La Nina Is A Little Stronger

La Nina is a little stronger.

Fig. 1: The Nino SSTA regions for the past 12 weeks. The diagnostic trend is La Nina is stronger the past 2 weeks.

Discussion: Tropical convection is buoyant in the eastern tropical Indian Ocean to western Indonesia in-part due to the wet monsoon and presence of weak Madden Julian oscillation. The pattern described emerged in February and persists in March. The convection in the far West Pacific tropics leads to vast rising air currents in that tropical region. The low-level air is replaced by accelerating trade winds from the east. Southern oscillation index (SOI) is back into the positive phase as surface pressure lowers near Darwin and rises at Tahiti. The pattern described has allowed the previously very weak La Nina in February to regain some strength (Fig. 1). The weakening of La Nina earlier this year was due to a transient warm subsurface Kelvin Wave (Fig. 2). The Kelvin Wave eliminated much of the cool upper ocean anomalies sustaining La Nina in February (Fig. 3). However, the Kelvin Wave is weakening in March and there is some cooling of the upper ocean in the eastern equatorial Pacific regenerating. Climate Impact Company will issue a new ENSO forecast for 2022 into 2023 by Tuesday March 8^th.

Fig. 2: Upper-ocean heat anomalies across the equatorial Pacific Ocean.

Fig. 3: Upper-ocean heat across sectors of the equatorial Pacific Ocean on a monthly basis.