Why this is important? SSWEs like what's occurring in the S hem now accelerate the poleward, descending branch of the BDC >> tropical branch accelerates to compensate = tropical stratosphere & tropopause cooling thru adiabatic expansion. You can see that very clearly below: https://t.co/d2DcyozoXq pic.twitter.com/XHs12WpxSt

— Eric Webb (@webberweather) August 26, 2019