A dramatic formation of stratocumulus stratiformis radiatus cloud stretching from one horizon to another as typical of this variety forming broad and parallel bands. Later on stratocumulus volotus or roll clouds were witnessed over parts of Malta mainly over Birzebbugia and the western side. The clouds looked thick as the airmass was moist and very turbulent. The first thumbnail is a panoramic view of the same cloud showing its large extent over the sky. In fact, the weather sounding on the third thumbnail showed lots of wind shear and a relatively unstable low-level airmass capped by an inversion allowing the cloud to start rolling in itself. The second thumbnail photo is an upper-level cumulonimbus cloud during a thunderstorm stretching from an altitude of 4.8km up to 12km and it looks buffetted due to lots of wind shear.
This occurred as a line of bad weather in association with an unusually late mid-latitude cyclone or low pressure system (not the typical Spring heat lows) that developed over North Africa moved northeastwards passing over the Maltese Islands as depicted by the SLP chart on the fourth thumbnail. This chart is in line with the clouds over the visible satellite and the rain radar imagery on the fifth and sixth thumbnails respectively. The unstable airmass having originated from a much warmer area and passing over a very cool sea as depicted by ‘Il-Kaptan’ app, the pre-cold frontal airmass following this line of bad weather had cooled significantly inhibiting thunderstorm development at low-levels. During the late afternoon, fog enveloped the higher elevations of Malta as explained in the cloud post here ‘Frontal Zone‘ which was a very rare weather event for late May in Malta. Brief situation: A wintry low pressure system due to a strong jet stream forming over hot Africa and moving towards the cooler Central Mediterranean leading to a general stabilization and cooling of the airmass unlike in Winter when the warmer sea gives rise to instability hence the formation of low-based cumuliform clouds with sometimes heavy thunderstorms.