Building a berth wind-window proxy from Merak station wind

When people ask for berth or ferry "operability," they usually want a simple question answered: how often is the wind below a working threshold, and how does that change by season? A full metocean design basis needs more. A short sample note can still show the method with real station wind.

I built one for Merak / Sunda Strait from BMKG automatic weather station (AWS) hourly mean wind for 2020--2025. The point was not to sell a productized report. It was to show what a desk-study page should contain: source, period, thresholds stated as SAMPLE, a monthly window view, and an honest limits list.

The wind source is BMKG Merak AWS. I use hourly means over a fixed window, not a handful of storm days. That gives a climate-style exceedance curve and a month-by-month proxy of hours below / above chosen speeds. Direction matters for a berth, so a wind rose sits next to the speed story. None of that replaces a site-specific criteria set agreed with the operator.

For thresholds I used 15 kt (amber) and 21 kt (red) only as a proxy. Those numbers follow BMKG operational ferry thresholds I work with at the desk. They are not a client design basis. In the sample they mark "hours that look busy" versus "hours that look available" under that proxy alone. If your jetty stops work at a different speed, or cares about gusts instead of hourly means, the percentages move.

The sample PDF is here: SAMPLE Merak / Sunda Strait metocean berth operability note. It walks through wind climate, a short return-level sketch on annual maxima, the monthly wind-window proxy, and a shorter current climate from BMKG HF radar near Merak (2023--2025). Currents sit beside the wind story because berthing and towage in a narrow strait are not wind-only decisions.

For the current science, I point to the ASCMO paper on HF radar surface current forecasting in the Sunda Strait: doi:10.5194/ascmo-12-221-2026. That work is about forecast method comparison in a narrow tropical strait. The sample note is climate and operability framing. They share the same place and the same operational motivation, not the same deliverable.

What the sample does not claim matters as much as what it shows. It is wind-only as the main operability proxy. The current record is shorter than the wind record. Multi-year observational waves for that period are not in the note. SAMPLE thresholds are illustrative. A real scope would lock criteria with the client, extend waves where needed, and treat extremes with the record length they deserve.

That is the shape I want an operability note to have: named BMKG sources, clear years, a proxy that is labeled as a proxy, links to the deeper current work where it helps, and a limits section that does not hide behind nice plots.