Module f14

Step 5. Data Available before Landing: Weather

Recall that weather stations on the ground produce aviation routine reports of weather observations every hour (METARs). If the weather is changing rapidly, then a special off-hour observation is made and is reported as a SPECI.

In addition to the observations described above, Environment & Climate Change Canada (ECCC) produces terminal aerodrome forecasts (TAFs) of the weather expected at the airport.

Also, ECCC produces forecasts for large areas, and these forecasts are presented as a map graphic called Graphic Area Forecasts (GFA).

Synopsis (Overview of the weather situation)

A high pressure region stretched from Hudson Bay (Canada) to eastern Kentucky (USA). A low pressure system was northeast of Quebec city. From this low was a weak front or trough of bad weather extending along the St. Lawrence River and over southern Ontario.

Graphic Area Forecast

Valid for your scheduled arrival time at Toronto. For the greater Toronto area, isolated thunderstorms (CB clouds) with tops to 45,000 feet above sea level (asl) are forecast, with visibilities of 1 statute mile (sm) in heavy rain and mist under those thunderstorms. Also expected are scattered towering cumulus (cumulus congestus) clouds with tops to about 20,000 feet above sea level with visibilities of 6 sm in heavy rain showers and mist.

SIGMET (Significant Weather Warning)

Valid for your scheduled arrival time at Toronto. A band of thunderstorms was observed on radar, satellite, and lightning detection displays. The band was orientated in a northweast - southeast direction, had broken coverage of cumulonimbus clouds, and was not moving. Toronto was under this band of storms. Thunderstorm tops were 44,000 feet above sea level.

TAF (Terminal Aerodrome Forecast)

(Note, you did NOT receive this forecast before arriving at the airport.)
Starting 10 minutes before arriving at the airport: Surface wind 300 degreesTrue at 8 knots, visibility greater than 6 sm, broken cloud layer at 4000 feet agl (above ground level); temporarily, visibility 2 sm in thunderstorms and rain, broken cumulonimbus cloud layer at 2000 feet agl.

Starting 2 minutes before arriving at the airport: surface wind 320 degreesTrue at 10 knots, visibility greater than 6 sm, broken cloud layer at 4000 feet agl; temporarily visibility 5 sm in light rain showers and mist; 30 per cent probability of visibility reducing to 2 sm in thunderstorms and rain, broken cumulonimbus cloud layer at 2000 feet agl.

METAR (Meteorological Aviation Report) or (Meteorological Aerodrome Report)

This is a report of the current weather that was observed 2 minutes before you arrived at the airport. (Note, you did NOT receive this weather report before arriving at the airport.)

Winds 290 degreesTrue at 11 knots, visibility 4 sm in heavy rain and thunderstorms, broken towering cumulus cloud layer at 5100 feet agl, broken cloud layer at 14 000 feet agl, temperature 23 degC, dew point 22 degC, altimeter 30.02 in. Hg (inches of mercury), remarks towering cumulus 6/8, altocumulus 1/8, cumulonimbus associated, cloud-to-cloud lightning visible to the southwest and northwest, sea level pressure 1016.4 hPa.

UBC ATSC 113 Weather for Sailing, Flying & Snow Sports

Last modification: May 2017