The passage of the low pressure wave over parts of America was accompanied by multiple extreme events in mid-December 2021.
17 December 2021
17 December 2021
By Ivan Smiljanic (CGI)
Multiple records were observed across affected states related to tornadoes, strong wind, dust, and even high temperatures in the far north.
Figure 1 shows the moment when the synoptic wave passed over the Rockies, behind which the lee cyclogenesis took place. Cold air behind the front rushed down the mountain, producing the 'winter haboob' (observe the thicker, mostly north--south oriented linear feature moving eastwards, from Denver onward), enhancing the dust lifting and pushing the squall line convergence (with associated tornado events), supporting also the wildfires in the south of the observed domain (Figure 2). The cyclone later moved towards the north-eastern states, pushing the warmth to the far north (record temperature anomalies).
Strong synoptic dynamics were represented with abundance of red shades in Airmass RGB (associated to tropospause lowering, PV anomaly and cyclone deepening), while the strong magenta shades in Dust RGB confirm the thick and relatively high reaching dust clouds (Figure 3).
Figure 4 shows the Dust RGB in motion, showing the moments when the synoptic wave passed the Rockies and when the strong wind started picking up the dust from the ground.
The so-called 'cirrus' channel also detected the dust cloud formation, mostly over Kansas (Figure 5). Due to the fact that this is a 'water vapour (WV) absorption channel', the brighter the dust cloud the higher it is (provided similar optical thickness). Aside from dust clouds, wave clouds behind the mountain range were nicely picked up with this NIR1.3 channel.
The best of both worlds is provided by the so-called 'sandwich product', a simple combination of Dust RGB and NIR1.3 imagery (Figure 6).
Widespread, Damaging, Unusual December Storm Spawns Derecho, Tornadoes in the Plains, Midwest (The Weather Channel)
Strong winds and tornadoes sweep through Great Plains and Midwest (CBS)
Dust storm over Kansas (KAKE News/Twitter)
Dust storm over Boulder (David Roche/Twitter)