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Tropical Storm Irwin Forecast Discussion


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000
WTPZ45 KNHC 261450
TCDEP5

Tropical Storm Irwin Discussion Number  17
NWS National Hurricane Center Miami FL       EP102017
800 AM PDT Wed Jul 26 2017

Satellite images and microwave data indicate that Irwin's cloud
pattern has significantly deteriorated since yesterday. It now
consists of a tight circulation center located just to the south of
an area of deep, but not too well organized, convection.
Consequently, the initial intensity has been decreased to 55 kt
based on lower Dvorak T-numbers from all agencies. The environment
does not support significant weakening, but is not favorable for
much intensification either. The NHC forecast calls for a slight
weakening today, and shows no change in intensity for the
next 5 days. Although the intensity forecast is a little bit
different from the previous one due to the lower current intensity,
it does not change the general trend expressed in previous NHC
forecasts.

Irwin is moving toward the west-southwest or 255 degrees at 6 kt.
Currently, the cyclone is embedded within weak steering currents,
and Irwin will probably continue on the same slow west-southwest
track during the next day or two. After that time, Hurricane Hilary
is forecast to pass well north of Irwin, and the steering currents
will change to southerlies, and most of the models agree that Irwin
should begin to move with a northerly component in the wake of
Hilary. This is reflected in the official NHC forecast which in fact
is close to the multi-model consensus TVCN, and is not very
different from the previous one.

FORECAST POSITIONS AND MAX WINDS

INIT  26/1500Z 15.6N 122.1W   55 KT  65 MPH
 12H  27/0000Z 15.3N 123.0W   45 KT  50 MPH
 24H  27/1200Z 14.9N 124.1W   45 KT  50 MPH
 36H  28/0000Z 14.5N 125.0W   45 KT  50 MPH
 48H  28/1200Z 14.5N 125.5W   45 KT  50 MPH
 72H  29/1200Z 15.0N 125.0W   45 KT  50 MPH
 96H  30/1200Z 17.5N 125.0W   45 KT  50 MPH
120H  31/1200Z 20.5N 126.0W   45 KT  50 MPH

$$
Forecaster Avila