Image caption
One way to track the polar vortex is through potential vorticity, which describes the amount of rotational energy, or "spin," in a parcel of air. This animation shows daily potential vorticity in the stratosphere in February 2025. The darkest blues represent the coldest, most isolated air. In the second week of February, the vortex remained strong, but began to stretch out over North America. NOAA Climate.gov animation by Breanna Zavadoff, based on ERA5 reanalysis data.