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Tropical Storm Irwin Discussion Number  11
NWS National Hurricane Center Miami FL       EP102023
500 AM HST Tue Aug 29 2023
 
Irwin has been devoid of any organized convection since about 03
UTC. Its well-defined low-level circulation is fully exposed in
conventional satellite imagery. If the cyclone is unable to produce
convection soon, it is in danger of degenerating to a post-tropical
cyclone later today. Based on earlier scatterometer data, the
initial intensity is set at 35 kt, with these winds confined to the
northern portion of the circulation.
 
Cooler waters and a drier, more stable airmass along Irwin's track
do not bode well for its future as a tropical cyclone. In addition,
deep-layer westerly shear is forecast to increase beyond 48 h. So
while some intermittent bursts of convection cannot be ruled out
during the next couple of days, the overall environment does appear
conducive for Irwin to generate persistent organized convection
going forward. The updated forecast shows Irwin as a post-tropical
remnant low in 24 h, but this could occur even sooner if current
trends continue.
 
The storm is moving quickly westward at about 15 kt. A motion just
south of due west is expected during the next day or so while Irwin
is steered by a low- to mid-level ridge to its north. The steering
ridge is forecast to weaken later this week, which should cause the
cyclone to slow down and gradually turn more west-northwestward and
northwestward at days 4-5. The NHC track forecast lies very close to
the previous prediction.
 
 
FORECAST POSITIONS AND MAX WINDS
 
INIT  29/1500Z 19.6N 129.1W   35 KT  40 MPH
 12H  30/0000Z 19.3N 131.1W   35 KT  40 MPH
 24H  30/1200Z 19.0N 133.7W   30 KT  35 MPH...POST-TROP/REMNT LOW
 36H  31/0000Z 19.1N 135.7W   30 KT  35 MPH...POST-TROP/REMNT LOW
 48H  31/1200Z 19.3N 137.3W   30 KT  35 MPH...POST-TROP/REMNT LOW
 60H  01/0000Z 19.5N 138.7W   30 KT  35 MPH...POST-TROP/REMNT LOW
 72H  01/1200Z 19.7N 139.9W   25 KT  30 MPH...POST-TROP/REMNT LOW
 96H  02/1200Z 20.0N 141.4W   25 KT  30 MPH...POST-TROP/REMNT LOW
120H  03/1200Z 21.5N 143.0W   25 KT  30 MPH...POST-TROP/REMNT LOW
 
$$
Forecaster Reinhart
 
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