Canadian Hurricane Centre Forecasting

Satellite Forecasting at the Canadian Hurricane Centre

The CHC, along with the Atlantic Storm Prediction Centre, gathers important weather data from two orbiting satellites. One of these satellites is a polar orbiting satellite which orbits the Earth around the North and South poles at a height of about 850 kilometres. The other satellite is a geostationary satellite and remains in the same place about 35, 000 kilometres above the equator. The geostationary satellite follows an orbit above the equator at the same rate as the equator turns - one cycle per day.

Both satellites take two main types of photographs: visual and infrared. The infrared photographs measure the temperature of the surface beneath it (the earth, sea clouds, etc…) as it is radiated back into space. Dark and light colours represent the amount of radiation. For example, a white colour represents a surface that is a lot colder than a grey colour. Visible satellite images provide information about the observed cloud cover as indicated by the amount of solar radiation reflected from the clouds. The reflectivity of an object is a measure of its albedo. Both images can indicate shape and texture. A rough surface would indicate cumulus type clouds while a smoother surface would indicate stratus type clouds. The pictures can determine the temperature of the ocean water, the presence of circulation, and the height of moisture in the atmosphere. Knowing these factors is vital in the forecasting of tropical cyclones. See How to Interpret a Satellite Image.

Click here to see a geostationary satellite image of Hurricane Hortense Latest Satellite Image

Radar Forecasting at the Canadian Hurricane Centre

MSC - Atlantic operates radar stations in Gore and Marion Bridge, Nova Scotia; Chipman, New Brunswick; Marble Mountain and Holyrood, Newfoundland and Labrador. Radar works by sending out a radio wave at a very high frequency. When the radio signal hits raindrops, part of the signal bounces back to the radar at the speed of light. By measuring the time it takes for the signal to bounce off of raindrops or snowflakes and return to the station, it can be determined how far away the objects are. If the signal does not bounce back, then the area is clear (no rain or snow). Also, the percentage of radar beam that bounces back to the radar indicates the amount of rain or snow that is falling. Generally, the higher the percentage of radar beam that bounces back, the more rain or snow. The measured time of the signal bouncing back to the station is then translated into a colour pixel on a computer generated image. The colours can range from light blue (a little rain) to light pink (a lot of rain). The values that these colours represent can change from time to time so it is important to look at the legend carefully. See How To Interpret A Radar Image.

In tropical and post-tropical cyclone forecasting, radar is essential in order to determine current precipitation amounts and forecast future precipitation amounts. Since a new image is received by Environment Canada every ten minutes, precipitation trends can be observed and predicted.

Click here to see a radar image of Hurricane Hortense Latest Radar Image

Buoys in Forecasting

The Environmental Monitoring Division of the Meteorological Service of Canada - Atlantic Region has a series of 8 buoys in the Atlantic Ocean that are used in hurricane forecasting. Environment Canada maintains these buoys, with support from the Canadian Coast Guard.

Location of the buoys

The Environment Canada Oceanographic Data Acquisition Systems (ODAS) weather buoys are moored off the coasts of Nova Scotia and Newfoundland. The data collected from the weather buoys are used hourly by meteorologists. The buoys have a large hull and two masts with several types of monitoring equipment. They measure average wind speed and direction, maximum wind speed, wave height and period, atmospheric pressure, air temperature, and sea surface temperature. Every hour, the buoys transmit the data via satellite to several weather centres in North America.

The ODAS weather buoys are essential for CHC hurricane forecasting. Unlike satellite data, the data received from weather buoys does not require any interpretation. The buoys report actual values.

Click here to see an example of buoys at work during Hurricane Danielle

Computer Programs at the Canadian Hurricane Centre

The cornerstone of the Canadian Hurricane Centre is a workstation using a multitasking, X-Window environment providing the meteorologist with simultaneous displays of satellite imagery, numerical guidance, forecast bulletins, and observational data from around the world. The software program, Hurricane Forecasting Graphical Interface (HURR), enables the forecaster to view historical and real-time tropical cyclone information, plot data, construct storm tracks, and translate track data into text bulletin.

Click here to see a product of the HURR program

Canadian Hurricane Centre Bulletins

The CHC issues Prognostic Messages and Information Statements when a tropical storm, hurricane, or post-tropical storm is forecast to enter the Response Zone within 72 hours. These statements are issued every 6 hours until the storm no longer poses a threat to Canadian waters or territory. Position and intensity update bulletins are issued every 3 hours when significant effects from a tropical storm, hurricane, or post-tropical storm are expected over land.

Click here to see two examples of CHC Information Statements.

Related Links:

• What is the Canadian Hurricane Centre?
• Canadian Hurricane Centre's Responsibilities