Fog at Port of Santos: why the shutdown is total

In the early hours of August 22, 2024, dense fog covered the Santos estuary. At 4:50 AM, the Port Authority suspended navigation at the largest port in Latin America: visibility had dropped below 500 meters, the safety limit for maneuvers in the channel. The port only resumed operations at 12:10 PM, after more than seven hours closed. During the same period, ferries between Santos and Guarujá stopped, and eight crossings along the São Paulo coast were interrupted.

It was not an isolated episode. Between early July and the first half of August of that year, 90% of the port's shutdowns had fog or mist as the cause.

Anyone who plans line-up knows the scene: vessel ready to maneuver, berth free, cargo positioned at the dock. And nothing moves.

Why fog shuts down the entire port

We analyzed the official shutdown records for the Port of Santos between 2021 and 2023. The port was completely closed for approximately 269 hours during this period. Wind and gusts accounted for 58% of these hours, low visibility for 28%, and waves for 14%. Fog was the second largest cause of total port closure.

The most revealing data point, however, lies in the type of restriction. Waves usually produce partial restrictions: some maneuvers continue, others wait. Fog is one of the few hazards that closes the Port of Santos entirely. In the three years analyzed, low visibility appears only as a cause of total closure.

The reason is operational. Navigation in the channel depends on visual range. Below the safety limit, the maritime authority suspends maneuvers for all vessels, from container ships to bulk carriers. There is no such thing as a half-open port.

Santos' geography favors this phenomenon. The proximity of the Serra do Mar mountain range induces orographic fog, the coastal condition produces advection fog, and the passage of cold fronts in autumn and winter adds frontal fog. The result shows up in the historical record: fog-related closures concentrate in the early mornings of the cold months and last, on average, about 4 hours per event.

The risk is not the fog. It is the waiting it spreads

It is worth separating two things that daily operations tend to blend together. Fog is the climate hazard. The risk is what it produces in operations: closed channel, suspended maneuvers, a queue of vessels, and an entire line-up to replan.

And here lies the economic difference of total closure. When a berth closes due to waves, the impact is localized. When the channel closes due to fog, there is no priority cargo: all vessels wait, so all cargo waits. The exporter watches the vessel's window slip away. The importer sees the input delayed at the factory gate. The shipping agency renegotiates scheduling with the shipping line. The terminal reschedules shifts and equipment. Road and rail carriers hold or redirect flow that was already en route to the dock. Every hour the channel stays closed multiplies into hours of waiting distributed across the entire chain, with costs in demurrage, staying, and replanning.

Four hours of average closure may seem minor. But timing amplifies the effect: fog closes the port precisely in the early morning and start of the day, when the queue of scheduled maneuvers has already formed. The morning delay pushes back the entire day.

Fog is not a surprise. It is seasonality

An unsensationalized reading of the historical record brings good news: fog in Santos follows a pattern. It has a preferred season (autumn and winter), a preferred time (early morning and morning), and known physical mechanisms. A phenomenon with a pattern is a manageable phenomenon.

Three practices separate operations that suffer from those that anticipate:

1. Treat fog as a planning variable, not an unforeseen event. If your cargo depends on Santos, the cold months concentrate visibility-related closures. Critical windows scheduled for early morning during this season deserve an alternative plan from the design stage.

2. Monitor visibility forecasts at the level of your asset. Public forecasts describe the city. The decision happens in the channel, at the bar, and at the berth. Predicting closure requires hyperlocal visibility forecasting combined with the closure history of that specific port.

3. Communicate with the chain before closure, not after. An alert issued hours in advance changes the conversation with the shipping line, agency, exporter, and carrier: reordering the line-up, holding trucks at the regulating yard, or bringing forward a maneuver costs far less before the fog than during it.

From forecast to decision

It was to shorten the path between these three steps and the daily routine of operators that we created the AI Climate Agent. It answers natural language questions such as "what is the chance of fog-related closure at my terminal tomorrow morning?" and anticipates weather hazard alerts for the exact point of your operation, from the port to the road segment. The same logic applies to those who ship, act as agents, or transport cargo: information that the channel will close is worth more when it arrives before the queue forms.

If your logistics operation has already paid the price of a foggy dawn, try the AI Climate Agent for free and see how many hours in advance that decision could have been made. [LINK_TRIAL_A_CONFIRMAR]

Try the Climate Agent on your operation, with a free 14-day trial and no credit card:

Sources

CNN Brasil (08/22/2024): closure of the Port of Santos from 4:50 AM to 12:10 PM due to fog, visibility below 500 m, suspension ordered by the Port Authority, interrupted crossings, and the data point of 90% of shutdowns due to fog/mist between July and the first half of August 2024. https://www.cnnbrasil.com.br/nacional/neblina-paralisa-operacoes-do-porto-de-santos-por-7-horas/

i4sea analysis based on official shutdown records for the Port of Santos (2021 to 2023): 269h07m of total closure over the three-year period; 58% wind/gusts, 28% low visibility, 14% waves; low visibility with no occurrence of partial closure; average duration of visibility events of 4h05m; concentration in early mornings/mornings of autumn and winter; formation mechanisms (orographic, advection, frontal).