Hurricane NORBERT

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HURRICANE NORBERT DISCUSSION NUMBER  14
NWS NATIONAL HURRICANE CENTER MIAMI FL       EP142014
200 PM PDT FRI SEP 05 2014

Even though Norbert's cloud pattern remains fairly well organized in
satellite imagery, cloud top temperatures in the central dense
overcast have been slowly warming since this morning. Nevertheless,
an Air Force Reserve Unit Hurricane Hunter aircraft reported maximum
flight-level winds of 92 kt and peak SFMR winds of 76 kt in the
northeastern quadrant, with a minimum pressure of 966 mb. These data
support an initial intensity estimate of 80 kt for this advisory.

While Norbert will be moving over above-normal SSTs of 27-29 deg C
west of the southern Baja California peninsula during the next day
or so, some northeasterly shear and an influx of drier and more
stable air over the western part of circulation should contribute to
a slow weakening. After that time, Norbert should reach
substantially cooler waters and other thermodynamic variables should
become much less favorable. These negative factors should result in
a near-rapid weakening of the cyclone in 2-3 days, and remnant low
status is forecast in 3 days. Encountering even cooler waters on
day 4-5 and an increase in shear, Norbert should spin down further
and dissipate just beyond the end of the forecast period. The NHC
intensity forecast has not changed from the previous one and is near
the multi-model consensus IVCN.

Satellite and aircraft fixes indicate an initial motion toward the
northwest or 325/7 kt. Some re-building of the mid-level ridge to
the north of Norbert should cause a slight bend of the track toward
the left during the next day or two.  After that time, Norbert is
expected to reach the western edge of the ridge and encounter a
weakness caused by a mid-latitude trough advancing eastward from
offshore of the California coast.  This synoptic pattern should
result in a gradual northward turn during with some decrease in
forward speed. The mid-level center of the cyclone is likely to move
rapidly northeastward into the southwestern United States on days
3-4, leaving the low-level center meandering offshore the west-
central Baja California peninsula until dissipation. The NHC
forecast track is little changed from the previous one, and lies on
the far eastern side of the guidance envelope and east of the multi-
model consensus TVCE.

The hurricane-force wind radii have expanded in the northeastern
quadrant based on SFMR data from the aircraft and now extend out 40
n mi from the center. Any deviation to the right of the forecast
track would bring hurricane conditions onshore in the hurricane
warning area.

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  05/2100Z 23.6N 112.2W   80 KT  90 MPH
 12H  06/0600Z 24.3N 113.3W   75 KT  85 MPH
 24H  06/1800Z 25.0N 114.4W   70 KT  80 MPH
 36H  07/0600Z 25.8N 115.6W   60 KT  70 MPH
 48H  07/1800Z 26.5N 116.6W   45 KT  50 MPH
 72H  08/1800Z 28.4N 117.7W   30 KT  35 MPH...POST-TROP/REMNT LOW
 96H  09/1800Z 29.2N 117.6W   20 KT  25 MPH...POST-TROP/REMNT LOW
120H  10/1800Z 29.5N 117.4W   15 KT  15 MPH...POST-TROP/REMNT LOW

$$
Forecaster Kimberlain

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