The Fujiwhara Effect is a binary interaction between two nearby tropical cyclones (or other cyclonic vortices) in which they begin to rotate around a common midpoint when they get close enough—typically on the order of a few hundred nautical miles (about 300–750 nm, depending on storm size). The phenomenon is named for Japanese meteorologist Sakuhei Fujiwhara, who first described it in 1921.

Outcomes include orbiting, merging, or one storm absorbing the other; stronger systems tend to dominate. These behaviors are summarized by NOAA here: NWS explainer and NOAA NESDIS overview.

How close do storms have to be?

While there’s no single hard cutoff, the NWS Glossary places the interaction range around 300–750 nautical miles (≈345–863 miles), varying with storm size. Contemporary broadcast meteorology often references a ~1,400 km (~870 mi) ballpark for notable interactions; see this WESH explainer.

Why it matters in Florida

When two systems begin to influence each other, their tracks can bend, stall, slingshot, merge, or end with one system getting absorbed—creating forecast challenges and surprise shifts. NOAA outlines these interaction outcomes and forecast implications here: NWS and NESDIS.

Famous (and well-documented) Fujiwhara cases

2017 East Pacific: Hurricanes Hilary & Irwin

This textbook interaction was documented in real time by the National Hurricane Center. Forecast discussions explicitly cite the Fujiwhara dynamics affecting both tracks—see Hilary Discussion #19 and Irwin Discussion #14.

1995 Atlantic: Hurricane Iris & Tropical Storm Karen

The NHC’s official report states: “Iris began a Fujiwhara interaction … with Tropical Storm Karen,” leading to Karen’s eventual absorption. Primary sources: NHC Tropical Cyclone Report: Iris (PDF), NOAA/NCEI 1995 Season Summary (web), and NOAA Seasonal Review PDF.

Note: You’ll sometimes see references to Iris interacting with Humberto in 1995. The best primary-source evidence clearly documents the Fujiwhara between Iris and Karen (see the links above).

What to watch for during a potential Fujiwhara setup

• Converging tracks: Two named systems drawing within a few hundred nautical miles. (NWS Glossary)
• Weird jogs or stalls: Orbital motion can bend or pause tracks. (NWS explainer)
• Asymmetric outcomes: A stronger cyclone can dominate and absorb a weaker one. (NOAA NESDIS)

Comfort cake & coping with chaotic cones 🍰

Fujiwhara seasons are high-anxiety for Floridians—so yes, comfort rituals matter. If you miss the old tradition of the Publix Hurricane Cake, you’re not alone. You can support bringing it back by signing this petition: Bring Back Publix Hurricane Cakes (Change.org). Coverage: Daytona Beach News-Journal.

Stay caffeinated & sane during the waltz

While the pros handle forecasting, you handle morale. Sip something bracing and keep the humor alive:

Bottom line

The Fujiwhara Effect is rare but real: two nearby cyclones can orbit, merge, or cannibalize—upending tracks and expectations. If the models hint at binary interaction, keep a close eye on official guidance and be ready for a wobble (or three). Learn the basics: NWS explainer • Technical definition: NWS Glossary • Classic case study: Irwin/Hilary NHC discussion.