The large meander ended in April 2025 after seven years and nine months. Ninety-seven monthly current fields and observations from the coast place that change in context.
South of Japan, the Kuroshio bends away from the coast into a broad offshore loop. The large-meander episode that began in August 2017 ended in April 2025, after seven years and nine months—the longest in the Japan Meteorological Agency’s record since 1965. JMA announced that conclusion on August 29, 2025. JMA announcement
An ocean change and the confirmation of that change can be separated by months. That interval is part of the work of following a moving current. This project looks across 97 monthly fields, from August 2017 to August 2025, to place the long detour and the water that followed it in the same view.
Monthly mean surface currents in March (left) and May (right) 2025. The same extent, 127–146°E and 26–38°N, and speed scale are used. JMA dates the end of the large meander to April. Generated using E.U. Copernicus Marine Service Information; 10.48670/moi-00021. Natural Earth. Visualization: SORAH.
A current along the southern coast
The Kuroshio travels north through the East China Sea and enters the Pacific through the Tokara Strait between Kyushu and Amami Oshima. It follows Japan’s southern coast before turning east off the Boso Peninsula. Its path can remain relatively close to shore or swing far offshore south of Honshu. JMA: the KuroshioJMA identifies the large-meander state through two conditions: sustained separation from Cape Shionomisaki, and a path south of 32°N off the Tokai region. The tip of the Kii Peninsula and the sea to its east provide the geographic anchors for understanding the bend. JMA announcement
Rocky shoreline at Cape Shionomisaki, Kushimoto, Wakayama, December 23, 2022. Kzaral · Source · CC BY 2.0 Proportional resize and JPEG compression only.
A long episode with a changing shape
The path continued to evolve during the episode. In October 2020, a cold eddy separated from the current and the loop temporarily contracted; the large offshore bend returned the following month. February 2025 brought another temporary contraction. JMA: long-term path variationsLate April 2025 marked a more lasting change. After another eddy separation, the contracted path persisted. JMA reported signs of an ending on May 9, then continued monitoring with the Japan Coast Guard before confirming April as the endpoint in August. The persistence of the new configuration was central to that decision. JMA announcement, JMA annual assessment
The current kept flowing eastward. Outside the large-meander state, its route can pass north of Hachijojima on a nearshore path or south of the island on an offshore path. Its relationship with the coast continues to change. JMA path classifications
Reading the offshore ocean from a harbor
One clue comes from the difference in sea level between Kushimoto and Uragami in Wakayama Prefecture. When the Kuroshio approaches Cape Shionomisaki, Kushimoto’s sea level is more strongly affected and the difference tends to increase. When the current moves offshore, the difference tends to become smaller and steadier. Shore-based observations help reveal a much larger offshore pattern. JMA: tide-level differences
The Kushimoto tide-gauge station in Wakayama, Japan. Photograph date unavailable. Source: Wakayama Local Meteorological Office, JMA. Image content unchanged. Source · Reuse terms
Tide measurements at Kushimoto began in 1895. The station’s history records its destruction by the 1946 Nankai earthquake tsunami and the resumption of observations in 1950. Such long-running measurements join subsurface temperature records and satellite sea-surface temperature imagery in the broader assessment of the current. Kushimoto station history, JMA assessment
A route read by ships and fisheries
The current’s position helps determine economical shipping routes and the location of fishing grounds. During a large meander, cold water can rise between the loop and southern Honshu, creating a cold-water mass that also influences fishing grounds. Warm-water intrusions can sometimes raise coastal sea levels from Tokai to Kanto. JMA: effects of the large meanderLook from the current back toward the shore and the curve takes on another meaning. For a ship leaving port, it is part of the conditions for planning a passage. For people fishing nearby, it is one of the clues used to read the sea. Connecting the offshore pattern to local outcomes requires continued observations of currents, temperature, sea level and fishing grounds.
The water continues
The visualization uses monthly surface currents from the Copernicus Marine reanalysis, which combines an ocean model with observations. Satellite and in-water measurements are brought into a shared grid, allowing a wider ocean to be examined through time. GLORYS12 product descriptionThe 2025 endpoint marked the close of one long-lived path south of Japan. With the coastline held still, the maps reveal both a shape that persisted for seven years and nine months and a sea that kept moving afterward. The next view from a familiar shore may carry a sense of that larger moving geography.
Data and representation
The project covers August 2017–August 2025, a total of 97 monthly fields. JMA’s large-meander interval runs from August 2017 to April 2025, seven years and nine months; the dataset includes four subsequent months. JMA supplies the event classification and dates.The adopted dataset remains canonical revision 6: GLORYS12V1, product GLOBAL_MULTIYEAR_PHY_001_030, monthly eastward and northward currents at 0.494 m depth, spanning 127–146°E and 16–48°N. Every second point of the approximately 1/12° source grid is sampled for rendering, giving approximately 1/6° spacing. Stored components are quantized in 0.04 m/s increments, with a recorded maximum component error of 0.019995 m/s. Missing values remain masked.
Particle direction follows the velocity vectors and color indicates speed on a fixed 0–1.5 m/s scale, saturated at the upper end. Interpolation between monthly vector fields and time compression make the distribution readable; particles are computational drawing points. The article’s March/May comparison reuses earlier graphics from the same product, covering 127–146°E and 26–38°N. Coastlines use Natural Earth 1:10m. The mapped quantities are reanalyzed surface-current direction and speed.
Generated using E.U. Copernicus Marine Service Information; 10.48670/moi-00021. Natural Earth. Visualization: SORAH. The Kushimoto photograph is supplied by JMA’s Wakayama Local Meteorological Office; its capture date is unavailable and its image content is unchanged. Source links and reuse conditions accompany the assets.
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SORAH Editorial
October 15, 2026
