**MADDEN-JULIAN OSCILLATION (MJO)**

**DIAGNOSTIC DISCUSSION**

**issued by**

**CLIMATE PREDICTION CENTER/NCEP**

**June 1, 2004**

**[Synopsis:]{.underline}** MJO activity is expected to be weak during
the next 2-4 weeks.

Since late 2003 significant MJO activity has contributed to
month-to-month fluctuations in the patterns of equatorial easterly winds
(Fig. 1) and tropical convection as represented by the pattern of
tropical Outgoing Longwave Radiation (OLR) anomalies (Fig. 2).
MJO-related weakening of the equatorial easterly winds occurred across
the western and central Pacific in early-mid January and in late March /
early April (Fig. 1). In spite of this activity, the easterlies were
stronger than normal through the period. During the past few months the
period of the MJO has increased from 30 days to 45 days (Fig. 2)

The fluctuations in equatorial easterly winds have contributed to
month-to-month variability in the surface and subsurface temperatures in
the equatorial Pacific. In particular, the MJO-related weakenings of the
equatorial easterly winds initiated eastward-propagating oceanic Kelvin
waves in early January and in early April 2004 (Fig. 3).

These conditions were associated with a deeper-than-average thermocline
and warmer-than-average upper-ocean temperatures in the western and
central Pacific.

During the first half of May 2004 the pattern of tropical convection
exhibited a stationary wavenumber 1 pattern, with enhanced convection
focused from the Bay of Bengal (100°E) to the Western Pacific (140°E)
and suppressed convection from 60° E to 60°W (Fig. 4). Subsequently, the
pattern of tropical convection became more disorganized, indicative of a
weakening of the MJO activity.

Both statistical and dynamical model forecasts indicate that MJO
activity will continue to be weak during the next 2-4 weeks (Figs. 5-6).
The Eulerian Wave Propagation (EWP) forecast shows an area of suppressed
convection (subsidence) over the western Pacific that is forecast to
propagate eastward to the Atlantic and an area of enhanced convection
(rising motion) that is forecast to propagate eastward to the Central
Pacific over the next several weeks (Fig. 5). The GFS has a similar area
of subsidence over the western Pacific, but it indicates that the
pattern will remain stationary or propagate slowly to the west during
the next 2 weeks. Given the recent trends in the strength of the MJO and
the observed atmospheric patterns discussed above, it is likely that the
MJO will continue to be weak during the next 2-4 weeks.

Weekly updates of SST, 850-hPa wind, OLR and features of the equatorial
subsurface thermal structure are available on the Climate Prediction
Center homepage at:

[http://www.cpc.ncep.noaa.gov.]{.underline}

**Climate Prediction Center**

**National Centers for Environmental Prediction**

**NOAA/National Weather Service**

**Camp Springs, MD 20746-4304**

**e-mail: [Wayne.Higgins@noaa.gov]{.underline}**

![](media/image1.png){width="5.210416666666666in" height="5.5in"}

**Figure 1. Time-longitude section (5°N-5°S) of anomalous 850-hPa zonal
wind (m s^-1^) (GDAS).**

**Contour interval is 2 ms^-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 by orange/red shading.**

![](media/image2.png){width="5.416666666666667in"
height="5.416666666666667in"}

**Figure 2. Time-longitude section (5°N-5°S) of anomalous Outgoing
Longwave Radiation (OLR) (Wm^-2^). The base period for computing
anomalies is 1979-1995. 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/image3.png){width="4.506944444444445in"
height="5.333333333333333in"}

Figures 3. Time-longitude section (5°N-5°S) of anomalous depth of the
20C isotherm in the Pacific Ocean. The contour 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/image4.png){width="3.4166666666666665in"
height="2.0881944444444445in"}

![](media/image6.png){width="3.4166666666666665in"
height="2.2847222222222223in"}

![](media/image7.png){width="6.875in" height="0.4166666666666667in"}

**Figure 4. Daily IR Temperatures (K) and 200-hPa velocity potential
anomalies (10^6^ m^2^s^-1^) on May 9, May 14, May 19, and May 24.
Velocity potential anomalies are proportional to divergence with green
(brown) contours corresponding to regions in which convection tends to
be enhanced (suppressed).** **The base period for computing anomalies is
1971-2000.**

![](media/image8.png){width="5.0in" height="5.75in"}

**Figure 5. Fourty-day forecast of 200-hPa velocity potential anomalies
(10^6^ m^2^s^-1^) based on EWP zonal harmonics (ref?).**

![](media/image9.png){width="4.75in" height="2.75in"}

![](media/image9.png){width="4.75in" height="0.5833333333333334in"}

**Figure 6. Fifteen-day forecast of 200-hPa velocity potential anomalies
(10^6^ m^2^s^-1^) based on the NCEP GFS (ref?).**