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Tropical Storm Irwin Discussion Number  26
NWS National Hurricane Center Miami FL       EP102017
200 PM PDT Fri Jul 28 2017

Although Irwin's structure on visible satellite images looks well
organized, infrared data show that the convection is not very deep,
and the cyclone lacks an inner core. Dvorak T-numbers have not
changed much and still support an initial intensity of 50 kt. Some
moderate shear will be affecting the cyclone during the next 24 to
36 hours, but it is not expected to be strong enough to disrupt the
cloud pattern and result in weakening. On this basis, the NHC
forecast calls for only small fluctuations in intensity during that
period. Thereafter, the circulation is expected to reach cooler
waters, and weakening should then begin. This process will continue
until Irwin and Hilary merge in about 96 hours or sooner.

Irwin continues to be embedded in light steering currents, and
the cyclone has barely moved today.  Little motion is anticipated
during the next 12 hours, but by Saturday, Irwin should be steered
northward and northwestward by the southerly flow in the wake of
Hilary. Track guidance is in good agreement for the next 3 days, but
beyond that time, models become uncertain in how the interaction of
Hilary and Irwin will take place. The NHC forecast continues to call
for the merging of the two weakening cyclones.


FORECAST POSITIONS AND MAX WINDS

INIT  28/2100Z 14.9N 125.0W   50 KT  60 MPH
 12H  29/0600Z 15.0N 125.0W   55 KT  65 MPH
 24H  29/1800Z 15.8N 125.0W   55 KT  65 MPH
 36H  30/0600Z 16.8N 125.3W   50 KT  60 MPH
 48H  30/1800Z 18.7N 126.0W   40 KT  45 MPH
 72H  31/1800Z 22.5N 128.0W   35 KT  40 MPH
 96H  01/1800Z...DISSIPATED

$$
Forecaster Avila

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