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Hurricane Aletta Discussion Number  15
NWS National Hurricane Center Miami FL       EP022018
300 AM MDT Sat Jun 09 2018

Aletta's cloud pattern has continued to gradually degrade
overnight.  The eye is no longer apparent in infrared satellite
pictures and the overall cloud pattern has become less symmetric
due to the effects of southerly wind shear.  Recent microwave
imagery also shows that the southwestern portion of the inner
core has eroded and most of the convective banding is located
over the northeastern portion of the circulation. Subjective and
objective Dvorak T-numbers have decreased and a blend of the
Final-T and CI-numbers yields an initial intensity estimate of
95 kt.

Aletta should continue to weaken during the next day or two as the
vertical wind shear increases and the cyclone moves over gradually
decreasing sea surface temperatures.  These conditions are expected
to cause a rapid decrease in intensity during the next 24 to 36 h.
After that time, Aletta is forecast to move over SSTs below 26
degrees Celsius and into a less favorable thermodynamic environment,
which should result in a continued spin down and degeneration
of the system to a remnant low within 72 hours.  The intensity
guidance is in fairly good agreement and the NHC intensity forecast
is close to the ICON consensus.

The initial motion estimate remains 285/5 kt. There has been
no significant change to the track forecast reasoning since the
previous advisory.  Aletta should continue to move around the
southwestern portion of a mid-level ridge over northwestern Mexico
during the next day or so.  After Aletta weakens and becomes a more
vertically shallow system, it should turn westward, then
southwestward in the low-level trade wind flow.  The overall
guidance envelope has once again shifted southward and the updated
NHC track forecast has been moved in that direction to be closer to
the various consensus aids.

FORECAST POSITIONS AND MAX WINDS

INIT  09/0900Z 16.2N 112.7W   95 KT 110 MPH
 12H  09/1800Z 16.6N 113.5W   80 KT  90 MPH
 24H  10/0600Z 17.0N 114.6W   60 KT  70 MPH
 36H  10/1800Z 17.2N 115.6W   45 KT  50 MPH
 48H  11/0600Z 17.2N 116.9W   35 KT  40 MPH
 72H  12/0600Z 17.0N 119.1W   25 KT  30 MPH...POST-TROP/REMNT LOW
 96H  13/0600Z 16.6N 120.6W   20 KT  25 MPH...POST-TROP/REMNT LOW
120H  14/0600Z 16.0N 121.8W   20 KT  25 MPH...POST-TROP/REMNT LOW

$$
Forecaster Brown

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