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Hurricane AMANDA (Text)

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HURRICANE AMANDA DISCUSSION NUMBER  20
NWS NATIONAL HURRICANE CENTER MIAMI FL       EP012014
800 AM PDT TUE MAY 27 2014

Amanda's eye has again disappeared from the infrared and
first-light visible imagery from GOES-West this morning.  However,
microwave imagery from the TRMM and SSMI polar-orbiting satellites
still indicated a small, complete eyewall was present.  Using
a blend of final T and Dvorak current intensity estimates from TAFB
and SAB suggests an intensity of 100-105 kt, while the ADT estimate
of 125 kt appears to be too high.  The initial intensity is set at
105 kt, but this may be slightly too strong if the current
deterioration of the convective structure continues.  The initial
wind radii are primarily based upon a 0518Z ASCAT-A scatterometer
pass.

The microwave imagery fixes allow for a fairly confident assessment
of the initial position and motion of Amanda.  The hurricane is
moving toward the north-northwest - 340 degrees - at about 5 kt, due
to the steering influence of an upper- to mid-level low to its
northwest and a ridge to its northeast.  These features should
continue to slowly advect Amanda toward the north or north-northeast
for the next three days or so, before a strong northeast-southwest
oriented ridge builds north of the tropical cyclone.  That ridge,
along with a weakening Amanda being steered by the low-level flow,
should result in Amanda turning to the southwest in the latter part
of the forecast period.  The models are in generally good agreement
with this scenario, but differ some on when the turn occurs, and
thus how far to the north Amanda reaches.  On the extremes, the GFS
has Amanda getting farthest to the north at 21N while the UKMET only
has the cyclone reaching 17N before the turn occurs.  The official
forecast is a blend of the farther north TVCE variable consensus
technique and the farther south previous official forecast.

The CIMSS analysis and the GFS-based SHIPS both indicate southerly
vertical shear of about 20 kt affecting Amanda.  While the shear is
anticipated to diminish quite a bit by all of the dynamical models
in about two days, the moisture and instability should decrease
significantly at the same time.  The dynamical models very quickly
weaken Amanda, while the dynamical-statistical guidance shows more
gradual weakening.  However, it appears that the SSTs being used in
SHIPS/LGEM are biased high by about 1 degree C along the track of
Amanda, which would suggest that these statistical techniques are
somewhat too strong. The official forecast is very similar to
the IVCN variable consensus model and the previous advisory.
However, if current convective trends continue and the statistical
models do indeed turn out to be biased high, then this forecast may
be conservative in how quickly Amanda falls apart.


FORECAST POSITIONS AND MAX WINDS

INIT  27/1500Z 14.7N 112.3W  105 KT 120 MPH
 12H  28/0000Z 15.2N 112.3W   90 KT 105 MPH
 24H  28/1200Z 15.8N 111.8W   75 KT  85 MPH
 36H  29/0000Z 16.6N 111.2W   60 KT  70 MPH
 48H  29/1200Z 17.5N 110.6W   50 KT  60 MPH
 72H  30/1200Z 18.5N 110.0W   40 KT  45 MPH
 96H  31/1200Z 18.0N 110.5W   30 KT  35 MPH
120H  01/1200Z 17.5N 111.5W   25 KT  30 MPH...POST-TROP/REMNT LOW

$$
Forecaster Landsea

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