Hurricane Roslyn Discussion Number 13
NWS National Hurricane Center Miami FL EP192022
900 PM MDT Sat Oct 22 2022
Roslyn remains a formidable hurricane with a symmetrical Central
Dense Overcast containing very intense, deep convection. An eye has
been occasionally evident on the enhanced IR imagery. Convective
banding features are most prevalent over the eastern and
southeastern portions of the circulation. Upper-level outflow is
well-defined over the northern semicircle of the system. The
current intensity is held at 115 kt in accordance with subjective
Dvorak CI numbers from SAB and TAFB.
The hurricane has made its expected turn to the north and the
initial motion is now near 360/10 kt. The expected steering regime
through Sunday remains about the same as before. Roslyn should move
around the western periphery of a mid-tropospheric high, and to the
east of a broad trough near the Baja California peninsula. The track
guidance is in good agreement on a north-northeastward motion with
further acceleration, bringing the system ashore over the Mexican
state of Nayarit on Sunday. The official track forecast is just
slightly to the left of, but not significantly different than, the
previous NHC prediction. This is also very close to the latest
dynamical model consensus and in between the GFS and ECMWF tracks
which have come into better agreement.
Prior to landfall, some increase in southwesterly shear over Roslyn
is predicted by the global models. Therefore, slight weakening is
possible during the next 12 hours. Nonetheless, given the conducive
thermodynamic environment including very warm ocean waters with SSTs
of 29 deg C or higher, it is expected that Roslyn will still be near
major hurricane intensity when its center crosses the coastline.
After landfall, rapid weakening will occur over the mountainous
terrain of western Mexico.
Key Messages:
1. Roslyn is forecast to be at or near major hurricane strength
when it passes near and makes landfall along the west-central coast
of Mexico tonight and Sunday, accompanied by damaging winds and a
dangerous storm surge. Preparations within the Hurricane Warning
area along the west-central coast of Mexico should be rushed to
completion.
2. Heavy rainfall could lead to flash flooding and possible
landslides in areas of rugged terrain over coastal southwestern and
west-central Mexico.
Tropical Storm Roslyn Discussion Number 4
NWS National Hurricane Center Miami FL EP192022
400 PM CDT Thu Oct 20 2022
Satellite imagery shows that Roslyn has become a little more
organized this afternoon, with the formation of a curved convective
band near the center in the eastern semicircle. The various
subjective and objective satellite intensity estimates have
increased a little since the last advisory, and the initial
intensity is increased to 40 kt in best agreement with the CIMSS
satellite consensus. It should be noted that Roslyn looks a little
sheared, with the center near the western edge of the convection
and a lot of curved low cloud lines apparent west of the
convection. It is uncertain why the cyclone looks this way since
the analyzed vertical wind shear is less than 10 kt.
The initial motion is now 280/6 kt. A mid- to upper-level ridge is
located over Mexico north and northwest of Roslyn, while a
deep-layer low pressure area is located several hundred miles
southwest of the coast of southern California. The large-scale
models forecast both of these features to move eastward, with Roslyn
expected to recurve to the north and northeast between them. While
the track guidance is in good agreement with this general scenario,
there is a significant spread in the guidance regarding how far west
the cyclone will move before recurvature. The GFS is on the right
side of the envelope, bringing the center near Cabo Corrientes in
roughly 60 h and inland over mainland Mexico thereafter. On the
other hand, the ECMWF and UKMET are about 150 n mi west of the GFS
at that time, keeping the center farther offshore and showing a
more northerly landfall point in mainland Mexico. Overall, the
guidance envelope has shifted a little to the west since the last
advisory. The new forecast track is also shifted west of the
previous track, but it lies to the east of the consensus models out
of deference to the previous forecast and the GFS.
Roslyn remains over warm sea surface temperatures in a moist,
light-shear environment. These conditions are likely to persist
for the next 60-72 h, and they should allow Roslyn to steadily
intensify. After that time, the intensity forecast becomes more
uncertain due to a forecast increase in shear, the possibility of
dry air entrainment, and the uncertainty of how much land
interaction will occur. The new intensity forecast is again
similar to the previous forecast and calls for a peak intensity of
85 kt before landfall in mainland Mexico. After landfall, rapid
weakening is expected, with the cyclone dissipating over the
mountains of Mexico between 96-120 h.
Key Messages:
1. Roslyn is forecast to become a hurricane before it passes near
or over the west-central coast of Mexico late Saturday and Sunday,
accompanied by strong winds and a potentially dangerous storm surge.
Interests along the coast of southwestern and west-central Mexico
should closely monitor the progress of this system. A tropical
storm watch has been issued for part of this area, and additional
hurricane or tropical storm watches could be required tonight or
on Friday.
2. Heavy rainfall could lead to flash flooding and possible
landslides in areas of rugged terrain over coastal southwestern
Mexico.
Tropical Storm Roslyn Discussion Number 4
NWS National Hurricane Center Miami FL EP192022
400 PM CDT Thu Oct 20 2022
Satellite imagery shows that Roslyn has become a little more
organized this afternoon, with the formation of a curved convective
band near the center in the eastern semicircle. The various
subjective and objective satellite intensity estimates have
increased a little since the last advisory, and the initial
intensity is increased to 40 kt in best agreement with the CIMSS
satellite consensus. It should be noted that Roslyn looks a little
sheared, with the center near the western edge of the convection
and a lot of curved low cloud lines apparent west of the
convection. It is uncertain why the cyclone looks this way since
the analyzed vertical wind shear is less than 10 kt.
The initial motion is now 280/6 kt. A mid- to upper-level ridge is
located over Mexico north and northwest of Roslyn, while a
deep-layer low pressure area is located several hundred miles
southwest of the coast of southern California. The large-scale
models forecast both of these features to move eastward, with Roslyn
expected to recurve to the north and northeast between them. While
the track guidance is in good agreement with this general scenario,
there is a significant spread in the guidance regarding how far west
the cyclone will move before recurvature. The GFS is on the right
side of the envelope, bringing the center near Cabo Corrientes in
roughly 60 h and inland over mainland Mexico thereafter. On the
other hand, the ECMWF and UKMET are about 150 n mi west of the GFS
at that time, keeping the center farther offshore and showing a
more northerly landfall point in mainland Mexico. Overall, the
guidance envelope has shifted a little to the west since the last
advisory. The new forecast track is also shifted west of the
previous track, but it lies to the east of the consensus models out
of deference to the previous forecast and the GFS.
Roslyn remains over warm sea surface temperatures in a moist,
light-shear environment. These conditions are likely to persist
for the next 60-72 h, and they should allow Roslyn to steadily
intensify. After that time, the intensity forecast becomes more
uncertain due to a forecast increase in shear, the possibility of
dry air entrainment, and the uncertainty of how much land
interaction will occur. The new intensity forecast is again
similar to the previous forecast and calls for a peak intensity of
85 kt before landfall in mainland Mexico. After landfall, rapid
weakening is expected, with the cyclone dissipating over the
mountains of Mexico between 96-120 h.
Key Messages:
1. Roslyn is forecast to become a hurricane before it passes near
or over the west-central coast of Mexico late Saturday and Sunday,
accompanied by strong winds and a potentially dangerous storm surge.
Interests along the coast of southwestern and west-central Mexico
should closely monitor the progress of this system. A tropical
storm watch has been issued for part of this area, and additional
hurricane or tropical storm watches could be required tonight or
on Friday.
2. Heavy rainfall could lead to flash flooding and possible
landslides in areas of rugged terrain over coastal southwestern
Mexico.
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