Eastern Pacific Basin Tropical Cyclones

Tropical Storm Pamela Forecast Discussion


000
WTPZ41 KNHC 111513 CCA
TCDEP1

Tropical Storm Pamela Discussion Number   6...Corrected
NWS National Hurricane Center Miami FL       EP162021
900 AM MDT Mon Oct 11 2021

Corrected to update Key Messages

Pamela's convective pattern has undergone a pronounced bursting 
phase since the previous advisory, including significant lightning 
activity in the inner-core region near the center, with formation 
of a Central Dense Overcast (CDO) now evident. However, the 
lightning ceased about 5 h ago and the CDO has recently become a 
little disheveled looking along with pronounced warming of the 
cloud tops compared to the much colder cloud tops colder than -85C 
just a few hours ago. The advisory intensity has been increased to 
55 kt based on an average of satellite intensity estimates of 
T4.0/65 from TAFB, T3.0/45 kt from SAB, and T3.5/55 kt from 
UW-CIMSS ADT.

Pamela has slowed down significantly since the previous advisory, 
and the motion estimate is now northwestward or 320/07 kt. A 
northwestward motion should continue today as Pamela approaches an 
east-to-west-oriented subtropical ridge axis situated along 19-20N 
latitude. By late tonight, the storm is forecast to turn slowly 
northward, followed by a motion toward the northeast at a faster 
forward speed by Tuesday night. As Pamela gets caught up in the 
moderate southwesterly flow between the subtropical ridge to its 
south and an approaching mid-latitude trough to the northwest, the 
cyclone should continue to accelerate northeastward on Wednesday 
until Pamela makes landfall along the southwest coast of Mexico. The 
new NHC forecast track is a tad to the right of and slightly faster 
than the previous advisory track, and close to the middle of the 
tightly packed simple- and corrected-consensus track model envelope.

The recent disruption in Pamela's convective pattern has likely 
been due the cyclone having entrained a slug of dry air. However, 
this convective hiatus will likely  be short-lived due to the robust 
inner-core wind field noted in earlier ASCAT wind data, which should 
allow for Pamela to mix out any dry air. Moderate northerly shear is 
forecast to subside over the next 24 hours, giving way to the 
development of an upper-level anticyclone over the storm, along 
with an impressive outflow pattern developing in the northern 
semicircle. The combination of a tight inner-core wind field, low 
vertical shear, very warm sea-surface temperatures, and a moist 
mid-level environment should allow for Pamela to rapid intensify 
for the next 36 hours -- possibly even right up until Pamela 
reaches the coast of Mexico.  The latest official intensity 
forecast is very similar to the previous advisory, and is an average 
of the consensus intensity models IVCN and NOAA-HCCA, an remains  
at the high end of the intensity guidance. Pamela is expected to 
become a dangerous major hurricane prior to landfall.  After inland 
occurs, rapid weakening is expected as the storm moves over the 
rugged terrain of west-central Mexico. However, higher elevations 
could still receive tropical-storm force winds after Pamela moves 
well inland.

An Air Force Reserve Hurricane Hunter aircraft is scheduled to 
investigate Pamela Tuesday late morning and early afternoon.


Key Messages:

1. Pamela is forecast to be a major hurricane when it reaches the 
coast of west-central mainland Mexico on Wednesday, and 
life-threatening storm surge and dangerous hurricane-force winds are 
possible within the Hurricane Watch area.  Residents in this area 
should monitor the progress of Pamela and follow any advice given by 
local officials.

2. Pamela is expected to pass near or south of the southern tip of 
the Baja California peninsula as a hurricane Tuesday night and early 
Wednesday, 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.


FORECAST POSITIONS AND MAX WINDS

INIT  11/1500Z 16.8N 108.1W   55 KT  65 MPH
 12H  12/0000Z 17.8N 108.9W   70 KT  80 MPH
 24H  12/1200Z 19.3N 109.3W   85 KT 100 MPH
 36H  13/0000Z 21.1N 108.8W  100 KT 115 MPH
 48H  13/1200Z 23.3N 107.1W  105 KT 120 MPH
 60H  14/0000Z 25.7N 104.9W   35 KT  40 MPH...INLAND
 72H  14/1200Z 29.1N 100.8W   25 KT  30 MPH...POST-TROP/INLAND
 96H  15/1200Z...DISSIPATED

$$
Forecaster Stewart



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