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HURRICANE DOLORES DISCUSSION NUMBER  20
NWS NATIONAL HURRICANE CENTER MIAMI FL       EP052015
300 AM MDT THU JUL 16 2015

Enhanced B-D curve infrared and microwave imagery show that Dolores
is exhibiting annular hurricane characteristics this morning, with
its distinctly symmetric, thick eyewall donut-shaped appearance,
large 30 nmi eye, and a lack of well-defined rainbands.  Decreasing
26-28C sea surface temperatures and light southeasterly shear appear
to be promoting Dolores' cloud pattern.  For this advisory, the
initial intensity is held at 100 kt based on a blend of subjective
and objective satellite intensity estimates.  Because of Dolores'
annular structure, only slight weakening is expected through the
36 hour period.  Afterward, a sharp decrease in SSTs, a more stable
thermodynamic environment, and increasing vertical shear should
cause the cyclone to weaken more quickly.

After smoothing out the trochoidal oscillations, the long-term
motion is estimated to be 300/6.  There is no significant change to
the track forecast philosophy.  Dolores should continue to be
steered by the flow produced by the building subtropical ridge and
move on a west-northwestward to an eventual northwestward heading
around the western periphery of the anticyclone.  Much uncertainty
and large spread exists in the guidance suite beyond 72 hours.
Global and hurricane models either show a turn toward the
west-northwest in response to the building ridge or, a northwest to
north-northwest track due to a mid- to upper-level trough
approaching from the northwest.  The NHC forecast basically splits
these two solutions and follows the GFEX and TVCN multi-models, and
is a little to the right of the previous advisory.

FORECAST POSITIONS AND MAX WINDS

INIT  16/0900Z 19.5N 111.4W  100 KT 115 MPH
 12H  16/1800Z 20.0N 112.4W   95 KT 110 MPH
 24H  17/0600Z 20.6N 113.9W   90 KT 105 MPH
 36H  17/1800Z 21.0N 115.6W   80 KT  90 MPH
 48H  18/0600Z 21.6N 117.1W   65 KT  75 MPH
 72H  19/0600Z 24.5N 120.1W   45 KT  50 MPH
 96H  20/0600Z 28.0N 122.5W   35 KT  40 MPH
120H  21/0600Z 30.5N 124.0W   30 KT  35 MPH...POST-TROP/REMNT LOW

$$
Forecaster Roberts

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