Skilful Real‐Time Seasonal Forecasts of the Dry Northern European Summer 2018

Dunstone, Nick; Smith, Doug; Hardiman, Steven C.; Eade, Rosie; Gordon, Margaret; Hermanson, Leon; Kay, Gillian; Scaife, Adam A.

doi:10.1029/2019gl084659

Cited by 18 publications

(24 citation statements)

References 29 publications

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“…An anticyclonic circulation anomaly over northern Europe during the summer was correctly predicted by Met Office longrange forecasts (Dunstone et al, 2019). Ensemble forecasts started at the beginning of November 2017 and May 2018 predicted increased risk of a dry summer across northern Europe, and these were presented, along with other evidence, to UK government contingency planners in May 2018.…”

Section: The Atlantic Sea-surface Temperature (Sst) Tripolementioning

confidence: 70%

“…Conversely, there is no significant skill in the north European mean temperature from these predictions, shown in the right panel of Figure 6, with the exception of the long-term trend component. Dunstone et al (2019) demonstrate, using a set of perturbation experiments, that the pattern of north Atlantic SSTs in May 2018 (and compared to 1976 in Figure 7), sometimes referred to as the north Atlantic tripole pattern, correlates with northern European rainfall through the process of a northward-shifted jet stream responding to the meridional temperature gradient of the north Atlantic sector. They go on to note that, although the North Atlantic SST tripole likely contributed to the observed circulation changes of summers, such as 1976 and 2018, the model produced only a very weak signal, which is often found in predictions of north Atlantic atmospheric variability (Scaife and Smith, 2018).…”

Section: The Atlantic Sea-surface Temperature (Sst) Tripolementioning

confidence: 89%

“…Regional SST Figure 7 also shows that SSTs in the proximity of the United Kingdom were notably warmer than average through summer 2018 in the fig.1 of Dunstone et al 2019. The domain is based on land areas of northern Europe (for details, see Dunstone et al, 2018).)…”

Section: Drivers Of the Uk Summermentioning

confidence: 97%

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Drivers of the UK summer heatwave of 2018

McCarthy

Christidis

Dunstone

et al. 2019

Weather

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Section: The Atlantic Sea-surface Temperature (Sst) Tripolementioning

confidence: 70%

Section: The Atlantic Sea-surface Temperature (Sst) Tripolementioning

confidence: 89%

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Drivers of the UK summer heatwave of 2018

McCarthy

Christidis

Dunstone

et al. 2019

Weather

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“…Duchez et al (2016) argues that not the cold North Atlantic anomaly itself, but the resulting enhanced meridional SST gradient favored the high pressure dominance and temperature extremes over Europe. Another approach was made by the study of Dunstone et al (2019), who extended the European high-pressure response even to a tripole pattern of North Atlantic SST's.…”

Section: Lead-lag Correlationsmentioning

confidence: 99%

Impact of North Atlantic SST and Jet Stream anomalies on European Heat Waves

Krüger

Kedzierski

Bumke

et al. 2020

Preprint

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Abstract. European heat waves have increased during the two recent decades. Particularly 2015 and 2018 were characterized by a widespread area of cold North Atlantic sea surface temperatures (SSTs) in early summer as well as positive surface temperature anomalies across large parts of the European continent during later summer. The European heat wave of 2018 is further suggested to be induced by a quasi-stationary and high-amplified Rossby wave pattern associated with the so-called quasi-resonant amplification (QRA) mechanism. In this study, we evaluate the North Atlantic SST anomalies and the QRA theory as potential drivers for European heat waves for the first time in combination by using the ERA-5 reanalysis product. A composite and correlation study reveals that cold North Atlantic SST anomalies in early summer favour a more undulating jet stream and a preferred trough-ridge pattern in the North Atlantic–European sector. Further we found that cold North Atlantic SSTs promote a stronger double jet occurrence in this sector. Thus, favorite conditions for a QRA signature are evident together with a necessary preconditioning of a double jet. However, our wave analysis covering two-dimensional probability density distributions of phase speed and amplitude does not confirm a relationship between cold North Atlantic SSTs and the QRA theory, compositing cold SSTs, high double jet indices (DJIs) or both together. Instead, we can show that cold North Atlantic SST events enhance the dominance of transient waves. In the presence of a trough during cold North Atlantic events, we obtain a slow-down of the transient waves, but not necessarily an amplification or stationarity. The deceleration of the transient waves result in a longer duration of a trough over the North Atlantic accompanied by a ridge downstream over Europe, triggering European heat episodes. Although a given DJI preconditioning may also be subject to the onset of certain QRA events, our study found no general relation between cold North Atlantic SST events and the QRA diagnostics. Our study highlights the relevance of cold North Atlantic SSTs for the onset of high European temperatures by affecting travelling jet stream undulations (but without involving QRA in general). Further attention should be drawn not only to the influence of North Atlantic SST year-to-year variability, but also to the effect of the North Atlantic warming hole as a negative SST anomaly in the long term, which is projected to evolve through climate change.

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“…The positive summer NAO is also associated with a northwestern extension of the Azores high and an eastward shifted Icelandic low 29 , suggesting an inter-dependency among the variability of summer NAO, blocking, and Azores High. In addition, the North Atlantic SST 10,16,31 and tropical Atlantic convective anomalies 25 can also play a role in the development of European heatwaves, which indicates the potential contribution of ocean temperature anomalies. Improving the dynamical links among heatwave-related circulation regimes as well as ocean temperature anomalies in the forecast model will contribute to extending the prediction range for European heatwaves.…”

mentioning

confidence: 99%

The 2018 summer heatwaves over northwestern Europe and its extended-range prediction

Kueh

Lin

2020

Sci Rep

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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). 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. The major contributor to the heatwave over WE was AL. These causal relationships remained valid when the evolution of warm spells was considered. 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. However, the predictions of heatwave occurrence and significance for the two regions are unsatisfactory. BL and AL can be predicted 2 weeks in advance, resulting in the successful predictions of warm spells over SC and WE. Although variations in Azores High and NAO were captured in the forecasts, their contribution to the warm spells remains unclear.

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Skilful Real‐Time Seasonal Forecasts of the Dry Northern European Summer 2018

Cited by 18 publications

References 29 publications

Drivers of the UK summer heatwave of 2018

Drivers of the UK summer heatwave of 2018

Impact of North Atlantic SST and Jet Stream anomalies on European Heat Waves

The 2018 summer heatwaves over northwestern Europe and its extended-range prediction

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