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Subseasonal prediction of extreme heat over Australia. www.cawcr.gov.au. Debbie Hudson Andrew Marshall, Chris White, Oscar Alves, Harry Hendon, Matthew Wheeler, Griff Young S2S Conference 10-13 February 2014. Motivation.

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  1. Subseasonal prediction of extreme heat over Australia www.cawcr.gov.au Debbie Hudson Andrew Marshall, Chris White, Oscar Alves, Harry Hendon, Matthew Wheeler, Griff Young S2S Conference 10-13 February 2014

  2. Motivation • Increasing demand for subseasonal forecast guidance in Australia • Large-scale impacts of heat extremes e.g. health, agriculture, infrastructure • Trend towards more frequent and intense heat waves is projected to continue • Recent record-breaking Australian heat waves, e.g. The Centre for Australian Weather and Climate ResearchA partnership between CSIRO and the Bureau of Meteorology Summer 2013 (4 Jan) Summer 2009 (7 Feb) Spring 2009 (August) Summer 2014 (13-17 Jan)

  3. January 2014 heatwave Infrastructure Bushfires http://www.abc.net.au/news/2014-01-13/grape-growers-fear-heatwave-will-destroy-crops/5197208 Health http://www.abc.net.au/news/2014-01-16/bushfire-threat-as-australia-south-east-suffers-heatwave/5204250 http://www.theage.com.au/victoria/anger-over-spike-in-deaths-during-record-victorian-heatwave-20140126-31gxb.html http://www.dailymail.co.uk/news/article-2539626/Widespread-heatwave-causes-bushfires-court-chaos-Australian-Open.html Agriculture http://smh.drive.com.au/roads-and-traffic/heatwave-likely-cause-of-large-crack-on-west-gate-bridge-20140120-314w4.html http://www.sbs.com.au/news/article/2014/01/15/heatwave-conditions-prompt-health-warning http://www.theage.com.au/comment/more-power-to-the-people-as-heatwave-hits-20140116-30xir.html http://www.abc.net.au/news/2014-01-15/fire-crews-on-alert-as-south-east-australia-sizzles-in-heatwave/5200424

  4. Subseasonal forecasting using POAMA DataAssimilation Ensemble of forecasts Coupled climate model Atmos/Land IC Atmospheric Model BAM T47L17 POAMA 3hr OASIS Coupler Coupled breeding method produces perturbations for burst ensemble Weather forecast Ocean IC Ocean Model ACOM2 (lat 0.5~1.5º; lon 2º; 25 lvls) Seasonal forecast Real-time: ensemble of 33 forecasts updated twice-weekly Hindcast set: • 1981-2010 • Ensemble (n=33) 3x every month (1st, 11th, 21st) • Forecasts out to 9-months The Centre for Australian Weather and Climate ResearchA partnership between CSIRO and the Bureau of Meteorology

  5. Capturing the teleconnection: large-scale drivers and heat extremes Madden Julian Oscillation MJO ENSO IOD Indian Ocean Dipole El Niño Southern Oscillation OLR’ Marshall, Hudson et al. 2013 Clim Dyn White, Hudson et al. 2013 Clim Dyn U500 & MSLP’ STR high (Tasman) MSLP EOF1 U500 & MSLP’ Blocking (split-flow) SAM Southern Annular Mode

  6. Capturing the teleconnection: ENSO Increased chance of heat extremes during El Niño Heat extreme: weekly-mean Tmax anomaly in highest decile (above 90th percentile) (observations) POAMA: using weeks 2 and 3 of the forecast Increased probability of extreme heat The Centre for Australian Weather and Climate ResearchA partnership between CSIRO and the Bureau of Meteorology Probability of weekly mean Tmax exceeding the 90th percentile, expressed as ratio to the mean probability

