Recent global weather events linked to El Niño?

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  • Recent sea surface temperatures anomalies around the globe. Areas in yellow and red show where sea surface temperatures are higher than normal. El Nino is characterised by higher than normal sea surface temperatures over the central and eastern Pacific Ocean (circled). Image credit: NOAA (El Nino Portal)

    A schematic showing the recent synoptic situation which has led to storms and flooding over Texas and neighbouring areas. Image credit: MeteoGroup

    Rainfall anomalies expected over India through the next ten days. The green areas show where above normal monsoon rain is expected. The yellow areas show where it is likely to remain drier than normal. Image credit: MeteoGroup

  • Recent global weather events linked to El Niño?
    30.05.2015 14:40

    The weather has been making the news headlines again this week, unfortunately with floods inundating parts of Texas, in the USA, and a deadly heat wave persisting across India. Whilst these events are occurring thousands of miles away from each other, could the local phenomenon called El Niño be to blame?

    In Texas, in excess of 150mm (>6 inches) of rain was recorded in rain gauges across Houston on Tuesday alone. By Friday, the worst of the rain had moved farther north, over the Dallas area, where severe flooding ensued, leaving thousands of homes without power.

    According to the US National Weather Service, the deluges helped to set a new record for the wettest May in Dallas-Fort Worth with over 400mm (>16 inches) of rain having fallen in the month so far.

    Meanwhile, residents across parts of India will have been desperate for rain to arrive after heat wave conditions persisted through the week. Some central and eastern parts of India have experienced temperatures in excess of 45C (113F) every day this week, around 5-6C above the May average. An unbearable temperature of 47C (117F) was recorded in the city of Daltonganj, in Jharkhand state, on Wednesday.

    The heat wave in India has, in part, been caused by drier and sunnier conditions than normal in the past week, whereas the country often experiences some sporadic cloud and rainfall just before the main monsoon arrives in June. Meanwhile, the torrential rains in Texas have been caused by hot, moist air moving in from the Gulf of Mexico and condensing out as rain along a ‘frontal boundary’ (which marked the boundary between the hot, moist air and cooler, drier air to the north-east).

    However, can some blame also be apportioned to the El Niño phenomenon?

    El Niño is an ocean-atmosphere phenomenon characterised by persistently above normal sea surface temperatures in the central and eastern Pacific Ocean. El Niño has long been recognised, being first observed by fishermen off the coast of South America in the 1600s, who noticed the development of unusually warm water in the Pacific Ocean. Indeed, the phenomenon is a natural one but occurs irregularly, anything from around every two to seven years.

    El Niño impacts the weather because it provides an additional heat source, effectively adding fuel to the weather. One of its most noticeable effects is an increased frequency of hurricanes over the Pacific due to the extra heat and moisture pumped into the atmosphere there. However, El Niño’s effects can be global, albeit usually most heavily felt in the tropics.

    In the USA, El Niño tends to be associated with a strengthening of a southern storm track during spring, bringing above normal amounts of rain to the Plains, including the Texas area which has been recently affected by the flooding. Over India, El Niño is associated with warmer and drier than normal conditions during spring and summer.

    However, the presence of an El Niño does not always mean that there will be flooding in Texas and droughts in India, it just raises the chances. Indeed, there are many other climatological factors or ‘drivers’ that can affect the weather in any one place.

    There is some good news for the residents of Texas and India. In Texas, the recent heavy rains have helped greatly towards eradicating the severe droughts that were ongoing until a few months ago. Furthermore, it will become drier and brighter there through the coming days, helping to alleviate the flood situation.

    In India, it looks like slowly becoming less hot through the next week as monsoonal rains start to make progress over the southern half of the country.

    By: Paul Mott