Weather Phenomena

Weather phenomena are events that can influence our normal weather conditions. The most famous and well known of weather phenomena are El Nino and La Nina.

El Nino is the occasional development of a warm ocean current replacing a cooler one along the coastline of Peru. A strong El Nino can cause an increase in surface water temperatures of over 5ºC, which results in a decrease of plankton that prefer a colder current. Low plankton levels mean less food for fish and as a result fish stocks and fishermen both suffer.

La Nina is El Nino’s opposite and cools the same waters off Peru’s coast. They take in turns to control the ocean’s temperatures, occurring every 2 to 7 years. They can last a few weeks, months or even years in the case of a strong El Nino from 1991-1995. This temperature change can affect a huge area. The El Nino of 1997-98 caused warming of ocean waters the size of the USA. El Nino causes an increase in the amount of heat absorbed by the air above which causes a shift in weather patterns around the world.

El Nino events usually bring heavy, torrential rain to South America and drought conditions to Indonesia and Australia. La Nina causes the opposite. Their effects can be felt much further away though by shifting the jet stream, storm tracks, and monsoons. Weak impacts of these weather phenomena are felt in the form of increased rainfall and flooding in central Europe and Southern England. In 1997-1998, coinciding with a strong El Nino, record winter temperatures were recorded in Europe, and 1998 was the warmest year on record globally. Hurricane and tropical storms reaching land doubled over the Caribbean and Gulf of Mexico during the last and powerful El Nino event of 1998.