Interactive demo

Weather windows: the slider, the series, the season

A fictional offshore operation (towing then connection of a floating wind turbine) analyzed on real ERA5 data off Belle-Île. Move the OPLIM slider: the readout and the chart recompute live on the displayed series.

The parameters below (default OPLIM, wind limit, TPOP, TC, alpha factor) are illustrative choices for this demonstration, not limits derived from a response analysis.

Operational limit OPLIM (Hs, in metres)

OPLIM in use: 1.50 m

Displayed excerpt

OPLIM in use

1.50 m Hs

Operability

75.4 %

TR = TPOP + TC

36 h

Windows ≥ TR

2 in excerpt

Persistence P50

138 h

The displayed Hs comes from an ERA5 wave grid cell located roughly 25 km from the target site — the wave product's resolution does not go finer than that. The effect of this offset on Hs is not measured here.

OPLIM

Operational limit

The environmental threshold beyond which the operation cannot continue. Here Hs = 1.50 m, an illustrative value for this demonstration, not derived from the vessel's response analysis.

An OPLIM for a real operation is sized on equipment response (roll, acceleration, slamming), not on a sea-state threshold picked upfront.

Climatology

The season decides, not the yearly average

The slider above recomputes a 30-day excerpt live. This calendar shows the full climatology, month by month, at fixed threshold steps — the argument the demo above cannot make on its own.

Climatology shown at the 1.50 m step (nearest to the slider), 31. The calendar does not follow the slider's exact value.

OPLIM threshold (m)	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec
0.75 m
1.00 m
1.25 m
1.50 m
1.75 m
2.00 m
2.25 m
2.50 m
2.75 m
3.00 m

Jan · 1.50 m

Operability

12.5 %

Persistence P50

20 h

Windows ≥ TR per month occurrence

1.0

Data honesty

What this demo is, and what it is not

This operation is fictional. It matches no real mission, no client relationship, no affiliation with any consortium or operator. The area is named "AO5 South Brittany, off Belle-Île"; Pennavel is cited only once, as the public reference for the chosen point.

OPLIM (1.50 m), the wind limit (12 m/s), TPOP (24 h), TC (12 h) and the alpha factor (0.75) are illustrative choices for this demonstration, not limits derived from a vessel response analysis.

The target site and the effective ERA5 grid cell do not coincide: the wave grid (~0.36° resolution) sits several kilometres from the site (distance shown next to the chart), the wind grid is closer. The effect of this positional offset on Hs is not measured here.

Wave data comes from ERA5 (Copernicus CDS reanalysis), not recalibrated against a buoy at this point either: the local bias is not measured. No order of magnitude is stated for either offset. See the scoreboard, which compares AI and physical models against real buoys.

Every figure on this page carries its dataset, its period and its point — never a bare order of magnitude.

Dataset: ERA5 reanalysis-single-levels-timeseries (Copernicus CDS) — 1994–2024 — Zone AO5 Bretagne Sud.

See the metocean AI scoreboard →