Arthur Street, flight director and festival organiser of Tiverton Balloon & Music Festival, walks us through his methodology of deciding “to fly or not to fly” at balloon festivals.

As flight director, my responsibility is to ensure the safety of the flights and the public at this festival. In the days prior to and during the weekend I primarily work closely with the Met Office using their various resources including Talk to a Forecaster and Aviation Forecasting Services Ballooning Forecasts by region, low level Spot Winds, TAFs, Airmet, Briefing charts 214 and 215, Synoptic Charts, Mesoscale and rainfall radar. Combining all these reports together I get a good picture of the likely weather conditions for the festival.

Highly weather dependent

As hot air ballooning is highly weather dependent activity, you need your forecasts to be as precise as possible. If I can be reasonably assured of these conditions for the planned time of flight plus 30 minutes margin thereafter, than I will declare the launch site open which allow the pilots to fly at their discretion (as with all aviation, the final fly/no fly decision is always at the pilots discretion). If I cannot be confident that conditions are going to be suitable then I will not allow the balloons to fly, disappointing as that might be for both the public and the balloon teams.

How the weather effects hot air ballooning

The main factor is the wind, ideally there needs to be less than 10 knots of wind on the surface and up to 300 – 500 feet and preferably less than 20 knots at 2,000 feet. Due to the size of the balloon envelope, standing the balloon upright in more than 10 knots is almost impossible.

Subject to not running out of land an experienced balloon pilot can land a balloon in 50% or more stronger surface winds than it is possible to inflate in, you just have to wait for the right size field straight ahead to come up.

Frequent problems we face in the summer are thermic activity and sea breezes. For this reason we only schedule mass ascents at balloon festivals first thing in the morning (just after sunrise) or last thing in the day (90 minutes or less before sunset). At this time of the day the air is at its most stable for hot air ballooning, as balloons do not fly in the dark.

Win tickets to the Tiverton Balloon & Music Festival

The Tiverton Balloon & Music Festival takes place on July 12-14 in Tiverton, Devon. Headline attractions include 40+ live music acts and 30 + hot air balloons of all shapes and sizes, taking to the skies every morning and evening subject to weather.

We’re giving away four pairs of tickets to this event, to win tickets comment below with the answer to the following question:

What does the wind speed have to be for a balloon to take off?
a) Less than 5 knots
b) Less than 10 knots
c) More than 10 knots

The closing date is Monday 8 July 2013.

Visit the Tiverton Balloon Festival website to find out more about the events and buy tickets.

Keep up to date with the weather for the festival on our events page.

Too windy for ballooning? Find activities for other weather conditions.