MaddenJulian Oscillation: Recent Evolution, Current Status and Forecasts

1
Madden/Julian Oscillation Recent Evolution,
Current Status and Forecasts
Update prepared by Climate Prediction Center / NC
EP
December 19, 2005
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Outline
Overview Recent Evolution and Current Condi
tions Madden Julian Oscillation Forecast
Summary

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Overview
The MJO continues to remain weak.
During the past week, convection in the central
eastern Hemisphere remained very active with
enhanced convection continuing from the eastern
Indian Ocean and the Bay of Bengal across
Indonesia and into the western Pacific Ocean.
Suppressed convection remains near the date line.
Strong westerly (easterly) low-level wind
anomalies associated with the area of enhanced
convection are located across the Indian Ocean /
Indonesia (western Pacific Ocean) regions
respectively. In many ways, conditions across the
global tropics resemble those of La Nina
conditions. Based on the latest observational ev
idence and statistical and dynamical forecasts,
the MJO is expected to remain weak during the
upcoming period. Although the MJO remains weak,
there are potential global benefits/hazards
during the forecast period. For both weeks 1 and
2, there is an increased chance of above average
rainfall from the eastern Indian Ocean across
Indonesia into the far western Pacific Ocean and
an increased chance of below average rainfall
along the equator in the central Pacific Ocean
due to a pattern suggestive of La Nina
conditions. During week 1, the Pacific northwest
coast of the US and British Columbia, Canada have
an increased chance of above average
precipitation, strong winds, and high seas as
multiple strong storm systems are expected to
impact these regions. Also, as a result of
continuing anomalous offshore flow, mainly in
response to enhanced convection in the Indian
Ocean, sections of southeast Africa are expected
to remain drier than average during week 1.
Tropical cyclones 7B and 25W will impact sections
of southeast Asia, Malaysia, and the Bay of
Bengal early during week 1 while there is an
increased chance of tropical cyclogenesis in the
southern Indian Ocean northwest of the coast of
Australia for both weeks 1 and 2 as convection
remains active and low-level westerlies become
more prevalent in this region.
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850-hPa Vector Wind Anomalies (m s-1)
Note that shading denotes the magnitude of the
anomalous wind vectors.
Westerly wind anomalies cover the equatorial
Indian Ocean and stretch into Indonesia
Easterly wind anomalies have strengthened across
the western Pacific Ocean
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Low-level (850-hPa) Zonal (east-west) Wind
Anomalies (m s-1)
Weaker-than-average easterlies or westerlies
(orange/red shading). Stronger-than-average east
erlies (blue shading).
Time
Equatorial easterly anomalies remain near the
date line
Strong westerly anomalies are evident in the
Indian Ocean
Longitude
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Outgoing Longwave Radiation (OLR) Anomalies
(7.5S-7.5N)
Drier-than-average conditions (/red shading)
Wetter-than-average conditions (blue shading)
Weak MJO activity was evident during July and
again in September as OLR anomalies propagated
eastward from the Indian Ocean to the western
Pacific Ocean.
Time
Enhanced convection has become quasi-stationary
across sections of the eastern Indian Ocean,
Indonesia and the western Pacific Ocean
Longitude
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Outgoing Longwave Radiation (OLR) Anomalies
(2.5N-17.5N)
Drier-than-average conditions (orange/red
shading) Wetter-than-average conditions (blue sh
ading)
During the past few weeks, the intensity and
coverage of enhanced convection north of the
equator has increased and is evident from the Bay
and Bengal to the western Pacific Ocean
Time
Longitude
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Anomalous OLR and 850-hPa Wind Last 30 days
During the past 30 days, a quasi-persistent
pattern of enhanced (suppressed) convection has
been evident across Indonesia (western Pacific
Ocean)
Easterly anomalies have been evident in the
western Pacific Ocean during the past month and
have strengthened during the last 10 days
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200-hPa Velocity Potential Anomalies (5S-5N)
Positive anomalies (brown shading) indicate
unfavorable conditions for precipitation.
Negative anomalies (green shading) indicate
favorable conditions for precipitation.
Weak to moderate MJO activity was observed from
July into November.
