1. Forecast Verification Research
Barbara Brown, NCAR
With thanks to Beth Ebert and Laurie Wilson
S2S Workshop, 5-7 Feb 2013, Met Office

2. Verification working group members
Beth Ebert (BOM, Australia)
Laurie Wilson (CMC, Canada)
Barb Brown (NCAR, USA)
Barbara Casati (Ouranos, Canada)
Caio Coelho (CPTEC, Brazil)
Anna Ghelli (ECMWF, UK)
Martin Göber (DWD, Germany)
Simon Mason (IRI, USA)
Marion Mittermaier (Met Office, UK)
Pertti Nurmi (FMI, Finland)
Joel Stein (Météo-France)
Yuejian Zhu (NCEP, USA)

3. Aims
Verification component of WWRP, in collaboration with WGNE, WCRP, CBS
(“Joint” between WWRP and WGNE)
Develop and promote new verification methods
Training on verification methodologies
Ensure forecast verification is relevant to users
Encourage sharing of observational data
Promote importance of verification as a vital part of experiments
Promote collaboration among verification scientists, model developers and forecast providers

4. Relationships / collaboration
WGCM
WGNE
TIGGE
SDS-WAS
HyMeX
Polar Prediction
SWFDP
YOTC
Subseasonal to Seasonal Prediction
CG-FV
WGSIP
SRNWP
COST-731

5. FDPs and RDPs Sydney 2000 FDP Beijing 2008 FDP/RDP SNOW-V10 RDP
FROST-14 FDP/RDP
MAP D-PHASE
Other FDPs: Lake Victoria
Intend to establish collaboration with SERA on verification of tropical cyclone forecasts and other high impact weather warnings
Typhoon Landfall FDP
Severe Weather FDP

6. SNOW-V10 Nowcast and regional model verification at obs sites
User-oriented verification
Tuned to decision thresholds of VANOC, whole Olympic period
Model-oriented verification
Model forecasts verified in parallel, January to August 2010
User
Relatively high concentration of data available for the Olympic period.
Status
Significant effort to process and quality-control observations
Multiple observations at some sites  observation error

7. Wind speed verification (model-oriented)
Visibility verification (user-oriented)

8. FROST-14 User-focused verification Model-focused verification
Threshold-based as in SNOW-V10
Timing of events – onset, duration, cessation
Real-time verification
Road weather forecasts?
Model-focused verification
Neighborhood verification of high-resolution NWP
Spatial verification of ensembles
Account for observation uncertainty
Anatoly Muravyev and Evgeny Atlaskin came to the Verification Methods Workshop in December, and will be working on the FROST-14 verification.

9. Promotion of best practice
Recommended methods for evaluating cloud and related parameters
Cloud document is just out! Originally requested by WGNE, has been in the works for some time. Has recommendations for standard verification of cloud amount and related variables such as cloud base height, vertical profile of cloud amount, using both point-based and spatial observations (satellite, cloud radar, etc.)

10. Promotion of best practice
Verification of tropical cyclone forecasts
Introduction
Observations and analyses
Forecasts
Current practice in TC verification – deterministic forecasts
Current verification practice – Probabilistic forecasts and ensembles
Verification of monthly and seasonal tropical cyclone forecasts
Experimental verification methods
Comparing forecasts
Presentation of verification results
JWGFVR is also preparing a document describing methods for verifying tropical cyclone forecasts, in support of GIFS-TIGGE and the WMO Typhoon Landfall FDP. It will include standard methods for assessing track and intensity forecasts, probabilistic and ensemble forecast verification, and a review of recent developments in this field. In addition to track and intensity, we also recommend methodologies for TC-related hazards – wind, heavy precipitation, storm surge.

11. Verification of deterministic TC forecasts

12. Beyond track and intensity…
Track error distribution
TC genesis
Wind speed
Most tropical cyclone verification (at least operationally) focuses on only 2 variables: track location and intensity.
Since a great deal of the damage associated with tropical storms is related to other factors, this seems overly limiting
Some additional important variables:
Storm structure and size
Precipitation
Storm surge
Landfall time, position, and intensity
Consistency
Uncertainty
Info to help forecasters (e.g., steering flow)
Other?
Tailoring verification to help forecasters with their high-pressure job and multiple sources of guidance information
Precipitation (MODE spatial method)

13. Promotion of best practice
Verification of forecasts from mesoscale models (early DRAFT)
Purposes of verification
Choices to be made
Surface and/or upper-air verification?
Point-wise and/or spatial verification?
Proposal for 2nd Spatial Verification Intercomparison Project in collaboration with Short-Range NWP (SRNWP)

14. Spatial Verification Method Intercomparison Project
International comparison of many new spatial verification methods
Phase 1 (precipitation) completed
Methods applied by researchers to same datasets (precipitation; perturbed cases; idealized cases)
Subjective forecast evaluations
Weather and Forecasting special collection
Phase 2 in planning stage
Complex terrain
MAP D-PHASE / COPS dataset
Wind and precipitation, timing errors 14

15. Outreach and training Verification workshops and tutorials
On-site, travelling
SWFDP (e.g., east Africa)
EUMETCAL training modules
Verification web page
Sharing of tools

16. 5th International Verification Methods Workshop Melbourne 2011
Tutorial
32 students from 23 countries
Lectures and exercises (took tools home)
Group projects - presented at workshop
Workshop
~120 participants
Topics:
Ensembles and probabilistic forecasts
Seasonal and climate
Aviation verification
User-oriented verification
Diagnostic methods and tools
Tropical cyclones and high impact weather
Weather warning verification
Uncertainty
Special issue of Meteorol. Applications in early 2013
THANKS FOR WWRP’S SUPPORT!!
Had some trouble with participants getting their visas on time – some countries missed out (Ethiopia, China came late). Could use advice/help from WMO on this.

