Question - cloud suck v thermic climb

[Graeme]

This may sound like a daft question but when I was out the other day and did a little thermalling I was thinking how would I know if I was still climbing in thermic lift or being sucked up by a cloud. How do you know the difference and what is the threshold from one to the other?

[John Wallis]

In a perfect world as you approach the top of a thermal the lift usually gets less you will find this on a high pressure day as the pressure limits the vertical development. When you're in a low pressure system the clouds are usually much bigger (Big cauliflower tops) These are the boys that will give you the cloud suck you mentioned. Be cautious with these clouds

Plus there's no such thing as a daft question

[gary stenhouse]

as john says the lift often lightens closer to base however if you start going up faster as your approaching you are in cloudsuck and you will be into cloud.

[Graeme]

Cheers chaps - I've experienced high pressure thermals a few times and the drop in lift just under the inversion - which I haven't been able to break through yet.

But when there's clouds overhead in low pressure from what you say the process would be - eg strong thermic lift then stronger cloud suck lift as you approach base? At which point in relation to the height of cloud base would this normally occur?

Can you judge the point in the climb to avoid being sucked up or do you just take evasion action upon noticing your climb rate has increased?

[ron freeman]

Generally Graeme, The bigger the cloud the more suck you will have.. so never take your eyes off a building cloud !

To produce strong thermals you need 'Good lapse rate' 'powerful vertical sun' & 'dry large areas that heat up well.

Wet thermals (with moisture) they will be stronger in the middle and slow down near the top of the thermal. This is why when you are in a thermal pilots below you tend to always catch you up because they are in better lift.

A lot of pilots think they have lossed the centre of their thermal when reaching the top and end up flying out of it looking for better lift..

Always fly to the edge of the cloud well before reaching cloudbase as to avoid being sucked into it.

Blue thermals (dry air) are normally nasty buggers.. lots of little cores low down then a good core higher up, thats if you have managed to stay in it !

[brian day]

If you look up at the cloud at about 45 deg, 10 - 11 o'clock (2-3) and you can see the edge, you should be able to fly to the side of the cloud and avoid going into it. Obviously this is just a generalisation, but a good rough rule of thumb. If your climb rate starts to increase start to take avoiding action, one more turn is usually to late, you can always dip your toe back in for a top up, but once in the white room, it's very disorientating, wet and frightening, especially the first time.

[colin keightley]

As its very rare I thermal fly, quite often even getting into the wispies has me crapping myself