Summary of the 2018 HEPEX ‘Breaking the Barriers’ Workshop, Melbourne Australia.

Contributed by David Robertson, James Bennett, QJ Wang, Daehyok Shin, Andy Wood, Maria-Helena Ramos, Ilias Pechlivanidis and Fredrik Wetterhall.

More than 120 HEPEXers from 15 countries descended on Melbourne, Australia, for three days of sunshine, science and applications at the 2018 HEPEX ‘Breaking the Barriers’ Workshop.

The meeting kicked off with a warm welcome from the local organizing team (James Bennett, QJ Wang, David Robertson and DH Shin) and a series of short talks recognizing the importance of water predictions and science, and from an elder of the Wurundjeri people, who stressed the long history of indigenous peoples living in balance with the land and water. The Workshop was supported by CSIRO, the University of Melbourne and the Bureau of Meteorology.

The participants had the opportunity to listen and interact during the 38 oral presentations (including 3 keynote speeches and 10 invited talks), and 40 posters, whilst the open discussion sessions allowed sharing of experiences and insights. Here, we only select and summarize a few out of the numerous high quality presentations.

Hannah Cloke’s keynote talk “Fly me to the moon” set the stage by reviewing the last decade of progress in flood forecasting for the UK and challenges in taking flood forecasts to a global scale. Hannah above all highlighted the need to ‘be brave’ in trying new approaches, which stayed in the minds of participants for the rest of the workshop.

Subsequent presentations on day one reported on projects assessing the quality of global and regional forecasts of flash floods, riverine flooding, drought and seasonal streamflow generated by land system models harnessing and compiling global impact databases to support verification. Florian Pappenberger highlighted that a greater focus on integrating the land surface as part of Earth System prediction is likely to be the key to extending prediction skill.

A healthy diversity of methods were showcased, including multi-model approaches and data assimilation to improve estimates of modeling and forecast uncertainty, the coupling of coarse land surface models (LSMs) to sub-grid routing and high-resolution hydrologic/hydraulic modeling, and the use of GPU-based computing for forecasting.

The second day of the meeting opened with a description of the EDgE Copernicus proof-of-concept, which is comparing the performance LSMs for seasonal to sub-seasonal (S2S) forecasting in Europe and contrasting skill arising from ESP versus GCM-based predictions. The focus pulled back to methodological questions related to downscaling, merging and pre-processing of weather and climate forecasts, investigating predictability at S2S scales, and highlighting the advancement of dynamical national systems in countries such as New Zealand and China.

Talks also delved into using radar-based rainfall and ensemble approaches to flash flood forecasting. Verification was also discussed, with talks showing new systems for meteorological forecast verification in Australia as well as challenging HEPEX’s hydrologists to think more carefully about what we verify, and how event performance may affect user confidence in forecasts and their effectiveness in motivating action.

The keynote talk of the day was a blockbuster, with Dasarath “Jaya” Jayasuriya, the Director of Public Safety for the Bureau of Meteorology, who dispensed rare wisdom on how forecasting fits within Australia’s national services for managing resources and risk, including insights into forecast-related objectives, mindsets and constraints from the producer side to the public user side. Among other topics, his comments on how BoM navigates the path of serving different users while promoting overall acceptance of forecasts (perhaps through hands on case studies that raise awareness in the field), were illuminating.

HEPEX Day 3 began with a focus on S2S forecasts, with an SMHI effort characterizing predictability (through watershed initial conditions and climate) using collections of geophysical attributes, and work in the UK to understand and enhance climate / drought predictability through the incorporation of NAO variability. The conversation turned toward forecast product development and communication, highlighting the importance of co-development of forecast services with users (see also the SWICCA Copernicus proof-of-concept).

The day’s keynote speaker, Matthew Bethune of the Murray Darling Basin (MDB) Authority, provided a bracing real-world overview of the use of hydrologic models to support decision making in the MDB, highlighting the difficult challenges of making robust release decisions to supply customers at lead times (days to weeks) during which weather, climate and river conditions are highly uncertain. Among the methodological needs raised in the talk, the need to know how climate change may impact current methods for prediction was also raised.

The final talk session of the meeting shifted to examples of real-world predictions for operations, both in flood warning and in hydropower operations for several systems. These talks provide inspiring case studies for effective implementations of ensemble techniques for energy management, underscoring the sense that HEPEX-style forecasting is becoming a reality for groups ready to ‘be brave’ and make the effort to implement ensembles. In addition, the speakers described methodological experiments aimed at finding the best strategies, suggesting that many questions are still of interest. Ensemble research is not a solved problem!

The presentations made available by the authors can be downloaded from here.

HEPEX closed out the meeting with breakout groups, an interactive digital survey, and a closing discussion to take stock of where HEPEX should go. Many aims of HEPEX – including the operational adoption of ensemble hydrologic prediction for the benefit of society – have evolved from being a dream in 2004 to being realized operationally in a number of countries. What then are the key challenges HEPEX should pursue in the next 10 years?

The detailed results of this discussion will be summarized in a future blog, but for now it is clear that challenges do remain (particularly in continuing to communicate the value of ensemble systems), and also many opportunities. This will be an ongoing conversation, so start thinking and contributing – where should HEPEX focus its efforts, what are the big challenges, and how can you help make it happen?