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Tropical Storm Pamela Forecast Discussion Number 6
2021-10-11 17:13:22| National Hurricane Center (East Pacific)
Issued at 900 AM MDT Mon Oct 11 2021 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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