Ever wonder why hot air balloons are grounded when it looks okay outside? Lots of factors must be considered before going flying, especially here in Bristol and Bath. Click to read more!
So what is the ideal weather for ballooning? This is something we get asked a lot. Hot air ballooning is completely weather dependant and the weather in the UK is very unpredictable, as we all know. But even if winds are calm on the ground and conditions seem good, it could be a very different story at a few thousand feet. So, what weather can and can’t balloons fly in?
Balloons need light, stable winds and dry conditions to fly, but many other things need to be taken into consideration. The wind direction and strength at 500ft, 1000ft and 2000ft are available to pilots on ballooning forecasts and are essential. There could be a gentle breeze on the surface but blowing more than 25 knots (kts) at the height you will be flying in.
Flying high above the clouds during a early morning flight. Photo: Liam Whitelock
What are the limits on wind speed?
The limit is around 20kts at 2000ft with lighter winds at lower level but ideally it would be much less. Good conditions are up to 8kts on the surface. As the wind increases it becomes more difficult for the pilot to control the balloon and inflation can become very tricky. No wind at all is great although won’t get you very far, and, however in Bristol that would be far from ideal.
It’s possible to fly in much higher winds and you can find plenty of videos of balloons flying in foreign countries inflating and taking off in crazy weather, but this wouldn’t happen in the UK.
Can balloons fly in rain?
The simple answer is no. Although it is possible, it’s unpleasant for passengers. But flying or tethering in rain can also have more serious effects on the envelope by deteriorating the fabric (ripstop nylon and hyperlast).
As you will have seen, a petrol fan blows cold air into the envelope and when fully inflated, using the burner the pilot fires propane into the mouth of the envelope. Hot air rises in cold air. This causes the top and crown ring of the balloon to become very hot reaching temperatures of 85 degrees Celsius. If rainwater has gathered on the balloon, it could reduce its flying life considerably.
What else should be considered before flying?
Low cloud bases under 1000ft and poor visibility is an important factor as if you’re unable to see where you’re going, there’s not much point in flying. It’s also not safe. Of course if there are any storms nearby flights will be cancelled.
A stunning flight from the maize field near Bath alongside Anana and local pilot Ben Alford. Photo: MJ Ballooning
What’s it like flying in Bristol and Bath?
In this country, the prevailing winds come from the west which is a good direction for flying in our region. From main launch site Ashton Court this will take balloons over the city and out to Wick and Keynsham. Pilots will often aim for a particular landing site such as Talbot Farm or the old chocolate factory in Keynsham.
Westerly winds are great from Bristol unless they are too slow. Generally, around 8-10kts is preferred to ensure a safe flight to the other side of the city. Bristol airport is also nearby, so a north easterly is no good. An easterly direction will often see Bristol teams divert to Bath and fly back towards south Bristol or Bishop Sutton and Chew Valley lake. This is unless it’s slow enough to fly to Nailsea from Ashton Court. Sometimes it's a matter of getting up, going to the launch site and letting off a helium balloon to determine the winds, which is known as a met balloon.
A particularly tricky direction is a south easterly especially when there’s a steady wind, as this takes balloons from Ashton Court towards Avonmouth and teams from Bath over central Bristol. Finding a suitable landing site can be challenging. So, taking all this into account you wouldn’t think that ballooning in Bristol, in particular Ashton Court, would be any good with the River Severn, the airport and a huge city over the trees, but once airborne the views are simply incredible. And it all started in the 1970s thanks to Don Cameron.
View over Ashton looking towards Clifton and the Suspension Bridge. Photo: MJ Ballooning
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