halcyon

Ceyx and Alcyone were deeply in love. One day Ceyx had to leave on a journey. Alcyone begged him not to go, because she was afraid he would die during a storm at sea. But he left anyway.

Sure enough, a storm destroyed Ceyx's ship, and everyone aboard drowned. Back at home, Alcyone waited for Ceyx to return. She prayed to the gods for him every day. The goddess Juno took pity on her and sent a messenger in a dream to tell her of her husband's death.

When Alcyone awoke, she was distraught. She went down to bluff where she had waited for Ceyx to return. In the distance she saw a corpse floating toward shore. When it was close enough, she recognized Ceyx. She jumped into the water, so she could die and be with him, but the gods took pity on them and transformed both of them into birds.

Now every year there is one week of very calm water at sea. During this time Alcyone floats in her nest on the sea until her eggs hatch. After the young birds are born, the spell is broken. Those seven days are called Alcyon or, more commonly, Halcyon days, a time of peace and tranquility.

Which of the following phrases might a meterologist use to describe the weather on a halcyon day?