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 June 27, 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 in the western Pacific during mid-April
  associated with this MJO activity did not extend
  far enough east to initiate another Kelvin wave.
• The MJO has been weak since the middle of May.
  Over the last week convection has been persistent
  over the eastern Indian Ocean, Bay of Bengal and
  South China Sea regions. The westerly anomalies
  in the eastern Indian Ocean continue to extend
  eastward toward Indonesia, while the easterly
  anomalies in the western Pacific have been
  persistent for the last several weeks. Forecasts
  of the MJO continue to indicate weak MJO activity
  over the next 1-2 week period.
• An increased chance of above normal rainfall
  exists for Southeast Asia, the Bay of Bengal
  region and sections of India for weeks 1 and 2.
  For Central America there exists a increased
  chance of above normal rainfall for week 1.
  Tropical cyclone activity in the eastern Pacific
  basin is expected to be at or above normal. If
  the area of convection and upper-level
  divergence, located over the eastern Indian
  Ocean/western Indonesian region, continues to
  extend eastward there is an increased risk of
  above normal rainfall for the tropical western
  Pacific to the east of the Philippines.

4
850-hPa Vector Wind Anomalies (m s-1)
Note that shading denotes the magnitude of the
anomalous wind vectors.
Easterly anomalies have been persistent over the
tropical western Pacific.
Westerly anomalies have returned to the eastern
Pacific.
Westerly anomalies continue to extend eastward
toward the western Pacific.
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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. After a sustained period of
easterly anomalies, westerly anomalies returned
to the tropical western Pacific in April.
Time
The latest period of sustained westerly anomalies
occurred in late May. Currently broad scale
easterly anomalies are observed west of the date
line over the tropical Pacific. Westerly
anomalies have continued to extend eastward over
the Indian Ocean towards the western Pacific.
Longitude
6
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 was strong from late March through mid
May, but has weakened over the last month.
Currently convection is located over eastern
Indian Ocean and western Indonesia.
Longitude
7
Outgoing Longwave Radiation (OLR) Anomalies
(2.5N-17.5N)
Drier-than-average conditions (orange/red
shading) Wetter-than-average conditions (blue
shading)
Time
Over the last 3 weeks convection has been
concentrated over the Indian Ocean.
Longitude
8
Anomalous OLR and 850-hPa Wind last 30 days
The northward displacement of convection is
evident over the Southeast Asian region in the
middle part of the period. The ITCZ over the
eastern Pacific has been weak over the period.
Over the last 10 days convection has been
concentrated over the eastern Indian Ocean.
Over the last 20 days easterly anomalies have
been persistent over the tropical western
Pacific. The anomalous westerlies in the
tropical eastern Pacific developed in the middle
part of the period.
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200-hPa Velocity Potential Anomalies (5S-5N)
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. The MJO has
been weak over the last month. Currently
broad-scale upper-level convergence is found over
the tropical Pacific with an area of upper-level
divergence centered near 100oE.
Time
Longitude
10
200-hPa Vector Winds and Anomalies (m s-1)
Note that shading denotes the magnitude of the
anomalous wind vectors.
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Heat Content Evolution in the Eq. Pacific

• 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.
• 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
  with no new Kelvin wave activity.

Time
Longitude
12
Empirical Forecast Based on the Real-time
Multivariate MJO index
Weak MJO activity is forecasted for the next 6-10
day period.
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Potential Global Hazards Week 1
3
1
2

• Increased chance of above average rainfall.
• Tropical storm Calvin will impact the eastern
  Pacific west of Central America.
• Increased chance of above average rainfall.

14
Potential Global Hazards Week 2
1

• Increased chance of above average rainfall.

15
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 in the western Pacific during mid-April
  associated with this MJO activity did not extend
  far enough east to initiate another Kelvin wave.
• The MJO has been weak since the middle of May.
  Over the last week convection has been persistent
  over the eastern Indian Ocean, Bay of Bengal and
  South China Sea regions. The westerly anomalies
  in the eastern Indian Ocean continue to extend
  eastward toward Indonesia, while the easterly
  anomalies in the western Pacific have been
  persistent for the last several weeks. Forecasts
  of the MJO continue to indicate weak MJO activity
  over the next 1-2 week period.
• An increased chance of above normal rainfall
  exists for Southeast Asia, the Bay of Bengal
  region and sections of India for weeks 1 and 2.
  For Central America there exists a increased
  chance of above normal rainfall for week 1.
  Tropical cyclone activity in the eastern Pacific
  basin is expected to be at or above normal. If
  the area of convection and upper-level
  divergence, located over the eastern Indian
  Ocean/western Indonesian region, continues to
  extend eastward there is an increased risk of
  above normal rainfall for the tropical western
  Pacific to the east of the Philippines.