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Tropical Storm LORENZO


Tropical Storm Lorenzo Discussion Number   7
NWS National Hurricane Center Miami FL       AL132019
1100 AM AST Tue Sep 24 2019

Lorenzo's structure has not changed much during the morning.  A
small central dense overcast continues over the center with
multiple curved bands within the circulation.  A recent ASCAT pass
showed winds just over 45 kt to the north of the center, but given
sampling considerations, the initial intensity remains 55 kt, which
matches Dvorak classifications provided by TAFB and SAB.

Despite the brief interruption in the strengthening trend,
sufficiently warm waters, low shear, and an ambient moist air mass
should foster intensification during the next several days.
Because Lorenzo has not strengthened further since the previous
advisory, the persistence factor has caused the Rapid
Intensification (RI) Index (a 25-kt increase in 24 hours) to drop
from 53 percent to 23 percent.  In addition, the overall guidance
envelope is showing slightly lower peak intensities in 3-4 days.
The NHC intensity forecast remains near the upper edge of the
guidance for much of the forecast period, lying closest to the HWRF
and the Florida State Superensemble.  RI is still a possibility, but
as of yet we have not observed a low-level cyan ring in 37-GHz
microwave imagery, which is usually a harbinger of an RI episode.

The initial motion remains west-northwestward, or 285/14 kt.
Lorenzo is located to the south of a mid-level ridge which extends
from Morocco and Madeira Island westward to 40W.  Ridging is
relatively non-existent west of 40W due to a mid-/upper-level low
over the central Atlantic and Tropical Storm Jerry over the western
Atlantic.  With this pattern in place, Lorenzo is expected begin
recurving around the ridge axis over the central Atlantic on days
3-5.  During that period, the track guidance envelope is bracketed
by the easternmost GFS and westernmost ECMWF models, which are
about 350 nm apart on day 5.  This spread isn't too significant,
and the updated NHC track forecast is only shifted slightly
eastward from the previous one, very close to the two corrected
consensus aids.


INIT  24/1500Z 12.4N  29.3W   55 KT  65 MPH
 12H  25/0000Z 12.9N  31.3W   65 KT  75 MPH
 24H  25/1200Z 13.6N  34.0W   75 KT  85 MPH
 36H  26/0000Z 14.2N  36.6W   85 KT 100 MPH
 48H  26/1200Z 15.0N  38.8W   95 KT 110 MPH
 72H  27/1200Z 18.0N  41.9W  100 KT 115 MPH
 96H  28/1200Z 21.1N  44.3W  105 KT 120 MPH
120H  29/1200Z 23.9N  45.3W  100 KT 115 MPH

Forecaster Berg