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老農民版夜神月|2021-8-21 14:16
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Hurricane Grace Discussion Number 31
NWS National Hurricane Center Miami FL AL072021
1000 PM CDT Fri Aug 20 2021
Hurricane Grace has rapidly intensified this evening. Deep cold
convection has been wrapping around the center, with some evidence
of mesovorticies rotating within the eyewall following the GOES-16
GLM lightning data. The Air Force Reserve Hurricane Hunters arrived
in Grace around 0000 UTC and found that the storm had intensified
into Category 2 hurricane with the pressure dropping down to
967 mb, which is a pronounced deepening rate of 2 mb per hour
compared to the previous advisory. More recently, the aircraft was
able to pass through the northeastern eyewall, and recently found
flight level winds up to 115 kt with SFMR winds of 105 kt. These
observations support Grace being upgraded to a major hurricane this
advisory, with maximum sustained winds of 105 kt.
Some additional strengthening is possible while Grace remains over
the very warm waters in the Bay of Campeche, though the hurricane
should be making landfall tonight within the next 3-6 hours just
south of Tuxpan, Mexico. By tomorrow morning, the storm should be
well inland, and rapid weakening will likely be underway over the
very mountainous terrain of mainland Mexico. The latest NHC
intensity forecast now had Grace dissipating over Mexico in about
36 hours. However, as discussed in previous advisories, while the
low-level circulation is expected to dissipate, the mid-level vortex
is forecast to survive the passage of Mexico, and this feature is
likely to lead to the development of a new tropical cyclone in the
eastern Pacific basin later this weekend or early next week.
Center fixes from the aircraft indicate that Grace has stayed on a
mostly due westward heading, at 270/9 kt. This general motion,
though with a bit more southward component should continue through
landfall and dissipation. This southward deflection over often
occurs with strong hurricanes in this region, due to the
topographical effects of the wind field to the north ascending over
the higher terrain. The official NHC track is very similar to the
previous advisory, and remains near the middle of the guidance
consensus.
Key Messages:
1. Hurricane conditions and dangerous storm surge are likely along
portions of the coast of eastern mainland Mexico beginning tonight
and tomorrow morning within the Hurricane Warning area from Puerto
Veracruz northward to Cabo Rojo.
2. A dangerous storm surge is likely near and to the north of the
where the center of Grace crosses the coast of Mexico.
3. 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 21/0300Z 20.7N 96.3W 105 KT 120 MPH
12H 21/1200Z 20.3N 97.9W 75 KT 85 MPH...INLAND
24H 22/0000Z 20.0N 100.9W 45 KT 50 MPH...INLAND
36H 22/1200Z...DISSIPATED
$$
Forecaster Papin/Beven
NNNN
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