Thursday, August 16, 2012

El Niño - La Niña Update - Forecast, August 2012

It appears that an El Niño is in the process of developing in the pacific Ocean.  Although there are many factors that influence weather and climate, El Niño  has a significant influence.  It is anticipate that it will be a weak to at most moderate El Niño so the impact on weather in Nebraska this winter will be somewhat limited.  Any value above 0.5 on the scale (left axis) is considered an El Niño.  Approximately 80% of the computer modesls area forecasting an El Niño  and 20% of the models are forecasting "neutral condition (i.e. neither El Niño  or La Niña )

Look for a forecast (outlook) for our winter weather in a later post at the Climate Corner.

Here is the summary found at the International Research Institute (IRI) for Climate and Society.

Synopsis: El Niño conditions likely to develop during August or September 2012.
ENSO-neutral conditions continued during July 2012 despite above-average sea surface temperatures (SST) across the eastern Pacific Ocean (Figure 1). Reflecting this warmth, most of the weekly Niño index values remained near or greater than +0.5C (Figure 2). The oceanic heat content anomalies (average temperature in the upper 300m of the ocean) also remained elevated during the month (Figure 3), consistent with a large region of above-average temperatures at depth across the equatorial Pacific (Figure 4). Although sub-surface and surface temperatures were above average, many aspects of the tropical atmosphere were inconsistent with El Niño conditions. Upper-level and low-level trade winds were near average along the equator, while tropical convection remained enhanced over Indonesia (Figure 5). However, convection increased near and just west of the International Date Line, which may eventually reflect a progression towards El Niño. The lack of a clear atmospheric response to the positive oceanic anomalies indicates ongoing ENSO-neutral conditions.
Nearly all of the dynamical models favor the onset of El Niño beginning in July-September 2012 (Figure 6). As in previous months, several statistical models predict ENSO-neutral conditions through the remainder of the year, but the average statistical forecast of Niño-3.4 increased compared to last month. Supported by model forecasts and the continued warmth across the Pacific Ocean, there is increased confidence for a weak-to-moderate El Niño during the Northern Hemisphere fall and winter 2012-13. El Niño conditions are likely to develop during August or September 2012.
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 Niño are updated monthly in the Forecast Forum section of CPC's Climate Diagnostics Bulletin.

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