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HURRICANE ISELLE DISCUSSION NUMBER  18...CORRECTED
NWS NATIONAL HURRICANE CENTER MIAMI FL       EP092014
200 PM PDT MON AUG 04 2014

Corrected quasi-annual to quasi-annular

Iselle has an impressive signature on visible satellite imagery
with a solid central dense overcast surrounding a 25 n mi wide eye.
Final-T estimates from the UW-CIMSS ADT have fallen slightly, but
the CI number remains 6.3/122 kt.  Along with steady T6.0/115 kt
estimates from TAFB and SAB, the initial intensity is held at 120
kt.  There is not much change to the intensity forecast.  Due to
its quasi-annual structure, Iselle should only gradually weaken in
the short term while it moves over marginal sea surface temperatures
and in a relatively light-shear environment.  For that reason, the
NHC intensity forecast remains above the intensity guidance for the
first 24 hours.  Faster weakening is expected thereafter while the
cyclone spends about 24 hours over sub-26C water.  However, the
ocean warms again just to the east of Hawaii, which could allow
Iselle to maintain some intensity.  After 24 hours, the NHC
intensity forecast more closely follows the intensity consensus ICON
and the statistical LGEM, which tends to do a good job at the end of
the forecast period.

Iselle has been moving due westward, or possibly even wobbled just
south of due west, during the past few hours.  The initial motion
estimate is 270/9 kt, but Iselle's forward speed should begin to
decrease soon since the ridge to its north has weakened.  A
mid-level anticyclone is expected to develop and strengthen between
California and Hawaii in a day or two, forcing Iselle to turn
west-northwestward and accelerate starting in 36 hours.  The track
guidance has change very little on this cycle, and the updated NHC
forecast continues to bring the center of Iselle across the main
Hawaiian Islands between 72 and 120 hours.

Based on this forecast, Iselle should be crossing 140W just
before 1800 UTC on Tuesday.  If this forecast holds, then the
Central Pacific Hurricane Center in Honolulu, Hawaii, would assume
responsibility for Iselle and begin issuing advisories at 2100 UTC,
or 11 AM HST on Tuesday.


FORECAST POSITIONS AND MAX WINDS

INIT  04/2100Z 16.1N 137.4W  120 KT 140 MPH
 12H  05/0600Z 16.2N 138.5W  115 KT 135 MPH
 24H  05/1800Z 16.5N 140.3W  105 KT 120 MPH
 36H  06/0600Z 17.1N 142.9W   85 KT 100 MPH
 48H  06/1800Z 17.8N 146.1W   70 KT  80 MPH
 72H  07/1800Z 19.5N 153.0W   60 KT  70 MPH...NEAR HAWAII
 96H  08/1800Z 21.0N 159.0W   55 KT  65 MPH...NEAR HAWAII
120H  09/1800Z 22.5N 164.5W   45 KT  50 MPH...WEST OF HAWAII

$$
Forecaster Berg

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