What is “omega block”,?

An omega block is an extreme version of a “blocking high”, an area of high pressure which remains stationary for a prolonged period. It gets its name from the way that the jet stream bends around the high and the lows on either side of it, forming a shape resembling the Greek letter omega – Ω. This type of block can remain in place for weeks, preventing the normal eastward progression of weather systems. Last month’s blocking high fixed a lowpressure area over western Europe.