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Tropical Depression GREG


Tropical Depression Greg Discussion Number  35
NWS National Hurricane Center Miami FL       EP072017
800 PM PDT Tue Jul 25 2017

A new burst of convection has developed over the western side of
the circulation of Greg during the past couple of hours, helping to
maintain the system as a 30-kt depression. The current convection is
expected to be relatively short lived, however, as southerly shear
should increase over the cyclone due to a sharp upper-level shear
axis located to its southwest. At the same time, the cyclone will
continue to move into a drier and more stable airmass, and over
increasingly cooler waters. Over the next 24 hours, the shear is
expected to increase even further and turn out of the northwest.
This will induce further weakening, and organized deep convection
is expected to be sheared away from the system's circulation by
Wednesday night. Therefore, the NHC forecast calls for Greg to
degenerate into a remnant low by that time, but it could occur
sooner. The remnant low is then likely to open up into a trough by
day 4 or 5.

Greg has been moving northwestward at 310/12 kt. The forecast track
reasoning remains the same as the previous forecast, as low- to
mid-level troughing north of the depression should maintain a
northwestward or west-northwestward motion for the next 24 hours or
so. After that time, the remnant low should turn westward and then
west-southwestward, embedded in the low-level trade winds forced by
surface high pressure to the north. Model guidance is tightly
clustered through 36 hours, but then begins to spread a little,
likely due to differences in the strength of the low-level ridge.
The latest NHC track is near the GFS/ECMWF consensus.


INIT  26/0300Z 17.2N 138.8W   30 KT  35 MPH
 12H  26/1200Z 17.8N 139.7W   30 KT  35 MPH
 24H  27/0000Z 18.2N 141.2W   25 KT  30 MPH...POST-TROP/REMNT LOW
 36H  27/1200Z 18.3N 143.0W   25 KT  30 MPH...POST-TROP/REMNT LOW
 48H  28/0000Z 18.0N 144.7W   25 KT  30 MPH...POST-TROP/REMNT LOW
 72H  29/0000Z 17.0N 147.6W   20 KT  25 MPH...POST-TROP/REMNT LOW
 96H  30/0000Z 16.0N 150.5W   20 KT  25 MPH...POST-TROP/REMNT LOW
120H  31/0000Z...DISSIPATED

Forecaster Latto/Cangialosi