ENSO and Sea Surface Temperatures
The tropical Pacific Ocean is in a neutral state (no El Niño or La Niña), although equatorial Pacific sea surface temperature (SST) anomalies remain positive. The Southern Oscillation Index (SOI) was negative in August (–0.9), mainly as a result of higher pressures at Darwin, but the 3- month June–August mean was near zero (–0.2). The NINO3, NINO4, and NINO3.4 SST anomalies in August were all near +0.5 °C, which is slightly cooler than they have been the past three months. Equatorial outgoing long-wave radiation (OLR) anomalies show a region of suppressed convection on the Date Line; about 20° west of the Date Line, convection remains enhanced but has weakened since July. OLR anomalies elsewhere remain small, and equatorial winds are near normal. The main feature in the Equatorial Pacific subsurface temperature profile is a region of negative anomalies (–2°C) centred at about 100 m depth near 140°W, which has moved about 20° eastward and has weakened since July.
Most available models indicate neutral conditions, mostly with positive NINO3.4 anomalies, for the rest of 2005. The Scripps/MPI and LDEO dynamical models continue to develop a warm event over the summer, while the Linear Inverse Model predicts a cooling over the next several months. The latest US National Center for Environmental Predictions statement suggests neutral conditions for the rest of the year, with SST anomalies in the “NINO regions” weakening. The International Research Institute for Climate Prediction summary gives an 80–85% chance of neutral conditions persisting until to December, with a 10–15% chance of an El Niño developing, and 5% for La Niña.
Sea surface temperature anomalies (°C) for August 2005
Mean sea surface temperatures (°C) for August 2005
