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TROPICAL STORM ANDRES DISCUSSION NUMBER   3
NWS NATIONAL HURRICANE CENTER MIAMI FL       EP012015
300 PM MDT THU MAY 28 2015

The satellite presentation of Andres continues to improve, with a
band of convection now wrapping about three-quarters of the way
around the center.  A recent ASCAT pass revealed maximum winds
of about 50 kt, so the initial intensity has been increased
accordingly.  The scatterometer data also provided a better
estimate of the size of the tropical cyclone wind field, and the
tropical-storm-force wind radii have been adjusted outward.

The satellite data indicate that the center is located a bit
southwest of the previous estimate, but the overall initial motion
remains west-northwest or 295 degrees at 10 kt.  The track forecast
reasoning is unchanged from before.  Andres should move west-
northwestward to northwestward around the southwestern portion of a
mid-level ridge extending westward over the eastern Pacific from
central Mexico.  The 1200 UTC global models show more ridging to the
north of Andres late in the period than previous runs, which has
resulted in a westward shift in the track guidance.  The NHC
forecast has been adjusted westward, but it lies along the right
side of the guidance envelope.

Environmental conditions consisting of warm water and low shear
should allow for continued steady strengthening during the next
couple of days.  Although the latest SHIPS RI index shows a lower
chance of rapid strengthening during the next 24 hours than this
morning, it would not be surprising if rapid intensification
occurred.  The NHC forecast is near the upper end of the intensity
guidance and is closest to the SHIPS model.  After 72 hours, Andres
should begin to weaken when it encounters slightly cooler sea
surface temperatures and a drier and more stable airmass.

FORECAST POSITIONS AND MAX WINDS

INIT  28/2100Z 11.6N 112.5W   50 KT  60 MPH
 12H  29/0600Z 12.3N 113.6W   65 KT  75 MPH
 24H  29/1800Z 13.1N 114.7W   75 KT  85 MPH
 36H  30/0600Z 13.9N 115.3W   85 KT 100 MPH
 48H  30/1800Z 14.9N 116.0W   90 KT 105 MPH
 72H  31/1800Z 16.5N 117.7W   85 KT 100 MPH
 96H  01/1800Z 17.5N 120.0W   70 KT  80 MPH
120H  02/1800Z 18.0N 122.5W   55 KT  65 MPH

$$
Forecaster Brown

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