Madden/Julian Oscillation: Recent Evolution, Current Status and Forecasts

1. Madden/Julian Oscillation: Recent Evolution, Current Status and Forecasts Update prepared by Climate Prediction Center / NCEP January 25, 2005

2. Outline • Overview • Recent Evolution and Current Conditions • Madden Julian Oscillation Forecast • Summary

3. Overview • Through most of 2004 MJO activity has contributed to month-to-month fluctuations in the patterns of equatorial winds and tropical convection. • This activity has been associated with periods of westerlies in the western Pacific and weaker than average easterlies in the central Pacific which have initiated eastward-propagating oceanic Kelvin waves, contributing to a deeper-than-average oceanic thermocline and an increase in the surface and subsurface temperature anomalies in the central and eastern equatorial Pacific. • Beginning in early November and extending through mid December the MJO was weak. • The MJO strengthened in late December and currently suppressed convection is located in the eastern Indian Ocean/western Indonesia region. Enhanced convection is now evident across northeast Brazil. • Based on the recent evolution of the MJO and on statistical model forecasts, it is likely that the area of suppressed convection will shift eastward across Indonesia during the next 1-2 weeks. In addition, there are indications that enhanced convection may again develop in the Indian Ocean in the upcoming weeks. • Potential impacts in the global tropics during late January include increased chances of above average rainfall in northeast Brazil, southeast Africa and drier than average conditions across Indonesia.

4. Low-level (850-hPa) Zonal (east-west) Wind Anomalies Westerlies (western Pacific) and weaker-than-average easterlies (central/eastern Pacific) (orange/red shading) Stronger-than-average easterlies (blue shading) Time Over the last several months, westerlies have developed on several occasions across the western equatorial Pacific. Most recently, this occurred in mid January. During the last week, westerly anomalies are evident in northeast Brazil behind enhanced convection in proximity of the South Atlantic Convergence Zone (SACZ). Longitude

5. 850-hPa Vector Wind Anomalies (m s-1) Note that shading denotes the magnitude of the anomalous wind vectors. Westerly anomalies remain in the Indian Ocean and far western Pacific. Westerly anomalies have developed in northern South America to the west of enhanced convection.

6. Outgoing Longwave Radiation (OLR) Anomalies (7.5°S-7.5°N) Drier-than-average conditions (orange/red shading) Wetter-than-average conditions (blue shading) During October the MJO was active in the Indian Ocean and western Indonesia regions. Time The MJO, however, became weak in early November and remained weak through mid December. The MJO once again strengthened in late December. Currently suppressed convection is located in western Indonesia. Enhanced convection is evident during the last week in northeast Brazil. Longitude

7. 200-hPa Velocity Potential Anomalies 5oN-5oS Upper-level convergence (brown), upper-level divergence (green). The MJO was active in October with eastward propagation of upper-level convergence and divergence from the Indian Ocean into the Pacific. Time The MJO was weak from early November through mid December. The MJO became active in late December and eastward propagation of upper level divergence / convergence is evident the last few weeks. Longitude

8. 200-hPa Vector Winds and Anomalies (m s-1) Note that shading denotes the magnitude of the anomalous wind vectors. Anomalous upper-level westerlies are evident in the eastern Pacific Ocean west of South America.

9. Anomalous Depth of the 20°C Isotherm (m) (2°S-2°N) Shallower-than-average thermocline (blue shading); Deeper-than-average thermocline (orange shading). MJO-related weakening of the equatorial easterly winds initiated eastward-propagating oceanic Kelvin waves in early January, in early April, late June, late August and October and has contributed to a deeper-than-average oceanic thermocline in the central and eastern equatorial Pacific. Time The latest Kelvin wave initiated by westerly anomalies in early December has propagated into the equatorial central Pacific. Longitude

10. Niño Indices : Recent Evolution SST anomalies greater than or equal to +0.5 ºC are observed in the Niño 4, and Niño 3.4 regions. During late December, the Nino 3.4 and Nino 3 anomalies have decreased while the Nino 1+2 anomaly remains near zero. The warmth in the Niño 4, 3.4, and 3 regions and lack of significant warmth in the Niño 1+2 region indicates that a mid-Pacific warm (El Niño) episode has developed.

11. MJO Forecast (Based on Wheeler Fcst, OLR MJO Anomalies) Suppressed convection is expected to remain across Indonesia and weaken through the period. Enhanced convection is forecast to move into the Indian Ocean by week 2.

12. MJO Forecast (Based on Jones Fcst, OLR MJO Anomalies) Enhanced convection in the western Pacific is forecast to slowly shift eastward and weaken while suppressed convection is expected to dominate Indonesia by week 2.

13. Potential Global Impacts Composites of the MJO cycle indicate potential impacts for the global tropics during the next 1-2 weeks as: • Increased chances of above average rainfall in northeast Brazil in the region of the South Atlantic Convergence Zone (SACZ) • Generally drier than average conditions across Indonesia • Increased chances of above average rainfall in southeast Africa

14. Summary • Through most of 2004 MJO activity has contributed to month-to-month fluctuations in the patterns of equatorial winds and tropical convection. • This activity has been associated with periods of westerlies in the western Pacific and weaker than average easterlies in the central Pacific which have initiated eastward-propagating oceanic Kelvin waves, contributing to a deeper-than-average oceanic thermocline and an increase in the surface and subsurface temperature anomalies in the central and eastern equatorial Pacific. • Beginning in early November and extending through mid December the MJO was weak. • The MJO strengthened in late December and currently suppressed convection is located in the eastern Indian Ocean/western Indonesia region. Enhanced convection is now evident across northeast Brazil. • Based on the recent evolution of the MJO and on statistical model forecasts, it is likely that the area of suppressed convection will shift eastward across Indonesia during the next 1-2 weeks. In addition, there are indications that enhanced convection may again develop in the Indian Ocean in the upcoming weeks. • Potential impacts in the global tropics during late January include increased chances of above average rainfall in northeast Brazil, southeast Africa and drier than average conditions across Indonesia.