Massive cumulonimbus cloud with thick anvil. Such well developed cumulonimbus is very rare during Winter as when they do form, they normally develop between late August and October when the first cool airmasses enter into the Mediterranean Sea and becomes very unstable due to a much warmer sea (sea temperature would normally be at its peak at 26C during early September) hence leading to such clouds formation resembling those seen in more tropical regions. Such cloud tend to be heavy-rain producers and might cause other extreme phenomena such as severe wind gusts and large hail. However, this one seemed to have only produced one large clap of thunder and a heavy rain shower with small hail over some parts of Malta. The weather sounding showed quite a lot of instability for January. This combined with an upper trough and with an upper cold pool of air coupled with cold surface winds created a similar weather scenario which is similar to that which occurs during Autumn as cold air flowing over a warm sea created lots of instability. The first thumbnail, shows the same cloud beginning to loose some of its characteristics. The last thumbnail shows the next day visible satellite image feauturing cumulonimbus clouds on the seas of Northeast Libya as the low pressure system had moved southeastwards from the previous day. Should have there been a strong jet stream, this low pressure would have intensified even further.