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Tropical Storm Mario Discussion Number  13
NWS National Hurricane Center Miami FL       EP142019
900 AM MDT Fri Sep 20 2019

Microwave imagery since the last advisory indicates that Mario has
been able to maintain its low-level structure, but deep convection
is mostly displaced to the southwest of the cyclone's surface
center. This may be a sign that northeasterly shear has again
increased across Mario, at least for the moment. The intensity
estimate is still 55 kt based on Dvorak current intensity estimates
from TAFB and SAB, but objective values are lower.

Almost no change was made to the NHC intensity forecast. SHIPS
diagnostics from the GFS and ECMWF indicate that substantial
northeasterly shear will continue to affect Mario for the next
couple of days, and by the time the shear relaxes early next week,
the cyclone will have reached much cooler waters. Given that Mario
is in better shape than it was a day ago, some slight strengthening
is still shown in the short-term forecast, but only the GFS
explicitly forecasts Mario to reach hurricane strength. Nearly all
of the dynamical models forecast that Mario will lose its convection
and become a remnant low by 96 h or sooner, and this is reflected in
the NHC forecast.

The track forecast is very low confidence, evidenced by the fact
that the deterministic GFS and ECMWF are both outliers from their
respective ensembles run at the same time. In fact, both models are
outside of their associated guidance envelope and show Mario getting
very near the southern tip of the Baja California peninsula in a
couple of days. There is still considerable uncertainty as to how
much Mario and Lorena will interact during the next 2 or 3 days. The
NHC forecast continues to keep the two systems separate, showing
both systems moving generally northwestward in tandem at 48 h and
beyond. However, given the close proximity of the two cyclones, a
merger can not be ruled out. The NHC forecast has been shifted to
the right of the previous forecast, and lies near the middle of the
GFS and ECMWF ensemble envelopes. Significant changes may still be
required to the track forecast later today, and there is still a
chance that Mario could directly affect portions of the Baja
California peninsula.


FORECAST POSITIONS AND MAX WINDS

INIT  20/1500Z 17.9N 110.1W   55 KT  65 MPH
 12H  21/0000Z 18.6N 110.0W   60 KT  70 MPH
 24H  21/1200Z 19.8N 110.7W   55 KT  65 MPH
 36H  22/0000Z 21.1N 112.1W   50 KT  60 MPH
 48H  22/1200Z 22.3N 113.8W   45 KT  50 MPH
 72H  23/1200Z 25.0N 116.6W   30 KT  35 MPH
 96H  24/1200Z 26.0N 118.5W   25 KT  30 MPH...POST-TROP/REMNT LOW
120H  25/1200Z 25.0N 120.5W   20 KT  25 MPH...POST-TROP/REMNT LOW

$$
Forecaster Zelinsky

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