ZCZC MIATCDEP1 ALL
TTAA00 KNHC DDHHMM
Tropical Storm Pamela Discussion Number 7
NWS National Hurricane Center Miami FL EP162021
300 PM MDT Mon Oct 11 2021
Entrainment of dry mid-level air along with some modest
north-northwesterly mid-level shear has caused Pamela's low-level
circulation to become slightly exposed just northwest of the
somewhat ragged inner-core convection. Upper-level outflow, however,
has improved in all quadrants, with a narrow equatorward outflow
channel having developed in the eastern semicircle since the
previous advisory. Pamela's intensity was increased to 60 kt at
1800 UTC based on satellite current-intensity estimates of T4.0/65
kt from TAFB and T3.7/59 kt from UW-CIMSS ADT. However, 60 kt might
be a little generous at the 2100 UTC advisory time, given that the
low-level center has recently become partially exposed.
The motion estimate is northwestward or 320/06 kt. There is no
significant change to the previous forecast track or reasoning. This
current slow northwestward motion should continue this afternoon and
evening as Pamela approaches the western periphery of a deep-layer
subtropical ridge. Later tonight, the cyclone is expected to turn
slowly northward, followed by a faster northeastward motion by
Tuesday night as Pamela gets caught up in moderate southwesterly
flow ahead of a deep-layer mid-latitude trough approaching from the
northwest and west. This developing flow pattern is depicted quite
well by all of the global and regional models, and should result in
Pamela accelerating northeastward on Wednesday right up until the
storm makes landfall along the west-central coast of Mexico. The new
NHC forecast track has been shifted a little to the right again,
and is close to the middle of the tightly packed TCVE, GFEX,
NOAA-HCCA, and FSSE consensus track-model envelope.
The global and regional models are in very good agreement that the
current slight southeastward tilt to the vortex column should abate
within the next 6 hours or so, along with the dry mid-level air
mixing out. As a result, deep convection should re-fire near the
center later tonight, resulting in the development of an eyewall,
which will create the necessary chimney effect to allow Pamela to
resume its earlier rapid intensification trend. In fact, all of the
models now show strengthening right up until the cyclone makes
landfall on Wednesday due to the upper-level outflow pattern
expanding, along with the development of poleward and equatorward
outflow channels by late Tuesday. The new official intensity
forecast is basically the same as the previous advisory, and lies
near the upper-end of the intensity guidance. Pamela is still
expected to become a dangerous major hurricane prior to landfall.
After landfall occurs, rapid weakening is forecast due to the
cyclone moving over the rugged terrain of west-central Mexico.
However, the higher elevations of north-central Mexico could still
receive tropical-storm force winds after Pamela moves well inland.
Furthermore, deep moisture associated with Pamela will gradually
overspread much of north-central and northeastern Mexico late on
Wednesday, and then move into southern and central Texas on
Thursday, enhancing the rainfall potential in those areas.
An Air Force Reserve Hurricane Hunter aircraft is scheduled to
investigate Pamela on Tuesday during the late morning and early
afternoon to provide a better estimate of the cyclone's intensity.
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.
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 11/2100Z 17.2N 108.5W 60 KT 70 MPH
12H 12/0600Z 18.3N 109.0W 70 KT 80 MPH
24H 12/1800Z 20.0N 108.9W 85 KT 100 MPH
36H 13/0600Z 22.0N 107.8W 100 KT 115 MPH
48H 13/1800Z 24.3N 105.8W 45 KT 50 MPH...INLAND
60H 14/0600Z 27.4N 102.1W 30 KT 35 MPH...POST-TROP/INLAND
72H 14/1800Z 31.2N 97.7W 20 KT 25 MPH...POST-TROP/INLAND
96H 15/1800Z...DISSIPATED INLAND
$$
Forecaster Stewart
NNNN