Eastern Pacific Basin Tropical Cyclones

Tropical Storm Pamela Forecast Discussion


435 
WTPZ41 KNHC 120237
TCDEP1

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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