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Tropical Storm Lorena Discussion Number  11
NWS National Hurricane Center Miami FL       EP152019
900 PM MDT Thu Sep 19 2019

Geostationary satellite data and a recently received SSM/IS overpass
suggest that Lorena has gotten a little better organized since the
last advisory, with a central dense overcast forming near or over a
small mid-level eye seen in the microwave data.  However, the
various objective and subjective satellite intensity estimates
indicate that the cyclone has not yet regained hurricane strength.
The initial intensity is thus held at 60 kt.

The initial motion is a somewhat uncertain 305/9.  Lorena is
located between a mid- to upper-level ridge over northern Mexico
and Tropical Storm Mario to the south-southwest, while a large
mid- to upper-level trough is northwest of Lorena over the western
United States and the northeastern Pacific.  The potential for
Lorena to interact with Mario is producing a large spread in the
guidance and a low confidence track forecast.  Much of the track
guidance, including the GFS, HWRF, HMON, and the GFS ensemble mean
show Lorena turning so sharply westward around the north side of
Mario that it passes south of the Baja California peninsula.  At
the other extreme is the older version of the GFS, which forecasts
Lorena to moved northwestward up the Gulf of California due mainly
to the influence of the Mexican ridge and the U. S. trough.  The
ECMWF model forecasts a track generally over the Baja California
peninsula, while the UKMET shows a track into the southern Gulf of
California followed by a westward turn across southern Baja.  The
new forecast track is similar to the previous track in forecasting
Lorena to pass near the southern end of the Baja California
peninsula, then move generally northwestward near the west coast of
the peninsula.  The new track lies well to the right of the various
consensus models, but it lies to the left of the ECWMF and the old
GFS model.  Adjustments to the forecast track may occur once the
amount of influence Mario will have on Lorena become more apparent.

The intensity forecast is also very uncertain due to the track
forecast uncertainties.  The new intensity forecast is based on the
track forecast that keeps Lorena over the water near the west coast
of the the Baja California peninsula, with the cyclone re-gaining
hurricane status before it moves over colder sea surface
temperatures and eventually dissipates over the cold water.
However there are three alternate scenarios.  First, the GFS
suggests the possibility that Mario will absorb Lorena and cause it
to completely dissipate.  Second, the older version of the GFS, with
its forecast over the warm waters of the Gulf of California, would
could allow Lorena to be stronger than currently forecast.  Finally,
the ECMWF's track over the Baja California Peninsula would also
cause Lorena to weaken faster than currently forecast.

The forecast track requires new warnings and watches for portions
of Baja California del Sur.  Additional warnings and watches may be
required for this area on Friday.


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. 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  20/0300Z 22.3N 107.7W   60 KT  70 MPH
 12H  20/1200Z 22.6N 108.8W   65 KT  75 MPH
 24H  21/0000Z 23.1N 110.2W   70 KT  80 MPH
 36H  21/1200Z 23.9N 111.4W   70 KT  80 MPH
 48H  22/0000Z 24.8N 112.5W   60 KT  70 MPH
 72H  23/0000Z 27.5N 114.8W   35 KT  40 MPH
 96H  24/0000Z 29.5N 116.0W   25 KT  30 MPH...POST-TROP/REMNT LOW
120H  25/0000Z...DISSIPATED

$$
Forecaster Beven

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