Today, I’m excited to share that Harper is live, a side project that brings together two things I care deeply about: technology and surfing.

I built Harper because surf forecasts are fun to look at, but hard to understand. Most forecast sites are packed with charts, numbers, and models, yet still leave many surfers unsure about what those conditions actually mean in the water.

Harper takes a different approach. It brings the right data into one clean place, makes it consistent, and layers in real local surf knowledge, like which swell angles favor lefts over rights, the minimum swell size needed for certain waves to appear, and when a spot stops working and starts closing out. There are no webcams or live cameras. The focus is on understanding conditions and making better calls, not watching waves.

The result is clear, readable 10-day forecasts, daily AI-generated reports, and weekly digests that highlight what truly matters for your spots.

The goal is simple: help surfers better understand the forecast, save time, and miss fewer good days. Harper is free, currently in beta, and invite-only. If you’re curious, sign up and I’ll send you an invite. Feedback is always welcome and I'm happy to answer everyone.

I already added some of my favorite surfing spots in Europe and Brazil, especially in my hometown, but you can explore some of available spots:

• Supertubos
• Pico das Almas
• Praia do Futuro 🏠

Harper also offers an API. For non-profit organizations working on ocean protection or environmental conservation, the API is completely free, and I’m happy to personally help with the integration.

Plans for the future

WhenWhen I started building Harper, I expected to be a heavy user myself. I was mostly solving a problem I personally had. That said, there are a few things on the roadmap that are worth sharing:

• There are tons of secret spots around the world. What if surfers could add their own spots to Harper? Better yet, keep them private and share them only with friends. This would turn local knowledge into real data, giving your crew a better sense of when to score. This feature is already under active development.
• Extend the forecast horizon using additional ML-based techniques. Today, Harper supports a 10-day forecast, but the plan is to expand this to 20 days in Q1 2026.

You can follow our updates in our Changelog.

Some technologies I used

• Ruby on Rails, NextJS, Python
• LangChain, LLMs (from OpenAI and Gemini)
• Prefect workflows

I will write a new post specifically about it soon!