**MADDEN-JULIAN OSCILLATION (MJO)**

**DIAGNOSTIC DISCUSSION**

**issued by**

**CLIMATE PREDICTION CENTER/NCEP**

**October 31, 2005**

**[Synopsis:]{.underline}** The MJO is expected to remain weak during
the next 1-2 weeks.

The MJO remained weak during most of October with a signature closer to
that typical of the northern hemisphere summer MJO. During the past
month, one clear MJO event is evident as a couplet of
enhanced/suppressed convection, mainly north of the equator, shifted
northeastward from the Indian Ocean to the western Pacific Ocean (Fig.
1). Regions of upper-level divergence (convergence) also show signs of a
weak-moderate eastward propagating signal during October (Fig. 2). This
eastward shift in convection can also be seen in low-level wind
anomalies during the third week in October as westerly wind anomalies
extend across Indonesia (Fig. 3).

Most recently, the area of enhanced convection is repositioned mainly
across the eastern Indian Ocean, western Indonesia, and Southeast Asia
regions. There remains a large degree of uncertainty for the future
evolution of the MJO and based on the latest observational evidence and
model forecasts we expect the MJO to remain weak during the upcoming 1-2
week period. As always, close monitoring of the MJO is necessary to
identify signatures of a more coherent MJO signal.

Despite the weak MJO signal, there exists a few potential
benefits/hazards in the global tropics associated with the current MJO
activity. During week 1, we expect an increased chance of above average
rainfall stretching from the eastern Indian Ocean into the western
Pacific Ocean and an increased chance of tropical cyclone development in
the Bay of Bengal due to the weak enhanced phase of the MJO and above
average SSTs. During week 2, we expect a slight shift eastward in the
above average rainfall region and an increased chance of tropical
cyclone development across the western Pacific Ocean. There exists an
elevated risk of tropical cyclone activity in the Caribbean Sea during
week 1 due to continued warm SSTs and the likelihood of a few
disturbances entering this region. Also, Typhoon Kai-Tak will impact
Indochina, especially Vietnam, with high winds and heavy rains early
during week 1.

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 5 December 2005. 

**Climate Prediction Center**

**National Centers for Environmental Prediction**

**NOAA/National Weather Service**

**Camp Springs, MD 20746-4304**

> ![](media/image1.png){width="4.76875in" height="5.751388888888889in"}

**[Figure 1:]{.underline} Time-longitude section (2.5°N-17.5°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="5.552777777777778in"
> height="4.727777777777778in"}

**[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="5.375in" height="5.84375in"}

**[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.**