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Tropical Storm Grace Advisory Number 20
NWS National Hurricane Center Miami FL AL072021
500 AM EDT Wed Aug 18 2021
...OUTER BANDS WITH HEAVY RAINFALL AND GUSTY WINDS BEGINNING
TO SPREAD ACROSS THE CAYMAN ISLANDS...
...GRACE STILL FORECAST TO BECOME A HURRICANE LATER TODAY...
SUMMARY OF 500 AM EDT...0900 UTC...INFORMATION
ABOUT 40 MI...65 KM SSE OF GRAND CAYMAN
ABOUT 440 MI...710 KM ESE OF TULUM MEXICO
MAXIMUM SUSTAINED WINDS...65 MPH...100 KM/H
PRESENT MOVEMENT...W OR 280 DEGREES AT 16 MPH...26 KM/H
MINIMUM CENTRAL PRESSURE...998 MB...29.47 INCHES
WATCHES AND WARNINGS
CHANGES WITH THIS ADVISORY:
The government of Jamaica has discontinued the Tropical Storm
Warning for Jamaica.
The government of Cuba has discontinued the Tropical Storm Warning
for the southern coast Cuban provinces of Granma, Las Tunas, and
Camaguey. The Tropical Storm Watch for the southern coast of the
Cuban provinces of Ciego de Avila, Sancti Spiritus, Cienfuegos,
Matanzas have also been discontinued.
The government of Mexico has upgraded the Tropical Storm Watch to a
Tropical Storm Warning for the north and west coasts of the Yucatan
Peninsula from west of Dzilam to Campeche.
SUMMARY OF WATCHES AND WARNINGS IN EFFECT:
A Hurricane Warning is in effect for...
* Yucatan Peninsula of Mexico from Cancun to Punta Herrero,
A Hurricane Watch is in effect for...
* Cayman Islands
A Tropical Storm Warning is in effect for...
* Cayman Islands
* Yucatan Peninsula of Mexico from north of Cancun to Campeche
* Yucatan Peninsula of Mexico from south of Punta Herrero to Puerto
A Tropical Storm Watch is in effect for...
* Southern coast Cuban province of Pinar del Rio, as well as Isla
de la Juventud
A Hurricane Warning means that hurricane conditions are expected
somewhere within the warning area. A warning is typically issued
36 hours before the anticipated first occurrence of tropical-storm-
force winds, conditions that make outside preparations difficult or
dangerous. Preparations to protect life and property should be
rushed to completion.
A Hurricane Watch means that hurricane conditions are possible
within the watch area.
A Tropical Storm Warning means that tropical storm conditions are
expected somewhere within the warning area within 36 hours.
A Tropical Storm Watch means that tropical storm conditions are
possible within the watch area.
Interests elsewhere in the Yucatan Peninsula of Mexico should
monitor the progress of Grace. Additional watches or warnings may
be required later this morning.
For storm information specific to your area, please monitor
products issued by your national meteorological service.
DISCUSSION AND OUTLOOK
At 500 AM EDT (0900 UTC), the center of Tropical Storm Grace was
located near latitude 18.8 North, longitude 80.9 West. Grace is
moving toward the west near 16 mph (26 km/h). A general westward to
west-northwestward motion is expected for the next several days. On
the forecast track, the center of Grace will continue to move near
or over the Cayman Islands later this morning. Grace will approach
the Yucatan peninsula of Mexico tonight or early Thursday.
Maximum sustained winds have increased to near 65 mph (100 km/h)
with higher gusts. Grace is forecast to strengthen into a hurricane
by tonight, with some additional strengthening possible prior to the
center reaching the eastern Yucatan Peninsula.
Tropical-storm-force winds extend outward up to 115 miles (185 km)
from the center. A reporting station near Rum Point Beach on the
north shore of Grand Cayman recently measured a sustained wind of
40 mph (64 km/h) and a gust to 47 mph (76 km/h).
The estimated minimum central pressure is 998 mb (29.47 inches).
HAZARDS AFFECTING LAND
Key messages for Grace can be found in the Tropical Cyclone
Discussion under AWIPS header MIATCDAT2, WMO header WTNT42 KNHC
and on the web at
WIND: Tropical storm conditions are expected along a portion of the
southern coast of Cuba within the warning area and over the Cayman
Islands through this morning. Hurricane conditions are possible in
the Cayman Islands later this morning. Tropical storm conditions are
possible along the southern coast of Cuba within the watch area
through today. Hurricane conditions are expected within the warning
area in the Yucatan Peninsula of Mexico late tonight, with tropical
storm conditions beginning as early as this evening.
Grace is expected to produce the following rainfall amounts:
Over Jamaica, the Cayman Islands, portions of the Yucatan Peninsula
and Vera Cruz state....4 to 8 inches of rain with isolated maximum
totals of 12 inches are expected through Friday night. This heavy
rainfall could lead to flash and urban flooding, with mudslides
possible in Jamaica.
STORM SURGE: A storm surge could raise water levels as high as 1 to
3 ft above normal tide levels in portions of the Cayman Islands.
A dangerous storm surge will raise water levels by as much as 3 to 5
ft above normal tide levels along the immediate coast near and to
the north of where the center makes landfall in the northeastern
Yucatan Peninsula late tonight or early Thursday. Near the
coast, the surge will be accompanied by large and destructive waves.
SURF: Swells generated by Grace will spread westward from Jamaica
to the Cayman Islands, the southern coast of Cuba, and the Yucatan
Peninsula of Mexico. These swells are likely to cause
life-threatening surf and rip current conditions. Please consult
products from your local weather office.
Next intermediate advisory at 800 AM EDT.
Next complete advisory at 1100 AM EDT.