A rare example of clouds in sinking air called mammatus. These have pouch-like structures hanging from beneath the cloud resembling the udders of a cow. Mammatus can form on the underside of cumulonimbus, cirrocumulus, altostratus, altocumulus and stratocumulus. In this case, it formed under altocumulus hence the name `Altocumulus mamma`. For mammatus to form, the sinking air must be cooler than the air around it and have high liquid water or ice content. The latter condition could be easily confirmed from the meteogram shot since mid and upper level air were very moist. Mammatus can be long lived if the sinking air contains large water droplets or ice crystals since larger particles require greater amounts of energy for evaporation to occur. In our case, the chart at 500mb seem to indicate sinking air motion over Malta while the clouds themselves were brought over from Africa. Adapted from NOAA.