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Tropical Storm Grace Discussion Number  27
NWS National Hurricane Center Miami FL       AL072021
1000 PM CDT Thu Aug 19 2021
 
During the past few hours, the center of Grace has emerged over the
southwestern Gulf of Mexico.  The associated convection is
currently poorly organized and mainly occuring in a band to the
east of the center.  However, data from Air Force Reserve and NOAA
Hurricane hunter aircraft indicate that 55 kt surface winds are
occurring about 20 n mi northeast of the center, and that will be
the initial intensity for this advisory.  The aircraft also
reported that the minimum central pressure was near 994 mb.
 
Conditions appear favorable for re-intensification once the
convection becomes better organized near the center, a process
that could take several more hours.  The new intensity forecast
calls for a peak intensity of 75 kt in 24 h, just before the center
makes landfall on the coast of mainland Mexico.  The intensity for
this part of the forecast follows the trend of the intensity
guidance and is near the intensity consensus.  After landfall,
Grace is expected to weaken rapidly, with the circulation
dissipating over the mountains of Mexico just after 48 h.  The
remnants of Grace are expected to subsequently move into the
Pacific and develop into a new tropical cyclone there.
 
The cyclone has nudged a little northward since the last advisory,
and the initial motion is 280/14 kt.  Other than that, there is
little change to either the forecast philosophy or the forecast
track.  Strong mid-level ridging should steer Grace westward for
the next 12 h or so, followed by a west-southwestward motion through
48 h.  This motion should take the center across the southwestern
Gulf of Mexico to a landfall in mainland Mexico in just over 24 h.
After landfall, the cyclone should continue west-southwestward into
the mountains of Mexico until dissipation.  The new forecast track
is close to the consensus models and has only minor adjustments
since the previous forecast.
 
 
Key Messages:
 
1. 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.
 
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  20/0300Z 20.8N  91.8W   55 KT  65 MPH
 12H  20/1200Z 20.8N  93.7W   65 KT  75 MPH
 24H  21/0000Z 20.7N  95.9W   75 KT  85 MPH
 36H  21/1200Z 20.1N  98.2W   45 KT  50 MPH...INLAND
 48H  22/0000Z 19.6N 100.5W   25 KT  30 MPH...POST-TROP/REMNT LOW
 60H  22/1200Z...DISSIPATED
 
$$
Forecaster Beven
 
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