资源环境科技发展态势分析平台

The 2019 Atlantic hurricane season exhibited above-average Accumulated Cyclone Energy -60% of which was produced by Hurricanes Dorian and Lorenzo. Most tropical cyclone (TC) activity was concentrated in a similar to 6-week period from late August to early October. During the early part of the season, relatively TC-unfavorable conditions persisted in the main development region (MDR). The MDR environment became largely favorable in September, followed by an abrupt shift back to less conducive conditions in October coincident with a strongly positive Indian Ocean Dipole (IOD). The IOD produced an El Nino-like teleconnection pattern observed through 200-hPa velocity potential anomalies. In the subtropical Atlantic, above-average sea surface temperatures persisted for much of the season, which may have contributed to increased activity at higher latitudes. Given the neutral El Nino-Southern Oscillation conditions during the 2019 hurricane season, our study highlights the need for further analysis of IOD impacts on Atlantic TC activity.

Plain Language Summary In 2019, the Atlantic produced above-average hurricane activity according to Accumulated Cyclone Energy (ACE), an index that captures storm intensity and longevity. The two strongest hurricanes, Dorian and Lorenzo, contributed 60% of the season's total ACE. Most storms occurred in an active 6-week period from late August to early October when the environment became more favorable for hurricanes. But after that, conditions became less favorable when the western Indian Ocean became much warmer than normal and the eastern Indian Ocean became much colder than normal, an oceanic phenomenon referred to as a positive Indian Ocean Dipole. This strong positive Indian Ocean Dipole event produced sinking air across much of the tropics, including the Atlantic, a pattern that is like El Nino. Since knowledge of El Nino helps us predict Atlantic seasonal hurricane activity, it is possible that understanding more about the Indian Ocean Dipole's impacts on Atlantic hurricane activity will help us improve seasonal hurricane forecasts.