000 WTPZ41 KNHC 112056 TCDEP1 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