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TROPICAL STORM NEWTON DISCUSSION NUMBER   2
NWS NATIONAL HURRICANE CENTER MIAMI FL       EP152016
1000 PM CDT SUN SEP 04 2016

A pair of ASCAT passes late this afternoon indicated that the
depression was producing 30-35 kt winds on its southern side.
Since the last advisory, the circulation and convective pattern
have continued to improve, and both subjective and objective Dvorak
estimates have increased.  Based on all these data, the depression
is upgraded to Tropical Storm Newton with maximum winds of 35 kt.

There might be multiple low-level swirls rotating around a common
center, but the best estimate of the center yields an initial
motion of 340/7 kt.  Newton is located to the south of a
mid-tropospheric ridge which extends from Texas southwestward over
the Pacific.  However, an amplifying trough near California is
expected to shunt the ridge eastward within the next 24 hours,
which will help to accelerate Newton toward the northwest or
north-northwest during the next couple of days.  There is very
little spread among the track guidance, but most of the models
(with the exception of the EMCWF) are now a little faster than the
previous NHC forecast.  The new NHC forecast is therefore a little
faster, bringing the center of Newton very close to the extreme
southern Baja California peninsula in about 36 hours.  After that,
Newton is forecast to turn northward, moving over the Baja
California peninsula, the Gulf of California, and into northwestern
mainland Mexico by day 3.

Newton is over very deep, warm water at the moment, and SSTs are
expected to be between 28-30C until the cyclone reaches the Baja
California peninsula.  In addition, vertical shear is expected to
remain low for the next couple of days.  Therefore, Newton is
expected to strengthen before it reaches land, with rapid
intensification not out of the question.  The Rapid Intensification
Index currently shows a 1-in-4 chance of a 30-kt increase in winds
during the next 24 hours.  Most of the hurricane models, both
dynamical and statistical, are only showing modest strengthening,
but the global model fields indicate that Newton could be near
hurricane intensity when it is near the Baja California peninsula.
Therefore, the NHC intensity forecast now brings Newton to just
below hurricane intensity in 36 hours, which is at the high end of
the guidance.  Weakening should occur after 36 hours due to
interaction with land and increasing vertical shear.

Although the official forecast does not explicitly show Newton
becoming a hurricane, it will be close enough to hurricane strength
that the Government of Mexico has issued a hurricane warning for the
extreme southern Baja California peninsula.  Additional tropical
storm watches and warnings have been issued since Newton's wind
field is expected to expand.

FORECAST POSITIONS AND MAX WINDS

INIT  05/0300Z 17.0N 105.7W   35 KT  40 MPH
 12H  05/1200Z 18.4N 106.7W   40 KT  45 MPH
 24H  06/0000Z 20.2N 108.2W   50 KT  60 MPH
 36H  06/1200Z 22.3N 109.6W   60 KT  70 MPH
 48H  07/0000Z 24.7N 110.8W   55 KT  65 MPH...OVER BAJA PENINSULA
 72H  08/0000Z 29.9N 111.3W   35 KT  40 MPH...INLAND
 96H  09/0000Z 34.5N 109.5W   20 KT  25 MPH...POST-TROP/REMNT LOW

$$
Forecaster Berg

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