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Tropical Storm Aletta Discussion Number   4
NWS National Hurricane Center Miami FL       EP022018
300 PM MDT Wed Jun 06 2018

Aletta's cloud pattern has not become noticeably better organized
during the day, and the banding features are not very well
defined in enhanced infrared imagery.  There is a dry intrusion
over the northwest quadrant of the circulation with some
restriction of the upper-level outflow over that quadrant as well.
Dvorak classifications from both TAFB and SAB give a current
intensity of 35 kt but a recent scatterometer pass indicated that
the maximum winds are close to 40 kt, and that value will be used
for the advisory intensity.  Although the storm has not
strengthened since early this morning, it is anticipated that the
cyclone will be moving through fairly low vertical shear and over
SSTs of 28 or 29 deg C during the next few days.  This favorable
environment should cause intensification.   The official forecast,
which is close to the simple or corrected model consensus guidance,
continues to call for Aletta to become a hurricane by late Thursday
or early Friday.

High temporal and spatial resolution GOES-16 imagery suggested
multiple low-level swirls near the estimated center position.
Based on geostationary and microwave imagery along with the
scatterometer data, the initial motion continues to be slowly
westward or 270/7 kt.  The flow on the south side of a mid-level
ridge extending from Mexico into the eastern North Pacific should
continue to steer Aletta westward to west-northwestward over the
next few days.  In 3-4 days, most of the track guidance shows the
cyclone bending a little more to the right in response to a
weakness in the ridge.  As was the case in the previous cycle, the
GFS shows the northernmost track and the ECMWF the southernmost.
The official forecast lies between these extremes and is close to
the model consensus.  This is a tad slower than the previous NHC
forecast.

FORECAST POSITIONS AND MAX WINDS

INIT  06/2100Z 14.2N 107.9W   40 KT  45 MPH
 12H  07/0600Z 14.4N 109.0W   50 KT  60 MPH
 24H  07/1800Z 14.5N 110.0W   55 KT  65 MPH
 36H  08/0600Z 14.7N 111.0W   65 KT  75 MPH
 48H  08/1800Z 15.0N 112.0W   70 KT  80 MPH
 72H  09/1800Z 16.0N 113.6W   80 KT  90 MPH
 96H  10/1800Z 17.3N 115.6W   70 KT  80 MPH
120H  11/1800Z 18.0N 117.0W   45 KT  50 MPH

$$
Forecaster Pasch

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