Jeju Island's vortex street

Jeju lies south of the Korean peninsula. In winter, cold air pours off the continent from the north-west, and the island's volcano, Hallasan, sheds spirals into the cloud it makes over the warmer sea.

What the satellite saw

Spiral clouds drifting south-east of Jeju Island over a dark blue sea
Jeju, 19 February 2026: spirals peeling off south-east of the island in the winter monsoon. NASA Earth Observatory image by Michala Garrison, using MODIS data from NASA EOSDIS LANCE and GIBS/Worldview ("Showy Swirls Around Jeju Island"). Public domain.
The wake behind Jeju as Wind Tunnel draws it, the NASA photo of the real one laid over the lower right corner
Jeju in Wind Tunnel with Satellite photo on: the simulation, made in your browser, with NASA's photo in the corner.

NASA's Terra satellite photographed it with MODIS on 19 February 2026 (Earth Observatory, "Showy Swirls Around Jeju Island"). The spirals peel off to the south-east of the island.

NASA's note: the swirls need a wind between about 18 and 54 km/h. Weaker, the cloud slides smoothly past; stronger, the eddies cannot hold their shape.

Why Jeju

Height. The island rises to about 1,950 m at Hallasan, the highest peak in South Korea.

The winter monsoon. Cold, dry air off the continent crosses the Yellow Sea, picks up warmth and moisture, and builds a low deck of cloud: the dye the street is drawn in.

A steady bearing. The north-west wind holds for days in January and February.

Make it in Wind Tunnel

  1. Open the link below, or press Jeju under Island: the wind starts from 320°, north-west.
  2. Press Cloud under Look and Satellite under Colour: white cloud on a blue-grey sea, as the photo sees it.
  3. Turn on Satellite photo under Island to lay this photo over the corner of the frame, beside the flow.
  4. Choose 4K and 20 seconds under Save, and press MP4 once the street has formed.

Open Jeju in Wind Tunnel