000 WTPZ41 KNHC 121442 TCDEP1 Hurricane Pamela Discussion Number 10 NWS National Hurricane Center Miami FL EP162021 900 AM MDT Tue Oct 12 2021 Similar to this time yesterday, Pamela is undergoing an episodic convective bursting phase. The convection is likely being modulated by west-northwesterly mid-level shear of at least 15 kt that is undercutting the outflow layer, plus intrusions of dry mid-level air with humidity values near 55 percent, as analyzed in SHIPS diagnostics. The intensity at 1200 UTC was increased to 70 kt based on an average of subjective Dvorak satellite classifications of T4.5/77 kt from TAFB and T4.0/65 kt from SAB, and an objective estimate of 70 kt from UW-CIMSS ADT. An Air Force Reserve reconnaissance aircraft is currently en route to investigate Pamela's structure, intensity, and wind field. Pamela is moving northward or 010/11 kt. The hurricane is now on or just north of the east-west-oriented axis of a deep-layer subtropical ridge situated over central Mexico. The northward motion should continue this morning, followed by a turn toward the northeast by this afternoon or early evening as Pamela becomes embedded within southwesterly environmental flow ahead of a broad mid-/upper-level trough. That large-scale feature will cause the hurricane to accelerate tonight through Wednesday, with Pamela now expected to reach the coast of west-central Mexico just before 1200 UTC Wednesday morning. After the hurricane moves inland early Wednesday, Pamela, or its remnants should continue to accelerate northeastward across central and northern Mexico and into Texas by the end of the week. The latest NHC model guidance is tightly packed around the previous advisory forecast track, so no significant changes were required. The latest GFS- and ECMWF-based SHIPS intensity models output show that west-northwesterly 850-200-mb shear of at least 15 kt is allegedly affecting Pamela. However, shear analyses from UW-CIMSS indicate that the shear is less than 10 kt from the west. Once Pamela makes the northeastward turn, the deep-layer shear vector is forecast to back around to a southwesterly direction and become aligned with the hurricane's forward motion, which should help to lessen the negative effects of the vertical wind shear. Although the mid-level moisture is expected to be somewhat austere at only 50-55 percent, Pamela will be moving over sea-surface temperatures (SST) near 31 deg C, which is almost 1 deg C warmer than current SST values beneath the hurricane. This expected increase in ocean heat content, along with decreasing shear, should enhance the convective bursting phase that Pamela will likely undergo later tonight during the nocturnal convective maximum period, enabling the cyclone to strengthen to near major hurricane status before landfall occurs. The new NHC intensity forecast continues to indicate steady to rapid strengthening, and remains above all of the available intensity guidance. After landfall, Pamela is expected to rapidly decay due to interaction with the mountainous terrain of Mexico, with the cyclone ultimately dissipating over northern Mexico in 2 to 3 days. Another aircraft reconnaissance mission to investigate Pamela is scheduled for tonight at 0530 UTC. Although the cyclone is forecast to dissipate over the rugged 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 west-central 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 later today and tonight, 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 12/1500Z 20.4N 108.9W 70 KT 80 MPH 12H 13/0000Z 21.8N 108.3W 85 KT 100 MPH 24H 13/1200Z 24.1N 106.4W 65 KT 75 MPH...INLAND 36H 14/0000Z 27.1N 103.3W 30 KT 35 MPH...INLAND 48H 14/1200Z 30.7N 99.0W 25 KT 30 MPH...POST-TROP/REMNT LOW 60H 15/0000Z...DISSIPATED INLAND $$ Forecaster Stewart