Weather: El Niño strikes again

Monday, April 5, 2010

The well-known but not so well understood Pacific Ocean phenomenon caused turmoil in the world's weather patterns once more. But work is under way to improve predictions of such anomalies and make forecasts more effective and user-friendly

by HENRY HENGEVELD

Most of us well remember the El Niño winter of 12 years ago, when a series of ice storms swept across eastern Ontario and southern Quebec in early January. Those storms left millions of Canadians without electricity for an extended period of time, with particularly devastating effects on many farmers in the region.

El Niño is back at it again this winter. Although different from the 1997-98 events, it has once again turned global weather patterns upside down, seemingly sending everyone the "wrong" weather. 

December and January temperatures and total precipitation amounts across most of Ontario this winter have not been particularly unusual. However, the amount of precipitation that fell as snow has been well below the norm, particularly in south and central regions. In Windsor, for example, snowfall for the period was about 20 per cent below average, while that for the Toronto Pearson airport was almost half the norm. By mid-February, there was little snow cover to be seen across most of south central Ontario. Snowmobilers and cross-country skiers grumbled about the lack of snow cover, while city and county budget chiefs rejoiced with the low snow removal and salting costs. 

Unfortunately, thanks to El Niño conditions, Olympic organizers in Vancouver also had to go into damage control to deal with lack of snow on coastal mountains. Imagine having to truck snow onto ski hills – in Canada! 

The story was vastly different in other parts of the world. During much of December and January, unusually cold and snowy conditions prevailed across most of Europe and parts of Asia. England experienced the coldest January in 20 years. Accustomed to relatively little and temporary winter snow cover, parts of the country received upwards of 40 centimetres during January alone. 

In the United States, Texas had its first white Christmas since 1926. Heavy December rains dumped an unprecedented 66 centimetres of water on New Orleans. Just before Christmas, a major blizzard swept across the central states, hammering the eastern regions with heavy snow falls and triggering numerous tornados and hailstorms along its southern margin. Dubbed a "monster" storm, it left much of the eastern seaboard covered with more than half a metre of snow, and helped set new December snowfall records for many weather stations, including that in Washington, DC.

Five weeks later came "snowmageddon," another major storm that left as much as 90 centimetres of sticky snow over some localities in the same region. Ill-equipped to deal with so much snow, transportation in major cities in the region temporarily ground to a virtual halt.

A third major snow storm hit the region on Feb. 9, bringing another 25 to 40 centimetres of snow. At the time of writing, it appears likely that this will be the snowiest winter ever for the mid-Atlantic region. Ironically, by the time the third snowstorm had passed, accumulated winter snow fall for the area was about six times that for "snowy" southern Ontario!

Meanwhile, southern Australia fried under unusually intense heat conditions, and countries like Peru and Bolivia were deluged with excessive rainfall, both typical impacts of El Niño conditions.

Such major seasonal weather pattern anomalies can have large social and economic consequences, some positive but most negative. That is because the infrastructure within any given region is geared to "expected" weather and is often ill-equipped to cope with weather that may be common elsewhere but unusual within that region. 

Some two decades ago, the international weather community began a research program to help understand and predict the occurrence and evolution over time of slow weather-making ocean anomalies, particularly the problematic El Niño -La Niña oscillation that occurs in the tropical Pacific.

This research, to date, has resulted in a modest skill in predicting the behaviour of El Niño-La Niña phenomenon, as well as others such as the North Atlantic Oscillation. This skill, in turn, has allowed forecasters to develop seasonal weather forecasting models that provide qualitative guidance to consumers as to whether average monthly or seasonal temperature and precipitation conditions over the next 12 months are likely to be above, near or below normal.

By comparing results from a variety of models and forecast centres, they can also provide a measure of confidence in these projections. While the accuracy of these projections leaves much to be desired, it is undoubtedly better than that associated with the mystical prognoses provided by the likes of the Farmer's Almanac.

Such predictions have the potential for being particularly valuable for those sectors of the economy that are highly weather sensitive, including the agricultural sector. However, much needs to be done to improve their effective use.

One priority, of course, is to improve these forecasts themselves. Related research programs, including those in Canada, continue to work on that. However, there is also a need to bring those forecasts to users in a more usable format.

Given the large impacts that El Niños often have on the American economy, the U.S. weather service has launched two new initiatives to do just that. One is the establishment of the International Research Institute (IRI) for Climate and Society, based at Columbia University. IRI studies are specifically targeted at helping economic sectors significantly affected by climate variability to make better use of seasonal and annual forecasts.

Another is the Climate and Societal Interactions program, which is aimed at improving the understanding of how scientific information interfaces with environmental and societal decision-making, particularly with respect to climate. Other countries, including Australia and Brazil – both significantly affected by El Niño and La Niña events – are partners in this research.

At a recent workshop, investigators concluded that there is a need for appropriate mechanisms at the forecaster-user interface to provide for better two-way communications between users (such as farmers) and forecasters.

Among other things, forecasters need to better understand what information is useful and what isn't, and how that information can best be presented. Users, on the other hand, need a better appreciation of what forecasts can and cannot provide, and the credibility of the forecasts. If the various partners learn to trust each other and the forecast products became more practical, the usefulness of the forecasts can be improved substantially.

Seems obvious, but putting this into practice will take time, effort – and patience. BF

Henry Hengeveld is Emeritus Associate, Science Assessment and Integration Branch/ACSD/MSC, Environment Canada.