Eastern Pacific Basin Tropical Cyclones

Tropical Storm Pamela Forecast Discussion


285 
WTPZ41 KNHC 102040
TCDEP1

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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