Focus shifts from El Nino & La Nina to MJO

Environment Updates

While El Nino, La Nina events are important, the Madden-Julian Oscillation has impact

Surfersvillage Global Surf News, 7 February, 2013 : - - During January 2013, ENSO-neutral continued, although below-average sea surface temperatures (SST) prevailed across the eastern half of the equatorial Pacific. While remaining below average, a high degree of variability in the weekly Niño 3 and 3.4 indices was apparent during the month.

The oceanic heat content (average temperature in the upper 300m of the ocean) was also below-average, largely reflecting negative subsurface temperature anomalies in the eastern Pacific. At the same time, positive anomalies increased and expanded eastward to the central Pacific by late January.

The variability in both the ocean and atmosphere was enhanced during January, at least partially due to a strong Madden-Julian Oscillation (MJO). Consequently, the location of the MJO was reflected in the monthly averages of wind and convection. Anomalous upper-level winds were westerly over the eastern half of the equatorial Pacific, while low-level winds were near average.

Relative to December 2012, the region of enhanced convection shifted eastward and became more prominent over Indonesia and the western equatorial Pacific. Despite these transient features contributing to cool conditions, the collective atmospheric and oceanic system reflects ENSO-neutral.

The vast majority of models predict near-average SST (between -0.5oC and +0.5oC) in the Niño-3.4 region through the late Northern Hemisphere summer (Fig. 6). However, because model skill is generally low during April-June, there is less confidence in the forecast beyond the spring. Thus, ENSO-neutral is favored through Northern Hemisphere spring 2013 (see CPC/IRI consensus forecast).

This discussion is a consolidated effort of the National Oceanic and Atmospheric Administration (NOAA), NOAA's National Weather Service, and their funded institutions. Oceanic and atmospheric conditions are updated weekly on the Climate Prediction Center web site (El Niño/La Niña Current Conditions and Expert Discussions). Forecasts for the evolution of El Niño/La Niña are updated monthly in the Forecast Forum section of CPC's Climate Diagnostics Bulletin. The next ENSO Diagnostics Discussion is scheduled for 7 March 2013. To receive an e-mail notification when the monthly ENSO Diagnostic.

What is the Madden Julian Oscillation?

The MJO is an intraseasonal fluctuation or “wave” occurring in the global tropics. The MJO is responsible for the majority of weather variability in these regions and results in variations in several important atmospheric and oceanic parameters which include both lower- and upper-level wind speed and direction, cloudiness, rainfall, sea surface temperature (SST), and ocean surface evaporation. The MJO is a naturally occurring component of our coupled ocean-atmosphere system and the typical length of the MJO cycle or wave is approximately 30-60 days.

Current MJO Status:

The MJO remained active over the past week with the enhanced convective phase now nearing Africa. Eastward propagation is now more clear than over the last two weeks.

•Although there is considerable spread in the dynamical model MJO index forecasts, some of the most skillful models historically indicate a continuation of the MJO signal into the western Indian Ocean over the next two weeks.

•Based on recent observations and some MJO index forecasts, the MJO is forecast to remain active during the next two weeks with the enhanced phase entering the western Indian Ocean.

•The MJO favors enhanced rainfall across parts of the south central Pacific Ocean (Week-1), interior South America (Week-1) and southeast Africa and the Indian Ocean (Week 2). Suppressed convection is favored for the Maritime continent and parts of the western Pacific.

•For the U.S., the MJO favors, on average, the development of a mean trough across the western U.S. during mid-February suggesting elevated chances for below normal temperatures. As we approach the end of February, the MJO would favor troughing near or along the west coast and a tendency toward a mean ridge across the eastern U.S..

Check out more about the MJO

www.cpc.ncep.noaa.gov

Source: NOAA

Author: The Editors

Tags: La Nina, El Nino, NOAA, Forecast, Weather

Environment: Surfersvillage