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Tropical Storm Grace Forecast Discussion Number 26
2021-08-19 22:57:55| National Hurricane Center (Atlantic)
Issued at 400 PM CDT Thu Aug 19 2021 000 WTNT42 KNHC 192057 TCDAT2 Tropical Storm Grace Discussion Number 26 NWS National Hurricane Center Miami FL AL072021 400 PM CDT Thu Aug 19 2021 Grace has now been inland for almost 12 hours and the inner core structure has been gradually decaying. In fact, the low-level center is now partially exposed to the north of the mid-level vortex which still has the majority of the deep convection. The initial intensity has been lowered to 45 kt this advisory, assuming a bit more weakening of the low-level center has occurred since 1800 UTC. Environmental conditions appear favorable for Grace to restrengthen after the storm moves offshore this evening. However, it will take a bit of time for the inner-core to reorganize before a faster rate of intensification can occur. After that process occurs, significant intensification is possible, and the latest intensity forecast makes Grace a hurricane again by 24 hours and is near the upper end of the intensity guidance by 36 hours when Grace will be just inland over Mexico. However, it remains possible that the storm could intensify more than indicated between the 24 and 36 hour points, when both the global and regional high-res hurricane model guidance suggests Grace will be near peak intensity. Grace is still moving a bit north of due west at 280/13 kt. A continued westward to west-northwestward motion is expected for the next 6-12 hours and Grace should be emerging offshore of the western Yucatan Peninsula later this evening. Thereafter, a strong mid-level ridge oriented southwest-to-northeast ahead of Grace is likely to steer the cyclone towards the west, and then west-southwest as it nears mainland Mexico. The track guidance remains in good agreement, and the latest track forecast is quite similar to the previous one, staying close to the multi-model consensus aids. Although Grace is likely to dissipate by 60 hours over the high terrain of Central Mexico, the mid-level circulation should survive and emerge into the East Pacific. This feature could contribute to the formation of a new tropical cyclone in that basin. Key Messages: 1. Tropical storm conditions will continue this afternoon and evening across the northern Yucatan Peninsula but should subside later tonight. 2. Hurricane conditions and dangerous storm surge are likely along portions of eastern mainland Mexico beginning late Friday. A Hurricane Warning is in effect from Puerto Veracruz northward to Cabo Rojo. 3. Through the weekend, heavy rainfall across central and northern portions of the Yucatan Peninsula and Veracruz State should lead to flash and urban flooding. In addition, the heavy rainfall from Grace will be capable of producing mudslides in Veracruz. FORECAST POSITIONS AND MAX WINDS INIT 19/2100Z 20.6N 90.2W 45 KT 50 MPH...INLAND 12H 20/0600Z 20.8N 92.5W 55 KT 65 MPH...OVER WATER 24H 20/1800Z 20.7N 94.9W 70 KT 80 MPH 36H 21/0600Z 20.4N 97.0W 75 KT 85 MPH...INLAND 48H 21/1800Z 19.6N 99.4W 35 KT 40 MPH...INLAND 60H 22/0600Z...DISSIPATED $$ Forecaster Papin/Cangialosi
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