Madden/Julian Oscillation: Recent Evolution, Current

Status and Forecasts

Update prepared byClimate Prediction Center / NCEP

August 29, 2005

Outline

• Overview

• Recent Evolution and Current Conditions

• Madden Julian Oscillation Forecast

• Summary

Overview•During mid-March the MJO became active and completed two cycles around the global tropics that lasted until mid-May.

•An eastward propagating oceanic Kelvin wave initiated by persistent westerly anomalies near the date line in February reached the South American coast in April. There has been no additional oceanic Kelvin wave activity.

•The MJO remains weak. Convective anomalies across most of the equatorial global tropics are weak. Low-level easterly anomalies persist across the western Pacific while low-level westerly anomalies persist across the eastern Pacific.

•The MJO is expected to remain weak for the next 1-2 weeks.

•Potential benefits/hazards in the global tropics, however, still include an enhanced chance of tropical cyclone development for weeks 1 and 2 in the Atlantic Basin. Currently, powerful Hurricane Katrina is making landfall along the central Gulf Coast and will track inland. Across the western Pacific, Super Typhoon Talim and TD 14W are forecast to strengthen. Meanwhile, above average rainfall will persist across west-central Africa during week 1 & 2. In addition, there is an increased chance of above average rainfall across Southeast Asia during week 1.

850-hPa Vector Wind Anomalies (m s-1)

Note that shading denotes the magnitude of the anomalous wind

vectors.

Easterly anomalies remain across the western Pacific.

Westerly anomalies persist in the eastern Pacific.

Low-level (850-hPa) Zonal (east-west) Wind Anomalies (m s-1)

Longitude

Time

Weaker-than-average easterlies (orange/red shading).

Stronger-than-average easterlies (blue shading).

During June through early July, easterly anomalies dominated the western equatorial Pacific

Eastward propagating anomalies existed from mid-March until mid-May.

In early August, a period of westerly anomalies were evident in the western Pacific.

Anomalies remain weak during late August

Outgoing Longwave Radiation (OLR) Anomalies (7.5°S-7.5°N)

Drier-than-average conditions (orange/red shading)

Wetter-than-average conditions (blue shading)

Longitude

Time

The MJO was strong from late March through mid-May but has been very weak during June, July and August.

Current anomalies of either sign are weak across most of the equatorial global tropics.

Outgoing Longwave Radiation (OLR) Anomalies (2.5°N-17.5°N)

Drier-than-average conditions (orange/red shading)

Wetter-than-average conditions (blue shading)

Longitude

Time A period of enhanced convection north of the equator in the far western Pacific was evident during late July and early August.

During mid-August, suppressed convection north of the equator stretched from Indonesia into the western Pacific.

Anomalous OLR and 850-hPa Wind: Last 30 days

Enhanced convection developed across the eastern Pacific and central America during mid-August.

Easterly anomalies in the western Pacific north of the equator have shifted west during August.

200-hPa Velocity Potential Anomalies (5°S-5°N)

Negative anomalies (blue shading) indicate favorable conditions for precipitation.

Positive anomalies (orange/red shading) indicate unfavorable conditions for precipitation.

Longitude

Eastward propagating upper-level convergence and divergence is evident from March through Mid-May indicative of the strong MJO during this period.

The MJO has been weak since June. Regions of upper level divergence and convergence have generally been stationary with a eastward shift in late July and early August.

Time

200-hPa Vector Winds and Anomalies (m s-1)

Note that shading denotes the magnitude of the anomalous wind

vectors.

Anticyclonic flow aloft across the Gulf of Mexico

Through 2004 and 2005 there were several cases of eastward-propagating oceanic Kelvin waves (indicated by dashed black lines in the figure).

Each Kelvin wave was initiated when the easterlies weakened over the equatorial Pacific in association with Madden-Julian Oscillation (MJO) activity.

During February 2005, a strong Kelvin wave (initiated by persistent westerly anomalies near the date line unrelated to the MJO) developed and continued to strengthen during March and reached the South American coast during early April. Heat content has become above average in the western Pacific during July and August.

Heat Content Evolution in the Eq. Pacific

Longitude

Time

Empirical Forecast Based on the Real-time Multivariate MJO index

Weak MJO activity is forecast for the next 6-10 day period.

Potential Benefits/Hazards –Week 1

(1) Super Typhoon Talim is forecast to track west towards Taiwan and southeast China. TD 14W will slowly strengthen in the western Pacific.

(2) Powerful Hurricane Katrina will track inland and weaken.

(3) Increased chance of tropical cyclone development across the Atlantic Basin.

(4) Increased chance of above average rainfall across west-central Africa.

(5) Increased chance of above average rainfall across Southeast Asia.

4 51

2

3

Potential Benefits/Hazards – Week 2

(1) Increased chance of tropical cyclogenesis across the Atlantic Basin.

(2) Increased chance of above average rainfall across west-central Africa.

21

Summary•During mid-March the MJO became active and completed two cycles around the global tropics that lasted until mid-May.

•An eastward propagating oceanic Kelvin wave initiated by persistent westerly anomalies near the date line in February reached the South American coast in April. There has been no additional oceanic Kelvin wave activity.

•The MJO remains weak. Convective anomalies across most of the equatorial global tropics are weak. Low-level easterly anomalies persist across the western Pacific while low-level westerly anomalies persist across the eastern Pacific.

•The MJO is expected to remain weak for the next 1-2 weeks.

•Potential benefits/hazards in the global tropics, however, still include an enhanced chance of tropical cyclone development for weeks 1 and 2 in the Atlantic Basin. Currently, powerful Hurricane Katrina is making landfall along the central Gulf Coast and will track inland. Across the western Pacific, Super Typhoon Talim and TD 14W are forecast to strengthen. Meanwhile, above average rainfall will persist across west-central Africa during week 1 & 2. In addition, there is an increased chance of above average rainfall across Southeast Asia during week 1.