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Tropical Storm CHRIS


Tropical Storm Chris Discussion Number  13
NWS National Hurricane Center Miami FL       AL032018
500 PM EDT Mon Jul 09 2018

Satellite, Doppler radar, and Air Force reconnaissance aircraft data
this afternoon indicate that inner-core region of Chris has
improved in organization, and that the cyclone has strengthened
some. A peak 850-mb flight-level of 73 kt was measured in the
southwestern quadrant along with slightly rain-contaminated SFMR
surface winds of 53-59 kt. The central pressure has also decreased
to 997-996 mb. Based on these data, the intensity has been increased
to 60 kt for this advisory.

NOAA and Air Force Reserve reconnaissance fixes thus far today
indicate that Chris has essentially remained nearly stationary for
the past 9 hours. Steering should remain weak for the next 24 hours
or so due to the cyclone being trapped in a large break in the
subtropical ridge, thus little motion is expected.  However, by 36
hours and beyond, a deepening mid-latitude trough along the U.S.
Northeast and mid-Atlantic coasts is forecast to gradually lift out
Chris to the northeast, with more significant northeastward
acceleration occurring by 72 hours and beyond. Chris is expected to
move across the offshore waters of Atlantic Canada on days 4 and 5
as a powerful extratropical low, possibly passing over southeastern
Newfoundland around the 96-hour time period. The NHC model guidance
continues to show fairly significant along-track or speed
differences. As a result, the official forecast track remains close
to the consensus track models TVCN, HCCA, and FSSE.

A band of very dry mid-level air with humidity values less than 45
percent has completely encircled Chris, and the cyclone is beginning
to take on the appearance of an annular formed hurricane with a new
15-nmi-diameter, cloud-filled eye having within the central
convective cloud mass during the past couple of hours. The
well-defined inner-core wind field, in conjunction with the with
SSTs near 28 deg C and a low vertical wind shear regime, should act
to maintain inner-core convective development. The result should be
gradual strengthening over the next day or, with Chris becoming a
hurricane later tonight or Tuesday morning and reaching a peak
intensity of 80 kt by 36 hours. Gradual weakening should commence by
48 hours when the cyclone will be moving over cooler water and
southwesterly wind shear begins to increase to near 20 kt. By 72
hours and beyond, Chris will be over SSTs less than 20 deg C and
within stronger shear environment ahead of an approaching deep-layer
trough, which will induce a rapid transition to a powerful
extratropical cyclone before the system approaches Newfoundland in
about 96 hours. The extratropical low is forecast to merge with a
cold front in 96-120 hours, which should enhance the extratropical
transition process. The new NHC intensity forecast is just an update
of previous two advisories, and similar to the intensity model FSSE,
which is sightly higher than the HCCA and IVCN intensity consensus


INIT  09/2100Z 32.2N  74.4W   60 KT  70 MPH
 12H  10/0600Z 32.3N  74.3W   65 KT  75 MPH
 24H  10/1800Z 32.8N  73.6W   75 KT  85 MPH
 36H  11/0600Z 34.0N  71.9W   80 KT  90 MPH
 48H  11/1800Z 36.1N  69.0W   75 KT  85 MPH
 72H  12/1800Z 42.2N  61.5W   65 KT  75 MPH...POST-TROP/EXTRATROP
 96H  13/1800Z 48.3N  50.7W   50 KT  60 MPH...POST-TROP/EXTRATROP
120H  14/1800Z 52.0N  35.0W   35 KT  40 MPH...POST-TROP/EXTRATROP

Forecaster Stewart