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October 20, 2008

This study assesses the global impacts and real-time predictions of the MJO event that occurred from November 2007 to February 2008. It examines MJO event observations, prediction tools, and noteworthy impacts. The study also discusses the historical context and the interplay between the MJO event and La Nina. Overall, the study highlights the substantial impacts of this MJO event in both the tropics and extratropics.

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October 20, 2008

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  1. MJO Event of Nov 2007-Feb 2008: Assessment of Global Impacts and Real-Time Predictions Jon Gottschalck, Qin Zhang, Wanqui Wang, Yan Xue, Arun Kumar, Michelle L’Heureux, and Mike Halpert 33rd Annual Climate Diagnostics and Prediction Workshop Lincoln, NE October 20, 2008

  2. Outline • MJO event observations • Review of MJO prediction tools • Some noteworthy impacts

  3. Recent Historical Context • MJO activity generally low during last few years • Spring 2005 was last strong event • Winter 2007-2008 event robust, long-lived 90-Day running variance of MJO index

  4. OLR Anomalies Total Anomaly 120-Day Mean Removed Anomaly

  5. Spatial Tropical Precipitation Composite 1979-2007 Nov 2007 – Feb 2008

  6. MJO Index – November - February --Wheeler and Hendon (2004) --Multivariate EOF analysis (OLR, 850 / 200 hPa zonal wind) --Plotting of first two PCs (RMM1, RMM2) in phase space is a measure of MJO strength and location --Location of enhanced convective phase Cycle 1:Start: Nov 15 End: Dec 31 Cycle 2:Start: Dec 31 End: Feb 20 1. Farther from center of circle the greater the MJO strength 2. Counterclockwise movement indicates eastward propagation

  7. Example MJO Index Forecasts Green Line: GEFS Red Line: CFS Blue Line: CAM Thick line: Week 1, Thin line: Week 2 Accurate forecasts Maritime continent barrier?

  8. Overall MJO Index Forecast Skill • GEFS: Best skill during event at most leads • CAM: Slightly better skill at longer leads • CFSOP: Has its best skill for MJO mode 1

  9. Nino34 SST (K) 10S-10N U850 (m/s) 26 Nov 2007-21 Dec 2007 22 Dec 2007-16 Jan 2008 2007-2008 La Nina forecast strongly depends on MJO phase in initial conditions Courtesy Wanqui Wang

  10. Impacts - Northwest Australian Monsoon Enhanced phase Suppressed phases START MJO

  11. US Impacts • Pacific Northwest storminess – early December 2007 1. MJO enhanced convection in Pacific, strong extended Pacific Jet 2. Extreme precipitation and wind event, 18 fatalities, flooding • Heavy rain and snow across central California – early January 2008 1. MJO enhanced convection across the eastern IO and Indonesia, 2. Rossby wave dispersion enhanced an amplified mid-latitude flow 3. Much above-median precipitation in areas typically dry (La Nina)

  12. Pacific NW – Dec 2007 Central CA – Jan 2008 C A A C --Persistent, enhanced convection --Consistent with MJO composites --Contributes to Pacific Jet extension --Undercuts Pacific ridge --Consistent with MJO composites

  13. Summary • MJO event of winter 2007-2008 was strong and generally canonical • Strong interplay with La Nina was an important feature of this event • MJO index predictions from dynamical models showed considerable skill at times with event • CFS Nino 3.4 SST forecasts sensitive to phase of the MJO • Substantial impacts both in the tropics and extratropics

  14. Impact of Ocean Temperatures 120-Day Mean Removed Anomaly Sub-surface Temperature Anomalies Courtesy Yan Xue

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