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Hurricane NORBERT (Text)

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HURRICANE NORBERT DISCUSSION NUMBER   8
NWS NATIONAL HURRICANE CENTER MIAMI FL       EP142014
200 AM PDT THU SEP 04 2014

Recent microwave images, including a NASA GPM overpass at 0516 UTC,
indicate that Norbert has lost some organization during the past
few hours due to easterly vertical wind shear.  The low-level center
is in the northeastern part of the central convection with a
mid-level eye displaced to the southwest of the low-level center.
Satellite intensity estimates from TAFB and SAB are unchanged at 77
and 65 kt, and the CIMSS Advanced Dvorak Technique estimates an
intensity of 65 kt.  Based on these data, the initial intensity
remains 70 kt.

The microwave data indicate that the center of Norbert made a
northward turn since the previous advisory.  The initial motion is
a somewhat uncertain 325/5.  Norbert should continue on a general
northwestward motion during the next three days around the
southwestern periphery of a mid-level ridge that extends westward
across northern Mexico.  This part of the forecast track has
been nudged to the east based on the current position and motion.
After 72 hours, the guidance becomes more divergent due to
disagreements in how Norbert interacts with a mid/upper-level trough
over the northeastern Pacific.  The GFS and NAVGEM forecast Norbert
to turn northward, while the ECMWF is forecasting a westward turn
and a slower forward speed.  The other models are spread between
these extremes.  The later part of the new track forecast is similar
to the previous advisory, and is showing a slow northward motion as
a compromise between the extremes.

The dynamical models now suggest that moderate shear should
continue for the next 24-36 hours, and as a result the intensity
guidance shows less strengthening than 6 hours ago.  The new
intensity forecast is thus nudged downward.  Norbert should start
weakening by 48 hours as it reaches cooler sea surface
temperatures, and the system is forecast to degenerate to a remnant
low by the end of the forecast period.  The new intensity forecast
is in best agreement with the intensity consensus.

Moisture indirectly related to Norbert being pulled northward
around the eastern side of the cyclone's large circulation is
expected to spread across northern Mexico and into the southwestern
United States during the next few days. This could result in heavy
rains and life-threatening flash flooding in these areas. Please see
information from your local weather office for more details.


FORECAST POSITIONS AND MAX WINDS

INIT  04/0900Z 20.5N 109.7W   70 KT  80 MPH
 12H  04/1800Z 21.2N 110.4W   75 KT  85 MPH
 24H  05/0600Z 22.2N 111.4W   80 KT  90 MPH
 36H  05/1800Z 23.1N 112.4W   80 KT  90 MPH
 48H  06/0600Z 23.9N 113.6W   70 KT  80 MPH
 72H  07/0600Z 25.5N 116.0W   55 KT  65 MPH
 96H  08/0600Z 27.5N 118.0W   35 KT  40 MPH
120H  09/0600Z 29.0N 119.0W   25 KT  30 MPH...POST-TROP/REMNT LOW

$$
Forecaster Beven

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