The two panels show the potential temperature (a) and vorticity (b) as a function of time. All the quantities are defined at the vortex centroid where the vorticity is maximum. In a the red squares show the position of the aerosol bubble centroid according to CALIOP. The CALIOP centroid is defined by averaging the most extreme top, bottom, south and north edges. The arrows show the extension of the bubble in potential temperature space. The cyan line shows the upper envelope of the bubble as detected by OMPS-LP, the green line is a linear fit to the ascent of the vortex and the grey line shows a 10 K day−1 curve. In a, b, the black lines show the ECMWF 10-day forecast evolution, plotted every four days. The forecast evolution is only shown for the period where it maintains the vortex. The slight discrepancy between the analysis and the initial point of the forecast is because the 10-day forecast is produced from a slightly inferior 6-h analysis, due to real time constraints.