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 11, 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 enhanced convection is located from the eastern Indian Ocean into the western Pacific. Weak suppressed convection is located east of the date line. • Based on the recent evolution of the MJO and on statistical model forecasts, it is likely that the area of enhanced/suppressed convection will continue to shift eastward toward the central Pacific in the next 1-2 weeks.

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 during early December. Strong westerly anomalies are evident near 80oE behind enhanced convection in the eastern Indian Ocean. A couplet of westerly and easterly anomalies in the central Pacific indicative of the enhanced convection near the date line. Longitude

5. 850-hPa Vector Winds and Anomalies (m s-1) Note that shading denotes the magnitude of the total and anomalous wind vectors. Westerly anomalies have strengthened in the Indian Ocean sector near 90oE. Low-level convergence is evident near the date line in the area 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) MJO activity was more regular from late July through late August 2004 with a period of about 40-50 days. Time The MJO was weak from early November through mid December. In late December/early January, the MJO has strengthened and currently areas of enhanced (suppressed) convection are located from the eastern Indian Ocean into the western Pacific (central Pacific). 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 became weak in early November. The MJO strengthened late in December and eastward propagation of upper level divergence and convergence are now evident in Indonesia and the western Pacific. Longitude

8. 200-hPa Vector Winds and Anomalies (m s-1) Note that shading denotes the magnitude of the total and anomalous wind vectors.

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 most recently in October and has contributed to a deeper-than-average oceanic thermocline in the central and eastern equatorial Pacific. Time The latest Kelvin wave has propagated into the equatorial eastern Pacific and has aided in a greater than average thermocline depth in December. Longitude

10. Niño Indices : Recent Evolution SST anomalies greater than or equal to +0.5C 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) Enhanced convection in Indonesia and the western Pacific is forecast to propagate slowly eastward over the next 2 weeks to the west-central Pacific.

12. MJO Forecast (Based on Jones Fcst, OLR MJO Anomalies) Enhanced convection extending from the eastern Indian Ocean into the western Pacific is forecast to propagate into the western Pacific during the next 1-2 weeks. Suppressed convection is forecast in the Indian Ocean by week 2.

13. 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 enhanced convection is located from the eastern Indian Ocean into the western Pacific. Weak suppressed convection is located east of the date line. • Based on the recent evolution of the MJO and on statistical model forecasts, it is likely that the area of enhanced/suppressed convection will continue to shift eastward toward the central Pacific in the next 1-2 weeks.