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Tropical Depression Eight-E Discussion Number 3
NWS National Hurricane Center Miami FL EP082017
800 PM PDT Tue Jul 18 2017
The depression continues to produce small bursts of deep convection,
but microwave data and the last few visible images of the day
indicate that the low-level center is exposed to the northeast of
the thunderstorm activity. Visible imagery also shows a band of
cirrus flowing right over the depression's circulation, indicative
of about 25 kt of west-northwesterly shear. Since Dvorak intensity
estimates have not changed from six hours ago, the initial intensity
is held at 30 kt for this advisory.
The big question mark for both the depression's future track and
intensity is how it will interact with Tropical Storm Greg to its
east. All the global models show the depression swinging to the
southwest and south of Greg during the next several days as the two
circulations interact. The GFS model shows Greg becoming the
dominant cyclone, with the depression eventually dissipating.
However, the ECMWF and Canadian models seem to prefer the depression
becoming the dominant system and absorbing Greg. The UKMET is
somewhere in between, with the two circulations merging. Since Greg
is the stronger of the two systems at this point, we are favoring
that being the dominant one, and the new NHC forecast shows the
depression weakening over time and dissipating by 96 hours.
However, there is a lot of uncertainty in this forecast, and
adjustments would be needed if it becomes apparent that the
depression will end up being the dominant cyclone.
The depression is moving slowly westward with an initial motion of
270/4 kt. Regardless of the cyclone's future intensity, a more
pronounced interaction looks increasingly likely, and the track
guidance has shifted southward on this forecast cycle. As a result,
the updated NHC track forecast has also been shifted south of the
previous forecast, and it lies close to the various consensus aids.
This solution is not, however, quite as far south as the HWRF, GFS,
and HCCA models.
FORECAST POSITIONS AND MAX WINDS
INIT 19/0300Z 14.8N 119.9W 30 KT 35 MPH
12H 19/1200Z 14.6N 120.5W 30 KT 35 MPH
24H 20/0000Z 14.2N 121.2W 25 KT 30 MPH
36H 20/1200Z 13.7N 122.0W 25 KT 30 MPH
48H 21/0000Z 13.2N 122.6W 25 KT 30 MPH
72H 22/0000Z 13.3N 123.5W 25 KT 30 MPH