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14 FOUR SEASONS BREEZE | FEBRUARY 2022 "Understanding the Weather" – A Series by Mel Zeldin, Retired Meteorologist This past December was much wetter than normal and coming right after a bone-dry November. So, what caused this to happen? And why on Dec. 26 did Kodiak Alaska have a record-smashing high temperature of 67 degrees, while Beaumont only reached a high of 53 degrees? All this has to do with the positioning of high and low pressure systems across the Pacific Ocean and the jet stream, which is the driving force of the storm track. Jet streams are areas of strong, predominantly west-to-east winds occurring in the upper atmosphere where warm air pushing northward from the sub-tropics meets colder air moving southward from the arctic regions. Storms are pushed along by the jet stream. The illustration of the jet stream in Figure 1 shows a typical winter pattern with the jet stream pushing storms into the Pacific Northwest, while cold air plunges southward into the middle of the U.S. By contrast, an illustration of the weather pattern that dominated in December is shown in Figure 2. With the more typical jet stream, low pressure is dominant in the Gulf of Alaska. But in December, this pattern was replaced by high pressure in the Gulf of Alaska. Under this pattern, air streamed into Alaska from the southwest, bringing much warmer air to the southern portion of the state. And in response, air around that high pressure system forced cold, Canadian air southward along the west coast. The trajectory of that cold air was far enough off the coast to entrain Pacific moisture. And the combination of cold air and moisture were the key ingredients as the jet stream moved developing storms southward from northwest Canada. Why such patterns change like this is part of the somewhat chaotic nature of the atmospheric flows around the globe. Having said that, such patterns don't usually last for extended periods of time, and in this case persisted for probably two weeks longer than the norm. But it was only a matter of time for the jet stream and the overall storm track to move back to its more typical pattern and that change began around New Years Day. Variations in the pattern occur throughout the winter months, so a drier pattern does not mean we don't get storms. Short-term variations in the predominant winter weather pattern will continue to occur, but generally not over an extended period. On another topic, as an interest to the community, I have started a Weather Enthusiasts group on Nextdoor, and I post daily weather forecasts for the Pass Area whenever significant weather is expected in the foreseeable future. Anyone with access to Nextdoor is welcome to join the group. I am greatly appreciative of the many positive responses I have received since starting this endeavor. Why December Was Cold and Wet The upper air weather pattern and jet stream from late December A schematic illustration of the jet stream across the U.S.

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