Black Hole Pulse

Whereas a Dark Pulsar creates a slow wave which calms down the Hypersea for a significant while, a black hole can create the opposite. On the rare occasion that a black hole's relativistic jet comes anywhere near our shipping lanes, the effect is that of not just a storm, but a full hurricane. Hard to see coming, these black hole pulses can lead to fatalities.
Not as impactful as the Lux Aeterna in the Hyades cluster, where said jets are actually tearing into hyperspace itself, normal black hole pulses simply indirectly influence Starships passing by. The ripple effect created by the jets impacts dark matter in normal space, which in turn causes waves in the dark energy of the Hypersea. These waves do not impact Relativity, but greatly lower the local Tranquility.
Some compare the effect to a hurricane, others to a tsunami. The second might actually be rather apt, as an incoming black hole pulse actually does cause an initial rise in tranquility. For an expert Stormfarer, this may very well be the only clue they have to batten down the hatches. Some captains will immediately drop out of hyperspace to avoid the impact. Others will risk staying in, on account of it being very hard to tell from normal space whether the storm has passed.
Strangely enough, even though the jets originate from normal space and do not travel into hyperspace, the resulting black hole pulses impact hyperspace at a velocity far greater than the speed of light. Scientists currently suggest the pulses vibrate into the surface of hyperspace and cause an oscilation that then traverses through the membrane between normal space and the Hypersea. This theory is not yet fully supported, but it does offer a reasonable explanation that does not violate the laws of physics in normal space.