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Hurricane JIMENA


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HURRICANE JIMENA DISCUSSION NUMBER  18
NWS NATIONAL HURRICANE CENTER MIAMI FL       EP132015
800 PM PDT SUN AUG 30 2015

Jimena's cloud pattern has been in a remarkably steady state since
the last advisory.  The hurricane continues to maintain a large
circular eye that has warmed slightly, surrounded by a nearly
uniform ring of deep convection.  There is a faint asymmetry in the
convective distribution, suggestive of northerly or north-
northwesterly shear as diagnosed by the SHIPS model output.
Satellite classifications were T6.5/127 kt from TAFB and SAB, and
UW-CIMSS ADT values have held steady at 6.7/132 kt.  A blend of
these data is used to set the initial intensity at 130 kt.

Even though large-scale atmospheric conditions are forecast to
remain relatively favorable around Jimena during the couple of days,
the intensity guidance indicates that Jimena should begin to weaken
soon. The weakening appears to largely be a function of slowly
decreasing SSTs along the cyclone's path.  Some westerly shear and a
larger drop-off in oceanic heat content later in the forecast period
suggest continued gradual weakening should occur, but neither the
atmosphere nor ocean should produce conditions hostile enough to
result in the cyclone's rapid decline.  The one caveat to the
intensity forecast is that Jimena, already exhibiting some
characteristics of an annular hurricane, could weaken more slowly
than forecast.  The latest NHC intensity forecast is somewhat above
the multi-model consensus and is in best agreement with the HWRF
model that shows slower overall weakening.

Jimena's heading has been a bit more westerly since the previous
advisory, but a longer-term average motion estimate is 290/14. A
longwave trough, extending southwestward from the U.S. west coast,
has eroded the subtropical ridge ridge between 140-150W.  As Jimena
nears this weakness during the next few days, its forward speed
should gradually decrease on a slightly more poleward heading.  In
the absence of much steering from days 3 to 5, Jimena should drift
northwestward.  The latest NHC track forecast has hardly changed
from the previous one.


FORECAST POSITIONS AND MAX WINDS

INIT  31/0300Z 15.0N 132.5W  130 KT 150 MPH
 12H  31/1200Z 15.4N 134.4W  125 KT 145 MPH
 24H  01/0000Z 16.2N 136.8W  120 KT 140 MPH
 36H  01/1200Z 16.8N 138.6W  115 KT 130 MPH
 48H  02/0000Z 17.3N 140.0W  105 KT 120 MPH
 72H  03/0000Z 18.3N 141.9W   90 KT 105 MPH
 96H  04/0000Z 19.1N 143.0W   80 KT  90 MPH
120H  05/0000Z 20.2N 143.9W   70 KT  80 MPH

$$
Forecaster Kimberlain

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