Download Julia Slingo (Winter flooding)

Met Office Science Review Meetings 2014
MOSAC 19.19
SRG 11.19
Winter 2013/14 flooding
and implications for Met Office science
Julia Slingo, Met Office Chief Scientist
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A reminder of the weather and
its impacts
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Exceptional rainfall
Winter 2013/14 was the UK’s wettest
since records began, with 544.9mm
of rain: 165% of the average winter
rainfall.
It was also the wettest in the England
and Wales Precipitation series, dating
back to 1766
Rainfall (mm)
The country also saw the highest
number of rain days (62.3) since
records began
In a series from 1883, flow rates on
the River Thames remained
exceptionally high for longer than in
any previous flood episode.
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Days with >1mm of rain
Flood Forecasting
Centre: Flood Risk
Warnings
26 consecutive
days at Red
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• Estimated £200bn value of property in Thames floodplain, 1.1
million employees, 55000 properties
• Thames Barrier was closed 4 times in the 1980s, 35 times in
the 1990s, and 135 times since 2000.
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UK Floods 7th February 2014
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Heavy rain December 2013
deterministic model
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ensemble
Reliability Diagram for 3-hour
accumulations exceeding 10mm
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Huge Waves 6/7th January 2014
Met Office Wave Forecasts
using WAVEWATCH III
Global Significant Wave Height (m)
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UK Peak Period (seconds)
High Winds 12th February 2014
UKV (1.5 km)
Forecasts of
10m Wind
Speed (knots)
92 mph winds forecast
105 mph recorded in
Aberdaron in north-west
Wales
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Global Context of UK’s
severe weather
Winds in the upper troposphere (250 hPa)
Climatology
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La Nina impacts
on the jet stream
January 2014
Energy from West
Pacific rainfall driving
UK extremes
Rainfall anomalies (mm/day)
December 2013
SST anomalies
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La Nina impacts
on the jet stream
January 2014
Strong North Atlantic Storm Track
Winds in the lower troposphere (850 hPa)
Climatology
January 2014
Linked to strong
polar vortex, positive
Arctic Oscillation and
westerly phase of the
QBO
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Contribution of climate change
Clausius Clapeyron
2x Clausius Clapeyron
De Bilt rain gauge data:
Change in hourly rainfall
intensity with temperature
Lenderink & Van Meigaard 2008
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Contribution of climate change
Latest results
from
climateprediction.
net attribution
study
© Crown copyright Met Office
Summary
• The weather experienced by the UK last winter was
exceptional
• This was partially driven by convection in the tropical west
Pacific
• The conditions were also enhanced by a westerly QBO and
strong polar vortex which strengthened the North Atlantic jet
• There isn’t yet any definitive evidence that climate change
played a role in the conditions: but all the evidence
suggests there is a link to climate change
“Colleagues across the House can argue about whether that is
linked to climate change or not. I very much suspect that it is”
David Cameron
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Implications for Science
• Is the jet stream changing its behaviour?
• Are Atlantic storms becoming more intense?
• How well do we capture the interactions between
the tropics and the extratropics?
• What resolution do we need in our atmosphere and
ocean models to answer these questions?
• Can we detect changes in rainfall intensity/duration
at the sub-daily timescale?
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Questions and answers
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