The Calm Is Over: Twin Hurricanes Threaten Fujiwhara Dance in the Atlantic
The calm is over. Mid-September marks the climatological peak of the Atlantic hurricane season, when sea-surface temperatures and atmospheric conditions align to produce the most frequent and intense storms. Yet until recently, the Atlantic basin had been eerily quiet. For weeks, not a single tropical depression, let alone a full-blown hurricane, managed to develop.
Now, the pendulum has swung dramatically. Forecasts show that by next week, two hurricanes are on track to approach the American coastline simultaneously. More intriguingly, there are indications they could begin interacting with one another through the rare Fujiwhara effect — a phenomenon where two nearby cyclones begin orbiting around a shared axis. If one of the storms grows stronger, it may eventually dominate and absorb the weaker, creating an even more complex hazard scenario. The week ahead promises to be both challenging and scientifically fascinating for meteorologists.
Why the Switch From Silence to Frenzy?
The rapid activation of cyclogenesis across both the Atlantic and the Pacific is not coincidental. Several large-scale atmospheric and oceanic factors have converged:
Sea-surface temperatures (SSTs) are running 1–1.5 °C above normal across large parts of the tropical Atlantic and western Pacific.
Vertical wind shear, which inhibits storm development by tilting storm cores, has weakened due to a reconfiguration of the subtropical jet stream.
The African easterly jet has been more vigorous in recent weeks, providing a conveyor belt of well-organized tropical waves across the Atlantic.
In the Pacific, the Madden–Julian Oscillation (MJO) is currently in a phase that enhances convection, further encouraging storm formation.
This combination created a “perfect corridor” for multiple cyclones to form nearly simultaneously after weeks of suppressed activity.
Fujiwhara?? When two hurricanes interact, they can sometimes pivot around one another. Next week there will likely be 2 tropical cyclones (perhaps 2 hurricanes) offshore. If they are strong enough, and are close enough, a #Fujiwhara may happen. Here’s how it works. Between the 2… pic.twitter.com/9PcEPQ5y8T
Narda has matured into a Category 1 hurricane, with sustained winds near 75 mph (120 km/h) and central pressure dipping below 990 mb. Satellite imagery shows a developing eye surrounded by symmetric convection. The storm’s track points northwestward, steering into open waters before recurving north.
Peripheral rainbands are already brushing parts of the eastern Caribbean, triggering flash-flood watches. Though direct landfall is not imminent, high seas and rip currents are expected along Puerto Rico and the northern Lesser Antilles.
Tropical Storm Humberto
Humberto remains loosely organized, with maximum sustained winds near 50 mph (85 km/h) and central pressure above 1000 mb. Convection is displaced east of the circulation center due to modest wind shear.
Forecast models suggest gradual intensification as upper-level conditions improve. If strengthening occurs, Humberto could become a hurricane within several days. For now, its broad moisture field is the primary hazard, with heavy rainfall expected across the Leeward Islands and potential landslides in mountainous terrain.
Tropical Depression Ragasa – Western Pacific
Ragasa has only recently been classified as a tropical depression. The system’s structure remains disorganized, but environmental conditions — SSTs exceeding 84 °F (29 °C), moist mid-levels, and decreasing shear — favor development.
Guidance suggests a steady westward track toward the South China Sea. If convection consolidates, Ragasa could reach tropical storm strength within 48 hours, with the Philippines most at risk for heavy rain and flooding by early next week.
Typhoon Bualoi – Category 1
In the western Pacific, Typhoon Bualoi has strengthened into a Category 1 storm, with winds of 80 mph (130 km/h) and pressure near 985 mb. A well-defined eye is visible on satellite imagery, and outflow is robust in all quadrants.
The typhoon is tracking northwestward toward the Ryukyu Islands and may further intensify in the next 48 hours. Japan faces significant rainfall totals, with localized amounts exceeding 8–12 inches (200–300 mm), raising risks of flash flooding and coastal inundation.
Hurricane 94L – Category 1
Invest 94L has organized into a Category 1 hurricane, spinning in the central Atlantic. Winds are near 75–80 mph (120–130 km/h), with pressure around 985–990 mb.
Its forecast path bends northwestward, keeping it over open ocean, though Bermuda is under advisories for large swells and dangerous surf. Mariners in the region face hazardous seas, with wave heights exceeding 15–20 feet (5–6 meters).
Tropical Storm Gabrielle
Gabrielle, one of the largest systems currently active, remains a tropical storm with winds of 60 mph (95 km/h). While not exceptionally intense, Gabrielle’s broad wind field creates widespread impacts.
The storm is moving northeast toward the Azores, which are bracing for torrential rain, gale-force winds, and potential coastal flooding. Long-range models suggest Gabrielle could transition into a post-tropical system but still retain strong winds as it heads toward western Europe later this week.
Tropical Depression Neoguri
Neoguri is still a weak system, with sustained winds near 35 mph (55 km/h) and central pressure around 1006 mb. Wind shear continues to disrupt its organization, preventing rapid strengthening.
Nevertheless, the depression has already brought heavy rains to island communities in Micronesia, causing transport delays and localized power outages. If conditions improve, Neoguri may intensify into a tropical storm in the coming days.
FUJIWHARA EFFECT: Can two hurricanes combine to create a super hurricane? Thankfully no! How they interact or “dance” is called the rare #Fujiwhara effect. There’s a lot of buzz recently on social media about it because of the possibility between Humberto and potential… pic.twitter.com/Ti5N7TN6Od
The most scientifically captivating development is the potential Fujiwhara interaction between two Atlantic systems — currently Hurricane Narda and Hurricane 94L. If both maintain hurricane strength while moving into proximity, they could begin orbiting around each other.
This interaction often leads to erratic tracks that models struggle to resolve. In some cases, the stronger system absorbs the weaker, consolidating into a single, more powerful hurricane. If such a scenario unfolds near the western Atlantic, it could complicate forecasting for the U.S. East Coast and Bermuda, demanding close monitoring in the coming days.
Outlook
The sudden surge of storms after a prolonged lull underscores the volatile nature of the tropics during peak season. With multiple systems active across the Atlantic and Pacific, the next week will test coastal preparedness from the Caribbean to East Asia.
Meteorologists emphasize that even weaker tropical depressions can produce life-threatening flash floods, while stronger storms like Bualoi or Narda carry both wind and surge hazards. The simultaneous activity across basins is a reminder of how oceanic and atmospheric variability can synchronize to unleash bursts of tropical energy after weeks of relative quiet.
As September winds down, the basin-wide message is clear: the tropics are fully awake, and the 2025 season still has much more to deliver.
Gleb Perov is the founder and chief meteorologist of POGODNIK, a leading weather forecasting service in Eastern Europe. With over 15 years of hands-on experience in meteorology and climate analysis, he has worked private weather services. Gleb is the author of numerous scientific and analytical publications on climate, magnetic storms, and atmospheric processes. He regularly collaborates with major international agencies such as NOAA, ECMWF.
