Hurricane RACHEL

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HURRICANE RACHEL DISCUSSION NUMBER  17
NWS NATIONAL HURRICANE CENTER MIAMI FL       EP182014
800 AM PDT SUN SEP 28 2014

Rachel's cloud pattern has become much less organized. The central
dense overcast has taken on a distorted appearance, with cold-topped
deep convection more asymmetrically distributed.  An intermittent
eye seen earlier in nighttime visible imagery disappeared several
hours ago.  Although Dvorak intensity estimates are unchanged from
0600 UTC, the initial intensity estimate is lowered to 70 kt, given
the recent degradation of the cyclone's satellite signature.  A
considerable increase in southwesterly shear is expected during the
next 24-48 hours in association with a deep mid-latitude trough
passing through the western United States.  The increase in shear,
coupled with substantially less conducive thermodynamic factors, are
expected to result in steady weakening that could become more rapid
than indicated in the forecast.  The NHC wind speed forecast shows a
faster rate of weakening relative to the previous one, but remnant
low status is still indicated by day 3.

Rachel continues on a slow north-northwestward track, or 340/06, on
the western periphery of a mid-level ridge near western Mexico.
The cyclone's forward speed is expected to decrease further during
the next day or so as it reaches a col area, and Rachel may come to
a temporary halt in about 36 hours.  With significant weakening
occurring during this time, a much-shallower Rachel should begin to
come under the influence of the low-level trade wind flow after
this time and turn southwestward and westward with increasing
forward speed.  The NHC track forecast is similar to the previous
one and the bulk of the track guidance but not as far south and
west as the ECMWF solution.  Only the GFS continues to insist on
a track farther to the right and faster as a consequence of a
stronger and more coupled vortex, responding to the deep-layer flow
associated with the previously mentioned mid-latitude trough.


FORECAST POSITIONS AND MAX WINDS

INIT  28/1500Z 21.5N 117.2W   70 KT  80 MPH
 12H  29/0000Z 22.0N 117.4W   65 KT  75 MPH
 24H  29/1200Z 22.4N 117.5W   55 KT  65 MPH
 36H  30/0000Z 22.3N 117.7W   45 KT  50 MPH
 48H  30/1200Z 22.1N 117.9W   35 KT  40 MPH
 72H  01/1200Z 21.3N 118.6W   25 KT  30 MPH...POST-TROP/REMNT LOW
 96H  02/1200Z 21.0N 120.0W   20 KT  25 MPH...POST-TROP/REMNT LOW
120H  03/1200Z 20.5N 122.5W   15 KT  15 MPH...POST-TROP/REMNT LOW

$$
Forecaster Kimberlain

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