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Tropical Storm Roslyn Discussion Number 6
NWS National Hurricane Center Miami FL EP192022
400 AM CDT Fri Oct 21 2022
Roslyn's structure has evolved since the previous advisory. A more
distinct core of deep convection appears to be developing, and
infrared satellite images have even shown hints of an eye feature
during the past few hours. An elongated convective band now
extends around the northeastern and southeastern quadrants of the
circulation. Based on consensus Dvorak estimates of T3.5 from TAFB
and SAB, and a CI number of 3.4 from the UW-CIMSS ADT, Roslyn is
now estimated to have maximum winds of 55 kt.
Recent scatterometer data and conventional satellite images
indicate that Roslyn's center is a bit to the northeast of where it
was estimated to be last evening, and the initial motion is
west-northwestward, or 300/6 kt. The track forecast reasoning has
not changed. Roslyn is expected to recurve around the western edge
of a mid-level area of high pressure that will migrate eastward
across Mexico during the next couple of days. In 2 to 3 days,
Roslyn and its remnants are then expected to accelerate
north-northeastward in the flow ahead of an approaching deep-layer
mid-latitude trough. With the exception of the UKMET model (which
is a western outlier), there is very little cross-track spread
among the other track models, and most of the differences are in
the forward speeds after 36 hours. The biggest change in this
forecast package is that with the northeastward adjustment of
Roslyn's center, the entire official track forecast has been
shifted east of the previous prediction, and lies close to the
updated TVCE and HCCA consensus aids.
If Roslyn is indeed developing a better-defined core, environmental
conditions could support rapid intensification (RI). The SHIPS RI
indices are now showing a 50 to 60 percent chance of a 30-kt
increase in intensity over the next 24 hours, and the HWRF,
COAMPS-TC, and HCCA consensus aids are all showing RI. RI is
therefore now explicitly forecast, and Roslyn should reach
hurricane strength later today. In 36 to 48 hours, an increase in
southwesterly shear could induce some weakening, but regardless,
Roslyn is expected to reach the coast of west-central Mexico as a
hurricane. Rapid weakening is expected after landfall, and
although the official forecast shows a remnant low over northern
Mexico in 72 hours for continuity, Roslyn is likely to have
dissipated by that time.
Given the relocation of Roslyn's center and the updates to the
forecast, hurricane and tropical storm warnings are now in effect
for portions of the west-central coast of Mexico. Hurricane
watches have also been extended northward along the coast.
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 and will likely be extended
northward later today.
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 21/0900Z 16.2N 103.8W 55 KT 65 MPH
12H 21/1800Z 16.6N 104.6W 70 KT 80 MPH
24H 22/0600Z 17.4N 105.5W 85 KT 100 MPH
36H 22/1800Z 18.7N 106.2W 95 KT 110 MPH
48H 23/0600Z 20.5N 106.2W 95 KT 110 MPH
60H 23/1800Z 23.0N 105.1W 70 KT 80 MPH...INLAND
72H 24/0600Z 25.7N 103.3W 25 KT 30 MPH...POST-TROP/REMNT LOW
96H 25/0600Z...DISSIPATED
$$
Forecaster Berg
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