Extreme weather is becoming more difficult to predict

Over the last few centuries, societal changes have resulted in an increased buildup of carbon emissions in Earth’s ozone layer, which ultimately drives global warming. It is widely known that this cycle will increase the likelihood of extreme weather events. What many people do not know, however, is that climate change is making it increasingly difficult for scientists to accurately forecast extreme weather in the short term. 

To navigate this issue, a team of leading meteorologists led by the Institute of Atmospheric Physics is exploring new weather prediction techniques. Their latest study suggests that the improvement of meridional potential vorticity gradient (PVy) modeling could be the key to progress. The researchers discovered that during extreme cold events across East Asia and North America in the last two months of 2022, the PVy was abnormally weak. 

Through the analysis of the atmospheric circulation that occurred during the final months of 2022, the team found that large and stationary blocking weather patterns prevented other weather systems from following their path. This ultimately prolonged the extreme cold weather conditions in both North America and East Asia. The phenomenon was directly correlated with the unusually weak PVy readings.

“In our previous study, we found that frequent cold waves were more likely to occur in mid-latitude Asia in the upcoming 2022-2023 winter season under the background of a warm Arctic and a cold tropical Pacific,” explained study lead author Yao Yao. “ In our current study, we wanted to know what actually caused these cold surges and if the cold events in North America and East Asia were related.”

This prediction proved accurate; throughout the first half of the 2022-2023 winter season, extreme cold events have been more frequent in Asia’s middle latitude areas. Furthermore, a weak connection was identified between East Asia’s cold weather in late November 2022 and the “bomb cyclone” and tornadic outbreaks across North America in mid-late December 2022. 

Whilst these findings have led to progress in understanding recent extreme cold weather events, low PVy levels have overall been identified to create less favorable conditions for weather pattern predictability. It is understood that existing models simply cannot accurately predict the movement of blocking weather patterns when the PVy levels are so low. 

“Low Arctic sea ice and La Niña favor the reduction of mid-latitude potential vorticity gradients (PVy), but there are many other factors affecting this gradient,” explained Yao Yao. 

“The next step is to identify these factors and try to establish a relatively sound statistical model, which is important for short-term weather and climate prediction. Once these factors are determined through future study, blocking weather pattern predictability will increase.”

The findings of the study may help improve future extreme weather forecasting, which could reduce the likelihood of casualties and economical loss associated with unexpected cold snaps. 

The research is published in the journal Advances in Atmospheric Sciences. 

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By Calum Vaughan, Earth.com Staff Writer

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