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Tropical Storm Irwin Discussion Number  37
NWS National Hurricane Center Miami FL       EP102017
800 AM PDT Mon Jul 31 2017

Although the structure of Irwin remains well organized, deep
convection has been on the decline during the past several hours due
to the influences of cool, 24 deg C water and dry air.  An average
of the latest Dvorak classifications from TAFB and SAB, and ADT
values from CIMSS at the University of Wisconsin support lowering
the initial wind speed a little to 45 kt.

The intensity forecast is straightforward.  Continued steady
weakening is expected due to even cooler waters, and drier and more
stable air along the path of the cyclone.  The NHC intensity
forecast calls for Irwin to degenerate into a remnant low in about
24 hours, and dissipate by 72 hours.  This forecast is an update of
the previous one.

Irwin is moving north-northwestward at 12 kt in the wake of
Post-Tropical cyclone Hilary, and this motion is expected to
continue for about another day.  Thereafter, a slower motion toward
the northwest is forecast when the shallow remnant low is steered by
low-level southeasterly flow.  The models remain tightly clustered
and have changed little this cycle, so only minor adjustments were
made to the previous NHC track forecast.

FORECAST POSITIONS AND MAX WINDS

INIT  31/1500Z 21.9N 127.3W   45 KT  50 MPH
 12H  01/0000Z 23.6N 128.1W   35 KT  40 MPH
 24H  01/1200Z 25.6N 129.3W   30 KT  35 MPH...POST-TROP/REMNT LOW
 36H  02/0000Z 27.2N 130.6W   25 KT  30 MPH...POST-TROP/REMNT LOW
 48H  02/1200Z 28.4N 131.9W   20 KT  25 MPH...POST-TROP/REMNT LOW
 72H  03/1200Z...DISSIPATED

$$
Forecaster Cangialosi

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