1. Met Office GPC Adam Scaife Head of Monthly to Decadal Prediction Met Office
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2. GloSea5 Global Seasonal Forecast System 5
Model: HadGEM3H N216L85O(0.25)
Initialisation: NWP state + NEMOVAR + Sea Ice
Winter Hindcasts: 24 members starting around 1 November 20 years: 1992/3 – 2012/13
Now Operational: 2 members per day -> 2 months members per day -> 7months
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3. Operational forecasts: January 2013
Observations
Signals appearing in forecasts from 21st Dec
Warning provided to Dept for Transport 4th Jan
Prolonged snow from ~Jan 20th onwards
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4. Winter NAO hindcasts Correlation score = 0.62
Extended to 20 years and 24 members for DJF
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5. Seasonal Skill for surface climate
Forecast skill
from NAO alone
Storms
Temp
Wind
Skilful predictions of extreme events months ahead
Skill in E Atlantic and Europe is from the NAO
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Scaife et al 2014

6. Large ensembles are needed
24 member ensemble shows strong sensitivity to ensemble size
Nothing special about 0.62 and higher values are possible!
More members is important -> see later comment about Met Office & KMA
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7. Real Time Forecast Delivery
Re-insurance
users
WMO LC
Global Framework
For Climate Services
National Met
Services
Met Office
Monthly-Seasonal
Forecasts
US-IMME
UK Gov
Departments
EUROSIP
IRI
International Research Inst.
For Climate and Society
Energy sector
Users
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8. Planned Changes 2014 2016/17 – Increased HPC
Seasonal
Joint System with KMA -> 80 members each month!
Decadal:
HadGEM3 N96L85O(0.1) -> HadGEM3H N216L85O(0.25)
Anomaly Initialisation -> Full Field Initialisation
2016/17 – Increased HPC
Monthly – Seasonal - Decadal
HadGEM3H N216L85O(0.25) -> N512O(0.25)
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9. Summary:
Recently implemented N216 atmosphere and 0.25deg ocean Global Seasonal Forecast System 5
Skilful extratropical forecasts for NAO, Europe & America
Low signal to noise – this is a paradox and a key research topic
Risk of daily extremes governed by large scale flow
Predictability of useful quantities like storminess or windspeed
Further Development:
Much work to do with partners on predicting impacts…
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10. Met Office SLP forecast ensemble mean
Met Office forecasts from October showed enhanced westerlies for Nov-Jan:
NDJ
Met Office SLP forecast ensemble mean
In October we issued an increased risk of mild, wet and stormy weather for November to January:
"The probability that UK precipitation for November-December-January will fall into the driest of our five categories is close to 15% and the probability that it will fall into the wettest category is approximately 25% ”
“…increased risk of windier periods or storms and heavy rainfall, over northwestern Europe during the late autumn and early winter“
This also fed into a successful European RCOF prediction last October.
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11. The Quasi-Biennial Oscillation was cited as one of the drivers (tropical Pacific also involved)
NDJ
QBO effect (hPa)
Nov-Jan 2013/14
after Scaife et al, GRL, 2014
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