One such pattern is called an "Omega block." The name comes from a resemblance to the Greek letter Ω on a weather map. It’s created when two low-pressure systems become cut off from the main flow of the jet stream, and a high-pressure system is sandwiched in between them.
This type of pattern usually results in cooler, wetter weather where the lows are situated and drier, warmer weather where the high is located.
Omega blocks are usually large, which means they are one of the more stubborn blocks to break down. This can create concerns about flooding where the wet weather persists and drought worries where the dry weather happens.