© Crown copyright Met Office Improving forecasting of disruption due to convection within UK airspace Paul Maisey and Katie Brown ECAM, European Meteorological Society, University of Reading 12 th September 2013

© Crown copyright Met Office Contents This presentation covers the following areas Convective conditions and impacts on aviation Context: London airspace Case studies Results Future work

© Crown copyright Met Office Development of deep convection Moisture, instability, lift Depth of cloud enables freezing Ice crystals break up and become electrically charged in the turbulent airflows in the cloud Charge separation results in a discharge of electrical activity

© Crown copyright Met Office Convective impacts on aviation

© Crown copyright Met Office London airspace LTMA – London Terminal Manoeuvring Area One of the busiest airspace sectors in the world 5 London airports 4 holding patterns

© Crown copyright Met Office LTMA forecast 5-day forecast Day 1 detail Forecaster-generated Based on all available data

© Crown copyright Met Office Case studies

© Crown copyright Met Office Method of analysis 20 convective cases chosen from summers of 2011 & 12 Range of over- and under-forecasts Forecast compared with subjective assessment of ATM impact Forecast and observations used to analyse synoptic situation and scale of convection Aim: to identify unique characteristics of disruptive situations

© Crown copyright Met Office Convection modelling tools & techniques Precipitation rate Lifted Index CAPE Lightning Index Lightning Risk

© Crown copyright Met Office Case 1 Potential for isolated thunderstorms but most likely to occur, and indeed did occur, overnight Disruption to air traffic minimal

© Crown copyright Met Office Significant convective event, some of worst surface flooding in UK in last 5 years, mostly in north, inc. 10cm diameter hail Very high CAPE values, highly developed convective cells High Lightning Risk Case 2

© Crown copyright Met Office Capping lid not released in LTMA, but disruption resulted from broad band of convective cells to northwest Case 2

© Crown copyright Met Office Key results Case studies indicated some factors that are relevant to assessing the ATM impact of convection: Storm location Storm speed of movement and orientation Spatial extent and intensity Time of arrival

© Crown copyright Met Office Storm location and duration Location: Disruption from storm cells varies across the LTMA, depending on the proximity to flight paths, airports, etc. Duration: Residence with airspace (e.g. band oriented perpendicular to wind or parallel to wind)

© Crown copyright Met Office Extent, intensity and timing 3D extent of storm can have a significant impact Isolated convective cells generally cause less disruption than bands of convective (embedded) rain Aircraft able to manoeuvre around individual storms Timing of storms in relation to traffic activity reflects in impact Overnight activity unlikely to impact network when most airports are closed Impact during peak flying times likely to be more significant (although not at Heathrow which operates at full capacity throughout the day)

© Crown copyright Met Office Summary Forecasters provided with updated guidance on LTMA impact of convection, including: The four key factors relating to disruptive convection Information on how ATC use the forecast Selected case studies used as examples of relevant and significant disruptive situations

© Crown copyright Met Office Further work: models, tools & techniques UKV precipitation rateMOGREPS-UK

Further work: impacts modelling Indicate LTMA vulnerability using available traffic density Combine with convection forecast to provide improved forecast guidance, focussing on short term Extend to other airspaces © Crown copyright Met Office

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