Climate security

Cyclones in the Pacific made it snow in Rome, and soon that weather will hit the U.S.

That’s the polar vortex splitting into two vortices earlier this month. Normally the vortex swirls around the North Pole, only occasionally dipping down into lower latitudes. But in mid-February, two tropical cyclones formed and started pumping heat into the atmosphere. That warming destabilized the polar vortex and forced it to split, which hasn’t happened in five years.

One of those sister vortices headed down toward eastern Europe and caused record-breaking cold snaps there, along with the snow in Rome. Normally, Europe gets most of its weather patterns off the Atlantic Ocean—winds generally travel around the world from west to east—and that makes most of the continent warmer than equivalent latitudes in North America. But when that vortex descended, it interrupted the normal weather pattern.

Similarly, most of the U.S. has had unusually high temperatures in the last week because we’re in a La Niña year, when we tend to have warmer winters. But the other half of that polar vortex is coming for us. Kind of.

If you live in the Western U.S., meteorologists predict you’ll see snow by mid-week. The Rockies will definitely get hit, and the Southern California mountains could see a foot of snow. Most lower-lying areas will only get a few inches.