Eastern Pacific Basin Tropical Cyclones

Tropical Storm Roslyn Forecast Discussion


516 
WTPZ44 KNHC 212043
TCDEP4

Tropical Storm Roslyn Discussion Number   8
NWS National Hurricane Center Miami FL       EP192022
400 PM CDT Fri Oct 21 2022

Satellite imagery shows that Roslyn continues to gradually become 
better organized, with the center now embedded in a well-defined 
central dense overcast.  In addition, convective banding has 
increased outside of the CDO, suggesting that the dry air earlier 
seen in the circulation is mixing out.  Various subjective and 
objective satellite intensity estimates have nudged upward, so 
the initial intensity is increased to 60 kt.  The wind radii have 
been adjusted downward based on data from a recent ASCAT overpass.

The latest imagery and the scatterometer data confirm that Roslyn 
has been moving to the left of the previous forecast, and the 
initial position for this advisory is a slight re-location.  The 
initial motion is a somewhat uncertain 295/6.  Overall, there is no 
change in the track forecast philosophy, as Roslyn is still 
expected to recurve around the western edge of a mid-level ridge 
that will migrate eastward across Mexico during the next couple of 
days.  This will lead to the center passing near or a little west 
of Cabo Corrientes in about 36 h, followed by landfall in mainland 
Mexico.  However, a combination of the current westward nudge and 
an eastward shift in the track guidance results in the new forecast 
track being to the west of the previous track through 24 h and a 
little to the east of the previous track after that time.  The new 
forecast is also faster to bring the center to the coast of Mexico, 
with landfall now shown between 36-48 h.  The new forecast track 
lies near the consensus models through 24 h, and thereafter lies a 
little to the west of the consensus models.

Roslyn has a small inner core, and light vertical wind shear 
conditions are expected during the next 24-30 h.  Since the dry air 
seems to be mixing out, this should allow Roslyn to steadily to 
rapidly intensify during this time.  The rapid intensification 
indices in the SHIPS model suggest a good chance of 25-35 kt of 
strengthening during the next 24 h, and the new intensity forecast 
calls for a possibly conservative 25 kt of strengthening during 
this time.  After that time, the latest large-scale models 
forecast increasing shear, and there is uncertainty on how soon 
land interaction will occur.  Based on this, the intensity forecast 
shows a little more strengthening through 36 h, followed by rapid 
weakening after the center makes landfall.  The system should 
dissipate completely over the mountains of Mexico between 60-72 h.

The new forecast requires a northward extension of the hurricane
warnings and watches along the coast of Mexico and for the Islas 
Marias.  Additional watches and warnings could be required tonight 
and Saturday.


Key Messages:

1. Roslyn is forecast to be a hurricane when it passes near and
makes landfall along the west-central coast of Mexico late Saturday
and Sunday, accompanied by strong winds and a potentially dangerous
storm surge.  A Hurricane Warning is now in effect for a portion of
the west-central coast of Mexico.

2. Heavy rainfall could lead to flash flooding and possible
landslides in areas of rugged terrain over coastal southwestern and
west-central Mexico.


FORECAST POSITIONS AND MAX WINDS

INIT  21/2100Z 16.4N 105.0W   60 KT  70 MPH
 12H  22/0600Z 17.0N 105.8W   75 KT  85 MPH
 24H  22/1800Z 18.3N 106.3W   85 KT 100 MPH
 36H  23/0600Z 20.2N 106.1W   90 KT 105 MPH
 48H  23/1800Z 22.6N 105.0W   50 KT  60 MPH...INLAND
 60H  24/0600Z 25.7N 102.9W   25 KT  30 MPH...POST-TROP/REMNT LOW
 72H  24/1800Z...DISSIPATED

$$
Forecaster Beven




Source link