A thundery shower with graupel or snow pellets had passed over the southern side of Malta. Graupel could be considered as a hybrid between snow and hail. In Malta, snow pellets are only possible during the cold months when surface temperature is about +10C and lower. Hence, it is considered as wintry precipitation. Such precipitation only falls from cumulus and cumulonimbus clouds similar to the one photographed hours later whose upper part was rendered very diffuse possibly due to accumulation of ice crystals. Graupel requires that a snow flake or crystal inside cumuliform clouds interact with super-cooled water droplets inside the cloud which would then instantly freeze upon it forming a particle of small ice encasing the snow nucleus. In fact, the first thumbnail fully confirms the preciptation type which consisted of a very small, whitish, non-transparent and roundish ball of ice particles having snow-like characteristics such as that it could somewhat stick to form a snowman. The graupel or snow pellet had a diameter of less than 5mm and it was easily crushed when cars passed over it and also made plenty of sounds unlike soft hail which is quit. As the process implies, there needs to be some sort of turbulence or convection in order for the crystal to bump into super-cooled water droplets, a process which only happens within cumuliform clouds hence such formation is practically impossible inside stratiform clouds such as nimbostratus.

The weather sounding on the fourth thumbnail showed conditions ideal for graupel to form being an unstable atmosphere with plenty of moisture at all levels leading to the production of super-cooled water droplets inside cumuliform clouds. However, at around 1300 metres, the freezing level was rather high for such a phenomena depicting the unpredictability of weather. The trigger for the cumuliform cloud formations and subsequent wintry precipitation was an extended upper trough shown in the fifth thumbnail further fuelled by the inflow of a cold airmass over a warmer Mediterranean Sea as depicted in the satellite image of the sixth thumbnail. By the way, the third thumbnail photo shows a photometeor being a double rainbow arc that is a primary rainbow followed by a secondary bow with inverted colours from the main bow. Since rainbows require both sunshine and falling rain acting as a prism, this photometeor can only occur when having cumuliform cloud formations or an approaching or departing rainfall event having at least part of the sky completely clear.