Noctilucent clouds behave unusually – as a rule, they begin to fade at the end of July, and then completely disappear in August, which is a seasonal pattern.
However, this year the noctilucent clouds by the end of July became even more intense. Kairo Kiitsak took this picture in the town of Simun in Estonia. According to him, on July 26, the noctilucent clouds over the city looked amazing. In general, they could be watched for 3 hours.
These clouds also appeared in the south of Poland, where they were admired by Marek Nikodem before the sunrise on July 28. He noted that this was a real surprise, because, as a rule, the season of noctilucent clouds in Poland ends on July 25.
Noctilucent clouds are formed when summer water vapor rises to the top of the atmosphere and envelops meteor smoke. The mesospheric winds contribute to the formation of the resulting ice crystals in the noctilucent clouds. In 2017, a thermal wave in the mesosphere melted these crystals, which led to a short period of absence of noctilucent clouds. Could something like that happen, but the opposite happened at the end of the season of noctilucent clouds? Perhaps the cooling in the mesosphere extended the season? Another possibility is the solar cycle. Previous studies have shown that noctilucent clouds can sometimes become more intense during the solar minimum. At present, such conditions are in effect – in recent months the activity of the Sun has fallen to zero.