Hurricane NORBERT

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HURRICANE NORBERT DISCUSSION NUMBER  16
NWS NATIONAL HURRICANE CENTER MIAMI FL       EP142014
200 AM PDT SAT SEP 06 2014

Norbert continued to rapidly intensify through about 06Z.  Since
then, the hurricane appears to have peaked in intensity, with the
eye becoming less distinct and the cold cloud tops in the eyewall
becoming asymmetric.  Satellite intensity estimates at 06Z were 115
kt from TAFB and 102 kt from SAB, while the CIMMS ADT estimates
peaked at 110 kt.  Based on these data, the initial intensity is
increased to 105 kt as a compromise between these estimates and the
decay of the cloud pattern since 06Z.

The initial motion is now 315/7.  The track forecast reasoning
remains unchanged, as Norbert will be steered around the western
periphery of a mid-level ridge centered over the southern United
States through 48 hours. After that time, the ridge weakens as a
mid-latitude trough moves into the U.S. West Coast, which should
result in a weakening of the steering currents.  The track guidance
has come into better agreement that Norbert should move
northeastward or eastward after 72 hours, with several of the models
showing the remnants making landfall over the northern portion of
the Baja California peninsula.  The new forecast track reflects this
change in the guidance by showing an northeastward and eastward
drift after 72 hours.  The new forecast track is a little to the
right of the center of the guidance envelope through 48 hours, and
after that it is slower than the consensus model TVCE.

The forecast track takes Norbert over steadily decreasing sea
surface temperatures.  The cyclone should thus weaken through the
forecast period.  Despite the higher initial intensity compared to
6 hours ago, the guidance is in good agreement that Norbert should
decay into a remnant low in about 3 days.  The new intensity
forecast is increased from that of the previous forecast through 36
hours, and then is similar to the previous forecast.  The new
forecast is in best agreement with the LGEM model.

Moisture from the remnants of Dolly and the Pacific ITCZ is being
advected northward by the outer circulation of Norbert across
northern Mexico and into the southwestern United States. This could
result in heavy rains and life-threatening flash flooding in these
areas during the next few days. Please see information from your
local weather office for more details.


FORECAST POSITIONS AND MAX WINDS

INIT  06/0900Z 24.6N 113.4W  105 KT 120 MPH
 12H  06/1800Z 25.2N 114.4W  100 KT 115 MPH
 24H  07/0600Z 26.0N 115.6W   85 KT 100 MPH
 36H  07/1800Z 26.9N 116.6W   65 KT  75 MPH
 48H  08/0600Z 27.8N 117.2W   50 KT  60 MPH
 72H  09/0600Z 29.5N 117.0W   30 KT  35 MPH...POST-TROP/REMNT LOW
 96H  10/0600Z 30.0N 116.5W   25 KT  30 MPH...POST-TROP/REMNT LOW
120H  11/0600Z 30.0N 116.0W   20 KT  25 MPH...POST-TROP/REMNT LOW

$$
Forecaster Beven

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