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Tropical Storm Grace was the final tropical cyclone to form during the below-average 1997 Atlantic hurricane season. Forming out of an extratropical cyclone on October 16, Grace peaked as a minimal tropical storm with winds of 45 mph (75 km/h) and a barometric pressure of 999 mbar (hPa; 29.5 inHg). Retaining some extratropical characteristics, the storm failed to organize due to strong wind shear. On October 17, convection associated with Grace diminished and the system eventually merged with a trough over the open waters of the Atlantic Ocean. As a tropical cyclone, Grace had no effects on land; however, the weather system associated with the storm's formation produced significant flash flooding across Puerto Rico, resulting in one fatality and leaving another person missing. Damages on the island amounted to $1.46 million (1997 USD; $1.99 million 2009 USD).
Tropical Storm Grace originated from a series of low pressure systems along the end of a trough that extended into the western Caribbean Sea in mid-October 1997. Gradually, the systems organized into a single cyclone and scattered convective activity developed in association with the low. On October 13, the low tracked over Puerto Rico and later Hispanola before emerging into the Atlantic Ocean. By the afternoon of October 14, the low was deemed extratropical by the National Hurricane Center as it intensified off the coast of the Dominican Republic. By the morning of October 15, the low attained gale-force winds, winds exceeding 40 mph (65 km/h), and began to track northwestward. Throughout the day on October 15, convection gradually developed over the center of the system and it intensified slightly.
Early on October 16, the storm had developed enough convective activity to be declared a tropical cyclone and was given the name Grace. At this time, the storm had attained its peak intensity with winds of 45 mph (75 km/h) and a barometric pressure of 999 mbar (hPa; 29.5 inHg). Although officially a tropical system, Grace still featured extratropical characteristics, namely remaining elongated along the trough that initially spawned the storm. Convection from Grace was also linked to another low pressure area roughly 575 mi (925 km) to the east-northeast. A large extratropical cyclone near Newfoundland produced strong vertical wind shear over the system, inhibiting further development. Rapidly tracking to the east-northeast, the tropical storm steadily weakened as convection diminished around the circulation center. By October 17, Grace had degenerated into an extratropical low before becoming indistinguishable within the trough it was located near.
Prior to becoming a tropical cyclone, the precursor to Grace produced moderate to heavy rainfall across Puerto Rico and the United States Virgin Islands. Most of Puerto Rico received between Template:Convert/and of rain. In southern areas of the island, some areas recorded over Template:Convert/in, with a peak amount of Template:Convert/in in Aibonito. Northern areas recorded much less rainfall, with some areas only receiving Template:Convert/in. In the nearby U.S. Virgin Islands, rainfall reached Template:Convert/in along western sides of the islands.
In Puerto Rico, these rains led to widespread flash flooding that cause significant damage in several municipalities. One person was killed in Las Piedras by these floods. Another person was reported missing in San Lorenzo after being swept away by a wall of water. Numerous rivers overflowed their banks, leading to 37 people seeking shelter across the island. Several landslides in addition to the flooding resulted in the closure of many roads and the destruction of bridges. In all, damages from the flooding amounted to $1.46 million (1997 USD; $1.99 million 2009 USD).
- ↑ 1.0 1.1 1.2 Edward N. Rappaport (November 5, 1997). "Tropical Storm Grace Preliminary Report". National Hurricane Center. http://www.nhc.noaa.gov/1997grace.html. Retrieved September 14, 2009.
- ↑ 2.0 2.1 David M. Roth (2009). "Formative stage of Grace - October 12–15, 1997". Hydrometeorological Prediction Center. http://www.hpc.ncep.noaa.gov/tropical/rain/grace1997.html. Retrieved September 14, 2009.
- ↑ Stuart Hinson (1998). "Puerto Rico Event Report: Flash Flood". National Climatic Data Center. http://www4.ncdc.noaa.gov/cgi-win/wwcgi.dll?wwevent~ShowEvent~309705. Retrieved September 14, 2009.
- ↑ Stuart Hinson (1998). "Puerto Rico Event Report: Flash Flood". National Climatic Data Center. http://www4.ncdc.noaa.gov/cgi-win/wwcgi.dll?wwevent~ShowEvent~309709. Retrieved September 14, 2009.
- ↑ Stuart Hinson (2009). "NCDC Storm Event Database". National Climatic Data Center. http://www4.ncdc.noaa.gov/cgi-win/wwcgi.dll?wwevent~storms. Retrieved September 14, 2009.