Where has all today’s upper cloud come from? Part II

For those are vaguely interested by the high cloud that invaded the skies across the UK yesterday, I did finally manage to track down a Watnall (Nottingham) ascent. As far as I can see the auto-sonde ascent at 11 UTC didn’t happen, or perhaps it did, only for the balloon to fall prey to an attack by a group of local vigilantes wielding bows and arrows clad in Sherwood green. Even though the ascent was ten hours later, it did show a N’NW’ly flow at 300 hPa which explained how the cloud was moving south in my satellite animation. The humidity, which are pretty high at this altitude, 89% at 28,000 feet, also confirms the cloud was thick cirrus and cirrostratus, with a base of around 25,000 feet and tops right up to the height of the troposphere at almost 35,000 feet.

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