[Tropical] Tropical Cyclone Discussion

[EMWIN Server]

WTNT43 KNHC 242048
TCDAT3

Tropical Storm Lorenzo Discussion Number   8
NWS National Hurricane Center Miami FL       AL132019
500 PM AST Tue Sep 24 2019

Based on recent microwave imagery and visible satellite loops, it
appears that there's been just enough westerly shear over Lorenzo
to disrupt the inner core and keep the storm from strengthening
through the day.  The CDO is slightly offset from the low-level
center, and prominent convective banding is mostly within the
southeastern semicircle.  Subjective intensity estimates remain
T3.5/55 kt from TAFB and SAB, and objective numbers have come up
slightly to around 60 kt.  However, since the morning scatterometer
data was running about 10 kt lower than the satellite estimates,
and the overall structure has not changed appreciably, the initial
intensity will remain 55 kt.

A mid-level high centered west of Madeira and the Canary Islands
continues to drive Lorenzo quickly westward, or 285/15 kt.  There
has been no change to the track forecast thinking.  A break in the
ridge over the central Atlantic is expected to cause Lorenzo to
begin recurving in about 48 hours, with the system ultimately
moving northward by the end of the foreast period.  The updated NHC
forecast has only been nudged westward, but this is mainly due to
the slightly faster initial forward motion.  Otherwise, the spread
in the guidance is still bounded by the GFS on the right and the
ECMWF on the left, which is mirrored by those models' respective
ensemble members.  The official forecast hedges toward the western
side of the guidance, roughly between the HCCA model and the other
consensus aids.

Global model guidance suggests that the westerly shear over Lorenzo
should abate during the next 24 hours, allowing another
intensification phase to begin.  Whether or not rapid
intensification occurs is difficult to know at this point until it
becomes clearer if the cyclone can develop a well-defined inner
core.  The intensity guidance has decreased further on this cycle,
but this is largely due to the hiatus in the strengthening trend
during the day.  There's still plenty of time for more
strengthening to occur, so out of an abundance of caution, I did
not lower the forecast peak intensities that have been shown in the
previous few advisories.  As such, the official forecast lies above
nearly all the guidance during the first 2-3 days, and then is
close to the HWRF and HCCA on days 4 and 5.


FORECAST POSITIONS AND MAX WINDS

INIT  24/2100Z 12.8N  31.0W   55 KT  65 MPH
 12H  25/0600Z 13.2N  33.0W   65 KT  75 MPH
 24H  25/1800Z 13.8N  35.6W   75 KT  85 MPH
 36H  26/0600Z 14.5N  38.1W   85 KT 100 MPH
 48H  26/1800Z 15.6N  40.0W   90 KT 105 MPH
 72H  27/1800Z 18.8N  42.9W  100 KT 115 MPH
 96H  28/1800Z 21.9N  45.1W  105 KT 120 MPH
120H  29/1800Z 24.9N  45.3W  100 KT 115 MPH

$$
Forecaster Berg
This weather bulletin was brought to you by:
www.nashvilleweather.net