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Tropical Storm Lorena Discussion Number  10
NWS National Hurricane Center Miami FL       EP152019
300 PM MDT Thu Sep 19 2019

The center and structure of Lorena was extremely difficult to
determine this morning after the core of the tropical cyclone
interacted with the mountainous terrain of southwestern Mexico.
The aircraft that was scheduled to investigate Lorena had mechanical
issues and was unable to complete its mission.  Thankfully, a
fortuitous GMI microwave overpass around 1800 UTC and more recent
ASCAT data has provided some clarity on the location and structure
of the cyclone.  According to that data, the center is located just
southwest of the Islas Marias, and the ASCAT revealed peak winds of
45-50 kt.  Given the typical undersampling of the ASCAT for in
small tropical cyclones, the initial intensity is set at 60 kt,
which is between the peak scatterometer winds and the higher
satellite estimates. Since the microwave data suggests that the
inner core appears to be somewhat intact, some strengthening is
expected while the cyclone moves over warm water and remains
in a low shear environment during the next 24 hours or so.  As a
result, Lorena is forecast to be a hurricane when it pass near or
over the southern Baja peninsula.  After that time, interaction
with land is likely to cause some decrease in wind speed.

Lorena has been moving faster than expected, and the initial motion
estimate is 315/11 kt.  The cyclone should turn west-northwestward
tonight as it moves between a mid-level ridge to its northeast and
Tropical Storm Mario to the southwest.  If Lorena remains separated
from Mario (as shown by the latest ECMWF), a turn back toward the
northwest is expected as the storm moves around the southwestern
portion of the ridge.  The new NHC track forecast lies between the
HFIP corrected consensus model and the latest ECMWF.

Although there is still quite a bit of uncertainty regarding the
exact track and intensity of Lorena, the government of Mexico has
issued a Hurricane Warning for a portion of the southern Baja
California peninsula.

Key Messages:

1. Heavy rainfall will continue over portions of the Mexican states
of Michoacan, Colima, and Jalisco during the next day or so. This
rainfall may produce life-threatening flash flooding and mudslides.

2. Tropical-storm-force winds are expected to continue along a
portion of the coast of southwestern Mexico through this evening.

3. Lorena is forecast to re-strengthen into a hurricane and bring
hurricane-force winds and heavy rainfall to a portion of the
southern Baja California peninsula beginning on Friday.  A Hurricane
Warning has been issued, and preparations to protect life and
property should be rushed to completion.


FORECAST POSITIONS AND MAX WINDS

INIT  19/2100Z 21.6N 107.0W   60 KT  70 MPH
 12H  20/0600Z 22.4N 108.3W   65 KT  75 MPH
 24H  20/1800Z 22.8N 109.8W   70 KT  80 MPH
 36H  21/0600Z 23.5N 111.1W   70 KT  80 MPH
 48H  21/1800Z 24.4N 112.2W   60 KT  70 MPH
 72H  22/1800Z 27.0N 114.2W   45 KT  50 MPH
 96H  23/1800Z 29.0N 115.5W   30 KT  35 MPH...POST-TROP/REMNT LOW
120H  24/1800Z...DISSIPATED

$$
Forecaster Brown

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