In general, this warming is similar to the major warming in late February of 2008, although this one is stronger.
On January 19th, two stratospheric anticyclones tilted poleward and the vortex split above 40 km. The vortex split along the 90 E and 90 W meridians leaving a vortex lobe over North America and another over Russia.
Above ~30 km, warm temperatures were located over the pole, between the two vortex lobes and the two anticyclones. In the upper troposphere, a large-amplitude wave moved eastward over North America; the wave trough underlies the vortex edge.
On January 20th, the anticyclones strengthened and the vortex split down to 35 km. Temperatures increased over the pole, marking the descent of the stratopause.
On the 21st, the anticyclones began to merge over the pole and the vortex split further.
On the 22nd, the vortex continued to split down to 25 km. The vortex lobe over North America was sheared in the vertical. Below ~35 km, the base of this lobe remained over North America. Above this, the vortex lobe detached and moved westward around the equatorward flank of the Aleutian High.
PV plots at 1000 K show a PV filament being drawn off the North American vortex lobe. High PV over the Pacific is associated with the upper vortex lobe that was sheared off the base.
On the 23rd, the vortex continued to split. Neither the anticyclone over the pole nor the vortex are detected above 40 km suggesting weaker circulations. At 1000 K (~40 km), PV plots show the split vortex with a lobe over North America and a lobe over China. The high PV filament remains over the Pacific.
On the 24th, the vortex was nearly split throughout the stratosphere. The anticyclones merged over the pole above 35 km. Lidars at Eureka and Sondrestrom sample in this anticyclone. PV at 1000 K shows that the vortex lobes have weakened and the PV filament has detached from the lobe over North America. At this altitude (~40 km), the vortex is made up of three distinct remnants.