17. Seamless verification
Seamless forecasts - consistent across space/time scales
single modelling system or blended
likely to be probabilistic / ensemble
climate
change
local
point
regional
global
Spatial scale
forecast aggregation time
minutes
hours
days
weeks
months
years
decades
NWP
nowcasts
decadal
prediction
seasonal
sub-
very
short
range
Which scales / phenomena are predictable?
Different user requirements at different scales (timing, location, …)

18. "Seamless verification" – consistent across space/time scales
Modelling perspective – is my model doing the right thing?
Process approaches
LES-style verification of NWP runs (first few hours)
T-AMIP style verification of coupled / climate runs (first few days)
Single column model
Statistical approaches
Spatial and temporal spectra
Spread-skill
Marginal distributions (histograms, etc.)
Seamless verification
It was not clear to the group how to define seamless verification, and the WG had a lively discussion on this topic.
One possible interpretation is consistent verification across a range of scales by for example applying the same verification scores to all forecasts being verified to allow comparison. This would entail greater time and space aggregation as longer forecast ranges are verified. Averaging could be applied to the EPS medium range and monthly time range, as these two forecast ranges have an overlapping period. Similarly the concept of seamless verification could be applied to the EPS medium range forecast and seasonal forecast. For example, verification scores could be calculated using tercile exceedance and the ERA Interim could be used as the reference system. Verification across scales could involve conversion of forecast types, for example, from precipitation amounts (weather scales) to terciles (climate scales). A probabilistic framework would likely be the best approach to connect weather and climate scales.
Perkins et al., J.Clim. 2007

19. "Seamless verification" – consistent across space/time scales
User perspective – can I use this forecast to help me make a better decision?
Neighborhood approaches - spatial and temporal scales with useful skill
Generalized discrimination score (Mason & Weigel, MWR 2009)
consistent treatment of binary, multi-category, continuous, probabilistic forecasts
Calibration - accounting for space-time dependence of bias and accuracy?
Conditional verification based on larger scale regime
Extreme Forecast Index (EFI) approach for extremes
JWGFVR activity
Proposal for research in verifying forecasts in weather-climate interface
Assessment component of UK INTEGRATE project
Models may be seamless – but user needs are not!
Nowcasting users can have very different needs for products than short-range forecasting users (more localized in space and time; wider range of products which are not standard in SR NWP and may be difficult to produce with an NWP model; some products routinely measured, others not; …)
Temporal/spatial resolution go together. On small spatial /temporal scales modelling/verification should be inherently probabilistic. The predictability of phenomena generally decreases (greatly) from short to very short time/spatial scales. How to assess/show such limits to predictability in verification?
Need to distinguish “normal” and “extreme” weather?
Nowcasting more than SR forecasting is interested not just in intensities of phenomena, but also in exact timing/duration and location. Insight in errors of timing/location is needed.
Different demands on observations, possibly not to be met with the same data sources?
From Marion:
We have two work packages kicking off this FY (i.e. now or soon). I am co-chair of the assessment group for INTEGRATE which is our 3-year programme for improving our global modelling capability. The INTEGRATE project follows on from the CAPTIVATE project. INTEGRATE project pages are hosted on the collaboration server. A password is needed (as UM partners you have access to these pages). The broad aim of INTEGRATE is to pull through model developments from components of the physical earth system (Atmosphere, Oceans, Land, Sea-Ice and Land-Ice, and Aerosols) and integrate them into a fully coupled global prediction system, for use across weather and climate timescales. The project attempts to begin the process of integrating coupled atmosphere-ocean (COA) forecast data into a conventional weather forecast verification framework, and consider the forecast skill of surface weather parameters in the existing operational seasonal COA system, GloSea4 and 5, over the first 2 weeks of the forecast. Within that I am focusing more on applying weather-type verification tools on global, longer time scales, monthly to seasonal. A part of this is a comparison of atmosphere-only (AO) and coupled ocean-atmosphere (COA) forecasts for the first 15 days (initially). Both are approaching the idea of seamless forecasting, i.e. can we used COA models to do NWP-type forecasts for the first 15 days, and seamless verification, i.e. finding some common ground in the way we can compare longer simulations and short-range NWP.

20. Questions What should be the role of JWGFVR in S2S?
Defining protocols? Metrics?
Guidance on methods?
Participation in activities?
Linking forecasting and applications?
What should be the interaction with other WMO verification activities?
E.g., Standardized Verification System for Long-range Forecasts (SVS-LRF); WGNE/WGCM Climate Metrics Panel
How do metrics need to change for S2S?
How do we cope with small sample sizes
Is a common set of metrics required for S2S?

21. Database comments Database should be designed to allow easy access for
Applications
Verification
Will need observations for evaluations and applications
Will these (or links to these) be included in the database?
Lack of obs can be a big challenge / detriment to use of the database
Access to data
For applications and verification often will not want a whole field or set of fields
Also may want to be able to examine time series of forecasts at points
Data formats and access can limit uses

22. Opportunities! New challenges
Methods for evaluating extremes
Sorting out some of the thorny problems (small sample sizes, limited observations, etc.)
Defining meaningful metrics associated with research questions
Making a useful connection between forecast performance and forecast usefulness/value
Application areas (e.g., precipitation onset in Africa)
A new research area
Using spatial methods for evaluation of S2S forecast patterns

23. Thank you