NAEFS is an initiative involving Canada, the United States and Mexico. NAEFS establish meteorological forecasts combining American and Canadian ensemble systems
The screen displays for a meteorological variable, a large format chart of North America containing the probability of occurence of an event for periods varying from 1 to 15 days. Probabilities are computed for each point in the chart by counting the number of members which forecast the event during the period, divided by the total number of members.
The part of the display screen which allows the selection of charts is as follow :
Probabilistic Products by period for NAEFSBefore explaining the different parts of this screen, it is necessary to distinguish between forecast and issued dates. The issued date is the date when the forecast process was initiated. The forecast dates are the dates defining the period of the generated chart. 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 probability for the current day issued that same day for precipitation amounts over 0.2 mm.
The selection options are divided in 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 period of the forecast by changing the beginning and ending forecast dates.
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 period.
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 product type. If the browser does not use JavaScript, a VIEW button will be present to activate the changes requested.
The next table gives a list of the probabilistic products available :
| Meteorological variable | Threshold | Number encounter |
|---|---|---|
| Precipitation | More than 0.2 mm | Everyday |
| More than 2 mm | At least one day | |
| More than 5 mm | At least one day | |
| More than 10 mm | At least one day | |
| More than 25 mm | At least one day | |
| Accumulation of precipitation | More than 0.2 mm | Everyday |
| More than 2 mm | Everyday | |
| More than 5 mm | Everyday | |
| More than 10 mm | Everyday | |
| More than 25 mm | Everyday | |
| More than 50 mm | Everyday | |
| Surface Wind Speed | Over 15 km/h | At least one day |
| Over 50 km/h | At least one day | |
| Over 90 km/h | At least one day | |
| Minimum Surface Temperature | Under 0°C | At least one day |
| Under -5°C | At least one day | |
| Under -15°C | At least one day | |
| Under -30°C | At least one day | |
| Maximum Surface Temperature | Over 0°C | At least one day |
| Over 15°C | At least one day | |
| Over 30°C | At least one day | |
| Windchill | Under -15 | At least one day |
| Under -30 | At least one day | |
| Under -40 | At least one day | |
| Under -55 | At least one day |