Warning Britain: The National Severe Weather Warning Service in action during three recent strong wind events A Fox, F Ralston & R Sherwin © Crown copyright Met Office

Public Warnings The National Severe Weather Warning Service (NSWWS) Developed following the Great Storm of October 1987 Warnings based on probability of pre-defined criteria being exceeded, e.g. 15 mm of rain in three hours Took little account of impacts

The current NSWWS Overhauled in 2011 Warnings ( 24 hours ahead), each Yellow, Amber or Red Rain, Wind, Snow, Ice and Fog Variable warning thresholds, dependent on location and previous weather More focussed on impacts of severe weather Consultation with partner agencies to determine likely impacts

Validity Warning Chief Forecaster’s assessment Weather Impact Matrix

Communicating uncertainty 15/16 December 2011

The probability of winds at a height of 1 km exceeding 60 kt at 0000 UTC on 16 December 2011, from the 0000 UTC run of the ECMWF EPS on 11 December. © Crown copyright Met Office Valid 15/1800 – 16/2359

Graphics issued 14 December 2011, showing ‘most likely’ and ‘low risk alternative’ tracks © Crown copyright Met Office

Updated graphic, 15 December 2011 © Crown copyright Met Office

A well-warned storm 8 December 2011

Yellow alert issued 06 Dec

First RED warning of the current NSWWS © Crown copyright Met Office Consistently forecast strong wind event Yellow alert first issued on 05 December Red warning issued on 07 December – high confidence of a high-impact event

12Z and 18Z analyses, 08 December 2011 © Crown copyright Met Office 12Z 18Z

What happened Winds speeds generally in accordance with the warning Gust 143 kt at Cairngorm (1237m amsl) Gust 91 kt at Tulloch Bridge Estimated 150,000 homes without power According to Traffic Scotland, around 20% less traffic on the roads than usual Hundreds of schools closed in advance Overall, reduced risk to life © Crown copyright Met Office

An entirely different animal 3 January 2012 © Crown copyright Met Office

A relatively short-notice RED © Crown copyright Met Office 31 Dec, 11:29 01 Jan, 10:51 02 Jan, 12:13 03 Jan, 08:14

DT 02/0600Z Gusts >70 kt DT 02/0600Z Gusts >80 kt DT 02/1800Z Gusts >80 kt DT 03/0600Z Gusts >80 kt MOGREPS probabilities for 03/0900Z

18Z, 02 Jan 00Z, 03 Jan 06Z, 03 Jan 12Z, 03 Jan The evolution © Crown copyright Met Office 18Z, 03 Jan

The event and impacts Gusts 80 kt at Glasgow Airport, 89 kt at Edinburgh Blackford Hill (134m amsl) – both major population centres All major motorway/trunk road bridges closed Strathclyde Fire and Rescue: 488 incidents by 1300 on 03 Jan, Fife &Lothian 270 incidents No rail services out of central Scotland – 856 fallen trees to remove from the lines! ~140,000 homes without power © Crown copyright Met Office

Thank you – any questions?