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August-September 2012 Slides for Met Office Seasonal Forecast Discussion 20 September 2012

August-September 2012 Slides for Met Office Seasonal Forecast Discussion 20 September 2012 Mike Blackburn National Centre for Atmospheric Science, University of Reading. Met Office Seasonal Forecast Discussion, 20 September 2012. Recent circulation

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August-September 2012 Slides for Met Office Seasonal Forecast Discussion 20 September 2012

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  1. August-September 2012 Slides for Met Office Seasonal Forecast Discussion 20 September 2012 Mike Blackburn National Centre for Atmospheric Science, University of Reading Met Office Seasonal Forecast Discussion, 20 September 2012

  2. Recent circulation • Circulation change at beginning of September (N.Hem, inc. Arctic) • Atlantic jet moved north – dry here, but not the forecast blocking signal? • Moderate MJO activity but strong S. American descent anomaly in September (expected lack of OLR signal for descent) • c.f. Autumn 2000 - possible origin of N. Atlantic wavetrain Met Office Seasonal Forecast Discussion, 20 September 2012

  3. Asian monsoon 2012 All India rainfall • Indian monsoon recovery since mid-August IITM, Monsoon Online

  4. Asian monsoon 2007-2012 Streamfn, σ=0.210 JJA 2007-2012 • Weak monsoon anticyclone in recent summers • Impact of La Niña bias? NOAA ESRL + SOEST, Hawaii

  5. MJO propagation - moderate amplitude continues Last 90 days ECMWF forecast CAWCR & CPC

  6. Tropical convection – recent S. American descent NOAA ESRL & CPC

  7. Descent over S. America + Caribbean Velocity potential anomaly, σ=0.210 16-31 August 2012 1-15 September 2012 NOAA ESRL (NCEP/NCAR Reanalysis)

  8. NH circulation change, Aug-Sept Streamfn. σ=0.210 16-31 Aug Z250, 45°-60°N July Streamfn. σ=0.210 1-15 Sept Aug Sept NOAA CPC & ESRL

  9. NH circulation change, Aug-Sept Streamfn. σ=0.210 16-31 Aug Z250, 45°-60°N July Streamfn. σ=0.210 1-15 Sept Aug Sept NOAA CPC & ESRL

  10. Northern hemisphere jet stream 250hPa Climatology: 1981-2010 Jun-Aug Sept Oct-Nov Jun to Aug: Climatology Sep: Climatology Oct to Nov: Climatology NOAA ESRL

  11. Northern hemisphere jet stream 250hPa 2007-2012 2007-2011 2007-2011 Jun-Aug Sept Oct-Nov Northward shift Northward shift Southward shift NOAA ESRL

  12. - END -

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