Just a Little Black Raincloud
For three days it rains in Arx. Three long, heavy days where it rains, and it does not let up, not even for a moment, with a howling wind with a howling wind that swirls and beats at the shutters of the windows. It's a miserable time, and people are tired, soggy, and a little depressed when it finally lets up and the wind dies down. But after it lets up, and people survey the damages to the city - which are fortunately minimal.
Until reports from the harbor come in. Fortunately, this is not a repeat of the Great Harbor Tragedy. But it does seem that a whirlpool has appeared at the mouth of the harbor that leads to the Mourning Sea, and Arvani ships are unable to pass it, even by skirting the edges. Eurusi, Cardian, and the Empire's ships seem to have no troubles, but Arvani ships are not doing well. Which doesn't help trade at all. Market prices rise for even the most basic of staples, and nothing seems to explain the sudden appearance of such a disruption to everyday life.