**MADDEN-JULIAN OSCILLATION (MJO)**

**DIAGNOSTIC DISCUSSION**

**issued by**

**CLIMATE PREDICTION CENTER/NCEP**

**October 3, 2005**

**[Synopsis:]{.underline}** The MJO may strengthen during early-mid
October

After a very active spring period, the MJO weakened substantially in
late May and this behavior continued throughout most of July. At that
time, however, the MJO strengthened but remained weak to moderate in
amplitude as areas of enhanced (suppressed) convection coherently
propagated eastward from the Indian Ocean into the western Pacific for
generally two cycles (Fig. 1). Regions of upper-level divergence
(convergence) also propagated eastward during this period also
completing two cycles around the global tropics (Fig. 2). A couplet of
westerly and easterly wind anomalies accompanied the MJO activity early
in September (Fig. 3). No additional Kelvin wave activity, however, has
developed for several months (Fig. 4).

More recently regions of upper-level divergence/convergence have become
much less coherent and defined indicating that a weakening of the MJO
has occurred during the middle to late part of September. There are
signs, however, that the MJO may again become more active during early
to mid October. Eastward propagation of the weak upper-level divergence
in combination with above normal SSTs may allow the MJO to strengthen.
Based on the latest observational evidence the MJO may become more
active by mid October with enhanced convection located in the eastern
Indian Ocean, Indonesia, and western Pacific Ocean regions by the end of
week 2.

Impacts associated with this expected strengthening of the MJO include
the following. During week 1, potential benefits/hazards in the global
tropics associated with the MJO signal include an increased chance of
above average rainfall in the Indian Ocean and western Indonesia areas.
During week 2, there is an increased chance of above average rainfall in
the eastern Indian Ocean, southeast Asia and western Pacific regions
associated with the continued evolution of the MJO.

This discussion is a consolidated effort of NOAA and its funded
institutions. Weekly updates for SST, 850-hPa wind, OLR and features of
the equatorial subsurface thermal structure are available on the Climate
Prediction Center web page at
[http://www.cpc.ncep.noaa.gov](http://www.cpc.ncep.noaa.gov/). The next
MJO Diagnostics Discussion is scheduled for 31 October 2005. 

**Climate Prediction Center**

**National Centers for Environmental Prediction**

**NOAA/National Weather Service**

**Camp Springs, MD 20746-4304**

> ![](media/image1.png){width="4.8381944444444445in"
> height="5.836805555555555in"}

**[Figure 1:]{.underline} Time-longitude section (7.5°N-7.5°S) of
anomalous Outgoing Longwave Radiation (OLR) (W m^-2^). Negative OLR
anomalies (wetter-than-normal conditions) are indicated by blue shading
while positive OLR anomalies (drier-than-normal conditions) are
indicated by orange/red shading.**

> ![](media/image2.png){width="5.508333333333334in"
> height="4.996527777777778in"}

**[Figure 2:]{.underline} Five day running mean time longitude sections
of the 200-hPa velocity potential anomalies averaged from 5°N to 5°S
from the realtime version of the NCEP/NCAR Reanalysis. Contour interval
is 3 x 10^6^ m^2^ s^-1^ with the brown (green) shading indicating areas
of upper-level convergence (divergence) respectively.**

![](media/image3.png){width="5.397916666666666in"
height="5.7347222222222225in"}

**[Figure 3:]{.underline} Time-longitude section (5°N-5°S) of anomalous
850-hPa zonal wind (m s^-1^) (GDAS).**

> **Contour interval is 2 m s^-1^. Dashed contours indicate negative
> anomalies. The base period for computing anomalies is 1979-1995.
> Stronger-than-average easterlies are indicated by blue shading and
> weaker-than-average easterlies or westerlies by orange/red shading.**
>
> ![](media/image4.png){width="4.479166666666667in"
> height="5.663194444444445in"}

**[Figure 4:]{.underline} Time-longitude section (5°N-5°S) of upper
ocean (0-300 m) heat content anomalies (^o^C) in the Pacific Ocean taken
from GODAS (Global Ocean Data Assimilation System). Greater heat content
(orange/red shading); lower heat content (blue).**