ZCZC MIATCDAT2 ALL
TTAA00 KNHC DDHHMM
 
Tropical Storm Grace Discussion Number  28
NWS National Hurricane Center Miami FL       AL072021
400 AM CDT Fri Aug 20 2021
 
Deep convection has increased near the center of Grace overnight 
with improved banding structure over the eastern portion of the 
circulation.  An Air Force Reserve Hurricane Hunter aircraft 
measured a peak 850-mb flight-level wind of 72 kt and SFMR winds of 
58 kt during the aircraft's final pass through the northern portion 
of the storm prior to 06Z.  Based on those observations, the 
initial wind speed was increased to 60 kt on the 06Z intermediate 
advisory, and it remains at that value for now.  Grace is close 
to re-gaining hurricane strength, and the next reconnaissance 
mission should be in the storm around 1200 UTC this morning. 

Grace will be moving over the warm waters over the Bay of 
Campeche today.  That, along with light to moderate vertical wind 
shear conditions, are expected to allow for re-intensification 
until landfall in mainland Mexico tonight.  The updated intensity 
forecast brings Grace to a 75-kt hurricane in 12 hours, and the 
storm could be slightly stronger when it makes landfall overnight.  
By 24 h, the center is forecast to be inland, and Grace will 
likely already to have begun to weaken.  Rapid weakening should 
occur on Saturday as Grace moves farther inland over the 
mountainous terrain of central Mexico, and the circulation is likely 
to dissipate in around 48 hours.  The remnants of Grace are expected 
to move into the Pacific where they are likely to spawn a new 
tropical cyclone.

The cyclone has been moving westward or 270/14 kt.  A strong 
mid-level ridge to the north of Grace should continue to steer the 
cyclone westward to west-southwestward until dissipation occurs in 
a couple days.  The new NHC track forecast is near the middle of 
the guidance envelope and is essentially unchanged from the 
previous advisory. 
 
Key Messages:
 
1. Hurricane conditions and dangerous storm surge are likely along
portions of eastern mainland Mexico beginning late today. A
Hurricane Warning is in effect 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  20/0900Z 20.7N  93.3W   60 KT  70 MPH
 12H  20/1800Z 20.6N  95.2W   75 KT  85 MPH
 24H  21/0600Z 20.3N  97.4W   70 KT  80 MPH...INLAND
 36H  21/1800Z 19.8N  99.7W   35 KT  40 MPH...INLAND
 48H  22/0600Z 19.4N 102.2W   20 KT  25 MPH...POST-TROP/REMNT LOW
 60H  22/1800Z...DISSIPATED
 
$$
Forecaster Brown
 
NNNN