Here's the scoop on today's pair of words: the very general verb dig refers literally to the breaking up or turning over of earth or sand, as with a shovel, spade, or bulldozer. Figuratively, it’s used to talk about finding or discovering something by effort or search: a gossip columnist might dig up some dirt (scandalous information) on a celebrity. The synonym delve has a narrower range of applications; it is most commonly used to refer to examining something carefully: the article delved into the issue of prison reform. Sometimes delve suggests sustained intensive research, more along the lines of the verb investigate. While the distinction seems clear enough today, when delve entered English (long before dig, mind you) it referred to digging up the earth in preparation for planting. Dig overtook delve as the go-to verb for such terrestrial matters, and nowadays the only shoveling delve does is through piles of information.
The noun clue refers to anything that serves to guide or direct in the solution of a problem or mystery: The clue led me to believe that it was Mr. Green in the billiard room! More generally, a clue is an idea or notion: I had no clue Mr. Green was planning a surprise party! The synonym inkling has a similar duality—it can refer to a slight suggestion or indication of something: They hadn’t given us an inkling of what was going to happen. Or to a vague notion or idea, that is, a slight understanding based on a hint or suggestion: They didn't have an inkling of how the new invention worked. Inkling, however, is used in a slightly more personal sense to talk about one’s intuition or what one suspects. In this way, inkling implies greater feeling or powers of intuition than the noun clue.
You can’t go wrong with the adjective stormy (stormy seas or a dark and stormy night) for describing things affected or characterized by a storm. Tempestuous is a valid synonym for stormy in this literal context (tempestuous ocean), as long as you’re aware that tempest is an old-fashioned, non-meteorological, literary word for “storm.” Tempestuous is more frequently used in its figurative sense of “turbulent or tumultuous,” and is a strong synonym for stormy’s figurative sense. Tempestuous is often used to describe relationships, as in a tempestuous marriage, full of passion and door-slamming. A difficult, unpredictable person prone to outbursts may themselves have a tempestuous personality. The word is also regularly called on to characterize social, political, and economic climates (the tempestuous years before the war).