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TROPICAL STORM ANDRES DISCUSSION NUMBER   4
NWS NATIONAL HURRICANE CENTER MIAMI FL       EP012015
900 PM MDT THU MAY 28 2015

Andres is continuing to intensify.  Although the cloud tops
near the center have recently warmed, the latest microwave and
conventional satellite images are now showing the formation of a
ragged eye.  An average of the latest intensity estimates is just
below hurricane strength, so the initial wind speed is set to 60
kt.

The storm appears to be moving to the west-northwest at about 9 kt,
a bit slower than before.  Andres should turn northwestward
tomorrow as a result of a slight weakness in the subtropical ridge.
In a few days, the ridge restrengthens, which should then steer
Andres more toward the west-northwest and west.  The latest models
have again shifted to the left, apparently due to a stronger ridge
than originally predicted, and the official forecast follows the
westward trend in the model consensus.

Although it seems clear that the cyclone should strengthen over the
next couple of days with generally favorable environmental
conditions, the amount of shear is a wild card for this forecast.
Most of the global models are showing shear values that are higher
than ideal for rapid intensification, and the shear is the biggest
inhibitor in the latest SHIPS RI index.  Andres has been moving
left of expected, however, which has been prolonging the lower shear
and warmest water conditions.  Thus, the new NHC wind speed forecast
will remain above most of the guidance, similar to the previous
prediction, and it would not be surprising if this forecast is too
low for the reasons given above.  After 48 hours, Andres should
begin to weaken when it encounters cooler waters and a more stable
air mass.

FORECAST POSITIONS AND MAX WINDS

INIT  29/0300Z 11.8N 113.3W   60 KT  70 MPH
 12H  29/1200Z 12.5N 114.4W   70 KT  80 MPH
 24H  30/0000Z 13.5N 115.4W   80 KT  90 MPH
 36H  30/1200Z 14.4N 116.2W   85 KT 100 MPH
 48H  31/0000Z 15.3N 116.9W   90 KT 105 MPH
 72H  01/0000Z 16.7N 118.9W   80 KT  90 MPH
 96H  02/0000Z 17.5N 121.5W   60 KT  70 MPH
120H  03/0000Z 18.0N 124.5W   45 KT  50 MPH

$$
Forecaster Blake

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