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| #1057946 (Received by flhurricane at: 11:09 PM 20.Aug.2021) TCDAT2 Hurricane Grace Discussion Number 31 NWS National Hurricane Center Miami FL AL072021 1000 PM CDT Fri Aug 20 2021 Hurricane Grace has rapidly intensified this evening. Deep cold convection has been wrapping around the center, with some evidence of mesovorticies rotating within the eyewall following the GOES-16 GLM lightning data. The Air Force Reserve Hurricane Hunters arrived in Grace around 0000 UTC and found that the storm had intensified into Category 2 hurricane with the pressure dropping down to 967 mb, which is a pronounced deepening rate of 2 mb per hour compared to the previous advisory. More recently, the aircraft was able to pass through the northeastern eyewall, and recently found flight level winds up to 115 kt with SFMR winds of 105 kt. These observations support Grace being upgraded to a major hurricane this advisory, with maximum sustained winds of 105 kt. Some additional strengthening is possible while Grace remains over the very warm waters in the Bay of Campeche, though the hurricane should be making landfall tonight within the next 3-6 hours just south of Tuxpan, Mexico. By tomorrow morning, the storm should be well inland, and rapid weakening will likely be underway over the very mountainous terrain of mainland Mexico. The latest NHC intensity forecast now had Grace dissipating over Mexico in about 36 hours. However, as discussed in previous advisories, while the low-level circulation is expected to dissipate, the mid-level vortex is forecast to survive the passage of Mexico, and this feature is likely to lead to the development of a new tropical cyclone in the eastern Pacific basin later this weekend or early next week. Center fixes from the aircraft indicate that Grace has stayed on a mostly due westward heading, at 270/9 kt. This general motion, though with a bit more southward component should continue through landfall and dissipation. This southward deflection over often occurs with strong hurricanes in this region, due to the topographical effects of the wind field to the north ascending over the higher terrain. The official NHC track is very similar to the previous advisory, and remains near the middle of the guidance consensus. Key Messages: 1. Hurricane conditions and dangerous storm surge are likely along portions of the coast of eastern mainland Mexico beginning tonight and tomorrow morning within the Hurricane Warning area from Puerto Veracruz northward to Cabo Rojo. 2. A dangerous storm surge is likely near and to the north of the where the center of Grace crosses the coast of Mexico. 3. Through the weekend, heavy rainfall across Veracruz, Puebla, Tlaxcala, Hidalgo, northern Queretaro, and eastern San Luis Potosi will lead to significant flash and urban flooding, along with the likelihood of mudslides. FORECAST POSITIONS AND MAX WINDS INIT 21/0300Z 20.7N 96.3W 105 KT 120 MPH 12H 21/1200Z 20.3N 97.9W 75 KT 85 MPH...INLAND 24H 22/0000Z 20.0N 100.9W 45 KT 50 MPH...INLAND 36H 22/1200Z...DISSIPATED $$ Forecaster Papin/Beven |