Supercells are among the most complex and dangerous severe convective storms due to their associated phenomena (lightning, strong winds, large hail, flash floods, or tornadoes). In this survey we study the supercell synoptic configurations and convective environments in Spain using the atmospheric reanalysis ERA5. Supercells are grouped into hail (greater than 5 cm) and non-hail events in order to compare and analyze the two events. The results reveal statistically significant differences.

This study of changes in temperature and wind since 1979 met its twin aims of (i) increasing confidence in some findings of the latest IPCC assessment and (ii) identifying changes that had received little or no previous attention. It reports a small overall intensification and shift in position of the North Atlantic jet stream and associated storms, and a strengthening of tropical upper-level easterlies. Increases in low-level winds over tropical and southern hemispheric oceans are confirmed.

Mesocyclones are the rotating updraught of supercell thunderstorms that present a particularly hazardous subset of thunderstorms. A first-time characterisation of the spatiotemporal occurrence of mesocyclones in the Alpine region is presented, using 5 years of Swiss operational radar data. We investigate parallels to hailstorms, particularly the influence of large-scale flow, daily cycles and terrain. Improving understanding of mesocyclones is valuable for risk assessment and warning purposes.

Extratropical cyclones are relevant in the western South Atlantic and influence the climate of ocean surface wave. Propagating atmospheric features from the South Pacific to the South Atlantic are relevant to the cyclones and waves, and its intensified westerlies lead to more cyclones and, as a consequence, to higher wave heights. The opposite happens with its weakening. These features are similar to the so-called Pacific South American patterns and present periods between 30 and 180 d.

Attribution of the causes of extreme temperature events has become active research due to the wide-ranging impacts of recent heat waves and cold spells. Here we show that a purely observational approach based on atmospheric circulation analogues and resampling provides a robust quantification of the various dynamic and thermodynamic contributions to specific extreme temperature events. The approach can easily be integrated in the toolbox of any real-time extreme event attribution system.

Vertical motion on horizontal scales of a few hundred kilometers can influence cloud properties. This motion is difficult to measure directly but can be inferred from the area-averaged mass divergence. The latter can be derived from horizontal wind measurements at the area’s perimeter. This study derives vertical properties of area-averaged divergence from an extensive network of atmospheric soundings and proposes an explanation for the variation of divergence magnitudes with area size.

This study focused on exploring if off-season tropical cyclones, those that develop outside of the peak months, have been increasing over time in the Atlantic Ocean and Pacific Ocean basins and if that higher frequency could be explained by climate variability or change. We found that off-season tropical cyclones are exhibiting an increase in total numbers by decade in the North Atlantic and East Pacific ocean basins and that climate change explained much of the increasing trends over time.