Jeffreys Bay (Supertubes) Alert Guide

Eastern Cape, South Africa · part of the Jeffreys Bay (Supertubes) spot guide

J-Bay is forecast-only and unusually wind-gated, so its alert uniquely includes a wind condition: it fires only when a long-period SW swell coincides with a light west-to-northwest offshore — the alignment that lines Supertubes up end to end. The height below is an open-ocean model reading, not the breaking face.

The forecaster's checklist

1. 1.Watch for a deep Southern Ocean low or a Cape cold front tracking southwest of the Cape, aiming a long SW fetch up the coast so swell wraps Cape St. Francis into the bay.
2. 2.Give it about three to five days; Southern Ocean groundswell shows up on the models several days out, with cleanest confidence 48 to 72 hours ahead.
3. 3.Run on models and charts — there is no near buoy, so J-Bay is called from GFS-Wave, ECMWF, Surfline, Swellnet and the South African Weather Service, verified against webcams, not instruments.
4. 4.Demand the three-way alignment for a "Supers lining up end to end" day: long period (13 seconds and up), a SW direction near 215–235°, and a light west-to-northwest offshore over the morning.
5. 5.Play the wind clock: the classic call is a dawn session before the daytime southeast sea-breeze fills in, while the overnight and early offshore holds.

Local winds & tide

Best wind: W–NW offshore (unusually decisive here; the day-maker) — from 285° to 320° (WNW–NW).

J-Bay works across most of the tide — reports don’t converge on a mandatory stage, and swell and wind dominate the call far more than tide.

Dial it in