1. Seasonal Normal Weather Base
Sallyann Blackett
Gas Forecasting Manager

2. Seasonal Normal Weather - Contents
Background
Why Normal Weather Matters
Traditional method
Met Office project
Mod Proposal
Allow Met Office study output as a potential input to normal weather definition

3. Why do we need a seasonal normal?
Historic demand
Need to distinguish between demand change due to changes in consumer behaviour and connected load from short term changes due to weather
To enable budget comparison
To support pricing assumptions – both for Shippers and Transporters
On the day demand
Need an appropriate basis to measure weather impact from for allocation – included in SNET and CWV and allocation formula through AQ impact
Future demand
Need a basis to correct AQ to represent the future despite being based on historic demand
Need to be able to forecast future demand while the future climate is unknown, supporting investment decisions
Transporter 10 year statements
Supplier purchasing

4. What does code say?
The Network Code requires Tranporters to review, and if necessary revise all composite weather variables (CWVs) used for Network Code demand estimation purposes, at least every 5 years
Concurrent with the comprehensive review of CWVs is the Network Code requirement to update the basis used for seasonal normal weather
The Network Code requires that the basis (ie. the number and duration of years over which seasonal normal conditions are defined) is always such that the current year is never more than 6 years after the most recent year comprising the period used as the basis for seasonal normal conditions
The basis for seasonal normal weather is intended to meet Network Code obligations in respect of gas demand modelling along with improved weather correction of gas demand and more realistic assessments of annual quantities, which are more in line with recent weather experience

5. Background to Review of Normal Weather
What is the best “Normal Weather”?
Traditionally based on historic averages
Do not capture climate trends
Very long periods needed to smooth natural variability
Last major review was in 2005
Moved from 71yr to 17yr (Oct87-Sep04) basis
No global warming adjustment
What has happened since ?
Most months have been warmer than gas industry 17yr normal (22 out of the last 30 months)
Met Office/Energy Industry Global Warming Project (workstream 8 on Normal Weather)

6. Met Office/Energy Industry Project (EP2)
Looking at impact of Global Warming on Energy Industry
Energy Demand
Lines, Cables & Transformers
Urban Heat Island
Wind & Sea Level
Making use of UKCIP08
Work Package 8 on Normal Weather

7. Aims of WP8
Premise: observed climatological temperature averages are now unrepresentative as baselines for medium-term energy-demand planning
Core aim of WP8: improve the UK planning baseline by
predicting climate averages out to 2018 (using Met Office decadal prediction model*)
for temperature, windspeed, solar radiation
*Smith et al., Science, 2007
© Crown copyright Met Office

8. Method
Generate observed hourly station climatology from most recent data ( )
for 21 UK sites
Use DePreSys (combined with observed UK district data) to predict future monthly climatological averages for each UK district
Test for benefit of predicted climatologies over historical climatologies
Use predicted district monthly climatologies to adjust the observed station hourly climatologies
© Crown copyright Met Office

9. Predicted district climatology: mix of observations and predictions
decadal prediction
UK district temperature
predicted climatology:
31-year centred averages
Calibration adjustment at ‘join’
observations
Past climate
past
now
future
© Crown copyright Met Office

10. Output of Met Office Study
Hourly “Normal” Temperatures for 2008 to 2018 based on mix of actuals and decadal model forecasts
For all current gas weather stations
Warming is variable over the year
Validation of method over the historic period
3yr ahead prediction much better than 30yr climate or 15yr rolling average
Conclusion that modelling has insufficient skill for predicting Windspeed
Advice to use base climate data when defining CWV

11. New Normal – Annual Averages
Gas industry “normal”

12. Allow use of Met Office forecasts to provide a normal base in line with expected climate
Review in 5 years time
Alternative of continuously shifting “normal” would cause too much confusion

13. What does the Modification propose?
Code requirements oblige a review of seasonal normal ready for 1/10/2010
Current rules obligate the use of historic data
The Met office/Hadley Centre EP2 study provides data that could be used to produce a more representative base
Code would not currently allow use of this information
The modification proposes a small amendment to code to allow the use of forecast data in line with historic actual data to produce the seasonal normal
There is no obligation envisaged about how much to use