SPECIs explained

Photo by Tom Barrett on Unsplash


SPECI stands for special aerodrome meteorological report. These reports follow the same format as METARs but are issued when weather conditions significantly change between routine reports. While specific local criteria may be applied at individual aerodromes, the following general criteria are used in Canada:

Ceilings

The ceiling is defined as the lowest broken or overcast cloud layer. Few or scattered cloud layers are not considered ceilings and may not necessitate a SPECI. A SPECI is required if the ceiling lowers or forms at values less than the following:

The altitudes marked with an * require a SPECI only if the aerodrome is equipped with a precision approach.

Examples:

A SPECI is also required if the ceiling rises to or above the specified values.

Examples:

Sky Conditions

A cloud layer can range from few to overcast. If a new layer is observed below 1,000′ or the highest minimum altitude for IFR straight-in landing or takeoff after the METAR is published, a SPECI is required.

Example: If the METAR shows sky clear and a few clouds form at 500′, a SPECI is required.

Visibility

A SPECI is required if visibility decreases to values less than:

Visibilities marked with an * require a SPECI only if the aerodrome is equipped with a precision approach.

Examples:

A SPECI is also required if visibility increases to or above the specified values.

Examples:

Tornado, Funnel Cloud, Waterspout

A SPECI is required if a tornado (+FC), funnel cloud (FC), or waterspout (+FC) is observed, disappears, or has been reported within the past six hours by a reliable source.

Thunderstorm

A SPECI is required if thunderstorm activity (TS) starts, increases to heavy (+TS), or if 15 minutes pass without thunderstorm activity.

Precipitation

A SPECI is required when the following forms of precipitation start, stop (after 15 minutes), or change in intensity:

Obstruction of Vision

A SPECI is required when freezing fog (FZFG) starts or ends.

Wind

A SPECI is required if wind speed doubles from the previous report and exceeds 30 kts. A SPECI is also required if there is a significant change in wind direction.

Temperature

A SPECI is required when the temperature increases by 5 degrees Celsius or more if the previously reported temperature was 20°C or higher, or if it decreases to a value of 2°C or lower.

AIM Reference: MET 8.4

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