Two Atlantic tropical cyclones could test Fujiwhara? Humberto, Imelda trackers prompt Bermuda watch
Forecasters say a direct collision between Humberto and Invest 94L (Imelda) is unlikely, but the rare Fujiwhara interaction remains a theoretical possibility as the storms evolve.
Two tropical cyclones in the Atlantic are tracking on a path that could trigger the Fujiwhara effect, a rare meteorological interaction in which two storms orbit a common center. While the scenario is possible in theory, forecasters say the odds of a direct collision are low, and Humberto and Imelda are likely to remain separate as they move through the open Atlantic and Caribbean.
Tropical Storm Humberto formed in the North Atlantic and is currently packing about 50 mph winds, moving northwest at roughly 8 mph in the Sargasso Sea. It is expected to become a hurricane by Friday night and rapidly intensify into a major Category 3 storm by early next week. At this time, there is high confidence the center will stay out to sea and away from the United States, though Bermuda could see impacts from outer bands or a track shift. There is also the potential for some extra rainfall in the Carolinas from a brief moisture intrusion on the storm’s periphery.
Imelda, initially identified as Invest 94L, is a cluster of storms pushing rain across Puerto Rico, the Virgin Islands and Hispaniola. Forecasters say it could strengthen into a tropical storm or hurricane in coming days, with potential threats to the Georgia and Carolina coasts including damaging winds, life-threatening storm surge and heavy rainfall beginning Sunday. The system could be disrupted by the mountains of the Dominican Republic, slow its development, and stall near the Bahamas or just south of Florida before turning toward Bermuda. The forecast also notes the possibility that Imelda could be pulled north by a larger upper-level low-pressure system and front that are producing rain from the Gulf Coast to New England, which would affect its track and timing.
The Fujiwhara effect — named after Japanese meteorologist Sakuhei Fujiwhara who described the phenomenon in 1921 — occurs when two cyclones come within about 900 miles of each other for tropical systems (1,200 miles for non-tropical systems). When that happens, the storms can rotate around a shared center, sometimes merging into a single larger storm, or, if one is stronger, the stronger may absorb the other. In the most widely cited Atlantic example, Hilary and Irwin in 2017 danced in the open ocean but did not threaten land. Satellite imagery and post-analysis show the two systems circling and exchanging energy, a pattern that can complicate forecast timing and intensity.
Forecast models struggle with these interactions because each storm’s size, intensity and exact path influence the outcome. In the Atlantic basin, the Fujiwhara effect is rare, and forecasters say it tends to occur far from land when it does happen. The West Pacific sees more frequent interactions simply because it produces more tropical cyclones each year. When such an interaction occurs, the result can range from a harmless drift to the formation of a larger, more powerful system, to the two storms simply rotating around a point and weakening.
Two storms on potential collision trajectories are a reminder of the decision-tree nature of tropical forecasting. Fox Weather meteorologist Greg Diamond has emphasized that, for Humberto and soon-to-be Imelda, the higher-odds scenario is that a large upper-level low-pressure system and a front currently producing rain from the Gulf Coast to New England would pull Imelda north rather than allowing a Fujiwhara interaction with Humberto. If that scenario plays out, Humberto and Imelda would maintain enough distance to avoid a Fujiwhara merge.
There is no immediate threat to the United States from Humberto, according to Diamond, who noted confidence that the hurricane’s center will remain offshore. Bermuda, however, should monitor the forecast closely, as outer bands could brush the island next week if the system’s track shifts or intensifies beyond projections. Meanwhile, Imelda’s evolution remains uncertain; its ultimate path could take it toward the Georgia or Carolinas coasts, threaten South Florida or stall near the Bahamas before edging toward Bermuda, depending on how the steering patterns evolve over the next several days.
Meteorologists caution that the situation is fluid and that intensity forecasts for tropical cyclones, especially those in proximity to each other or to upper-level features, carry substantial uncertainty. The public should stay tuned to official forecasts from the National Weather Service and regional forecast offices and heed any local advisories, particularly along the Georgia and Carolina coasts and Bermuda. As the season continues, the potential for complex interactions underscores the importance of precise: monitoring, preparedness and flexible planning for coastal communities along the Atlantic seaboard.
