NCAS-Climate, University of Reading  

Mike Blackburn
NCAS-Climate, University of Reading

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Extreme Events

State of the Climate annual reports, NOAA.

Workshop on attribution of climate-related events, August 2010.

UK rainfall, April-July 2012

Read an article on the recent record rainfall.

Comment from the Met Office and University of Reading.

Article by David Shukman on the BBC website.

Met Office: UK rainfall maps   April   June   and   UK climate summaries.

The Record Wet Autumn of 2000 in Western Europe

Mike Blackburn and Brian Hoskins

The Autumn (Fall) season of 2000 saw record rainfall and widespread flooding in western Europe. It was the wettest Autumn in England and Wales since records began in 1766, and several regions from France to Norway received double their average rainfall.

This exceptional weather was linked to a persistent large-scale pattern of unusual conditions stretching across the Atlantic and northern Europe, the "Scandinavia pattern", with low pressure near the UK and a strong Scandinavian ridge. A regression analysis has shown that wet UK Autumns during the preceding 40 years were also associated with this pattern.

Using a simplified numerical model of the global atmosphere, our research suggests that the pattern was triggered by unusually dry weather over the tropical west Atlantic and South America in Autumn 2000. Experiments using this (barotropic) model have shown that anomalous upper-level convergence and sinking of air in this region in Autumn would give rise to a Rossby wavetrain remarkably similar to the observed pattern over Europe.

The "Scandinavia pattern" of the Autumn flow had been identified previously as one of a number of patterns of northern hemisphere variability by Barnston and Livezey (1987, Mon. Wea. Rev., 115, 1083-1126), but had not been associated with wet Autumns in western Europe. The pattern was originally named "Eurasian Type-1" by Barnston and Livezey but it has subsequently been renamed the "Scandinavia pattern" in an extended version of their analysis at NOAA's Climate Prediction Centre (CPC). It is CPC's index of the strength of the pattern that we have used in this study.

Variations in the winter climate of western Europe have been linked to a different pattern, the North Atlantic Oscillation (NAO), in recent years. From the 1960s to the 1990s the positive phase of NAO, with strengthened westerly flow into Europe, became more prevalent in winter. In Autumn 2000, however, the phase of NAO varied from month to month so that, in the seasonal average, the observed flow did not project strongly onto the NAO pattern. In contrast, the period of wet Autumn weather coincided with persistence of the Scandinavia pattern, from its onset in mid September until its decay in mid December. In the subsequent winter months, which have also been wetter than average in the UK, the wet periods have coincided with further occurrences of the Scandinavia pattern.

This work is being submitted for publication.

Copy of a less specialist paper submitted 10/2001 (pdf).

Poster accompanying a talk at the Royal Meteorological Society Conference 09/2001 (A4 size pdf) (A0 size pdf).

Copy of an article in the UGAMP Newsletter No 24, 03/2001 (pdf).

European Flooding during Summer 2002

Mike Blackburn, Brian Hoskins, Pete Inness & Julia Slingo

UGAMP Newsletter article containing preliminary results of a study into the European flooding and the Indian monsoon failure during Summer 2002 (PDF).

Article on the European flooding and monsoon drought of Summer 2002, from the latest edition of NERC's Planet Earth publication (PDF).

A0 poster on Summer 2002 A0 poster: postscript : pdf

A4 poster: postscript : pdf

PDF version of a slide for the FREE meeting on Summer 2002.

Powerpoint presentation on 2002 European Floods, Indian Monsoon and ENSO (9.7Mbytes).

Monsoon online

Boscastle Flood, 16 August 2004

UK Met Office:
Boscastle flood rainfall observations and statistics.

Cambourne sounding for 12UTC on 16th August.
The atmosphere was close to moist-neutrality and was moist in depth. There was little directional wind shear up to the tropopause, with the wind almost parallel to the north Cornish coast.

Data for precipitation averaged over England and Wales from the Met Office place 2004 as the 5th wettest August since records began in 1766. Monthly precipitation in 2004 was 156.5mm, compared with the long term average of 82.7mm and the 1961-1990 average of 77mm.
Plot of the historical data for August.

June/July 2007 UK Floods

During much of June and July 2007 the Atlantic jet-stream was displaced equatorward of its normal position (comparison). At the same time, a quasi-stationary wave pattern persisted from the north Pacific over north America and the Atlantic to Europe, with an upper-air trough close to the UK.
This large-scale environment led to weather systems tracking further south than normal towards the UK, and to in-situ developments associated with the upper-air potential vorticity (PV) anomaly over the UK.

Animation of the dynamical tropopause potential temperature, which includes the periods of intense rainfall on 25 June and 20 July. In each case there was a cold air anomaly over the UK, almost cut off, associated with a PV maximum in the upper troposphere (the period 29/06 - 05/07 is missing).

Met Office rainfall   May   June   July   JJA
Special Issue of the Royal Meteorological Society's journal Weather on the 2007 Summer floods, including a paper by Blackburn, Methven and Roberts on the Large-scale context for the UK floods in summer 2007.

Walker Institute press release and meteorological context
CEH report

July 20 - Central/Southern England Floods
Hertmonceux sounding for 00UTC on 20 July.
Hertmonceux sounding for 12UTC on 20 July.
Ahead of the system at 00Z, the atmosphere was close to moist-neutrality, almost saturated through the depth of the troposphere, with total column water vapour ~30kg/m2. The sounding is unstable to a relatively small amount of lifting. By 12Z drier air aloft has reached Hestmonceux.

Pakistan floods and Russian heatwave, July 2010

Mike Blackburn, Andy Turner, Brian Hoskins

Read a statement on the recent extreme weather.

Further information is available as a Walker Institute news article.

Attribution discussion (draft) by Martin Hoerling, NOAA ESRL.

More Information and animations

Current research on Extreme Seasons

We are currently investigating persistent Atlantic weather regimes associated with extreme seasonal precipitation in the UK and parts of continental Europe during Summer 2007 and Autumn 2000. This began as a PhD project from October 2007 to June 2011, funding Ricardo Fonseca.

UK Flooding-related links

DEFRA Flood Management information.

Environment Agency Flooding information.

CEH water research theme.

FRMRC, Flood Risk Management Research Consortium is an EPSRC-led programme.

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National Centre for Atmospheric Science
Mike Blackburn   14 September 2016
Department of Meteorology
University of Reading
PO Box 243, Reading RG6 6BB, UK

University of Reading