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Tropical Storm Irwin Discussion Number  28
NWS National Hurricane Center Miami FL       EP102017
200 AM PDT Sat Jul 29 2017

Convection associated with Irwin has changed little over the past
several hours, with weak convection in ragged bands occurring
primarily in the southeastern semicircle.  Satellite intensity
estimates have also changed little since the last advisory, so the
initial intensity remains 50 kt.  Some strengthening is possible
today while the storm remains over warm sea surface temperatures.
After that, Irwin should weaken over waters that cool to near 23C
near the 96 h forecast position.   As mentioned in the discussion
for Tropical Storm Hilary, the model guidance is diverse as to the
eventual fate of Irwin as it interacts with Hilary, with the
possibilities ranging from the early merger shown by the Canadian
model to the ECMWF scenario of the two systems dissipating
separately but in close proximity.  The forecast leans more to the
ECMWF solution and shows Irwin dissipating after 96 h to the north
of Hilary or its remnants.

Irwin is currently nearly stationary. A northward motion is
expected to begin later today.  Then, as the cyclone moves around
the eastern and northern side of Hilary, a turn toward the
north-northwest is expected in about 36 h, followed by a
northwestward motion near the end of the cyclone's life.  The new
forecast track is similar to the previous track through 48 h, and it
is shifted westward after that in agreement with the various
consensus models.


FORECAST POSITIONS AND MAX WINDS

INIT  29/0900Z 14.9N 124.9W   50 KT  60 MPH
 12H  29/1800Z 15.7N 124.9W   55 KT  65 MPH
 24H  30/0600Z 17.1N 125.1W   50 KT  60 MPH
 36H  30/1800Z 19.2N 125.7W   45 KT  50 MPH
 48H  31/0600Z 21.7N 127.0W   35 KT  40 MPH
 72H  01/0600Z 25.5N 130.0W   25 KT  30 MPH...POST-TROP/REMNT LOW
 96H  02/0600Z 27.5N 133.5W   20 KT  25 MPH...POST-TROP/REMNT LOW
120H  03/0600Z...DISSIPATED

$$
Forecaster Beven

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