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Hurricane Chris Discussion Number  22
NWS National Hurricane Center Miami FL       AL032018
1100 PM AST Wed Jul 11 2018

Chris is quickly unraveling, with its eye completely disintegrating
a few hours ago and the convective pattern showing the hallmarks of
the onset of extratropical transition.  Earlier microwave data
actually showed that the hurricane had a concentric eyewall
structure, but the mid-level eye was already being stripped away
from the low-level center due to increasing southwesterly shear.
Chris's initial intensity is set at 75 kt based on a blend of
final T- and CI-numbers from TAFB and SAB.

The hurricane is accelerating toward the northeast with an initial
motion of 050/25 kt, and the acceleration is expected to continue
for the next 48 hours while the cyclone moves ahead of a deep-layer
trough located over eastern Canada.  After 48 hours, Chris is
forecast to slow down to the south of Iceland when it interacts
with another deep-layer low.  The track guidance is tightly
clustered very close to the previous official forecast during
the first 72 hours, with only a little more model spread and
deviation from the previous forecast at 96 hours.  Therefore, the
only change to the updated NHC track forecast is to slow down the
storm a little on day 4 while it's located south of Iceland.  Chris
may still exist on day 5, but there's too much uncertainty among
the models to extend the official forecast at this point.

Chris is currently moving over a few warm eddies along the Gulf
Stream, but the hurricane's center will move across the North Wall
within the next 6 hours and head toward much colder waters.
Vertical shear will also be increasing further over the next 24
hours, and Chris is expected to be fully embedded within a frontal
zone within 18-24 hours.  The NHC official forecast calls for Chris
to complete extratropical transition just before the center reaches
extreme southeastern Newfoundland within 24 hours, and the cyclone's
intensity should gradually decrease while it moves across the North
Atlantic.  The intensity forecast is close to the tropical model
guidance for the first 12-24 hours but then sides closer to the GFS
and ECMWF guidance during the remainder of the forecast.

Chris's wind radii have been adjusted slightly based on a 0034 UTC
ASCAT pass.

FORECAST POSITIONS AND MAX WINDS

INIT  12/0300Z 39.6N  63.0W   75 KT  85 MPH
 12H  12/1200Z 42.6N  59.2W   65 KT  75 MPH
 24H  13/0000Z 46.9N  52.9W   55 KT  65 MPH...POST-TROP/EXTRATROP
 36H  13/1200Z 50.2N  44.8W   45 KT  50 MPH...POST-TROP/EXTRATROP
 48H  14/0000Z 53.1N  35.0W   40 KT  45 MPH...POST-TROP/EXTRATROP
 72H  15/0000Z 59.6N  21.0W   35 KT  40 MPH...POST-TROP/EXTRATROP
 96H  16/0000Z 62.0N  15.0W   30 KT  35 MPH...POST-TROP/EXTRATROP
120H  17/0000Z...DISSIPATED

$$
Forecaster Berg

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