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Around this time of year, you often hear the terms “torrential rain” and “guerrilla downpour” (localized heavy rain).
But did you know there’s a big difference between the two—in how they form and the kinds of damage they cause?

These two types of heavy rain can also have a major impact on train operations. So here’s a clear breakdown to help you understand the difference! 🚃🌧️

◆ What is Torrential Rain? 🌧️🌩️

Torrential rain refers to heavy rainfall that continues for several hours over a relatively narrow area.
Sometimes, rainfall can exceed 100 mm or even reach several hundred millimeters, causing significant disasters.

🔹 Key Points

• Caused by cumulonimbus clouds 🌩️ forming repeatedly over the same area

• Often associated with stationary fronts during the rainy season, or typhoons 🌀

• Can lead to widespread flooding 🌊 and deep-seated landslides ⛰️ (deep-seated collapse)

For example, during Japan’s rainy season, if a weather front stalls over the same region, prolonged rain can occur in one area, causing large-scale flooding across rivers and communities.

◆ What is a Localized Downpour? 🌦️⚠️

Also known as a “guerrilla downpour”, this type of rain is intense and highly localized—falling in just one spot for a short time.
In just a few dozen minutes, several dozen millimeters of rain can suddenly pour down.

🔹 Key Points

• Triggered by rapidly developing cumulonimbus clouds 🌩️

• Occurs when hot, humid southern winds 🌡️ mix with cold air aloft 🌬️, creating an unstable atmosphere ⚡

• Can cause flash floods in small to mid-sized rivers, urban flooding, and shallow landslides ⛰️

Sudden downpours can lead to flooded roads, submerged subways, and inundated train stations…
It’s a major cause of urban disasters, so be alert for sudden weather changes!

◆ Impacts on Trains 🚉

Both torrential and localized rain can seriously affect train operations 🚨.
Flooded tracks, landslides, and damage to bridge supports can lead to delays and even suspended service.

Sometimes, it may be sunny at your station, but trains are delayed because of heavy rain in another area—
that’s the power of localized storms. ☀️➡️🌧️

◆ In Conclusion 🌈

Torrential rain tends to last longer and affect wide areas.
Localized downpours are short, sudden, and intense—but hit very specific spots.

Knowing the difference can help you make better decisions when heading out, commuting, or checking train operation info 🧳.
If the sky starts to look suspicious, check the real-time weather on Ima-Tetsu 🔍 to see what’s going on above you!