My Blog Archive List

Show more

Forecast Models











  1. CIPS
  2. AWIPS
  3. WxCaster
  4. Weather.US
  5. PSU E-Wall
  6. Tropical Tidbits
  7. Hurricane Model Plots
  8. Metrogram Generator
  9. Harris WeatherCaster
  10. ISU Automated Data Plotter
  11. Experimental NWS Graphics
  12. NCEP SREF Plume Forecasts
  13. WPC Short Range Surface Forecast Maps
  14. Climate Prediction Center - Teleconnections
  15. NOAA ESRL Historical Temperature Anomalies
  16. NOAA ESRL Historical Divisional Temp/Preicp Anomalies









What is the MJO, and why do we care?


The articles posted on this blog have described ENSO, its regional and global impacts, and the challenge of forecasting it, among several other topics. Here we introduce another important player on the tropical stage: the Madden-Julian Oscillation, or MJO. While the MJO is a lesser-known phenomenon, it can have dramatic impacts in the mid-latitudes. Several times a year the MJO is a strong contributor to various extreme events in the United States, including Arctic air outbreaks during the winter months across the central and eastern portions of the United States.

So what is the MJO?

Imagine ENSO as a person riding a stationary exercise bike in the middle of a stage all day long. His unchanging location is associated with the persistent changes in tropical rainfall and winds that we have previously described as being linked to ENSO. Now imagine another bike rider entering the stage on the left and pedaling slowly across the stage, passing the stationary bike (ENSO), and exiting the stage at the right. This bike rider we will call the MJO and he/she may cross the stage from left to right several times during the show.

So, unlike ENSO, which is stationary, the MJO is an eastward moving disturbance of clouds, rainfall, winds, and pressure that traverses the planet in the tropics and returns to its initial starting point in 30 to 60 days, on average. This atmospheric disturbance is distinct from ENSO, which once established, is associated with persistent features that last several seasons or longer over the Pacific Ocean basin. There can be multiple MJO events within a season, and so the MJO is best described as intraseasonal tropical climate variability (i.e. varies on a week-to-week basis).

The MJO was first discovered in the early 1970s by Dr. Roland Madden and Dr. Paul Julian when they were studying tropical wind and pressure patterns. They often noticed regular oscillations in winds (as defined from departures from average) between Singapore and Canton Island in the west-central equatorial Pacific (Madden and Julian, 1971; 1972; Zhang, 2005).

The MJO consists of two parts, or phases: one is the enhanced rainfall (or convective) phase and the other is the suppressed rainfall phase. Strong MJO activity often dissects the planet into halves: one half within the enhanced convective phase and the other half in the suppressed convective phase. These two phases produce opposite changes in clouds and rainfall and this entire dipole (i.e., having two main opposing centers of action) propagates eastward. The location of the convective phases are often grouped into geographically based stages that climate scientists number 1-8 as shown in Figure 1.


For the MJO to be considered active, this dipole of enhanced/suppressed convective phases must be present and shifting eastward with time. An animated illustration that depicts the global scale and eastward propagation of these two phases of the MJO is shown here (Fig. 2: animation).


What’s behind the pattern?


Let’s dig a little deeper and look at some of the characteristics within these two convective phases (Figure 3). In the enhanced convective phase, winds at the surface converge, and air is pushed up throughout the atmosphere. At the top of the atmosphere, the winds reverse (i.e., diverge). Such rising air motion in the atmosphere tends to increase condensation and rainfall.


In the suppressed convective phase, winds converge at the top of the atmosphere, forcing air to sink and, later, to diverge at the surface (Rui and Wang, 1990). As air sinks from high altitudes, it warms and dries, which suppresses rainfall.

It is this entire dipole structure, illustrated in Figure 3, that moves west to east with time in the Tropics, causing more cloudiness, rainfall, and even storminess in the enhanced convective phase, and more sunshine and dryness in the suppressed convective phase.  

The changes in rainfall and winds described above impact both the Tropics and the Extratropics, which makes the MJO important for extended-range weather and climate prediction over the U.S. and many other areas. The MJO can modulate the timing and strength of monsoons (e.g., Jones and Carvalho, 2002; Lavender and Matthews, 2009), influence tropical cyclone numbers and strength in nearly all ocean basins (e.g., Maloney and Hartmann, 2000), and result in jet stream changes that can lead to cold air outbreaks, extreme heat events, and flooding rains over the United States and North America (Higgins et al. 2000, Cassou, 2008, Lin et al. 2009, Zhou et al., 2012, Riddle et al., 2013, Johnson et al., 2014).

The MJO can produce impacts similar to those of ENSO, but which appear only in weekly averages before changing, rather than persisting and therefore appearing in seasonal averages as is the case for ENSO.

Future posts will focus on the details of how we monitor and assess the strength of the MJO, provide details on impacts and the reasons for those impacts, and describe the current state of MJO predictability.  Realtime MJO information that is updated daily or weekly can be found on the NOAA CPC MJO webpage.

Click On This Link To Go Back To The Home Page.


Comments

My Current Davis Vantage Pro Plus Weather

Storm Prediction Center Mesoscale Discussions

NWS Storm Prediction Center (SPC)

NWS Storm Prediction Center (SPC)
Current Watches In Effect

Storm Prediction Center

Storm Prediction Center
Severe Weather Outlooks/Watches - Click On The Map To Open It.

NWS Watch/Warning/Hazards Map

NWS Watch/Warning/Hazards Map
Click On The Map To Go To The Live Link.

NWS 12-Hour Surface Map Forecast

NWS 12-Hour Surface Map Forecast
Click On The Map To Open It Up.

NWS Midland Web Page

NWS Midland Web Page
Click On The Map To Open It Up

NWS Midland Radar

NWS Midland Regional Forecast

Eddy County Watches & Warnings

Lea County Watches & Warnings

Culberson County - Guadalupe Mtn's Watches & Warnings

NWS Albuquerque Web Page

NWS Albuquerque Web Page
Click On The Map To Open It Up

Cannon AFB Radar

NWS Albuquerque Radar

NWS Albuquerque Regional Forecasts.

Chaves County Watches & Warnings

Lincoln County Watches & Warnings

NWS El Paso Web Page

NWS El Paso Web Page
Click On The Map To Open It Up

Holloman AFB Radar

NWS El Paso/Santa Teresa Radar

NWS El Paso/Santa Teresa Regional Forecasts.

Otero County Watches & Warnings

NWS Lubbock Web Page

NWS Lubbock Web Page
Click On The Map To Open It Up

NWS Lubbock Radar

NWS Lubbock Regional Forecasts.

Regional Radar

Regional Radar
Click On The Map To Enlarge It

CoCoRaHS Daily Rainfall Map

Cloudcroft Live Webcam