Line of cumulus clouds formed locally over the Maltese Islands due to the sea breezes opposing winds in an otherwise almost calm wind field. This was clearly depicted on the visible satellite image in the first thumbnail. The second and third thumbnails are another view of the cloud line and a closeup on the cloud composition of cumulus radiatus respectively. The weather sounding showed a humid airmass at the surface with the air becoming drier and cooler higher up. This combined with landmass heating caused the clouds to form but the air was not unstable enough for thunderstorm clouds to develop. These clouds then spread horizontally (stratocumulus) before dying out completely in the evening. The instability chart (fifth thumbnail), unlike the weather sounding, showed higher CAPE values (meaning more instability) located just over the Maltese Islands. Such clouds over Malta seem to occur in broad areas of relatively high pressure.