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| #1057843 (Received by flhurricane at: 10:51 AM 20.Aug.2021) TCDAT2 Hurricane Grace Discussion Number 29 NWS National Hurricane Center Miami FL AL072021 1000 AM CDT Fri Aug 20 2021 Grace is a strengthening tropical cyclone. Its structure has continued to improve in satellite imagery this morning, with more pronounced curved banding in its northern and eastern semicircles and good upper-level outflow. An Air Force Reserve Hurricane Hunter aircraft measured a peak 850-mb flight-level wind of 92 kt and peak SFMR winds of 74 kt during a pass through the northeast quadrant earlier this morning. These data support increasing the initial intensity of 75 kt, which makes Grace a hurricane once again. Dropsonde data from the aircraft indicate the minimum pressure has fallen to 982 mb. The warm waters of the Bay of Campeche are expected to support additional intensification through landfall in mainland Mexico later this evening or tonight, despite some light to moderate northerly wind shear. Since the reconnaissance data revealed Grace is strengthening quicker than previously forecast, the official NHC intensity forecast was increased in the short-term. Grace is now forecast to become a 90-kt hurricane in 12 h, which lies on the high end of the intensity guidance. The center of Grace will be well inland by 24 h, and rapid weakening is forecast thereafter as the cyclone moves over the mountains of central Mexico. Although Grace is forecast to dissipate by 48 h, its remnants will likely move into the eastern Pacific and lead to the development of a new tropical cyclone later this weekend or early next week. The cyclone is moving just south of due west, or 265/12 kt. Grace should continue moving westward to west-southwestward through landfall to the south of a mid-level ridge over the northern Gulf of Mexico. The official NHC track forecast remains near the middle of the guidance envelope and has been adjusted just a bit southward based on the latest multi-model consensus aids. Key Messages: 1. Hurricane conditions and dangerous storm surge are likely along portions of eastern mainland Mexico beginning late today within the Hurricane Warning area from Puerto Veracruz northward to Cabo Rojo. 2. Through the weekend, heavy rainfall across Veracruz, Puebla, Tlaxcala, Hidalgo, northern Queretaro, and eastern San Luis Potosi will lead to flash and urban flooding, along with the likelihood of mudslides. FORECAST POSITIONS AND MAX WINDS INIT 20/1500Z 20.6N 94.3W 75 KT 85 MPH 12H 21/0000Z 20.4N 95.9W 90 KT 105 MPH 24H 21/1200Z 20.0N 98.2W 55 KT 65 MPH...INLAND 36H 22/0000Z 19.4N 101.1W 35 KT 40 MPH...INLAND 48H 22/1200Z...DISSIPATED $$ Forecaster Reinhart/Cangialosi |