The 2015 Drought

St. John in early to mid-2015 is experiencing a drought such as we have not felt since the 1970s.

I began keeping daily rain records for Trunk Bay in late 1983 after a 20+ inch rain in April of that year piqued my interest in doing so. Probably following in my great grandfather’s footsteps as he was Chief Meteorologist with the US Weather Bureau for the US Caribbean in the very early 1900s in Puerto Rico.

But back to 2015. With the exception of above average rainfall in February, the rest of the year so far has been unusually dry. Both January and March had below average rains. However, April and May have been devastating to plants and cisterns. With only .55 inches in April and .14 inches in May, that is well below the average of 7.64 inches for those two months combined.

While some rains have fallen on parts of St. Thomas and St. John, at Trunk Bay we actually had 28 straight days with no measurable rainfall, and only tiny amounts before and after that — the second longest since I started measuring rain in 1983 (we had 37 days in May/June 1985 but that was preceded by 2.9” the day before). This drought has been worse so far than the driest year I have recorded of 27.19 inches in 1994 where the driest month still had 1.14 inches of rain.

The year to date rainfall for 2015 has been 9.74 inches and the average year to date rainfall is 14.58 inches. The average annual rainfall at Trunk Bay from my records is 48.43 inches (1984 to 2014). It remains to be seen if the rest of the year lets us get anywhere near that.

We can certainly see the results of this on our hillsides. Many trees have turned red and/or brown as their leaves have reacted to the lack of water before falling off. We can see through vegetation that is normally dense. Even giving plants sparing amounts of water (to conserve our cisterns) seems to have little effect. And this drought is certainly also having an effect on wildlife.

Undoubtedly, many animals are succumbing to a lack of water and vegetation to eat. The long period of above average rainfall that we have had for the past decade and a half has enabled some species, such as the deer, to flourish, having abundant food and water to raise their young. Similarly, a lack of rain can mean less land-based nutrients washing into the sea which feeds plankton which in turn feed the small schooling fish (“fry”) that the seabirds need to feed their young for a successful nesting season. Droughts like this can be a significant controlling factor in the rise and fall of populations of many species.

I do not have an explanation for why we are experiencing this drought but the weather patterns seem to be causing the moisture bands coming off South America to miss us. Some have pointed to a more southerly Bermuda High and upper level wind patterns keeping the moisture from reaching us.

While it is good news that the El Nino in the Pacific may result in a below average Atlantic hurricane season, it also may mean fewer tropical waves and storms to bring us rain. For now we must just keep conserving our water and wishing (dancing?) for rain.