Formation of mid to high-based cumuliform cloud (base at an altitude of at least 5km) due to the arrival of an African low pressure combined with instability at that level caused by steep-level lapse rate. Note that only surface air features change when desert air moves over the Mediterranean Sea with air higher up remaining practically unmodified. The second thumbnail shows the formation of arranged fish-bone structured high-level clouds pending the passage of an African low pressure system which formed late for the period.