Saturday, 19 July 2014

Regional Drought

Jamaica, as is the case for much of the region, is now experiencing drought conditions. Wildfires are burning, vegetation is drying up and water storage levels are currently approaching crisis levels. Take Jamaica, for example, a recent news report suggests that water resources in the Kingston Metropolitan are on the brink of being depleted. To be specific, the report suggests that only One month's supply of water in Corporate Area is available. Except for may be Cuba and the Bahamas, the rest of the Caribbean is experiencing below normal rainfall, and drought conditions could get worse if conditions continue as is.

Figure 1: Dry vegetation in central Jamaica. Source of image: Personal photo

What's causing the drought?

May, generally marks the commencement of the Caribbean's secondary wet season. But seasonal rainfall has been below normal since then. Why, you may ask? The most likely reason would be El Nino, though climate change may exacerbate these conditions, the evidence to support this theory is inconclusive. El Nino has not been declared, but sea surface temperature anomalies have been at or close to the 0.5 Celsius threshold since mid April. The southern oscillation index was out of sync with warming equatorial Pacific sea surface temperatures, but recent downward spikes in the index suggests that the official declaration may be on the horizon.

Figure 2: Sea surface temperature (SST) anomalies, note the warmer than average SSTs across the equatorial and northern Pacific. Source of image: Tropical Tidbits

The subtropical jet is further south in El Nino/warm ENSO years, this will generally increase the upper level winds across the Caribbean and the tropical Atlantic, which enhances vertical wind shear across the aforementioned area. These conditions tend to suppress tropical cyclone development, with accompanying dryer than normal conditions in the main development region.

Figure 3: El Nino effects during June through August. Source of image: National Weather Service

The forecast suggests that drought conditions will persist up to September, so I would urge my fellow islanders conserve water, as it seems as if conditions will get worse before they get better.