RAF VOLMET: weather for British military airfields on 5450 kHz

What you hear

A steady automated voice reads airfield weather in a loop: the airfield's name, the time of the observation, wind, visibility, cloud, temperature and QNH, and then, at the end of each report, something you never hear on a civil VOLMET: a colour. "Colour state blue", "colour state green", "amber", "red". Each report takes about twenty seconds, the cycle runs through a couple of dozen airfields, the station identifies itself and the loop starts again.

The colour is a military shorthand for how flyable the weather is. Blue is the best, with a high cloud base and long visibility; then come white, green, yellow, amber and red as the cloud gets lower and the visibility shorter, and black means the airfield is unusable for a reason other than the weather. A pilot hears one word and knows at once whether a diversion there is possible. For the listener it is the quickest way to tell a fine day in Lincolnshire from a foggy one on the Moray Firth.

Who transmits and why

The broadcast serves military crews, mainly of the Royal Air Force, who need current weather for the airfields they fly from and the ones they might divert to: Brize Norton, Northolt, Lossiemouth, Coningsby, Waddington, Marham, Valley and others, plus bases abroad such as Akrotiri in Cyprus and Gibraltar. The list changes over the years as airfields open, close and change role, so an unexpected name is not a mistake. HF reaches an aircraft anywhere between Britain and the Mediterranean with no infrastructure beyond the transmitter itself, and the service has run for decades on the same pair of frequencies.

The transmitter is in England; the program's catalogue places it in the south of the country.

When and where to listen

RAF VOLMET is on 5450 kHz and 11253 kHz, both in upper sideband and both listed as continuous. 5450 kHz is the frequency for the evening, the night and the early morning, and for anyone within a thousand kilometres or so of England by day as well; across Europe it is a reliable catch from dusk onwards and often all day in winter. In full daylight 11253 kHz reaches further, which is why the catalogue lists it as the daytime row.

Receivers in Britain hear 5450 kHz as a strong local signal. From the Netherlands, Germany, Denmark and Poland it arrives by skywave with a slow fade, and from further east it is best in the hours of darkness. The voice is clear enough that the single word of the colour state gets through even when the rest of the report fades.

In ShackDeck

Station catalogue → Aviation → RAF VOLMET. The program selects a public receiver that covers 5450 kHz, tunes it and sets USB; the broadcast is continuous, so there is nothing to wait for. No receiver, antenna or account of your own is needed. The daytime outlet has its own row, RAF VOLMET 11253.