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Tropical Storm Lorena Forecast Discussion

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WTPZ45 KNHC 200844

Tropical Storm Lorena Discussion Number  12
NWS National Hurricane Center Miami FL       EP152019
300 AM MDT Fri Sep 20 2019

A series of METOP-B microwave composite images reveal an improved
inner core this morning with a distinct banding eye feature and
developing outer bands in the east portion of the cyclone.  Lorena
is close to hurricane strength, and the initial intensity of 60 kt
is a compromise of the subjective and objective satellite intensity
estimates, and a SATCON analysis of 57 kt.

Lorena is expected to re-gain hurricane strength very soon as it
passes near or over the southern tip of the Baja California
peninsula.  Some further intensification is forecast before the
cyclone traverses much cooler oceanic sea surface temperatures
beyond the 36-hour period.  Lorena is expected to degenerate into a
remnant low in 3 days, however, the chances of the cyclone
interacting and becoming absorbed by Tropical Storm Mario in 48
hours or so have increased significantly.  Regardless of the
possible interaction scenario, dissipation of Lorena will occur in
less than 4 days.

The initial motion is estimated to be west-northwestward, or 290/8
kt. The cyclone is currently situated between a mid- to upper-level
tropospheric ridge over northern Mexico and larger Tropical Storm
Mario to the southwest, while a high amplitude shortwave trough,
northwest of Lorena, approaches the west coast of the United States.
The global and regional guidance has become more aligned with the
interaction with Mario in a couple of days, and has shifted
considerably toward the west away from the Baja California
peninsula.  Subsequently, a major shift of the official forecast has
been made to the left of the previous forecast, but the NHC track
still lies well to the east of the various multi-model consensus
models.  At this point, only the legacy GFS global model fails to
show binary interaction with Mario.

Wind radii adjustments were made based on 0334 UTC scatterometer

Key Messages:

1. Lorena is expected to bring heavy rainfall to the far southern
Baja California Sur today into Saturday, with flash flooding

2. Lorena is forecast to bring hurricane-force winds to a portion of
the southern Baja California peninsula today, where a Hurricane
Warning is in effect. Preparations to protect life and property
should be rushed to completion.


INIT  20/0900Z 22.3N 108.5W   60 KT  70 MPH
 12H  20/1800Z 22.5N 109.6W   65 KT  75 MPH
 24H  21/0600Z 22.7N 110.7W   70 KT  80 MPH
 36H  21/1800Z 23.1N 112.0W   65 KT  75 MPH
 48H  22/0600Z 24.1N 113.4W   55 KT  65 MPH
 72H  23/0600Z 26.4N 115.5W   30 KT  35 MPH...POST-TROP/REMNT LOW

Forecaster Roberts