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Tropical Storm Pamela Discussion Number 3
NWS National Hurricane Center Miami FL EP162021
400 PM CDT Sun Oct 10 2021
The cyclone has strengthened since last night, with deep convection
persisting over the system's low-level center for much of the
morning. Over the past few hours, there has been evidence of some
northeasterly shear impacting the cyclone, and the center has become
partially exposed. Despite this shear, a 1528 UTC scatterometer
overpass revealed an area of 35 to 38-kt winds in the northeastern
quadrant. Therefore, the depression has been upgraded to 40-kt
Tropical Storm Pamela.
Pamela is moving west-northwestward, or 290/13 kt to the south of a
strong mid-tropospheric ridge. A weakness is forecast to develop in
the ridge early this week as a mid- to upper-level trough digs
southward over the western United States and northern Mexico. The
cyclone is forecast to slow its forward motion and turn northwest,
and then north into this weakness late Monday through Tuesday.
By Tuesday night, Pamela should begin to get caught in the
southwesterly flow between the ridge and trough and turn
northeastward. The track model guidance continues to be in very
good agreement on this scenario and the latest NHC forecast track
is nearly unchanged from the previous one. Based on the forecast
track, the center of the cyclone should pass near or south of the
southern tip of the Baja California peninsula Tuesday night or
early Wednesday, then reach the coast of west-central mainland
Mexico by late Wednesday.
The current northeasterly wind shear is about 10-15 kt based on the
most recent UW-CIMMS analysis, and this is also recognized by both
the EC and GFS-SHIPS guidance. This magnitude of shear is forecast
to persist for the next 18-24 h before subsiding to under 10 kt by
36 h. Pamela will be passing over very warm waters near 30 C until
it reaches the coast of Mexico while embedded in a moist
atmospheric environment. Therefore, despite the shear, steady
strengthening is expected, and a faster rate of intensification is
possible after 36 h. The latest NHC intensity forecast is close to
the IVCN consensus solution, but is slightly below the HFIP
corrected consensus HCCA, which indicates that Pamela could become a
major hurricane prior to landfall along the coast of mainland
Mexico.
Key Messages:
1. Pamela is forecast to be at or near major hurricane intensity
when it reaches the coast of west-central mainland Mexico by late
Wednesday, and could bring life-threatening storm surge, flash
flooding, and dangerous winds to a portion of that area. Residents
in this area should monitor the progress of this system and ensure
they have their hurricane plan in place.
2. Pamela is expected to pass near or south of the southern tip of
the Baja California peninsula as a hurricane Tuesday night or
early Wednesday, and could bring strong winds and heavy rainfall to
the extreme southern portion of the peninsula. Watches could be
required for portions of this area tonight or early Monday.
FORECAST POSITIONS AND MAX WINDS
INIT 10/2100Z 15.5N 105.9W 40 KT 45 MPH
12H 11/0600Z 16.0N 107.4W 50 KT 60 MPH
24H 11/1800Z 16.9N 108.8W 60 KT 70 MPH
36H 12/0600Z 18.1N 109.7W 70 KT 80 MPH
48H 12/1800Z 19.6N 109.9W 80 KT 90 MPH
60H 13/0600Z 21.2N 109.3W 90 KT 105 MPH
72H 13/1800Z 23.3N 108.0W 95 KT 110 MPH
96H 14/1800Z 28.1N 103.1W 25 KT 30 MPH...POST-TROP/INLAND
120H 15/1800Z...DISSIPATED
$$
Forecaster Latto
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