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Tropical Storm CHRIS


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Tropical Storm Chris Discussion Number  15
NWS National Hurricane Center Miami FL       AL032018
500 AM EDT Tue Jul 10 2018

The satellite presentation of Chris has improved overnight with an
increase in convective banding and the recent development of a
banding eye.  An earlier NOAA and an overnight Air Force Reserve
aircraft have noted the presence of a ragged 25 n mi wide eye, which
can also be seen in NWS WSR-88D radar imagery from Morehead City,
North Carolina.  Despite the increase in organization the Air Force
aircraft did not find winds to support hurricane strength.  In
fact, the plane only measured peak 850 mb flight level winds of 66
kt and SFMR winds of around 50 kt.  However, there is likely some
undersampling as the plane only made one pass through each quadrant.
Therefore the initial remains 60 kt, which is compromise between
the most recent satellite estimates and the lower reconnaissance
data.  The aircraft did report that the pressure has fallen to 993
mb.

Recent satellite and aircraft fixes suggest that Chris may be
beginning its much anticipated northeastward motion, albeit very
slow at the moment.  A large mid-latitude trough is forecast to drop
southeastward over eastern Canada and the northeastern United States
which should begin to steer Chris on a faster northeastward heading
over the next day or so.  As the trough deepens, Chris should
accelerate further as it becomes embedded within deep-layer
southwesterly flow ahead of the trough.  Chris is forecast to pass
well southeast of Nova Scotia in a couple of days, then move near
or over southeastern Newfoundland in about 72 hours.  The track
guidance remains in good agreement on this scenario, but some
speed differences remain.  The updated NHC track forecast is
similar to the previous advisory and lies between the slower ECMWF
and the various consensus aids.

As Chris begins to move northeastward, it will be leaving the area
of upwelled cooler waters and traversing warm SSTs during the
next 24 to 36 h.  This should result in strengthening and Chris is
expected to become a hurricane later today.  By 48 h, Chris will be
moving over colder waters north of the Gulf Stream and begin
interacting with a frontal system.  Extratropical transition is
expected to be complete in about 60-72 h, and the extratropical low
is forecast to gradually weaken after passing Newfoundland.  The
new NHC intensity forecast is closest to the Florida State
Superensemble, which is a little higher than the statistical
guidance.

FORECAST POSITIONS AND MAX WINDS

INIT  10/0900Z 32.6N  73.9W   60 KT  70 MPH
 12H  10/1800Z 33.1N  73.2W   70 KT  80 MPH
 24H  11/0600Z 34.4N  71.4W   75 KT  85 MPH
 36H  11/1800Z 36.5N  68.2W   80 KT  90 MPH
 48H  12/0600Z 39.7N  64.0W   75 KT  85 MPH
 72H  13/0600Z 46.5N  53.3W   60 KT  70 MPH...POST-TROP/EXTRATROP
 96H  14/0600Z 50.7N  38.5W   40 KT  45 MPH...POST-TROP/EXTRATROP
120H  15/0600Z 53.0N  23.0W   35 KT  40 MPH...POST-TROP/EXTRATROP

$$
Forecaster Brown

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