2025 Hurricane Season Retrospective

by Charles Powell (University of Cambridge) and Ruth Petrie 

The 2025 hurricane season was defined by extended periods of suppressed tropical cyclone activity punctuated by explosive bursts of intensity, marked by three Category 5 hurricanes. This pattern fits neatly into the model-predicted trend of increasing intensity of individual storms amid overall reduced activity.

• In the early season strong high-pressure systems and wind shear kept hurricane activity low despite very warm sea surface temperatures in the main development region.
• In the late season conditions became more favourable allowing for rapid intensification of storms like Hurricane Melissa.
• Short-lived influence from atmospheric waves triggered this season’s most powerful hurricanes when the background conditions became intermittently more favourable for development.

Early in the season, from June through July, the Atlantic basin was effectively locked down by anomalously high mean sea-level pressure (MSLP). This pattern promoted subsidence and drying of the mid-troposphere, while weak lapse rates and widespread warmth across the subtropical Atlantic further reduced large-scale convective support, despite the sea surface temperatures (SSTs) in the Main Development Region (MDR) being at near record highs. The suppressing environment was reinforced by a strong Tropical Upper Tropospheric Trough (TUTT), which amplified vertical wind shear and compounded the effects of high pressure and dry air, creating a hostile environment for tropical cyclogenesis.

By late summer, atmospheric conditions began to shift. Subtropical sea surface temperature anomalies weakened, mid-level humidity partially recovered, and the Caribbean developed into a region of enhanced convective potential. These improved thermodynamic parameters created an environment conducive to rapid intensification, as demonstrated by hurricanes such as Melissa, which leveraged these transient favourable conditions to achieve major hurricane status.

One of the most notable aspects of the 2025 season was the influence of equatorial wave forcing. Charles Powell (University of Cambridge), in collaboration with Inigo, has submitted a 2025 season retrospective to Weather, examining how clusters of intense tropical cyclone activity were associated with favourable phases of the Madden–Julian Oscillation (MJO) and eastward-propagating Kelvin waves. These wave events generated short-lived periods of enhanced upper-level divergence, creating localized conditions conducive to deep convection and storm development despite an otherwise unfavourable large-scale environment. This intermittent, wave-driven activity accounts for the season’s above-average Accumulated Cyclone Energy (ACE), concentrated within a small number of major hurricanes rather than distributed across numerous weaker systems.

The 2025 season was largely unfavourable for hurricanes but was punctuated by brief, wave-driven convective surges that produced some of the most powerful hurricanes on record. Even with ocean temperatures at historically high levels, this year highlights that hurricane formation still hinges on a delicate interplay of thermodynamic and atmospheric conditions.