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Tropical Storm IRWIN


Tropical Storm Irwin Discussion Number  34
NWS National Hurricane Center Miami FL       EP102017
200 PM PDT Sun Jul 30 2017

Although the mid-level eye feature is no longer evident in satellite
images, the compact circulation of Irwin is still fairly well
organized.  The convective pattern consists of a central dense
overcast with fragmented curved bands mostly to the south of the
center.  The Dvorak CI-numbers from TAFB and SAB remain 3.5/55 kt,
so the initial intensity is held at that value.

Irwin has now crossed the 26 deg C isotherm, and it will be headed
for even cooler waters during the next few days.  In addition, a
large area of stratocumulus clouds are wrapping into the western and
southern portions of the circulation, indicative of stable air
beginning to affect the system.  These unfavorable environmental
conditions should lead to steady weakening and ultimately cause
Irwin to degenerate into a remnant low in about 36 hours, or
possibly sooner.  The remnant low is now expected to dissipate by
day 4, following the global model guidance.  The NHC intensity
forecast is largely an update of the previous one and in line with
the bulk of the guidance.

Irwin is moving north-northwestward, or 335 degrees, at 8 kt
embedded in the flow in the wake of Hilary.  This motion with an
increase in forward speed is expected during the next day or two.
Once Irwin becomes a remnant low, the shallow system is expected to
turn a little to the left and slow down when it becomes steered by
the low-level flow.  The NHC track forecast is similar to the
previous one, and it lies close to the various consensus aids.


INIT  30/2100Z 18.5N 125.6W   55 KT  65 MPH
 12H  31/0600Z 20.3N 126.5W   50 KT  60 MPH
 24H  31/1800Z 22.6N 127.7W   40 KT  45 MPH
 36H  01/0600Z 24.7N 129.0W   30 KT  35 MPH...POST-TROP/REMNT LOW
 48H  01/1800Z 26.4N 130.5W   25 KT  30 MPH...POST-TROP/REMNT LOW
 72H  02/1800Z 28.1N 132.6W   20 KT  25 MPH...POST-TROP/REMNT LOW
 96H  03/1800Z...DISSIPATED

Forecaster Cangialosi