Local meteorologist David Epstein has a nice discussion of the medium-range weather forecast for the New England region on boston.com, January Will Arrive On A Cold Note. (His Weather Wisdom posts are very good in general.) El Nino and the Madden-Julian Oscillation (MJO) featured in his discussion. El Nino comes up pretty regularly in weather discussions but the Madden-Julian Oscillation? I’d never heard of it. From NOAA:
The Madden-Julian Oscillation (MJO) is a tropical disturbance that propagates eastward around the global tropics with a cycle on the order of 30-60 days. The MJO has wide ranging impacts on the patterns of tropical and extratropical precipitation, atmospheric circulation, and surface temperature around the global tropics and subtropics. There is evidence that the MJO influences the [El Niño/Southern Oscillation] cycle. It does not cause El Niño or La Niña, but can contribute to the speed of development and intensity of El Niño and La Niña episodes.
And MJO’s impact on the weather patterns in the US?
The MJO influences both precipitation and surface temperature patterns across the US. The two most significant impacts over the US during Northern Hemisphere winter are an increase in the frequency and intensity of heavy precipitation events along the US west coast, and an increase in the frequency and intensity of cold air outbreaks across the eastern US. The MJO also influences tropical cyclone activity in both the eastern Pacific and Atlantic basins during the Northern Hemisphere summer.
And the El Niño/Southern Oscillation (ENSO) is?… (emphasis mine)…
The El Niño-Southern Oscillation (ENSO) is a naturally occurring phenomenon that involves fluctuating ocean temperatures in the equatorial Pacific. The warmer waters essentially slosh, or oscillate, back and forth across the Pacific, much like water in a bath tub. For North America and much of the globe, the phenomenon is known as a dominant force causing variations in regional climate patterns. The pattern generally fluctuates between two states: warmer than normal central and eastern equatorial Pacific SSTs (El Niño) and cooler than normal central and eastern equatorial Pacific SSTs (La Niña).
Often, sea surface temperatures (SSTs) are used to identify this oscillation, but it is important to understand that changes in sub-surface ocean temperatures are the first to respond to an oncoming change in the ENSO phase. For instance, when ENSO is transitioning into a warm phase the sub-surface temperatures begin to warm above average, while a shallow layer of near average temperature remains at the surface. Eventually, the surface ocean temperatures will respond to the warming of the sub-surface temperatures, and a warm phase of the ENSO cycle ensues. The same cycle occurs, only opposite, for the cool phase of ENSO. When temperatures in the ENSO region of the Pacific are near average it is known as ENSO neutral, meaning that the oscillation is neither in a warm nor cool phase. Typically, atmospheric patterns during ENSO neutral are controlled more by other climate patterns (NAO, PNA) that vary on shorter timescales…
See also “What is ENSO?”
And some instructive pictures (associated text) re El Nino and La Nina from the NC State website linked to above:
Typical El Niño Effects: December Through February
Typical El Niño Effects: June Through August
Research conducted at the SCO indicates more storms and increased winter precipitation for the southeast during El Niño events. In contrast, decreased summer rainfall occurs during El Niño events, partly due to a decrease in the number of tropical cyclones that develop in the North Atlantic Basin.
Typical La Niña Effects: December Through February
Typical La Niña Effects: June Through August
Climatic conditions in North Carolina during La Niña conditions tend to be opposite those seen during El Niño events, including an increase in the number of tropical cyclones that develop in the North Atlantic Ocean.