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Tropical Storm Irwin Discussion Number  29
NWS National Hurricane Center Miami FL       EP102017
800 AM PDT Sat Jul 29 2017

Irwin's cloud pattern has not changed much since yesterday. It
consists of a low-level center just to the north of a cyclonically
curved convective band in the southern semicircle. An average
of the Dvorak intensity estimates supports a 50-kt tropical cyclone.
The circulation is still over warm waters and Irwin could maintain
the same intensity for another 12 hours or so. After that time, the
cyclone will begin to move over cooler waters resulting in gradual
weakening. Models still disagree if Hilary and Irwin will merge as
forecast by the GFS, or if both systems will dissipate nearby over
cool waters as suggested by the ECMWF. The NHC forecast opts for the
ECMWF proposal, but regardless of the solution, both system are
anticipated to be weak remnant lows or may have even dissipated by
then.

Today, I found Irwin basically in the same spot I left it yesterday.
It was anticipated that the cyclone was going to be meandering
for a while within very weak steering currents, but it appears
that this is about to change soon. Irwin will be influenced by the
southerly flow in the wake of Hilary, and the cyclone should begin
to move northward and northwestward with an increase in forward
speed during the next 12 hours and beyond. The track forecast is
similar to the previous one, and is basically on top of the
multi-model consensus TVCX and TVCN which have been the models with
the highest skill in forecasting Irwin so far.


FORECAST POSITIONS AND MAX WINDS

INIT  29/1500Z 15.1N 124.9W   50 KT  60 MPH
 12H  30/0000Z 16.2N 125.0W   50 KT  60 MPH
 24H  30/1200Z 17.8N 125.2W   45 KT  50 MPH
 36H  31/0000Z 20.1N 126.3W   40 KT  45 MPH
 48H  31/1200Z 22.3N 127.8W   30 KT  35 MPH
 72H  01/1200Z 26.0N 131.0W   25 KT  30 MPH...POST-TROP/REMNT LOW
 96H  02/1200Z 27.5N 134.0W   20 KT  25 MPH...POST-TROP/REMNT LOW
120H  03/1200Z...DISSIPATED

$$
Forecaster Avila

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