[californiadisasters] El Nino/La Nina Diagnostic Discussion (April 2013)

Synopsis: ENSO-neutral is favored into the Northern Hemisphere summer 2013.

During March 2013, ENSO-neutral continued, with slightly above average SSTs in the eastern portion of the basin (Fig. 1). Weekly values of all the Niño indices were between -0.5^oC and +0.5^oC during the month (Fig. 2). The oceanic heat content (average temperature in the upper 300m of the ocean) increased to near-average during the month (Fig. 3) as an area of above-average temperatures at depth moved eastward into portions of the eastern basin (Fig. 4). The Madden-Julian Oscillation (MJO) again contributed to increased atmospheric variability over the tropical Pacific. Low-level winds were near average, and upper-level winds were anomalously westerly across the equatorial Pacific. Convection was enhanced over the western equatorial Pacific and suppressed in the central basin (Fig. 5). Collectively, these features indicate the continuation of ENSO-neutral.

Most models forecast Niño-3.4 SSTs to remain ENSO-neutral through the Northern Hemisphere fall (Fig. 6), with dynamical models tending to predict warmer conditions (0^oC to 0.5^oC) than the statistical models (-0.5^oC to 0^oC). There is less confidence in the forecasts for the last half of the year, partly because of the so-called "spring barrier," which historically leads to lower model skill beginning in late spring. Thus, ENSO-neutral is favored into the Northern Hemisphere summer 2013 (see CPC/IRI consensus forecast).

Source: http://www.cpc.ncep.noaa.gov/products/analysis_monitoring/enso_advisory/ensodisc.html

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