If you feel like the weather has been out of control in much of the United States, you’re right. A weather pattern that stuck around longer than usual created a dangerous mix of conditions.
Millions of people across the country have experienced extreme weather for the past two weeks. There was unusual cold in the West, tornadoes and widespread floods have been slamming the central United States, and a record-breaking heat wave has been scorching the Southeast.
It’s not a coincidence. CNN meteorologists say it’s all tied to a jet stream pattern.
Jet streams are rivers of fast-moving air up in the atmosphere – around the altitude where planes normally fly – that push air masses, typically from west to east but not in a straight line. They are key to determining the weather as they separate cold air from warm air.
The jet stream pattern over the United States has been stuck for days, leaving cooler and wetter conditions in the West, and hotter and drier conditions in the East, CNN meteorologist Brandon Miller said.
“Where those two different air masses meet, you get ripe conditions for severe weather,” Miller said.
The pattern has been consistently in the same spot for the past two weeks, Miller said, “sparking severe weather pretty much every day in the middle of the country.”
May is traditionally the peak of severe weather, but it can continue into June and July, according to Miller.
Luckily, the jet stream is expected to shift Thursday, slowing down the severe weather outbreak.
There have been tornadoes for 14 days in a row
Tornadoes have now been reported somewhere in the US for 15 days straight.
At least eight tornadoes have been reported for 13 consecutive days – the longest streak on record in the country – in 22 different states, according to CNN meteorologists.
This constant tornado activity is also very rare.
“We have active periods similar to this every few years, but there is normally 1 or 2 days interspersed where the pattern shifts and we get a break with no tornadoes for a day or two,” Miller said.
It’s been a historically active tornado season. There were 500 eyewitness reports of tornadoes made in the 30 days between April 27 and May 27, according to the National Weather Service.
In the past 20 years, the US has seen as many tornadoes only four other times: 2003, 2004, 2008 and 2011.
Is this climate change?
It depends. Meteorologists don’t believe there is a link between the remarkable amount of tornadoes and climate change. Flooding is a different story.
All extreme weather events are not necessarily influenced by climate change. In the case of tornadoes, there are many variables that go into making a twister and “turning the lever up on temperature doesn’t just create more or less tornadoes,” Miller said.
But downpours in the Midwest have increased during the past century due to climate change, and more intense rainfall events are expected in the future, according to the National Climate Assessment, an interagency report that examines the impact of climate change.