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HURRICANE ISELLE DISCUSSION NUMBER  11
NWS NATIONAL HURRICANE CENTER MIAMI FL       EP092014
200 AM PDT SUN AUG 03 2014

The overall satellite presentation of Iselle hasn't changed much
during the past several hours with strong convection in the eyewall
and an eye which is intermittently obscured by cirrus clouds.
Satellite intensity estimates have not changed significantly, so
the initial wind speed will remain 95 kt.

Although Iselle is probably near peak intensity, it still has a
short window of time today to become a major hurricane.  It is not
likely to strengthen much, however, due to Iselle moving closer to a
less favorable thermodynamic environment. Since wind shear is
forecast to remain low, only gradual weakening is anticipated after
today while Iselle moves over marginal SSTs for the next couple
of days. One possible pitfall of this forecast is that, given the
forecast storm environment, Iselle could evolve into an annular
hurricane, which could delay the weakening during that time.  Late
in the period, an increase in both shear and drier air aloft will
probably help to weaken the storm while it approaches the Hawaiian
Islands. The official NHC intensity forecast is close to the
previous one and the intensity consensus.

The cyclone continues to move westward or 275/9.  A subtropical
ridge north of Iselle should steer the storm on this general path
for the next few days, with a slight deceleration expected in a day
or so due to the ridge temporarily weakening. Guidance is in very
good agreement through day 3, and the NHC forecast through that
time us basically an update of the previous one.  After that time,
Iselle should move on a more west-northwestward heading at a faster
forward speed due to the ridge rebuilding.  The model guidance has
shifted northward on this cycle, which seems reasonable given the
forecast synoptic pattern, and the official forecast is moved in
that direction.  It should be noted that the bulk of the guidance is
north of the latest NHC forecast at long range, and further
adjustments in that direction could be required on later forecasts.

FORECAST POSITIONS AND MAX WINDS

INIT  03/0900Z 15.3N 131.8W   95 KT 110 MPH
 12H  03/1800Z 15.4N 133.4W   95 KT 110 MPH
 24H  04/0600Z 15.6N 135.4W   90 KT 105 MPH
 36H  04/1800Z 15.7N 137.0W   85 KT 100 MPH
 48H  05/0600Z 15.7N 138.6W   80 KT  90 MPH
 72H  06/0600Z 16.0N 142.2W   65 KT  75 MPH
 96H  07/0600Z 17.3N 147.8W   55 KT  65 MPH
120H  08/0600Z 19.0N 154.0W   45 KT  50 MPH

$$
Forecaster Blake

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