Waves complete 2018 11 04 drivers#

Other persistent weather regimes over the Atlantic-European sector, such as subtropical ridge or Atlantic Low, have also been related to Western European heatwaves 16, 25, 27. In particular, most summertime European heatwaves are associated with atmospheric blocking 2, 3, 16, 19, 22, 25, 26. Irrespective of their location, heatwaves are commonly associated with high pressure systems and anomalous warm air masses 16, 17, 18, 19, 20, 21, 22, 23, 24.

Waves complete 2018 11 04 drivers#

Although severe and/or long-lasting heatwaves could be more predictable at the extended-range timescales, such as the 2010 Russian heatwave 14, 15, the skill of the prediction of blocking variability would largely control the forecast of the onset, duration, and amplitude of the heatwave 13.Ī reliable identification of the drivers of heatwaves can improve predictability and preparedness 16, 17, 18, 19. Slow varying drivers including Madden–Julian Oscillation, mid-latitude persistent flow regimes, and land–atmosphere interaction could be potential sources of the sub-seasonal predictability of European 2 m-temperature extremes 12, 13, 14, 15.

However, prediction of the occurrence of a given heatwave events over a specific location 3–4 weeks in advance remains a challenge. The exact timing of the evolution of hot extremes is also crucial for preparation. Skillful heatwave prediction at the sub-seasonal or extended-range timescales (2–4 weeks) can allow for more time for mitigation. Persistent and severe heatwaves pose serious threats to health and welfare. However, study of extended-range prediction for the 2018 summer European heatwaves has also been absent. Moreover, improved seasonal 10 and short-term 11 predictions have been made using reasonable representations of the SST tripole pattern and local SST/soil moisture content, respectively, for the 2018 summer dry and hot conditions. Previous studies have suggested several drivers for these 2018 summertime European heatwave and drought events, including persistent blocking 2, 6, subtropical ridge or tropical continental air flow 5, 7, an exceptionally strong stationary Rossby Wave-7 pattern 8, 9, prevalence of the positive phase of the summer North Atlantic Oscillation (NAO) 5, 9, the Atlantic sea-surface temperature (SST) tripole pattern 5, 10, local SST and soil moisture content 5, 11. While anthropogenic climate change could be responsible for certain proportion of these record-breaking warmth and precipitation deficits, natural variability was also indispensable factor 4, 5, 6. In the summer of 2018, prolonged and severe heatwave and drought conditions occurred across northwestern Europe, leading to socio-economic and environmental impacts 1, 2, 3, 4.

Although variations in Azores High and NAO were captured in the forecasts, their contribution to the warm spells remains unclear. BL and AL can be predicted 2 weeks in advance, resulting in the successful predictions of warm spells over SC and WE. However, the predictions of heatwave occurrence and significance for the two regions are unsatisfactory. A multi-model ensemble of real-time forecasts from the subseasonal to seasonal (S2S) database captured the evolution of the warm spells over SC and WE up to 3 weeks in advance.

These causal relationships remained valid when the evolution of warm spells was considered. The major contributor to the heatwave over WE was AL. The persistent blocking regime (BL) was the most influential contributor for the 2018 heatwave over SC, and both the Atlantic Low regime (AL) and North Atlantic Oscillation (NAO) were secondary contributors for the heatwave, but with different effect directions. This study investigated the drivers and extended-range prediction of the mid-July to early August 2018 heatwaves over northwestern Europe, focusing on regional heatwave events over Scandinavia (SC) and Western Europe (WE).