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TROPICAL STORM JIMENA DISCUSSION NUMBER   5
NWS NATIONAL HURRICANE CENTER MIAMI FL       EP132015
200 PM PDT THU AUG 27 2015

Visible images show that Jimena has several spiral convective bands
emanating away from the center, with the inner bands attempting to
consolidate into a ring of convection.  Dvorak estimates from TAFB,
SAB, and UW-CIMSS range between 45 and 55 kt, so the initial
intensity is set at 50 kt.  This estimate is also supported by a
1750 UTC ASCAT-B pass, which showed a 45-50 kt wind barb near the
center.  Jimena is in an environment of very low shear and abundant
moisture, and over sea surface temperatures near 30 degrees
Celsius, and the SHIPS Rapid Intensification (RI) index now shows
about a 50 percent chance of a 30-kt intensity change during the
next 24 hours.  Due to the very favorable conditions, RI is now
explicitly indicated in the NHC intensity forecast.  Environmental
conditions remain conducive for strengthening after 24 hours, and
Jimena is expected to be a major hurricane from 48 hours through
the end of the forecast period.  Since the statistical models seem
to have been doing a better job than the dynamical models on the
recent intensification rate, the updated NHC intensity forecast is a
blend of the previous forecast and the SHIPS and LGEM solutions.

Jimena has turned westward as expected, with an initial motion of
275/11 kt.  The cyclone remains located on the southern periphery
of a strong mid-level ridge, and this feature should continue
steering Jimena westward for the next 36 hours.  After that time, a
weakness in the ridge is expected to develop, which should cause
Jimena to turn west-northwestward through the end of the forecast
period.  The track guidance agrees on this scenario and is tightly
clustered for the entire forecast period.  The updated NHC track
forecast is close to the model consensus, and the only change from
the previous forecast is a slight southward shift during the first
48 hours.

FORECAST POSITIONS AND MAX WINDS

INIT  27/2100Z 12.4N 118.7W   50 KT  60 MPH
 12H  28/0600Z 12.5N 120.6W   65 KT  75 MPH
 24H  28/1800Z 12.5N 122.8W   80 KT  90 MPH
 36H  29/0600Z 12.6N 124.7W   95 KT 110 MPH
 48H  29/1800Z 13.0N 126.4W  105 KT 120 MPH
 72H  30/1800Z 14.3N 130.2W  120 KT 140 MPH
 96H  31/1800Z 16.0N 134.5W  120 KT 140 MPH
120H  01/1800Z 17.0N 138.0W  110 KT 125 MPH

$$
Forecaster Berg

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