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Hurricane Grace Discussion Number  23
NWS National Hurricane Center Miami FL       AL072021
1000 PM CDT Wed Aug 18 2021

Grace has become a bit better organized during the past several 
hours.  Cuban radar data indicates that the eye and eyewall have 
become better defined, and reports from Air Force Reserve and NOAA 
Hurricane Hunter aircraft show that the inner core circulation has 
become better defined.  There are also occasional attempts at eye 
formation in satellite imagery.  However, these changes have not 
yet resulted in significant intensification, with the maximum winds 
remaining near 70 kt and the central pressure hovering near 988 mb. 
One possible restraint on development is a dry slot that is seen
wrapping around the central core in both satellite imagery and 
Cuban radar data.

The center has jogged a little to the left during the past few 
hours, and the initial motion is now 280/16.  The hurricane should 
continue to move generally westward to west-northwestward for the 
next 24-36 h, followed by a westward to west-southwestward motion 
from 36-48 h.  This motion should bring the center over the 
Yucatan Peninsula of Mexico during the next 12 h, followed by 
passage across the southwestern Gulf of Mexico or the Bay of 
Campeche to a second landfall in mainland Mexico between 48-60 h.  
After that, the cyclone should continue moving into the mountains 
of Mexico until it dissipates.  The new forecast track is nudged a 
little south of the previous forecast, and it lies near the various 
consensus models.

Except for the aforementioned dry slot, conditions appear 
favorable for intensification before landfall on the Yucatan 
peninsula.  While not explicitly show in the intensity forecast, 
Grace could reach an intensity of 75-80 kt before it reaches 
Yucatan.  The cyclone should weaken some as it crosses the 
peninsula, then re-intensify over the Gulf of Mexico until it 
reaches mainland Mexico.  After final landfall in Mexico, Grace is 
expected to quickly weaken and dissipate over the mountains of 
Mexico just after 72 h.  The remnants of Grace are likely to emerge 
in the Pacific and possibly re-develop there, but the uncertainty 
of whether this will be the original center or a new center 
precludes forecast points over the Pacific at this time.
 
A Hurricane Watch and a Tropical Storm Watch have been issued for 
portions of mainland Mexico.
 
Key Messages:
 
1. Hurricane conditions and a dangerous storm surge are expected
in portions of the Hurricane Warning area in the eastern Yucatan
Peninsula of Mexico beginning during the next several hours.
Preparations to protect life and property should be rushed to
completion.
 
2. There is an increasing risk of hurricane conditions and dangerous
storm surge in portions of eastern mainland Mexico beginning late
Friday, and a Hurricane Watch has been issued for part of this area.
 
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  19/0300Z 19.8N  85.6W   70 KT  80 MPH
 12H  19/1200Z 20.3N  88.1W   70 KT  80 MPH...INLAND
 24H  20/0000Z 20.6N  91.4W   60 KT  70 MPH...OVER WATER
 36H  20/1200Z 20.7N  94.0W   65 KT  75 MPH
 48H  21/0000Z 20.5N  96.1W   75 KT  85 MPH
 60H  21/1200Z 20.0N  98.8W   35 KT  40 MPH...INLAND
 72H  22/0000Z 19.7N 101.6W   20 KT  25 MPH...POST-TROP/INLAND
 96H  23/0000Z...DISSIPATED
 
$$
Forecaster Beven
 
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