ENSO & SST

ENSO and Sea Surface Temperatures

The tropical Pacific Ocean is in a neutral state (no El Niño or La Niña), but equatorial Pacific sea surface temperature (SST) anomalies remain positive. The Southern Oscillation Index (SOI) rose to near zero in June, after a strong negative excursion in May. The 3-month April – June mean SOI was –0.9. The NINO3, NINO4, and NINO3.4 SST anomalies were all between +0.6 and +0.7 °C for June, and for April – June. Equatorial Pacific subsurface temperature anomalies are currently weak, slightly positive above 100m and slightly negative beneath that. The Madden-Julian Oscillation (MJO) has been inactive for the past several weeks and outgoing longwave radiation anomalies were generally small in June, apart from continued suppressed convection over Indonesia.

Most available models indicate neutral conditions (mostly with positive NINO3.4 anomalies) through the rest of 2005. The Japan Meteorological Agency (JMA) model has been revised, with a new bias-correction applied, reducing its persistently warm forecast into the neutral range. The Scripps/MPI model develops a warm event by Christmas, and a few others move in that direction. The latest US National Center for Environmental Prediction/Climate Prediction Center (NCEP/CPC) statement suggests neutral conditions through September – November, with considerable uncertainty towards the end of the year. The International Research Institute on Climate Prediction (IRICP) summary gives a 65% chance of neutral conditions persisting through to December, with a 30% chance of an El Niño developing, and 5% for La Niña.

Sea surface temperature anomalies (°C) for June 2005

Mean sea surface temperatures (°C) for June 2005