For radio waves the most important reflector is the ionosphere - signals which reflect from it will have their polarization changed unpredictably.

Tempos and dynamics change rapidly and unpredictably in order to reflect strong changes of emotion.

Additionally, if the demand for money does not change unpredictably then money supply targeting is a reliable way of attaining a constant inflation rate.

Conditions can change unpredictably with dramatic consequences.

It changes so unpredictably that shelling is impractical.

Does it change constantly, such as in a bubble sort or does it change unpredictably?

Eras Come and Go But what stirs the electorate can change quickly and unpredictably.

There were often many parties represented and the alliances and factions changed quickly and unpredictably.

The shapes of the miraged object are changing constantly and unpredictably.

Mark-to-market accounting can become inaccurate if market prices fluctuate greatly or change unpredictably.