Article - May 18, 2023
The 2022 typhoon season featured fewer typhoons than normal, but even a quiet season in the West Pacific typically has several significant typhoon impacts. Half of the ten typhoons that formed last season struck land. Southern and eastern China were hit, as was southern Japan and South Korea. The strongest typhoon impact was from Typhoon Noru, which struck southern Luzon in late September then tracked west to Vietnam. The major cities of Hong Kong, Tokyo, and Taipei had no significant impacts in 2022. The West Pacific has been relatively quiet so far this season, with only a weak, short-lived Tropical Storm Sanvu earlier in April.
The Northwest Pacific Typhoon Season Risk Map above shows risk areas for impact and the predicted number of storms.
For the past three hurricane seasons, La Niña, a cooling of the Tropical Pacific, has persisted. Typically, when the Tropical Pacific is cooler than normal, hurricane activity decreases there but is enhanced in the Atlantic Basin. For this season, it appears that La Niña has ended. Water temperatures in the tropical Pacific are steadily warming. The current forecast is for a 82% chance of an El Niño this summer/fall, up from 61% in the March forecast. We think that an El Niño is becoming much more likely. An El Niño development would typically result in below-normal hurricane activity in the Atlantic Basin. In past seasons with a stronger El Niño, the number of named storms was often less than ten. El Niño seasons also tend to end earlier, with fewer storms in October and November.
Another feature which can significantly influence Northwest Pacific typhoon activity is the Indian Ocean Dipole (IOD). The IOD is defined by the difference in sea surface temperatures between the eastern and western tropical Indian Ocean. The current forecast is for a positive (warm) phase through the summer. During a positive phase, air tends to rise over the Indian Ocean and sink over the western Pacific (particularly the South China Sea). This suppresses typhoon activity in the West Pacific basin. A positive IOD could be a significant inhibiting factor this season.
Most seasonal predictors are indicating that activity across the West Pacific will be a little below normal this season. An El Niño typically inhibits activity, but there is a question about its strength this summer and fall. Sinking air in the South China Sea due to the positive Indian Ocean Dipole combined with a developing El Niño could limit significant typhoon activity there. The European model is predicting a slightly below-normal season in the basin. Considering all of these factors, we think that activity will be a little below normal this year. Stronger typhoons may be concentrated farther north and east than is typical, threatening southeast China through Japan more than Vietnam.
The 2022 typhoon season featured fewer typhoons than normal, but even a quiet season in the West Pacific typically has several significant typhoon impacts. Half of the ten typhoons that formed last season struck land. Southern and eastern China were hit, as was southern Japan and South Korea. The strongest typhoon impact was from Typhoon Noru, which struck southern Luzon in late September then tracked west to Vietnam. The major cities of Hong Kong, Tokyo, and Taipei had no significant impacts in 2022. The West Pacific has been relatively quiet so far this season, with only a weak, short-lived Tropical Storm Sanvu earlier in April.