteria of a 
tropical cyclone, Irwin is being designated as a post-tropical 
cyclone with this advisory. A recent scatterometer pass showed a 
broad area of winds at or slightly above 30 kt in the northwestern 
quadrant, and so the initial intensity remains 35 kt.

The post-tropical cyclone is moving slightly south of due west 
(260/15 kt). A general westward motion at a gradually slower forward 
speed is expected over the next several days while Irwin is steered 
by a low-level ridge over the eastern Pacific. Gradual weakening is 
forecast as the shallow cyclone spins down over cooler waters and in 
a drier, more stable environment. While some intermittent bursts of 
convection could occur during the next couple of days, the overall 
environment does not appear conducive for Irwin to regenerate to a 
tropical cyclone.

This is the last NHC advisory on Irwin. For additional information 
on the post-tropical cyclone, please see High Seas Forecasts issued 
by the National Weather Service, under AWIPS header NFDHSFEPI, WMO 
header FZPN02 KWBC, and on the web at 
ocean.weather.gov/shtml/NFDHSFEPI.php
 
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  29/2100Z 19.1N 130.3W   35 KT  40 MPH...POST-TROPICAL
 12H  30/0600Z 18.9N 132.4W   30 KT  35 MPH...POST-TROP/REMNT LOW
 24H  30/1800Z 18.8N 134.7W   30 KT  35 MPH...POST-TROP/REMNT LOW
 36H  31/0600Z 18.8N 136.5W   30 KT  35 MPH...POST-TROP/REMNT LOW
 48H  31/1800Z 18.9N 138.0W   30 KT  35 MPH...POST-TROP/REMNT LOW
 60H  01/0600Z 19.0N 139.3W   25 KT  30 MPH...POST-TROP/REMNT LOW
 72H  01/1800Z 19.0N 140.3W   25 KT  30 MPH...POST-TROP/REMNT LOW
 96H  02/1800Z 19.0N 141.5W   25 KT  30 MPH...POST-TROP/REMNT LOW
120H  03/1800Z 19.5N 143.5W   20 KT  25 MPH...POST-TROP/REMNT LOW
 
$$
Forecaster Reinhart
 
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