April 2023 Climate Forecast Discussion

Apr 2023 Climate Forecast Discussion for May-Jul through Aug-Oct 2023

In March 2023, equatorial sea surface temperatures (SSTs) in the central-eastern equatorial Pacific Ocean remained at an ENSO-neutral level (the NINO3.4 index value in March 2023 was -0.01 °C). Weekly SST anomalies in the same region have remained very small for the last four weeks (as of the week of 05 April, the NINO3.4 index was 0.0 °C). According to the early-April CPC ENSO forecast, the tropical Pacific continue to experience ENSO-neutral state (neither El Niño nor La Niña), during boreal spring. As per the CPC forecast, there is a 62% probability that there will be a transition to El Niño during May-Jul 2023. Furthermore, it is anticipated that the El Niño category will remain the most probable category in the subsequent months. Consequently, an El Niño watch has been issued. Observations and model forecasts both indicate weak warm SST anomalies in the Atlantic Ocean, while forecasts also indicate the development of a positive Indian Ocean Dipole from May-Jul 2023 onwards.

The multi-model precipitation forecasts for May-Jul to Aug-Oct indicate gradually increasing probabilities of above-normal precipitation over the African Sahel, and of below-normal precipitation over northern South America, Central America and parts of the Caribbean, and over parts of the Maritime Continent, South Asia, as well as Australia. Increased probabilities of above-normal precipitation are also forecasted over the southeast South America and the Greater Horn of Africa in Jul-Sep and Aug-Oct. Many, though not all, of these precipitation patterns are consistent with historical El Niño events, pointing to the important of the SST predictions from these models.

For temperature, enhanced probabilities for above-normal temperature are forecasted over most land areas throughout the forecast period. Weakly enhanced probabilities of below-normal temperatures are forecast in May-Jul and Jun-Aug 2023 for some parts of northern South America, parts of Madagascar, including southeastern Australian regions. The forecasts continue to show the low probability of below-normal temperatures at those locations for the remainder of the forecast period, although the probabilities values and effective areas may decrease.