MaddenJulian Oscillation: Recent Evolution, Current Status and Forecasts

1
Madden/Julian Oscillation Recent Evolution,
Current Status and Forecasts
Update prepared by Climate Prediction Center /
NCEP May 17, 2005
2
Outline

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

3
Overview

• The Kelvin wave initiated by westerlies near the
  date line in late January 2005 has reached the
  South American coast and warming of the ocean
  waters along the west coast of South America has
  ended.
• During mid March the MJO became active and
  strong and completed one cycle around the global
  tropics with a period of approximately 45 days.
  Westerly anomalies during mid-April associated
  with this MJO activity do not appear to have
  extended far enough east to initiate another
  Kelvin wave.
• The MJO has weakened and become less coherent
  during the past week. The convective phase of the
  MJO is contributing to enhanced convection across
  South America/Central America and the Caribbean
  while suppressed convection is influencing
  eastern Africa and the Indian Ocean. Based on the
  latest evolution of the MJO and statistical model
  forecasts, it is likely during the next week that
  enhanced convection will continue to impact the
  western hemisphere and suppressed convection can
  be expected in the Indian Ocean.
• Impacts in the global tropics include the chance
  of above average rainfall across northern South
  America and southern central America into the
  Caribbean (week 1) with drier than average
  conditions across the eastern Africa, the Indian
  Ocean and Indonesia (week 1). Due to the current
  uncertainty of the MJO, any impacts in the global
  tropics during week 2 are unclear.

4
850-hPa Vector Wind Anomalies (m s-1)
Note that shading denotes the magnitude of the
anomalous wind vectors.
Easterly anomalies in the western Pacific have
weakened during the last five days.
5
Low-level (850-hPa) Zonal (east-west) Wind
Anomalies (m s-1)
Weaker-than-average easterlies (orange/red
shading). Stronger-than-average easterlies (blue
shading).
Westerly anomalies developed over the western
equatorial Pacific in early January and persisted
through February.
Time
Easterly anomalies in the western Pacific have
weakened while weak westerly anomalies extend
across the Indian Ocean into Indonesia.
Longitude
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Outgoing Longwave Radiation (OLR) Anomalies
(7.5S-7.5N)
Drier-than-average conditions (orange/red
shading) Wetter-than-average conditions (blue
shading)
The eastward propagation of the positive/negative
anomaly dipole over the Indian Ocean and
Indonesia (late December 2004-early January 2005)
was associated with the MJO.
Time
Enhanced convection became persistent in the
region of the anomalously warm water near the
date line during February.
The MJO has been strong since late March.
Enhanced convection has shifted east into
Indonesia but has weakened. Suppressed convection
is evident in Africa and the Indian Ocean.
Longitude
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Anomalous OLR and 850-hPa Wind last 30 days
Positive OLR anomalies (below-average rainfall)
developed over Indonesia during the middle of the
period. These positive anomalies have weakened
during the first 10 days of May.
Low-level (850-hPa) westerly wind anomalies (m/s)
observed over Indonesia and the western
equatorial Pacific have weakened during mid to
late April. Strong easterly anomalies are evident
during the last ten days.
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200-hPa Velocity Potential Anomalies
Positive anomalies (orange/red shading) indicate
unfavorable conditions for precipitation.
Negative anomalies (blue shading) indicate
favorable conditions for precipitation.
A stationary pattern of upper level divergence
developed during February as enhanced convection
remained near the date line. Beginning in
early-mid March, the MJO became quite active and
regular. Upper-level divergence propagated from
the western Indian Ocean across the Pacific and
through the western Hemisphere during a 45 day
period from mid March to early May. Currently,
upper-level divergence is evident in Indonesia.
Time
Longitude
9
200-hPa Vector Winds and Anomalies (m s-1)
Note that shading denotes the magnitude of the
anomalous wind vectors.
Equatorial upper-level wind anomalies across the
eastern Indian Ocean, Indonesia, and the western
Pacific have become weak.
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Heat Content Evolution in the Eq. Pacific

• Through 2004 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.
• Between August 2004 and January 2005 Kelvin wave
  activity weakened and the average heat content
  (0-300 m) decreased.
• During February 2005, a stronger Kelvin wave
  developed and continued to strengthen during
  March and reached the South American coast
  during early April. Heat content has returned to
  near average in the western and central Pacific.

Time
Longitude
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Empirical Forecast Based on the Real-time
Multivariate MJO index
Enhanced convection associated with the MJO in
Indonesia and the western Pacific is forecast to
dissipate early in the period while suppressed
convection is expected to shift east from the
Indian Ocean into Indonesia during the next 1-2
weeks.
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Potential Global Impacts Week 1
2
1

• (1) Increased chance of drier than average
  conditions stretching from central Africa to
  Indonesia.
• (2) Increased chance of above average rainfall
  across northern South America/southern Central
  America, and the Caribbean Sea

13
Potential Global Impacts Week 2
No impacts are expected
14
Summary

• The Kelvin wave initiated by westerlies near the
  date line in late January 2005 has reached the
  South American coast and warming of the ocean
  waters along the west coast of South America has
  ended.
• During mid March the MJO became active and
  strong and completed one cycle around the global
  tropics with a period of approximately 45 days.
  Westerly anomalies during mid-April associated
  with this MJO activity do not appear to have
  extended far enough east to initiate another
  Kelvin wave.
• The MJO has weakened and become less coherent
  during the past week. The convective phase of the
  MJO is contributing to enhanced convection across
  South America/Central America and the Caribbean
  while suppressed convection is influencing
  eastern Africa and the Indian Ocean. Based on the
  latest evolution of the MJO and statistical model
  forecasts, it is likely during the next week that
  enhanced convection will continue to impact the
  western hemisphere and suppressed convection can
  be expected in the Indian Ocean.
• Impacts in the global tropics include the chance
  of above average rainfall across northern South
  America and southern central America into the
  Caribbean (week 1) with drier than average
  conditions across the eastern Africa, the Indian
  Ocean and Indonesia (week 1). Due to the current
  uncertainty of the MJO, any impacts in the global
  tropics during week 2 are unclear.