Tide High Low Interval Brazil

Coastal Tide Cycles & Low/High Water Timing

Brazilian coastal waters run on a semi-diurnal tidal regime, which means 2 high + 2 low tides per 24h 50min. From one high water to the next you get roughly 12h 25min, and that lag traces back to the Moon's 24h50min transit. How big the range gets depends heavily on where you are along the 7,491 km of shoreline. It runs 1–2 m on the SE/S coasts (Santos, Rio, Florianópolis) and climbs to 3–4 m on the NE (Recife, Salvador). On the Equatorial coast (AM, AP, PA) it reaches 4–7 m. Outside the Bay of Fundy, the planet's biggest tides happen right around Marajó Island.

When the Moon is new or full, spring tides (sizígia) run 20–40% bigger than the neap tides (quadratura) you see at the quarter phases. Every year the DHN (Diretoria de Hidrografia e Navegação da Marinha) puts out official tide tables covering 100+ Brazilian ports, and CPRH and the harbour authorities pass the same numbers along to local pilots and recreational boaters.

Applications

Harbour pilots lean on this when they schedule deep-draught arrivals. Sport fishermen use it to catch the outgoing tide at river mouths, and surfers watch it to know when a sandbar will reform. It also matters to intertidal researchers, to coastal engineers sizing seawalls, and to beach lifeguards who need to see dangerous rip currents coming at low water.

FAQ

Why does each tide arrive ~50 min later daily? The Moon orbits Earth the same way Earth spins, so a given meridian has to turn an extra 50 min to “catch up” with where the Moon sits that day.

Where are Brazil's biggest tides? Around Marajó Island (PA) and the Amazon delta, where spring tides hit 7 m and drive the pororoca tidal bore.

Are DHN tables free? They are. Every year the Marinha releases the Tábuas de Marés as a free PDF, plus an online lookup at marinha.mil.br/dhn.