Weather Radar - How to Use

Using Environment Canada's radar data can be quite beneficial in weather sensitive decisions. To assist users, a comprehensive table of contents is listed below.

Table of Contents

Using the Radar Images

The RADAR images can be broken down into 4 main sections.

  1. Animation - Playback Controls
  2. RADAR images
  3. Overlays
  4. Intensity Scale

1. Animation - Playback Controls

How you can use the playback controls. The following is an explanation of the common playback controls for the different views of the radar images.

  • The first picture loaded in your browser at any level of view is the latest image available. Any playback button which can produce an action will be in blue and clickable, while the buttons which can not produce an action will be in grey and disabled. The functionality of the buttons is determined by the position of the viewed image and the total number of images in the series.

    row of Playback controls

The displayed image will be, by default, the latest one available in a series of 7 or 10 images. The time interval between images is either 10 or 20 minutes. To animate the series of images, you first need to click the "Play" button in the playback controls above. The animation of the images will stop after 5 minutes of uninterrupted play. Re-selecting the play button will re-activate the animation. In addition, you can select the images individually.

The Playback Controls are as follows:

  • Play button Play: Used to "play" or activate the series of images in the loop.
  • Stop button Stop: Used to "stop" the series of images in the loop.
  • First image Button First Image: Used to loop back to the first image in the series.
  • Previous image button Previous: Used to move backward one image at a time.
  • Next image button Next: Used to move forward one image at a time.
  • Last image button Last Image: Used to loop ahead to the last image in the series.
  • Increase speed of animation button Increase the speed of the animation in the loop of images.
  • Decrease speed of animation button Decrease the speed of the animation in the loop of images.
  • reset speed to default setting Reset the speed of the animation to its original setting.

The Short Animation (1 hr) will be a series of 7 frames at 10 minute intervals and the Long Animation (3 hrs) will be a series of 10 frames at 20 minute intervals.

Default selection for Animation is Short (1hr).

2. Radar Images

Description of the three level views

2.1. National View

Weather radar animated graphic for Canada.

2.2. Regional View

Weather radar graphic for stations located in a Region

2.3. Local View

Weather radar graphic for a station

3. Overlays

All Overlays will appear upon selection and can be combined with other overlay layers.

By default, the cities layer is displayed at national, regional and local levels.

By default, the local level radars will also display circles, and roads.

4. Intensity Scale

The radar layer can be displayed in either eight or fourteen colour levels on the regional and local views.

By default the eight level colour palette is displayed.

Short term forecast

How to Estimate Motion of Precipitation in Radar Images?

By comparing a series of RADAR images, forecasters can observe the development of a disturbance, follow its trajectory, determine the intensity of precipitation, issue alerts or warnings, and fine-tune their forecasts. You too can apply a few techniques to make a short term forecast.

How to animate our RADAR images to make a short term forecast (1 to 3 hours)?

  1. Select a RADAR site.
  2. Click on the "Play" button to activate the controls.
  3. Observe the movement of the precipitation echoes on the screen.

Note: The local view radar image is oriented such that true North is located at the top of image.

Now, you need to determine the speed at which the echo is moving. This will allow you to forecast where it's likely to be in 1 or 2 hours. For this, you need to choose 2 images with a one hour interval.

Suggested method:

  • Back the pictures one hour from the time of the latest image and note where the precipitation echo is located.
  • Now go back to the latest image and measure the distance between the 2 echo positions.
  • Compare this to the distance between 2 of the concentric circles on the image.
  • Knowing that the distance between 2 circles is 40 kilometres you can estimate the speed at which the precipitation is moving and in what direction.
  • Knowing that "North" is located at the top of the image, echoes moving to the right, for example can be properly interpreted as moving eastward.

Example:

Let's say that precipitation echoes are moving from the west towards the radar and you want to know when the precipitation will reach the radar site (the centre point).

  • You have noted that the echoes on the image from an hour ago touch the 4th concentric circle (160 km from the RADAR).
  • The most recent image shows that the echoes have reached the 3rd concentric circle (120 km from the RADAR).
  • This means that the precipitation is moving at 40 km/h towards the RADAR.
  • If the speed of the precipitation doesn't change, you can expect that it will reach the RADAR in 3 hours.

You can also identify whether the intensity of precipitation is getting stronger or weaker by watching the color variations of the corresponding echoes. Similarly, you can identify the trend of precipitation (weakening or developing) by noting the expansion or contraction of the total coverage area in time.

Conclusion

You can now make your own short term forecast based on the movement of the RADAR echoes for any point on the RADAR screen.

All you need to do is:

  1. measure the distance between the echoes with a ruler,
  2. compare this with the concentric circles distance, and
  3. determine the speed at which precipitation is approaching.