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Predicting Severe Weather: Protecting Canadians

By:  Doug Whelpdale and Martin Charron with S&T Liaison

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The Problem

Providing an accurate forecast several days in advance of a severe weather event is a daunting scientific challenge, but essential for effective preparation and response to protect Canadians.

Canadians are no strangers to severe weather.  Winter storms – blizzards, heavy snowfalls and freezing rain – wreak havoc with transportation across the country.  Hurricanes and severe extra-tropical cyclones batter the east coast with rain, often resulting in flooding.  Summer heat waves, often accompanied by poor air quality in our major cities, increase mortality and morbidity rates among the frail and the elderly.  These and other severe weather events cause personal injury and loss of life, and damage to infrastructure and personal property from coast to coast to coast. To make matters worse, climate change brings with it the prospect of more frequent and more severe weather events.

Seeking Solutions through S&T

On October 31, 2006, a new version of the Global Environmental Multi-scale (GEM) model for global medium-range numerical weather prediction (NWP) was implemented operationally at the Canadian Meteorological Centre (CMC) in Dorval.

The science of weather forecasting has come a long way since Canada’s first storm warnings and general weather forecasts were issued in 1876.  Thanks to more computing power, better scientific knowledge, and improved global observing systems, 5-day forecasts today are as accurate as the 2-day forecasts of 30 years ago.  The most recent major improvement in weather and environmental prediction in Canada has been implementation of a new model for global medium-range numerical weather prediction, known as GEM MesoGlobal.

EC’s Gilbert Brunet with the supercomputer at the Canadian Meteorological Centre in Dorval | Photo: Guy Dansereau, ECEnvironment Canada is a world leader in weather forecasting.  Atmospheric scientists, meteorologists and computer experts from the Meteorological Research Division (Atmospheric Science and Technology Directorate) and the Development Division (Canadian Meteorological Centre) develop complex computer weather models that are run on one of Canada’s fastest supercomputers at the Canadian Meteorological Centre in Dorval.  These models simulate the physical processes controlling the behaviour of the atmosphere as it generates weather.  A forecast is produced by starting the model with the current conditions and running it forward in time to determine how the weather will develop and change in the future.

The new model represents five years of intensive effort to better understand processes that create hazardous weather and to use this knowledge to improve forecasts.  Major changes in the model include improved representation of key physical processes and finer model resolution.  (Model calculations are now made in a 33-km grid [instead of 100 km] around the world and in 58 atmospheric layers [instead of 28] above the earth’s surface.)  The new model, GEM MesoGlobal, generates weather forecasts with much finer detail and higher overall accuracy, in particular for predictions for three to 10 days in advance.  The result is much improved forecasts of severe weather, particularly for hurricanes and heavy rainfall.

Predictions with the new model compare very favourably with those of other leading world forecast centres - the European Centre for Medium-range Weather Forecasting (ECMWF) and the U.S. National Centers for Environmental Prediction (NCEP).  With the implementation of GEM MesoGlobal, EC has greatly improved its capacity to forecast high-impact weather at the medium range, notably patterns and intensity of precipitation, in particular heavy rain and the location and depth of depressions.

Transforming Knowledge into Action

Who can use these results?

GEM MesoGlobal is an integral part of Canada’s weather prediction system at the Canadian Meteorological Centre in Dorval.  The model is run twice each day to produce public medium-range forecasts of temperature, winds, precipitation and several other weather elements for all regions of Canada.  These forecasts are available online at EC’s Weatheroffice website.  

Cross-country skiers | Photo: Corel CorporationOperational weather professionals use the improved GEM MesoGlobal model and its forecasts to alert people to impending severe weather and its likely impacts up to ten days in advance.  Such warnings save lives and mitigate damage.  In early November 2007 Hurricane Noel roared through the Atlantic Provinces.  The event provided a demanding and successful operational test of GEM MesoGlobal.  The model provided consistent, reliable advance warning throughout the forecast period for this major storm.

Early information on the anticipated path and severity of the storm and its possible impacts helped emergency planners, responders and the media disseminate messages in a timely manner.  Homeowners were warned to expect fallen branches and trees, power outages, damage to the cladding and roofing of homes, localized flooding and wave damage to coastal infrastructure.

Every day citizens and stakeholders in Canada and abroad - farmers, insurance companies, the energy industry, safety organizations - use weather forecasts to guide their personal and business activities.  The likelihood of rain or snow, maximum temperatures, winds and many other meteorological variables are valuable elements of decision making.  Hydro Quebec, for example, is a frequent user of short- and medium-range precipitation forecasts to manage power production.  Government authorities responsible for safety issues related to river levels and flooding issue advisories and warnings based on three- to ten-day forecasts.

Other, more exotic uses of GEM MesoGlobal include tracking volcanic eruption plumes and releases of harmful chemicals and radioactive products.

The on-line availability of weather forecasts has greatly increased the accessibility and use of medium-range forecasts by many clients and stakeholders.

Forecasts from GEM MesoGlobal are distributed around the world and are used by several different national weather services and hurricane prediction centres.

The Recherche en Prévision Numérique group is currently developing a coupled atmosphere-hydrology modelling system with GEM MesoGlobal as its base.

A future trend in large-scale (global) modelling is to build comprehensive earth-system models with application to a wide range of environmental prediction issues.

GEM MesoGlobal positions Environment Canada well to couple atmospheric models with ocean, ice and hydrological models and to incorporate atmospheric chemistry, enabling significant advances in the broader field of environmental prediction. 

Benefits to Canadians

How does one place a value on lives that are not lost because fishermen heeded a timely weather warning and did not venture out to sea?  How do we calculate savings from vehicular accidents that did not happen when drivers listened to an ice storm forecast and stayed home?  Placing a dollar value on damage or loss of life that does not occur, as a result of an accurate and timely weather forecast for a severe weather event, is very difficult.

With the approaching landfall of Hurricane Juan in September 2003, a few alert Nova Scotians did take action on the basis of the weather forecast and advisories (see Canadian Hurricane Centre website).

"Before and after" photo of tree damage at Point Pleasant Park in Halifax | Photo: HDI Inc. for Environment Canada

  • Officials at Point Pleasant Park in Halifax took the unpopular step of closing the Park early.  This was a favourite place to watch incoming storms.  The morning after the storm hit 90% of the mature growth in the park was gone or damaged (60,000 to 75,000 trees).  Many lives were saved by keeping people out of harm’s way.
  • In anticipation of a record-level storm surge, marina operators in Dartmouth constructed makeshift, floating extensions to the pilings to which docks (and thus boats) were attached.  This allowed the docks to rise with the water level, yet remain securely tied to the pilings.  This pre-emptive action saved most of the docks and 75% of the moored boats (savings estimated in the several hundreds of thousands of dollars) in stark contrast to huge losses at other marinas in the path of the storm.

These are examples of how improved weather forecasts, and the underlying research and development that makes them possible, do benefit Canadians.  It is with such advance information, weather warnings, that Canadians have time to take actions to prepare for or avoid adverse weather.  As the old saying goes, “an ounce of prevention is worth a pound of cure.”

For more information:

Meteorological Research Division – Research and Development

Environment Canada Weatheroffice

Canadian Meteorological Centre

Canadian Hurricane Centre

S&T Liaison | Tel 905 315 5228 | Fax 905 336 4420
© Her Majesty the Queen in Right of Canada, represented by the Minister of Environment, 2008.
Catalogue No. En164-15/8-2008E-PDF; ISBN 978-1-100-10437-9