They are updated every 30 minutes.

The wind directions are given in magnetic and they may contain aerodrome information in addition to weather information.

They are based on Met Office forecasts for the next two hours.

They are broadcast centrally from National Meteorological Centres.

Visual from radiosondes

Visual with a polar orbit

Visual with a geostationary orbit

Infrared (IR) with a polar orbit

Thunderstorms develop over the valley.

Unstable air forms as the warm air comes over the valley.

An inversion forms as still air in the valley cools.

Orographic fog forms on the upwind side of the valley.

Arise in pressure

A drop in pressure

Irregular fluctuations

Approximately constant pressure

75%

95%

65%

50%

A downslope wind.

An anabatic wind.

An increase in dew point value.

An increase in ground humidity.

3

1

2

4

Descend. The indicated airspeed will decrease

Descend. The indicated airspeed will increase

Climb. The indicated airspeed will increase

Climb. The indicated airspeed will decrease

on the upwind side of the mountain range.

directly over the mountain range.

on the downwind side of the mountain range.

when instability is high.

(5) lightning; (3) gust front; (1) windshear.

(3) severe windshear; (5) windshear.

(1) lightning: (4) gust front; (3) windshear.

(3) no wind; (5) windshear; (1) lightning.