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Tropical Storm Pamela Discussion Number 8
NWS National Hurricane Center Miami FL EP162021
900 PM MDT Mon Oct 11 2021
Pamela continues to be affected by some modest northwesterly
mid-level shear that has caused the low-level center to be located
near the northwestern edge of the deep convection. This was evident
in an earlier AMSR2 microwave image that arrived shortly after the
release of the previous NHC advisory package. Recent objective and
subjective Dvorak T-numbers still support an intensity of around
60 kt, and that value is maintained as the initial wind speed for
this advisory. An Air Force Reserve reconnaissance aircraft is
scheduled to fly into the storm late tomorrow morning and early
afternoon to better provide a better assessment of Pamela's
structure, intensity, and wind field.
The guidance suggests that the shear that has been plaguing Pamela
should relax during the next 12-24 hours, allowing for
strengthening. Nearly all of the statistical and dynamical model
intensity guidance calls for strengthening, but they have trended
toward a lower peak intensity primarily due to the fact that Pamela
so far has not strengthened as much as expected. The NHC intensity
forecast again calls for Pamela to become a hurricane overnight or
early Tuesday, and shows the system nearing major hurricane strength
before it reaches the coast of mainland Mexico early Wednesday.
Although the official forecast is at the high end of the intensity
guidance, it is supported by the GFS model which has been consistent
in significantly deepening Pamela during the cyclone's approach to
Mexico on Tuesday and Tuesday night. After landfall, rapid weakening
should occur as the system moves over the mountainous terrain of
west-central Mexico, and Pamela is forecast to become a
post-tropical remnant low or dissipate by Thursday.
Pamela is moving north-northwestward or 335/7 kt. The track
forecast philosophy again remains unchanged this advisory. The
cyclone is forecast to turn northward tonight as it reaches the
western portion of a deep-layer subtropical ridge. A faster
northeastward motion is expected by late Tuesday as Pamela recurves
ahead of a broad mid-latitude trough moving into northwestern
Mexico. The track guidance is in very good agreement on the overall
evolution of the steering pattern, but there are still some
differences in how quickly Pamela accelerates northeastward on
Tuesday. Therefore, the NHC forecast is once again close to the
various multi-model consensus aids.
Although the cyclone could dissipate over the mountainous 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 southwestern 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 on Tuesday and Tuesday night,
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 the remnants of 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 12/0300Z 17.9N 108.9W 60 KT 70 MPH
12H 12/1200Z 19.2N 109.1W 70 KT 80 MPH
24H 13/0000Z 21.0N 108.5W 85 KT 100 MPH
36H 13/1200Z 23.1N 106.9W 95 KT 110 MPH
48H 14/0000Z 26.1N 103.3W 40 KT 45 MPH...INLAND
60H 14/1200Z 29.5N 99.5W 25 KT 30 MPH...POST-TROP/INLAND
72H 15/0000Z...DISSIPATED
$$
Forecaster Brown
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