We talk about a variety of atmospheric oscillations that govern our weather, but haven’t yet talked about one of the most important ones: The Madden Julian Oscillation or MJO… Simply put, the MJO deals with thunderstorm development (convection) in the tropics over the western Pacific Ocean and Indian Ocean. It usually cycles about every 30 to 60 days, is most active during weak La Nina or La Nada (neither El Nino or La Nina) events, or during the transition to an El Nino. However, it is usually very INACTIVE during an actual El Nino event. Below shows two graphics of how the MJO works, how it moves, and the usual impact once it propagates into the Eastern Pacific Ocean:
Usually, when the MJO is strong and active, our weather is usually pretty active. Has the MJO been strong recently? Lets check it out: The chart below tracks the MJO back to 2007. The red spikes above the zero line indicate strong MJO activity. The spikes below the zero line indicate very anemic MJO activity:
Notice that since the fall, the MJO has basically been inactive. That explains why many areas from California through the southwestern High Plains are suffering from drought, which have resulted from an inactive weather pattern for that region. Bottomline, when the MJO is not active, our storm track struggles to be active in the southwest part of the US.. In fact, one can draw direct a direct correlation with an inactive MJO and long periods of dry weather in the southwest part of the US.
Given how impactful the MJO can be on our immediate weather, it is important to track the strength of the cycle and how it is moving. Why? Because when an MJO event moves into specific regions around the world, it has different impacts in temperature and precipitation. What do I mean by regions? Well, take a look at the following graphic… This is called a Wheeler Diagram. It shows how strong the MJO is (farther away from center, the stronger it is) and what region (Western Pacific, Indian Ocean, etc) it is moving through across the globe:
The purple line that starts in the circle is where this cycle of the MJO started in mid to late March. This cycle is not that strong ( didn’t get that far away from the center circle) and is for all intents and purposes not having a huge influence. However, what is this cycle forecasted to do? Check out the ECMWF Model and its forecast below:
Notice that the ECMWF actually strengthens the MJO and takes it through region 8 and 1 as a pretty strong signal. BIG DEAL...what does that mean for us? The set of graphics below tells us in general what weather occurs when the MJO is in a specific region:
The above set of maps shows the GENERALLY expected weather pattern, when the MJO is in each phase/region. The left side deals with precipitation anomalies and the right side with temperature anomalies. Since the ECMWF model is forecasting the MJO to remain in phase/region 1 & 8 for a while, the historical analysis indicates we may stay slightly wetter than normal heading into May. Notice the green shading over Colorado during phase 1 and 8… Temperature-wise, you may also notice the “blue and purple” shading over Colorado when the MJO is in region 1 & 8. Thus, the composite precipitation and temperature analysis tells us that if the MJO is in region 1 & 8, out chances for being wetter and colder than normal are increased. That’s IF the MJO behaves as expected…
We are rapidly transitioning toward an El Nino episode, and it is usually during this type of transition that the MJO gets active. Could this be a sign of the MJO starting to get its act together and have a meaningful impact on our spring? Possibly, as longer range models still keep our weather pattern pretty active through May. To keep us reverting back to widespread drought as a state, we need more than just one month of an active MJO. Unfortunately, with the El Nino trying to come on strong, I think our window is limited in terms of MJO activity. I hope we make the most of it. Does that mean it won't rain if we don't have an active MJO? No, it doesn't take an active MJO to have decent moisture around here, but it sure helps...