In 2019, meteorologists nationwide began rating atmospheric rivers (AR), storms that have the potential for millions of dollars in losses and severe flooding. However, what exactly is an atmospheric river? It’s a long, narrow river of condensed water vapor in the atmosphere that moves with the weather. A strong river can carry between 7.5 -25 times the flow of water that passes through the mouth of the Mississippi River. These rivers in the sky can be 300 miles wide, a mile deep and more than 1,000 miles long. Most are small, but they can be massive and fast moving, and when the storms make landfall, they often release rain or snow, sometimes in large amounts. One atmospheric river can carry 10.5 trillion gallons of water a day. They account for 50 percent of the annual precipitation in California, are the West Coast’s big storms, and are responsible for 65 percent of the western USA’s extreme rain and snow events. The storms develop in the tropics and are also known as the Pineapple Express. They are a default feature of the entire global water cycle, and are present somewhere on the planet at any given time. There are predictions that climate change will cause atmospheric rivers to become 25% longer and 25% wider and carrying more water. This may lead to more flooding.
But atmospheric rivers don’t always act alone; they may bring a bomb cyclone with them. A bomb cyclone is a storm that forms when warm and cold air masses collide, and is a low-pressure system where the barometric pressure drops 24 millibars in 24 hours. This causes the storm to rapidly intensify, often bringing large amounts of snow or rain.
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