SPECI Parameters

Question 1

Wind direction

Answer 1

A change in mean direction of 30 degrees or more, the mean speed before or after the change being 20kt or more

A change in mean direction of 60 degrees or more, the mean speed before or after the change being 10kt or more

Question 2

Wind speed

Answer 2

A change in mean speed of 10kt or more

A change in gust speed of 10kt or more, the mean speed before or after the change being 15kt or more

Question 3

Prevailing visibility

Answer 3

Change from one of following ranges to another:

10km
5000m-9km
3000m-4900m
2000m-2900m
1500m-1900m
800m-1400m
750m or less

If RVR not available, additional ranges apply:

600m-750m
350m-550m
150m-350m
100m or less

Question 4

RVR

Answer 4

Only by local arrangement. Following visibility ranges apply:

800m or more
550m-750m
300m-500m
275m-175m
175m-50m
50m or less

Question 5

Minimum visibility

Answer 5

Onset or cessation of minimum visibility.

Or, if reported, if the minimum visibility changes from one of the following ranges to another:

10km
5000m-9km
3000m-4900m
2000m-2900m
1500m-1900m
800m-1400m
750m or less

Question 6

Present weather

Answer 6

Onset, cessation or change of intensity of any of the following weather phenomena:

• Freezing precipitation of any intensity
• Freezing fog
• Moderate or heavy precipitation including showers
• Thunderstorm with or without precipitation
• Squall, funnel cloud
• Low drifting or blowing snow, sand and dust

Question 7

Cloud

Answer 7

When the lowest layer of cloud (BKN or OVC) changes from one of the following ranges to another:

2000ft or more
1500ft-1900ft
1000ft-1400ft
700ft-900ft
500ft-600ft
300ft-400ft
200ft
100ft
<100ft

Or, when the lowest layer of cloud below 1500ft changes from 4 oktas or less to more than 4 oktas and vice versa.

Question 8

Temperature

Answer 8

Change of 2 or more degrees since last report.

Question 9

Pressure

Answer 9

When the as read pressure changes by 1 or more hPa since the last report.