On the reliability of seasonal climate forecasts. by Weisheimer, A, Palmer, T

“…Seasonal climate forecasts are being used increasingly across a range of application sectors. …”

Seasonal forecasts of the 20th century by Weisheimer, A, Befort, DJ, MacLeod, D, Palmer, T, O’Reilly, C, Strømmen, K

“…<p>New seasonal retrospective forecasts for 1901-2010 show that skill for predicting ENSO, NAO and PNA is reduced during mid-century periods compared to earlier and more recent high-skill decades.…”

Impact of snow initialization on sub-seasonal forecasts by Orsolini, Y, Senan, R, Balsamo, G, Vitart, F, Weisheimer, A, Doblas-Reyes, F, Carrasco, A, Benestad, R

“…The influence of the snowpack on wintertime atmospheric teleconnections has received renewed attention in recent years, partially for its potential impact on seasonal predictability. Many observational and model studies have indicated that the autumn Eurasian snow cover in particular, influences circulation patterns over the North Pacific and North Atlantic. …”

Impact of snow initialization on sub-seasonal forecasts by Orsolini, Y, Senan, R, Balsamo, G, Doblas-Reyes, F, Vitart, F, Weisheimer, A, Carrasco, A, Benestad, R

“…The influence of the snowpack on wintertime atmospheric teleconnections has received renewed attention in recent years, partially for its potential impact on seasonal predictability. Many observational and model studies have indicated that the autumn Eurasian snow cover in particular, influences circulation patterns over the North Pacific and North Atlantic. …”

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

“…We analyse the climatological representation and assess the seasonal prediction skill of wintertime extra‐tropical cyclones and windstorms in three multi‐member seasonal prediction systems: ECMWF‐System3, ECMWF‐System4 and Met Office‐GloSea5, based on hindcasts over a 20 year period (1992–2011). …”

Oceanic stochastic parametrizations in a seasonal forecast system by Andrejczuk, M, Cooper, F, Juricke, S, Palmer, T, Weisheimer, A, Zanna, L

“…Here we study the impact of three existing stochastic parametrizations in the ocean component of a coupled model, on forecast reliability over seasonal timescales. The relative impacts of these schemes upon the ocean mean state and ensemble spread are analyzed. …”

SEAS5: the new ECMWF seasonal forecast system by Johnson, S, Stockdale, T, Ferranti, L, Balmaseda, M, Molteni, F, Magnusson, L, Tietsche, S, Decremer, D, Weisheimer, A, Balsamo, G, Keeley, S, Mogensen, K, Zuo, H, Monge-Sanz, B

“…In this paper we describe SEAS5, ECMWF's fifth generation seasonal forecast system, which became operational in November 2017. …”

Assessment of representations of model uncertainty in monthly and seasonal forecast ensembles by Weisheimer, A, Palmer, T, Doblas-Reyes, F

Assessment of representations of model uncertainty in monthly and seasonal forecast ensembles by Weisheimer, A, Palmer, T, Doblas-Reyes, F

“…The probabilistic skill of ensemble forecasts for the first month and the first season of the forecasts is assessed, where model uncertainty is represented by the a) multi-model, b) perturbed parameters, and c) stochastic parameterisation ensembles. …”

Addressing model uncertainty in seasonal and annual dynamical ensemble forecasts by Doblas-Reyes, F, Weisheimer, A, Deque, M, Keenlyside, N, McVean, M, Murphy, J, Rogel, P, Smith, D, Palmer, T

“…Annual-mean predictions showed lower forecast quality than seasonal predictions. Only small differences between the systems were found. …”

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

“…Much of the forecast skill in the mid-latitudes on seasonal timescales originates from deep convection in the tropical belt. …”

Changing frequency of occurrence of extreme seasonal temperatures under global warming by Weisheimer, A, Palmer, T

“…This would correspond to an average return period of such anomalous warm seasons of almost one year. The reliability of these results is assessed using the bounding box technique, previously used to quantify the reliability of seasonal climate forecasts. …”

The link between North Atlantic tropical cyclones and ENSO in seasonal forecasts by Doane-Solomon, R, Befort, DJ, Camp, J, Hodges, K, Weisheimer, A

“…This study assesses the ability of six European seasonal forecast models to simulate the observed teleconnection between ENSO and tropical cyclones (TCs) over the North Atlantic. …”

The strong role of external forcing in seasonal forecasts of European summer temperature by Patterson, M, Weisheimer, A, Befort, DJ, O'Reilly, CH

“…These forcings may therefore provide an important source of forecast skill, even for timescales as short as a season ahead. However, the relative importance of external forcings for seasonal forecasts has thus far received little attention, particularly on a regional scale. …”

Flow dependent ensemble spread in seasonal forecasts of the boreal winter extratropics by MacLeod, D, O'Reilly, C, Palmer, T, Weisheimer, A

“…However this is difficult to estimate for seasonal hindcasts as they tend to have a relatively small sample size. …”

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. …”

Seasonal to annual ocean forecasting skill and the role of model and observational uncertainty by Juricke, S, Macleod, D, Weisheimer, A, Zanna, L, Palmer, T

“…Accurate forecasts of the ocean state and the estimation of forecast uncertainties are crucial when it comes to providing skilful seasonal predictions. In this study we analyse the predictive skill and reliability of the ocean component in a seasonal forecasting system. …”

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. …”

Seasonal prediction of tropical cyclones over the North Atlantic and Western North Pacific by Befort, DJ, Hodges, KI, Weisheimer, A

“…In this study, Tropical Cyclones (TC) over the Western North Pacific (WNP) and North Atlantic (NA) basins are analysed in seasonal forecasting models from five European modelling centres. …”

The ECMWF SEAS5 seasonal forecast of the hot and dry European summer of 2022 by Patterson, M, Befort, DJ, O'Reilly, C, Weisheimer, A

“…Nevertheless, this case study demonstrates that important features of at least some European summers are predictable at the seasonal timescale. …”