Time
Most recently, along the equator, anomalous
upper-level divergence (green) is strong over the
Indian Ocean, Indonesia and the far western
Pacific Ocean
Longitude
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200-hPa Vector Winds and Anomalies (m s-1)
Note that shading denotes the magnitude of the
anomalous wind vectors.
Anomalous anti-cyclonic gyre north of the equator
in southeast Asia associated in part with
enhanced convection in the eastern Indian Ocean /
Indonesia region.
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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 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 been above average in the
western Pacific since June while cooler water has
been observed across the eastern Pacific with a
westward extension evident during November.
Time
Longitude
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MJO Index (Magnitude and Phase)
The current state of the MJO as determined by an
index based on Empirical Orthogonal Function
(EOF) analysis using combined fields of
near-equatorially-averaged 850 hPa zonal wind,
200 hPa zonal wind, and satellite-observed
outgoing longwave radiation (OLR) (Wheeler and
Hendon, 2004). The axes represent the time series
of the two leading modes of variability and are
used to measure the amplitude while the
triangular areas indicate the phase or location
of the enhanced phase of the MJO. The farther
away from the center of the circle the stronger
the MJO. Different color lines indicate different
months.
The MJO has been weak during the months of
October and November indicated by periods of low
amplitude eastward propagation
Currently, the MJO remains weak as the projection
from the most recent data continues to be
located within the unit circle
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Statistical OLR MJO Forecast
The MJO is forecast to remain weak during the
next 6-10 days
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Global Forecast System Precipitation Forecast
The GFS expects copious amounts of rainfall to
continue across Indonesia and the western Pacific
Ocean during the upcoming week
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Potential Benefits/Hazards Week 1
1. An increased chance of above average rainfall
extending from the eastern Indian Ocean across
Indonesia into the western Pacific Ocean
2. An increased chance of below average rainfall
in the central Pacific Ocean 3. An increased chan
ce of below average rainfall across sections of
Kenya and Tanzania 4. An increased chance of abo
ve average precipitation, strong winds, and high
seas across the Pacific northwest and British
Columbia 5. Tropical cyclones 7B and 25W will imp
act sections of southeast Asia, Malaysia, and the
Bay of Bengal 6. An increased chance of tropical
cyclogenesis in the southern Indian Ocean off the
northwest coast of Australia
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Potential Benefits/Hazards Week 2
1. An increased chance of above average rainfall
extending from the eastern Indian Ocean across
Indonesia into the western Pacific Ocean
2. An increased chance of below average rainfall
in the central Pacific Ocean 3. An increased chan
ce of tropical cyclogenesis in the southern
Indian Ocean off the northwest coast of Australia
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Summary
The MJO continues to remain weak.
During the past week, convection in the central
eastern Hemisphere remained very active with
enhanced convection continuing from the eastern
Indian Ocean and the Bay of Bengal across
Indonesia and into the western Pacific Ocean.
Suppressed convection remains near the date line.
Strong westerly (easterly) low-level wind
anomalies associated with the area of enhanced
convection are located across the Indian Ocean /
Indonesia (western Pacific Ocean) regions
respectively. In many ways, conditions across the
global tropics resemble those of La Nina
conditions. Based on the latest observational ev
idence and statistical and dynamical forecasts,
the MJO is expected to remain weak during the
upcoming period. Although the MJO remains weak,
there are potential global benefits/hazards
during the forecast period. For both weeks 1 and
2, there is an increased chance of above average
rainfall from the eastern Indian Ocean across
Indonesia into the far western Pacific Ocean and
an increased chance of below average rainfall
along the equator in the central Pacific Ocean
due to a pattern suggestive of La Nina
conditions. During week 1, the Pacific northwest
coast of the US and British Columbia, Canada have
an increased chance of above average
precipitation, strong winds, and high seas as
multiple strong storm systems are expected to
impact these regions. Also, as a result of
continuing anomalous offshore flow, mainly in
response to enhanced convection in the Indian
Ocean, sections of southeast Africa are expected
to remain drier than average during week 1.
Tropical cyclones 7B and 25W will impact sections
of southeast Asia, Malaysia, and the Bay of
Bengal early during week 1 while there is an
increased chance of tropical cyclogenesis in the
southern Indian Ocean northwest of the coast of
Australia for both weeks 1 and 2 as convection
remains active and low-level westerlies become
more prevalent in this region.