1 Oct Mon 2018

LESLIE STRENGTHENS WHILE MEANDERING OVER THE CENTRAL ATLANTIC

Tropical Storm Leslie Discussion Number 20
NWS National Hurricane Center Miami FL AL132018
500 AM AST Mon Oct 01 2018

Leslie has become a little better organized overnight, with an
increase in convective banding over the northern and northwestern
portions of the circulation. ASCAT data around 0000 UTC revealed
40-45 kt winds over the northeastern quadrant of the cyclone and
with the increase in organization since that time, the initial
intensity has been raised to 50 kt. This is a little above the
consensus Dvorak intensity estimates of T3.0 (45 kt) from TAFB and
SAB. The shear that was affecting Leslie appears to have abated
somewhat and with the system forecast to move southwestward toward
slightly warmer waters, gradual strengthening is expected during the
next couple of days. Later in the period, Leslie is forecast to
move north-northeastward back over its previous track where cooler
upwelled waters are likely to produce some weakening. The updated
NHC intensity forecast shows a slightly higher peak intensity in 48
to 72 hours, but remains between the dynamical model guidance and
the higher statistical models.

Leslie continues to plod along with an initial motion estimate of
240/4 kt. The cyclone should move slowly southwestward to southward
during the next couple of days as it remains within an area of weak
steering currents. After that time, a shortwave trough to the
northwest of Leslie is expected to allow the tropical cyclone to
lift slowly north-northeastward by days 4 and 5. Although the
dynamical model guidance is in agreement on this overall scenario,
there is increasing cross-track (east-west) spread after 72 hours.
The latest run of the ECMWF has shifted westward and brackets the
western edge of the guidance envelope. The new NHC track forecast
has been shifted in that direction, but it is not as far left as the
various consensus aids out of respect of the previous track
forecast. Regardless of the details of the forecast track, Leslie
is still expected to meander over the central Atlantic through the
remainder of this week.

Large swells generated by Leslie when it was a strong extratropical
low will continue to affect portions of the southeastern coast of
the United States, Bermuda, the Bahamas, and most of the Greater and
Lesser Antilles for another day or two. These swells could cause
life-threatening surf and rip currents. Although the swells will
diminish some by mid-week, they will likely remain hazardous for the
same locations through the forecast period due to Leslie’s slow
motion.

FORECAST POSITIONS AND MAX WINDS

INIT 01/0900Z 33.4N 53.9W 50 KT 60 MPH
12H 01/1800Z 33.1N 54.5W 55 KT 65 MPH
24H 02/0600Z 32.2N 55.3W 60 KT 70 MPH
36H 02/1800Z 31.2N 55.8W 65 KT 75 MPH
48H 03/0600Z 30.6N 56.0W 70 KT 80 MPH
72H 04/0600Z 31.7N 55.2W 70 KT 80 MPH
96H 05/0600Z 35.0N 54.3W 65 KT 75 MPH
120H 06/0600Z 37.4N 52.0W 60 KT 70 MPH

$$
Forecaster Brown