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Hurricane Pamela Discussion Number 10
NWS National Hurricane Center Miami FL EP162021
900 AM MDT Tue Oct 12 2021
Similar to this time yesterday, Pamela is undergoing an episodic
convective bursting phase. The convection is likely being modulated
by west-northwesterly mid-level shear of at least 15 kt that is
undercutting the outflow layer, plus intrusions of dry mid-level air
with humidity values near 55 percent, as analyzed in SHIPS
diagnostics. The intensity at 1200 UTC was increased to 70 kt based
on an average of subjective Dvorak satellite classifications of
T4.5/77 kt from TAFB and T4.0/65 kt from SAB, and an objective
estimate of 70 kt from UW-CIMSS ADT. An Air Force Reserve
reconnaissance aircraft is currently en route to investigate
Pamela's structure, intensity, and wind field.
Pamela is moving northward or 010/11 kt. The hurricane is now on or
just north of the east-west-oriented axis of a deep-layer
subtropical ridge situated over central Mexico. The northward
motion should continue this morning, followed by a turn toward the
northeast by this afternoon or early evening as Pamela becomes
embedded within southwesterly environmental flow ahead of a broad
mid-/upper-level trough. That large-scale feature will cause the
hurricane to accelerate tonight through Wednesday, with Pamela now
expected to reach the coast of west-central Mexico just before 1200
UTC Wednesday morning. After the hurricane moves inland early
Wednesday, Pamela, or its remnants should continue to accelerate
northeastward across central and northern Mexico and into Texas by
the end of the week. The latest NHC model guidance is tightly
packed around the previous advisory forecast track, so no
significant changes were required.
The latest GFS- and ECMWF-based SHIPS intensity models output show
that west-northwesterly 850-200-mb shear of at least 15 kt is
allegedly affecting Pamela. However, shear analyses from UW-CIMSS
indicate that the shear is less than 10 kt from the west. Once
Pamela makes the northeastward turn, the deep-layer shear vector is
forecast to back around to a southwesterly direction and become
aligned with the hurricane's forward motion, which should help to
lessen the negative effects of the vertical wind shear. Although
the mid-level moisture is expected to be somewhat austere at only
50-55 percent, Pamela will be moving over sea-surface temperatures
(SST) near 31 deg C, which is almost 1 deg C warmer than current SST
values beneath the hurricane. This expected increase in ocean heat
content, along with decreasing shear, should enhance the convective
bursting phase that Pamela will likely undergo later tonight during
the nocturnal convective maximum period, enabling the cyclone to
strengthen to near major hurricane status before landfall occurs.
The new NHC intensity forecast continues to indicate steady to
rapid strengthening, and remains above all of the available
intensity guidance. After landfall, Pamela is expected to rapidly
decay due to interaction with the mountainous terrain of Mexico,
with the cyclone ultimately dissipating over northern Mexico in 2
to 3 days. Another aircraft reconnaissance mission to investigate
Pamela is scheduled for tonight at 0530 UTC.
Although the cyclone is forecast to dissipate over the rugged
terrain of Mexico, deep moisture associated with the system's
remnants are likely to spread over north-central and northeastern
Mexico on Wednesday, and then move into portions of the
south-central United States late Wednesday or Thursday.
Key Messages:
1. Pamela is forecast to be near major hurricane intensity when it
reaches the west-central coast of Mexico on Wednesday morning, and
life-threatening storm surge and dangerous hurricane-force winds
are expected within the Hurricane Warning area. Residents in this
area should follow any advice given by local officials.
2. Pamela is expected to pass south of the southern tip of the Baja
California peninsula as a hurricane later today and tonight, and
tropical-storm conditions are possible within the Tropical Storm
Watch area.
3. Heavy rains associated with Pamela are expected to move into the
Mexican States of Sinaloa and western Durgano along with southern
portions of Baja California Sur Tuesday and Wednesday. This will
pose a threat of significant and life-threatening flash flooding and
mudslides.
4. Heavy rains associated with Pamela are expected across portions
of central Texas and southeastern Oklahoma late Wednesday and
Thursday. This may result in flash and urban flooding.
FORECAST POSITIONS AND MAX WINDS
INIT 12/1500Z 20.4N 108.9W 70 KT 80 MPH
12H 13/0000Z 21.8N 108.3W 85 KT 100 MPH
24H 13/1200Z 24.1N 106.4W 65 KT 75 MPH...INLAND
36H 14/0000Z 27.1N 103.3W 30 KT 35 MPH...INLAND
48H 14/1200Z 30.7N 99.0W 25 KT 30 MPH...POST-TROP/REMNT LOW
60H 15/0000Z...DISSIPATED INLAND
$$
Forecaster Stewart
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