surfline publishes the spot forecast for the pontão de leblon here, and for the canto do leblon on this page - also by surfline, this clickable map shows the height of the waves on a number of beaches in both rio de janeiro and niterói- and this chart shows the forecast for all waves in rio's southern region.

this page, published and updated daily by the brazilian navy, shows the overall daily forecast for rio de janeiro state's coast, including waves (ondas), visibility (visibilidade), and  temperature ranges (temperatura) - on this link, the institudo estadual do ambiente - inea provides the suitability of several beaches, including leblon beach.