Contrasting the Synoptic Drivers of the UK Heatwaves of 1976, 2003, 2018 and 2022

Abstract: Summer heatwaves across the United Kingdom highly depend on the position of the polar jet stream and the sea surface temperature (SST) variability in the Atlantic Ocean. The phases of the Summer North Atlantic Oscillation (SNAO) have been examined as a conducive factor to the position of the jet stream that explains the Central England Precipitation (CEP) and Central England Temperature (CET) variability. However, these fluctuations are often determined by other large-scale circulations, which aid the understanding of the dominant air masses and heatwave characteristics. The Fennoscandian Index (SCAN) is additionally considered for the correlation and regression analysis with the CEP and CET for the four selected summers (1976, 2003, 2018 and 2022). The linear relationship of the SNAO is statistically significant (p < 0.05) with the CEP and CET variability. A strong negative correlation (r = -0.63) is observed during the positive phase and is associated with the precipitation deficiency due to poleward-shifted jet stream. Higher-than-normal air temperature reveals a lower association magnitude (r = 0.33), aligned with the position of the high-pressure system near the surface, with enhanced adiabatic air subsidence near the surface. Furthermore, the strongest SNAO summers (i.e. 1976 and 2018) are one of the warmest and driest for the United Kingdom in the analysed time series from 1950 and exhibit CET values exceeding the 98th percentile and CEP below the 2nd percentile –– or two standard deviations. Whilst the SCAN and SNAO relationship is statistically significant, the SCAN impact on the CET and CEP is minor due to the high-pressure system position and tilt over Fennoscandia, affecting the dominant airstream. The significance of the study contrasts the leading large-scale precursors and amplification factors with a detailed comparison of the selected test case studies and localised weather patterns, providing the foundational framework for a better understanding of the heatwave drivers across the United Kingdom.

Biography: A passionate-driven meteorologist with a Master of Science (MSc) degree in Applied Meteorology and Climate from the University of Reading. Currently enrolled as a PhD student in Climate Science at the University of Leicester, as a part of the National Centre for Earth Observation (NCEO) and University of Leicester's Water and Climate Group. Working on understanding and developing a simple energy balance model and the hydrological cycle improvement in collaboration with the University of Reading and the UK Met Office. Elected member of the Royal Meteorological Society (RMetS) as of October 2023.