Dic: brew (one of its meanings as a verb)

• We'd seen the storm brewing when we were out in the boat.
• At home a crisis was brewing.
• There's trouble brewing.

VERB : usu cont. | If a storm is brewing, large clouds are beginning to form and the sky is becoming dark because there is going to be a storm.

VERB : usu cont. | If an unpleasant or difficult situation is brewing, it is starting to develop.

... Cobuild