  7. Capturing the teleconnection: SAM Chance of heat extremes during negative SAM (-ve SAM: Equatorward shift of the mid-latitude westerly wind belt) The Centre for Australian Weather and Climate ResearchA partnership between CSIRO and the Bureau of Meteorology Probability of weekly mean Tmax exceeding the 90th percentile, expressed as ratio to the mean probability

  8. Capturing the teleconnection: MJO Examples: SON, phase 3 DJF, phase 8 OBS rain prob. (Wheeler et al. 2009) OBS extreme heat prob. POAMA extreme heat prob. The Centre for Australian Weather and Climate ResearchA partnership between CSIRO and the Bureau of Meteorology

  9. Capturing the teleconnection: persistent STR Tasman High Chance of heat extremes with a persistent high in the Tasman U500 & MSLP’ The Centre for Australian Weather and Climate ResearchA partnership between CSIRO and the Bureau of Meteorology Probability of weekly mean Tmax exceeding the 90th percentile, expressed as ratio to the mean probability

  10. Forecast skill: Windows of forecast opportunity associated with ENSO Skill (SEDI score) for forecasting extreme heat Tmax above the upper decile in JJA in weeks 2 and 3 of the forecast Skill when ENSO is weak/neutral Skill when ENSO is strong Skill better than for random forecasts The Centre for Australian Weather and Climate ResearchA partnership between CSIRO and the Bureau of Meteorology Symmetric Extremal Dependence Index (SEDI; Ferro and Stephenson, 2011)

  11. Forecast skill: Windows of forecast opportunity associated with the SAM Skill (SEDI score) for forecasting extreme heat Tmax above the upper decile in weeks 2 and 3 of the forecast Skill when negative SAM Skill when SAM is weak/neutral Teleconnection SON Teleconnection DJF Skill better than for random forecasts The Centre for Australian Weather and Climate ResearchA partnership between CSIRO and the Bureau of Meteorology

  12. Forecast skill: Windows of forecast opportunity associated with the MJO Skill (SEDI score) for forecasting extreme heat Tmax above the upper decile in weeks 2 and 3 of the forecast Skill when MJO phase 2 Skill when MJO is weak Teleconnection JJA Teleconnection SON

  13. Overall forecast skill ROC area: Tmax in upper quintile Fortnight 1 (week1+2) Fort 1 SON DJF MAM JJA SON Fortnight 1.5 (week2+3) DJF MAM JJA SON Fort 2 SON Fortnight 2 (week3+4) DJF SON JJA MAM

  14. Heat extremes case studies (Hudson et al 2014, in prep) 3-16 JAN 2013 OBSERVED FORECASTS for 3 Jan-16 Jan (initialised on the 27th Dec i.e. weeks 2 and 3) Upper quintile Tercile SEP 2013 OBSERVED FORECASTS for 1 Sep-30 Sep (initialised on the 22nd Aug) Upper quintile Tercile

  15. Heat extremes case studies (Hudson et al 2014, in prep) Attribution of heat extremes: case studies Example: Observations 8-21 Nov 2009 Teleconnection with extreme heat at this time of year phase 3 El Nino MJO SAM index (inverted) Blocking index (inverted) MJO phase 2 SAM (-ve) Persistent Tasman High (STRH) STRH Blocking (-ve) (i.e. no blocking)

  16. Summary • Increasing demand for subseasonal forecasts of heat extremes in Australia • Approach is to • Understand the large-scale climatic processes (e.g. state of the SAM) that lead to episodes of extreme heat over Australia • Examine the ability of POAMA to simulate the teleconnection and predict these large-scale processes • Explore and define skill of POAMA for making predictions of heat extremes, including identifying windows of forecast opportunity • Trialling different heat extreme indices for forecast products • POAMA shows promising skill in subseasonal prediction of heat extremes • There are windows of forecast opportunity related to state of the large-scale drivers. Skill is related to how well the model can predict the driver and capture the teleconnection. The Centre for Australian Weather and Climate ResearchA partnership between CSIRO and the Bureau of Meteorology

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