| Track: https://www.nhc.noaa.gov/refresh/graphics_at2+shtml/?cone#contents Satellite: https://www.star.nesdis.noaa.gov/GOES/floater.php?stormid=AL072021 Hurricane Grace Discussion Number 30 NWS National Hurricane Center Miami FL AL072021 400 PM CDT Fri Aug 20 2021 The satellite presentation of Grace has greatly improved over the past several hours. Deep convection has become more concentrated over the center, and the central dense overcast now appears more symmetric. Dropsonde winds and peak 850-mb flight level wind measured by the Air Force Hurricane Hunters around midday were consistent with an intensity of around 75 kt. However, the surface pressure has been gradually falling throughout the day, and recent satellite data suggest the hurricane is becoming better organized. Therefore, the initial intensity is raised to 80 kt for this advisory, which is supported by the latest UW-CIMSS objective ADT estimate. Given the high oceanic heat content within the southwestern Gulf of Mexico, additional strengthening is expected through Grace's landfall tonight. The 10-15 kt of northerly vertical wind shear over Grace does not appear to be having much of a negative effect on the cyclone at this time. Thus, the official NHC intensity forecast remains on the high end of the guidance envelope, and is closest to the statistical-dynamical models DSHP and LGEM. The current forecast shows Grace making landfall within the next 12-18 h. Once the center of Grace moves inland over the mountains of central Mexico, the cyclone should rapidly weaken and then dissipate by 48 h. However, its remnants appear likely to move into the eastern Pacific and lead to the development of a new tropical cyclone in that basin later this weekend or early next week. Earlier reconnaissance data indicate that Grace has slowed down a bit today, and its initial motion is estimated to be 265/9 kt. This general motion should continue through landfall as Grace is steered by a mid-level ridge over the northern Gulf of Mexico. The official NHC track forecast is slightly slower, but otherwise very similar to the previous one and lies near the center of the guidance envelope. Key Messages: 1. Hurricane conditions and dangerous storm surge are likely along portions of the coast of eastern mainland Mexico beginning this evening 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 significant flash and urban flooding, along with the likelihood of mudslides. FORECAST POSITIONS AND MAX WINDS INIT 20/2100Z 20.5N 95.1W 80 KT 90 MPH 12H 21/0600Z 20.4N 96.6W 90 KT 105 MPH...NEAR THE COAST 24H 21/1800Z 19.9N 98.9W 45 KT 50 MPH...INLAND 36H 22/0600Z 19.5N 101.9W 30 KT 35 MPH...INLAND 48H 22/1800Z...DISSIPATED $$ Forecaster Reinhart/Cangialosi Hurricane Grace Advisory Number 30 NWS National Hurricane Center Miami FL AL072021 400 PM CDT Fri Aug 20 2021 ...GRACE CONTINUES STRENGTHENING... ...EXPECTED TO MAKE LANDFALL ALONG EASTERN MAINLAND MEXICO TONIGHT... SUMMARY OF 400 PM CDT...2100 UTC...INFORMATION ---------------------------------------------- LOCATION...20.5N 95.1W ABOUT 150 MI...245 KM ESE OF TUXPAN MEXICO ABOUT 115 MI...185 KM NE OF VERACRUZ MEXICO MAXIMUM SUSTAINED WINDS...90 MPH...150 KM/H PRESENT MOVEMENT...W OR 265 DEGREES AT 10 MPH...17 KM/H MINIMUM CENTRAL PRESSURE...979 MB...28.91 INCHES WATCHES AND WARNINGS -------------------- CHANGES WITH THIS ADVISORY: None. SUMMARY OF WATCHES AND WARNINGS IN EFFECT: A Hurricane Warning is in effect for... * The coast of mainland Mexico from Puerto Veracruz to Cabo Rojo A Tropical Storm Warning is in effect for... * The coast of mainland Mexico from north of Cabo Rojo to Barra del Tordo A Hurricane Warning means that hurricane conditions are expected somewhere within the warning area, in this case within 12 to 24 hours. Preparations to protect life and property should be rushed to completion. A Tropical Storm Warning means that tropical storm conditions are expected somewhere withing the warning area, in this case within 12 to 24 hours. For storm information specific to your area, please monitor products issued by your national meteorological service. DISCUSSION AND OUTLOOK ---------------------- At 400 PM CDT (2100 UTC), the center of Hurricane Grace was located near latitude 20.5 North, longitude 95.1 West. Grace is moving toward the west near 10 mph (17 km/h), and this general motion is expected to continue through landfall. On the forecast track, the center of Grace is forecast to move across the southwestern Gulf of Mexico this evening, and then make landfall along the coast of mainland Mexico within the hurricane warning area tonight. Maximum sustained winds have increased to near 90 mph (150 km/h) with higher gusts. Strengthening is forecast until Grace makes landfall, with rapid weakening expected as Grace moves inland over the mountains of central Mexico. Hurricane-force winds extend outward up to 25 miles (35 km) from the center and tropical-storm-force winds extend outward up to 185 miles (295 km). The estimated minimum central pressure is 979 mb (28.91 inches). HAZARDS AFFECTING LAND ---------------------- Key messages for Grace can be found in the Tropical Cyclone Discussion under AWIPS header MIATCDAT2, WMO header WTNT42 KNHC and on the web at www.hurricanes.gov/graphics_at2.shtml?key_messages. STORM SURGE: A dangerous storm surge will raise water levels by as much as 4 to 6 ft above normal tide levels along the immediate coast within the hurricane warning area near and north of where the center makes landfall tonight. Near the coast, the surge will be accompanied by large and destructive waves. WIND: Hurricane conditions are expected within portions of the hurricane warning area in mainland Mexico tonight, with tropical storm conditions expected within the next few hours. Tropical storm conditions are expected within the tropical storm warning area in mainland Mexico by this evening. RAINFALL: Grace is expected to produce the following rainfall amounts: Over Veracruz, Puebla, Tlaxcala, Hidalgo, Queretaro, and eastern San Luis Potosi...6 to 12 inches of rain with isolated maximum totals of 18 inches are expected today through Sunday. Heavy rainfall from Grace will result in significant flash and urban flooding as well as mudslides. SURF: High surf generated by Grace will affect the southern Gulf of Mexico coastline today and continue into the weekend. These swells are likely to cause life-threatening surf and rip current conditions. Please consult products from your local weather office. NEXT ADVISORY ------------- Next intermediate advisory at 700 PM CDT. Next complete advisory at 1000 PM CDT. $$ Forecaster Reinhart/Cangialosi |