The 2021 typhoon season was relatively quiet across the Northwest Pacific, with a total of 22 named storms and only nine typhoons. The 30-year climatology for the Northwest Pacific is 26 named storms, 16 of which become typhoons. The 2022 season has started rather quietly as well, with only two named storms, Tropical Storm Megi and Typhoon Malakas, both during April. There have been very few disturbances that posed a significant development threat since April.
The primary driver of typhoon activity in the Northwest Pacific appears to be the state of El Niño Southern Oscillation (ENSO). ENSO is represented by the Oceanic Niño Index (ONI), which is defined as the 3-month average surface temperature anomaly for the Niño 3.4 region in the Tropical Pacific. When the sea surface temperature anomaly is less than 0.5C below normal over a three-month period, it is identified as a La Niña. Conversely, when the average sea surface temperature anomaly is greater than 0.5C for a three-month period, it is identified as an El Niño.
For the past two seasons, the tropics were dominated by a moderate to strong La Niña. During a La Niña, typhoon activity in the Northwest Pacific is significantly inhibited. Because of this persistent La Niña, the Northwest Pacific basin has been relatively quiet, with below-normal typhoon activity over the past two seasons.
In 2022, La Niña conditions are predicted to continue, even strengthening during the peak of the season from August through November. The forecast can be seen in the graphic below, the dark blue line representing a consensus of the models. This persistent La Niña is predicted to significantly inhibit typhoon activity across the Northwest Pacific this season.
Each year, the European model makes an attempt at seasonal tropical cyclone forecasts around the world. For 2022, the European model forecasts a below-normal season with a total of 23 named storms, including 14 typhoons (counting Tropical Storm Megi and Typhoon Malakas from April). The primary reason for this model’s predicting below-normal activity is its forecast of continued La Niña through the season.
Another feature that can influence Northwest Pacific typhoon activity is the Indian Ocean Dipole (IOD). The Indian Ocean Dipole (IOD) is defined by the difference in sea surface temperatures between the eastern and western tropical Indian Ocean. A negative (cool) phase typically results in enhanced rainfall across Indonesia, northwest Australia, and the southern South China Sea. This would tend to enhance tropical cyclone activity south of 10N across the South China Sea. Currently, the IOD is just entering a negative (cool) phase. That cool phase is predicted to last through November. This could enhance activity across the far southern part of the basin.