A “blocking” weather event is a persistent area of high pressure which can sit over an area for a long time period, blocking or shifting the movement of weather systems through the area. This commonly results in hot, dry weather in the area of blocking high pressure but can also result in catastrophic flooding in areas where the weather systems and the jet streams that push them around are shifted. As you might expect, blocking highs are often related to dry spells that can cause problems for forage and crop producers and lead to drought if they last long enough.
One question that climate scientists have is whether or not the frequency of blocking highs has changed over time, because if they occur more frequently you might expect the number and severity of droughts to also increase. It’s not an easy question to answer, though, because climate models are not good at producing these kinds of weather patterns reliably. So the answer so far is, we don’t really know. You can read more about blocking weather patterns and how scientists are looking at them here.
