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Tropical Storm Octave Discussion Number   4
NWS National Hurricane Center Miami FL       EP182019
800 AM PDT Fri Oct 18 2019

A 0941 UTC GCOM microwave overpass was instrumental in showing that
Octave's center is located to the east of the main convective mass,
and also well to the east of a more notable mid-level circulation.
Cloud tops have warmed during the past few hours, but the initial
intensity is being held at 40 kt based on ASCAT data from overnight.

The microwave data and recent conventional imagery show that Octave
is at least partially separating from the Intertropical Convergence
Zone (ITCZ).  The initial motion estimate is now slowly northward,
or 360/2 kt.  Any additional northward progress is likely to be
hindered in 24-36 hours due to the push of low-level northerly winds
in the wake of a trough which is dropping southward over the
Pacific.  After that push, there is some difference between the
models on whether Octave moves eastward or westward, so the NHC
forecast continues to show a meandering or slow looping motion
during the 5-day forecast period.

With Octave now moving out of the ITCZ, low-level dry air to the
west is wrapping into the cyclone's circulation, which is likely
causing the recent waning of convection.  SHIPS model diagnostics
indicate that mid-level relative humidity is currently 40-50
percent, and these values are expected to decrease to 30 percent or
lower in about 48 hours.  This decrease in moisture will also
coincide with an increase in southeasterly shear, and both factors
will likely contribute to a decrease in intensity--and a loss of
tropical cyclone status--during the next couple of days.  The new
NHC forecast closely follows the IVCN and HCCA aids and shows
weakening during the next day or two, with Octave likely to
degenerate into a remnant low within 48 hours.  The low is expected
to linger for several more days after that, but the environment
does not appear conducive for regeneration into a tropical cyclone.

FORECAST POSITIONS AND MAX WINDS

INIT  18/1500Z 10.6N 126.6W   40 KT  45 MPH
 12H  19/0000Z 11.1N 126.5W   40 KT  45 MPH
 24H  19/1200Z 11.6N 126.3W   35 KT  40 MPH
 36H  20/0000Z 11.6N 125.9W   30 KT  35 MPH
 48H  20/1200Z 11.2N 125.9W   30 KT  35 MPH...POST-TROP/REMNT LOW
 72H  21/1200Z 11.0N 126.4W   25 KT  30 MPH...POST-TROP/REMNT LOW
 96H  22/1200Z 11.5N 126.7W   25 KT  30 MPH...POST-TROP/REMNT LOW
120H  23/1200Z 12.5N 127.0W   25 KT  30 MPH...POST-TROP/REMNT LOW

$$
Forecaster Berg

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