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Tropical Storm Irwin Discussion Number 36
NWS National Hurricane Center Miami FL EP102017
200 AM PDT Mon Jul 31 2017
Irwin finally appears to be suffering from the effects of cooler
water. Deep convection associated with the cyclone has decreased
in coverage overnight, but the convection that remains is organized
in a band over the eastern portion of the circulation. Dvorak
T-numbers have started to decrease, and a blend of the various T-
and CI-numbers yields an initial wind speed estimate of 50 kt.
Irwin will be moving over SSTs of 22 to 23 deg C during the next 12
to 24 hours, which should cause the cyclone to quickly weaken.
In fact, Irwin is likely to degenerate to a remnant low in about
24 hours, when the deep convection dissipates. The global models
suggest that the low will dissipate in about 72 hours.
Irwin is moving north-northwestward at about 11 kt. The cyclone is
expected to continue on a north-northwestward heading today, then
slow down and turn northwestward on Tuesday as it moves around the
remnant circulation of Hilary. The latest track guidance is in
good agreement and no significant change from the previous NHC
track forecast was needed.
FORECAST POSITIONS AND MAX WINDS
INIT 31/0900Z 20.7N 126.7W 50 KT 60 MPH
12H 31/1800Z 22.4N 127.5W 40 KT 45 MPH
24H 01/0600Z 24.7N 128.7W 30 KT 35 MPH...POST-TROP/REMNT LOW
36H 01/1800Z 26.5N 130.0W 25 KT 30 MPH...POST-TROP/REMNT LOW
48H 02/0600Z 27.8N 131.2W 20 KT 25 MPH...POST-TROP/REMNT LOW