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Hurricane NORBERT (Text)

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HURRICANE NORBERT DISCUSSION NUMBER   9
NWS NATIONAL HURRICANE CENTER MIAMI FL       EP142014
800 AM PDT THU SEP 04 2014

Norbert has become a little better organized overnight, with the
TRMM and AMSR2 microwave sensors indicating that the low- and
mid-level centers have become more vertically aligned.  The cyclone
is still experiencing northeasterly shear though, given the
asymmetric shape on the latest satellite images. Dvorak intensity
estimates are all near 75 kt, so that will used as the initial wind
speed.  An Air Force Hurricane Hunter aircraft is en route to
investigate Norbert, and should provide a more precise estimate of
its intensity.

While moderate shear has been affecting the cyclone, it has not
been strong enough to prevent slow strengthening.  Although the
shear is not forecast to change much over the next few days,
Norbert is expected to move into an environment characterized by
cooler SSTs and drier, more stable air.  These negative factors
should cause some weakening on Friday, with a more significant
downward trend anticipated by late this weekend.  The latest NHC
forecast is close to a blend of the previous interpolated forecast
and the intensity consensus.  Norbert should become a remnant low in
about 4 days due to it moving over very cool waters west of Baja
California.

The track of Norbert has been quite erratic over the past 24 hours,
but a 12-hour motion still appears to be northwestward at about 6
kt.  A mid-level ridge is expected to remain over northwestern
Mexico, keeping Norbert on the same general course during the next
few days, offshore of Baja California.  At long range, model
guidance remains divergent on how much of a northward turn that
Norbert will take due to a mid-latitude trough weakening the ridge.
The 3-5 day track also partially depends on the intensity at that
time range, with a deeper system probably moving farther west, more
like the ECMWF solution.  Since there has not been much change to
the overall guidance, the new NHC forecast is about the same as the
previous one, and remains relatively close to the dynamical model
consensus.

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  04/1500Z 20.7N 110.4W   75 KT  85 MPH
 12H  05/0000Z 21.5N 111.1W   80 KT  90 MPH
 24H  05/1200Z 22.5N 112.2W   80 KT  90 MPH
 36H  06/0000Z 23.5N 113.3W   75 KT  85 MPH
 48H  06/1200Z 24.3N 114.5W   65 KT  75 MPH
 72H  07/1200Z 25.9N 117.0W   50 KT  60 MPH
 96H  08/1200Z 27.6N 118.6W   30 KT  35 MPH...POST-TROP/REMNT LOW
120H  09/1200Z 29.0N 119.0W   25 KT  30 MPH...POST-TROP/REMNT LOW

$$
Forecaster Blake

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