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St. John is surrounded by the Caribbean Ocean waters, south of the tropic of cancer, with the average temperatures of these coastal waters running between 77 and 84 degrees Fahrenheit. Although these surrounding seas keep the terrestrial climate cooler than other locations in the region, such as tropical mainlined Central America. Tradewinds blow from the east all year in this region and are at their strongest in the winter months. Due to the mean annual temperature at sea level, these islands are classified as subtropical.
St. John has a very warm dry climate with most precipitation events lasting only a short time. Due to this fact, you may only get a few millimeters of rain with each shower. “There is a pronounced east-west rainfall gradient similar to many of the less mountainous islands of the Lesser Antilles, where the east end receives less than (75 cm) annually and the west end over (150 cm). Rainfall tends to be distributed irregularly throughout the year and between years. The variable rainy season is from September to December but rainfall can be concentrated during tropical storms and hurricanes (geographic consulting).” With each precipitation event generating only a few mm of rain, this leads to a higher level of evapotranspiration and is therefore often higher than that of the rainfall. In addition, there are lower levels of groundwater and groundwater recharge only happens after larger storms, such as tropical storms or hurricanes that can saturate the land.
This Island is also positioned very near the Gulf Stream which and is subsequently threatened by more tropical storms or hurricanes. One of the most devastating Hurricanes to hit St. John was in 1989; Hurricane Hugo was a category 4 storm, with winds up to 225km. Storms of this nature are not only damaging to island structures, but also the coastal environments of islands, such as the coral reefs. Furthermore, prolonged periods of drought may typically from March to July. Coincidentally the hottest months are July through October, which corresponds with hurricane season.
In recent years, it has been discovered that global warming may be having an effect on the St. John. Due to the increasing water temperatures around the island and the lower salinity in the water caused by rain in the area, Coral Reefs have become more prone to the damaging effects of water chemistry and temperature. When the water temperature increases in these areas it is known to cause the “bleaching” of reefs, this means that reef is expelling the algae from its tissue, leaving it a white color. Coral reef is also known to have a smaller tolerance for changes in the salinity of water. Most of these changes do come from the water temperature and the rains, as the island has no permanent streams to increase the sediment runoff affecting the oceans.
St. John has a very warm dry climate with most precipitation events lasting only a short time. Due to this fact, you may only get a few millimeters of rain with each shower. “There is a pronounced east-west rainfall gradient similar to many of the less mountainous islands of the Lesser Antilles, where the east end receives less than (75 cm) annually and the west end over (150 cm). Rainfall tends to be distributed irregularly throughout the year and between years. The variable rainy season is from September to December but rainfall can be concentrated during tropical storms and hurricanes (geographic consulting).” With each precipitation event generating only a few mm of rain, this leads to a higher level of evapotranspiration and is therefore often higher than that of the rainfall. In addition, there are lower levels of groundwater and groundwater recharge only happens after larger storms, such as tropical storms or hurricanes that can saturate the land.
This Island is also positioned very near the Gulf Stream which and is subsequently threatened by more tropical storms or hurricanes. One of the most devastating Hurricanes to hit St. John was in 1989; Hurricane Hugo was a category 4 storm, with winds up to 225km. Storms of this nature are not only damaging to island structures, but also the coastal environments of islands, such as the coral reefs. Furthermore, prolonged periods of drought may typically from March to July. Coincidentally the hottest months are July through October, which corresponds with hurricane season.
In recent years, it has been discovered that global warming may be having an effect on the St. John. Due to the increasing water temperatures around the island and the lower salinity in the water caused by rain in the area, Coral Reefs have become more prone to the damaging effects of water chemistry and temperature. When the water temperature increases in these areas it is known to cause the “bleaching” of reefs, this means that reef is expelling the algae from its tissue, leaving it a white color. Coral reef is also known to have a smaller tolerance for changes in the salinity of water. Most of these changes do come from the water temperature and the rains, as the island has no permanent streams to increase the sediment runoff affecting the oceans.