a) Hold a workshop on the requirements & opportunities for capturing and quality controlling high resolution (in time & 3D space) observations of weather, hazards and their impacts, including the use of new ground-based remote sensing techniques, high density deployment of cheap sensors, and crowd sourcing. Liaise with the WMO Integrated Global Observing System (WIGOS) on the inclusion of convective-, turbulent- and urbanscale observing systems in the next Observation Impact Workshop. 

b) Hold a workshop to review current approaches to nowcasting and to make recommendations about future development directions using both simple physical representations of key processes and rapid update convective-scale DA/NWP systems.  

c) Inter-compare nowcast techniques using data from recent and planned field campaigns. 

d) Hold a workshop to review the current state of kilometre-scale data assimilation. 

e) Carry out an inter-comparison of coupled data assimilation systems. 

f) Hold a workshop & course on nonlinear coupled data assimilation. 

g) Develop a climatology of model error at kilometre-scale in regional reanalyses, stratified according to hazard-related processes, e.g. precipitation, convection, boundary layer 

h) Carry out an inter-comparison of advanced radar data assimilation systems, with a focus on object evaluation (e.g. storm initiation, timing & location) and prepare a review article. 

i) Carry out an inter-comparison of adaptive observing strategies and prepare a review article. j) Carry out a case-study inter-comparison to evaluate current capability for simultaneous synoptic and convective scale assimilation. k) Review the contribution of improvements in boundary layer and land surface assimilation to hazard prediction. 

l) Develop techniques to assess the sensitivity of hazard forecasts to observational inputs. 

m) Together with the Predictability & Processes theme, hold an inter-comparison of convective-scale modelling systems, using case studies, RDP datasets and reanalyses, with specific relevance to the selected hazards. Specific foci to include coupled models, performance in multiple scale cases, boundary layer performance. 

n) Review the validity of commonly used approaches to model parametrization at very high resolution and develop improved approaches. 

o) Together with the Predictability and Processes theme, quantify uncertainty in microphysics processes, parameters and fields, and assess the implications for the interaction with dynamical fields. 

p) Through a process of review, assessment and inter-comparison, develop a comprehensive suite of physically-based perturbations that accurately capture uncertainty in prediction of the selected hazards resulting from all scales and all components of coupled systems. 

q) Carry out an inter-comparison of kilometre-scale ensemble prediction systems and their products and prepare a review article. 

r) Together with the Evaluation theme, evaluate new approaches to ensemble verification, particularly with relevance to hazard predictions. 

s) Together with the Evaluation theme, evaluate improved ensemble diagnostics in case studies and FDPs 

t) Together with the Communication theme, identify gaps between the outputs of existing NWP systems and the requirements of forecasters and end users. Develop new useroriented products and evaluate in FDPs 

u) Explore the value of convective-scale reanalyses and ensemble reforecasts through comparison of model and observed climatologies of high impact weather and its precursors. 

v) Lead the cross-cutting activity to demonstrate and evaluate the benefit of enhanced observations, including dense networks of sensors focused on monitoring particular hazards (e.g. temperature for the heat hazard),  to the real-time production and communication of hazard warnings in FDPs. Document and publish results, including challenges in gathering, quality controlling and displaying the observations. 

w) Lead the cross-cutting activity, in collaboration with NMHSs and space-based Earth Observation agencies, building on the Committee on Earth Observation Satellites (CEOS) database and other initiatives, to create a catalogue of observations required for monitoring, forecasting, communicating and verifying weather-related hazards and their impacts, of the required spatial and temporal sampling and accuracy, and of candidate new and existing data sources. Promote implementation and real-time international exchange of these observations. 

x) Lead the cross-cutting activity to raise the level of expertise in high impact weather prediction by involving operational meteorologists in HIWeather research, particularly through evaluation activities in FDPs, testbeds and proving grounds, WMO Training Centres etc. 

y) Lead the cross-cutting activity to develop an international collaborative activity to collect social media, volunteer and other professional data for use in monitoring, nowcasting and data assimilation. 

z) Contribute to a cross-cutting activity to review and synthesise work on stochastic physics and model error in ensembles, and to promote new work, leading to publication of new recommendations for parametrization design for ensemble prediction systems aa) Contribute to a cross-cutting activity to review and publish the implications of uncertainty across the whole spectrum of the work of HIWeather and how these propagate to influence the ability to enhance resilience.