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TROPICAL STORM RACHEL DISCUSSION NUMBER  23
NWS NATIONAL HURRICANE CENTER MIAMI FL       EP182014
800 PM PDT MON SEP 29 2014

A burst of deep convection with cloud tops of -70C to -75C
developed during the late afternoon in the same region where
earlier ASCAT overpasses indicated several surface wind vectors of
40-43 kt. As a result, the intensity at 0000 UTC synoptic time was
maintained at 45 kt. However, over the past couple of hours, cloud
tops have warmed and decreased in areal coverage significantly, so
the advisory intensity has been lowered to 40 kt.

The initial motion estimate is 360/02 kt. Steering currents are
collapsing as Rachel moves into a large break in the subtropical
ridge created by a mid-latitude trough to the north of the cyclone.
As a result, Rachel is expected to become nearly stationary fairly
soon and meander in the same general area for the next 24 hours or
so. After that, the ridge to the north of what should be a
significantly weakened tropical cyclone is expected to build back
in as the mid-latitude trough lifts out, driving Rachel or its
remnants slowly toward the west or west-southwest until dissipation
occurs in 72-96 hours. The new NHC forecast track is similar to the
previous advisory track and the consensus model TVCE.

Rachel is not long for this world due to the combination of strong
southwesterly vertical wind shear, sea-surface temperatures less
than 26C, and a cooler and drier airmass working its way into the
inner core region of the cyclone. As a result, the storm is expected
to weaken to a remnant low pressure system within 24 hours and
dissipate by 96 hours. The official intensity forecast closely
follows a blend of the Decay-SHIPS model and the consensus
intensity model IVCN.

FORECAST POSITIONS AND MAX WINDS

INIT  30/0300Z 23.3N 117.5W   40 KT  45 MPH
 12H  30/1200Z 23.3N 117.8W   35 KT  40 MPH
 24H  01/0000Z 23.3N 118.1W   30 KT  35 MPH...POST-TROP/REMNT LOW
 36H  01/1200Z 23.2N 118.4W   25 KT  30 MPH...POST-TROP/REMNT LOW
 48H  02/0000Z 23.1N 118.7W   20 KT  25 MPH...POST-TROP/REMNT LOW
 72H  03/0000Z 23.0N 120.3W   15 KT  15 MPH...POST-TROP/REMNT LOW
 96H  04/0000Z...DISSIPATED

$$
Forecaster Stewart

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