Factors influencing the seasonal predictability of northern hemisphere severe winter storms by Hansen, F, Kruschke, T, Greatbatch, RJ, Weisheimer, A

“…We investigate the role of the tropics, the stratosphere, and atmosphere‐ocean coupling for seasonal forecasts of strong, potentially damaging, Northern Hemisphere extratropical winter wind storm frequencies. …”

The representation of winter Northern Hemisphere atmospheric blocking in the ECMWF seasonal prediction systems by Davini, P, Weisheimer, A, Balmaseda, M, Johnson, SJ, Molteni, F, Roberts, CD, Senan, R, Stockdale, TN

“…The simulation and prediction of winter Northern Hemisphere atmospheric blocking in the seasonal prediction systems from the European Centre for Medium‐Range Weather Forecasts (ECMWF) is analysed. …”

The role of the tropical West Pacific in the extreme northern hemisphere winter of 2013/14 by Watson, P, Weisheimer, A, Knight, J, Palmer, T

“…We find that seasonal forecasts with the tropical atmosphere relaxed towards a reanalysis give 2013/14 winter-mean anomalies with strong similarities to those observed in the Northern Hemisphere, indicating that low-latitude anomalies had a role in the development of the extremes. …”

Projections of northern hemisphere extratropical climate underestimate internal variability and associated uncertainty by O’Reilly, CH, Befort, DJ, Weisheimer, A, Woollings, T, Ballinger, A, Hegerl, G

Assessing the robustness of multidecadal variability in Northern Hemisphere wintertime seasonal forecast skill by O'Reilly, CH, Weisheimer, A, MacLeod, D, Befort, DJ, Palmer, T

“…Recent studies have found evidence of multidecadal variability in northern hemisphere wintertime seasonal forecast skill. …”

Variability in seasonal forecast skill of Northern Hemisphere winters over the 20th century by O'Reilly, C, Heatley, J, MacLeod, D, Weisheimer, A, Palmer, T, Schaller, N, Woollings, T

“…Seasonal hindcast experiments, using prescribed SSTs, are analysed for Northern Hemisphere winters from 1900-2010. Ensemble mean Pacific/North American index (PNA) skill varies dramatically, dropping towards zero during the mid-twentieth century, with similar variability in North Atlantic Oscillation (NAO) hindcast skill. …”

Benchmarking Northern Hemisphere midlatitude atmospheric synoptic variability in centennial reanalysis and numerical simulations by Dell'Aquila, A, Corti, S, Weisheimer, A, Hersbach, H, Peubey, C, Poli, P, Berrisford, P, Dee, D, Simmons, A

The northern hemisphere circumglobal teleconnection in a seasonal forecast model and its relationship to European summer forecast skill by Beverley, J, Woolnough, S, Baker, L, Johnson, S, Weisheimer, A

“…Third the model jet is systematically shifted northwards by several degrees latitude over large parts of the northern hemisphere, which may affect the propagation characteristics of Rossby waves in the model.…”

Dynamical mechanisms linking Indian monsoon precipitation and the circumglobal teleconnection by Beverley, JD, Woolnough, SJ, Baker, LH, Johnson, SJ, Weisheimer, A, O'Reilly, CH

“…The circumglobal teleconnection (CGT) is an important mode of circulation variability, with an influence across many parts of the northern hemisphere. Here, we examine the excitation mechanisms of the CGT in the ECMWF seasonal forecast model, and the relationship between the Indian summer monsoon (ISM), the CGT and the extratropical northern hemisphere circulation. …”

Predicting El Niño in 2014 and 2015 by Ineson, S, Balmaseda, M, Davey, M, Decremer, D, Dunstone, N, Gordon, M, Ren, H, Scaife, A, Weisheimer, A

“…Early in 2014 several forecast systems were suggesting a strong 1997/98-like El Niño event for the following northern hemisphere winter 2014/15. However the eventual outcome was a modest warming. …”

Seasonal forecast skill for extra‐tropical cyclones and windstorms by Befort, DJ, Wild, S, Knight, JR, Lockwood, JF, Thornton, HE, Hermanson, L, Bett, PE, Weisheimer, A, Leckebusch, GC

“…Small to moderate positive skill in forecasting the winter frequency of extra‐tropical cyclones and windstorms is found over most of the Northern Hemisphere. The skill is highest for extra‐tropical cyclones at the downstream end of the Pacific storm track and for windstorms at the downstream end of the Atlantic storm track. …”

Extratropical low-frequency variability in a three-level quasi-geostrophic atmospheric model with different spectral resolution by Weisheimer, A, Kurgansky, M, Dethloff, K, Handorf, DR

“…The objective of this study is to investigate the spatial and temporal structure of internal low-frequency atmospheric variability of the Northern Hemisphere using a minimum-complexity model of the extratropical circulation. …”

Validation of boreal summer tropical–extratropical causal links in seasonal forecasts by Di Capua, G, Coumou, D, van den Jurk, B, Weisheimer, A, Turner, A, Donner, R

“…We calculate causal maps based on the Peter and Clark momentary conditional independence (PCMCI) causal discovery algorithm, which identifies causal links in a 2D field, to show the causal effect of each of these patterns on circulation and convection in the Northern Hemisphere. The spatial patterns and signs of the causal links in SEAS5 closely resemble those seen in ERA5, independent of the initialisation date of SEAS5. …”

Impact of Eurasian autumn snow on the winter North Atlantic Oscillation in seasonal forecasts of the 20th century by Wegmann, M, Orsolini, Y, Weisheimer, A, van den Hurk, B, Lohmann, G

“…Besides the main 110-year ensemble of 51 members, we investigate a second, perturbed ensemble of 21 members where initial (November) land conditions over the Northern Hemisphere are swapped from neighboring years. …”

Remote control of North Atlantic Oscillation predictability via the stratosphere by Hansen, F, Greatbatch, R, Gollan, G, Jung, T, Weisheimer, A

“…Interannual variability of the NAO is best reproduced when perfect knowledge of the Northern Hemisphere (NH) stratosphere is available, together with perfect knowledge of SSTs and sea ice, in which case 64% of the variance of winter mean NAO is projected to be accounted for with a forecast ensemble of infinite size. …”