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Tropical Storm Lorenzo Discussion Number   4
NWS National Hurricane Center Miami FL       AL132019
500 PM AST Mon Sep 23 2019

Lorenzo is steadily getting better organized. Visible imagery before
sunset showed that the tropical storm has developed extensive
banding that wraps about 3/4 of the way around the circulation. An
1836 SSMIS overpass also shows this banding, but indicated that the
tropical storm has not developed a tight inner core. Satellite
intensity estimates range from 35 to 47 kt, and the intensity of the
system has been increased to 40 kt.

All indications are that Lorenzo is in a favorable environment for
strengthening, and all of the guidance continues to forecast that it
will become a hurricane during the next few days, perhaps as soon as
tomorrow. In fact, the SHIPS Rapid Intensification Index shows a
45 percent chance of a 25 kt or greater increase in Lorenzo's winds
during the next 24 hours.  Since the tropical storm doesn't have a
tight inner-core yet, the NHC forecast isn't quite as bullish, but
still shows steady strengthening, and Lorenzo could become a major
hurricane later this week.

The tropical storm is moving steadily westward with an initial
motion of 275/14. The new NHC track forecast is essentially just an
update of the previous one, and no substantial changes were made.
Lorenzo will likely move generally westward to west-northwestward at
a similar forward speed for the next few days, before turning
northwestward over the weekend. The global models are in very good
agreement on this scenario, but do differ on how soon Lorenzo will
turn northwestward. The NHC forecast is based primarily on HCCA, and
is on the left side of the guidance envelope. This is also closer to
the ECMWF and UKMET forecasts which delay the start of Lorenzo's
recurvature a little more than the GFS and its derived models.

FORECAST POSITIONS AND MAX WINDS

INIT  23/2100Z 11.3N  25.5W   40 KT  45 MPH
 12H  24/0600Z 11.7N  27.5W   50 KT  60 MPH
 24H  24/1800Z 12.4N  30.2W   60 KT  70 MPH
 36H  25/0600Z 13.1N  33.0W   70 KT  80 MPH
 48H  25/1800Z 13.6N  35.7W   75 KT  85 MPH
 72H  26/1800Z 15.4N  40.7W   85 KT 100 MPH
 96H  27/1800Z 18.3N  43.8W   95 KT 110 MPH
120H  28/1800Z 21.5N  46.5W  100 KT 115 MPH

$$
Forecaster Zelinsky

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