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Documentation on the mean standard deviation charts based on NAEFS (North American Ensemble Forecasting System)


The purpose of this site is to present the Standard deviation/mean charts based on Ensemble Forecasts issued every day for North America.

NAEFS (North American Ensemble Forecasting System)

NAEFS is an initiative involving Canada, the United States and Mexico. NAEFS establish meteorological forecasts combining American and Canadian ensemble systems.

Introduction and Description of Ensemble Forecast

The Canadian Ensemble Prediction System

The Canadian Ensemble System is composed of 20 members and 1 control member. The 20 members are based on the Global Environmental Multi-Scale model (GEM). The 20 models don't have the same physical parameterization, assimilation cycle or perturbed observations. Fore more information on Ensemble Forecast system, click here.

The American Ensemble Prediction System

The American Ensemble System is composed of 20 members with 1 control. Each member represents a perturbed forecast. Perturbations come from independent breeding cycles. More details on this system are available at the following links:

Display of charts

The charts display for a meteorological variable, a large format chart containing the mean and standard deviation of all the members of NAEFS, and gives access to a series of smaller charts (post stamps) for each member and for some other control models, for a given forecast date and a given issue date.


The part of the display screen which allows the selection of charts is as follow:

Standard Deviation/Mean Charts for NAEFS

Individual Members

Before explaining the different parts of this screen, it is necessary to distinguish between forecast and issued date. The issued date is the date when the forecast was generated. The forecast date is the date for which the forecast is needed. Right now, every day (at 0 UTC and 12 UTC) forecasts based on ensembles are issued for the next 15 days.

At first when the page is open, the chart displayed represents the forecast for the next day, issued today at 0 UTC.

The selection screen is divided into three lines.

The top line allows the selection of the charts issued date and time and gives access to the information screen.

The next line allows the user to change the forecast date.

At the right and left of the dates, arrows pointing respectively left and right are shown. Clicking on the left arrow will make the chart of the preceding day appear. The same way, clicking the right arrow will make the chart of the following day appear. If one of the arrows is missing, it means that there is no chart available for the corresponding day.

While clicking on the issued date arrows, it is possible that no forecast corresponds to a new issued date. In that case, the system will automatically put back the forecast date 24 hours after the issued date.

The last line is used to select the chart type. For now, seven meteorological variables are available. If the browser does not use JavaScript, a VIEW button will be available to activate the changes requested.

Finally, below the rectangle containing the 3 lines, it is possible to click on the mention Individual Members to view post stamp charts of the individual members composing the ensemble and some control members.

What we are doing


Need to travel Alberta Highway 93?

Go prepared with Highway 93 forecasts. Highway regions are available in the Alberta text forecast bulletin between Lake Louise and Jasper. (Photo by: Natalie Anderson)

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