The Climatological Character of Simultaneously Occurring Blocking Events

In this work, the climatological character of simultaneously occurring blocking events will be examined. Some previously published papers have proposed without strong evidence that simultaneously occurring blocking events are stronger and more persistent than those that occur in isolation. Simultaneous blocking events are defined as those that occur at the same time but in different parts of the Northern or Southern Hemisphere. Using the NCEP reanalyses, and the blocking archive at the University of Missouri, the character of simultaneously occurring blocking events is examined from the late 1960’s through 2025. Specifically, this study will examine the intensity, duration, and onset location of simultaneously occurring blocking events versus those that occur as singular events. This work found that the increase in block occurrences during the early 21st century has been, as expected, accompanied by an increase in simultaneously occurring blocking events in both the NH and SH. It was also found that in both hemispheres it is not generally true that simultaneously occurrence blocking events are stronger and more persistent than solitary blocking events. However, it may be true that simultaneous blocking events are either stronger and/or more persistent depending on the season or year. Additionally, in the Northern Hemisphere, Pacific Region blocking events have a greater chance of being part of a simultaneous blocking episode, while blocking in the European Sector has a greater probability of occurring as a singular event. In the Southern Hemisphere, blocking in the Western Pacific is less likely to be part of a simultaneous blocking episode. This information could be used to anticipate the weather for a region such as North America, which may experience more persistent weather regimes.