
A Japanese symbol of summer, cumulonimbus clouds have the power to cause heavy rain, thunderstorms, hailstorms, tornadoes, etc. Learn about them to protect yourself from sudden weather disasters!
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Are you ready if disaster strikes?
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Find out what you need to do by watching this program... "BOSAI: Be Prepared."
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The topic this time is "Cumulonimbus Clouds That Bring Disaster."
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Hi, I'm Bobby Judo, and today I'm on a rooftop in Shinjuku looking at the clouds.
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Known as a symbol of summer in Japan, cumulonimbus clouds can bring about serious weather disasters.
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They cause four hazardous phenomena: intensive heavy rain...
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lightning strikes...
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hailstorms...
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and tornadoes.
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How can we protect ourselves from these kinds of disasters?
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Weather forecaster Sasaki Kyoko will tell us how.
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Nice to meet you!
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Nice to meet you, too.
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Sasaki Kyoko provides municipalities and companies with weather information to help them take disaster prevention and other safety measures.
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Cumulonimbus clouds can cause disasters, so you should be prepared for the sudden changes in the weather they cause.
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I have a quiz question for you!
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Which of the following phrases in weather forecast is notable for suggesting cumulonimbus cloud development?
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1. The weather will turn bad from the west.
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2. Atmospheric conditions are unstable.
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"The weather will go downhill, starting from the west" means bad weather will spread toward eastern Japan, right?
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What does "atmospheric conditions are unstable" actually mean?
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Well, "unstable atmospheric conditions" refers to when a lot of water vapor flows up from near the ground to low in the sky or cold air flows into the sky above us.
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I'll take that one!
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Final answer?
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Yes, final answer. Final answer, No.2!
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The correct answer is No.2!
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When atmospheric conditions are unstable, cumulonimbus clouds tend to form and develop.
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Sudden downpours occur directly below a developing cumulonimbus cloud.
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One well-developed cloud contains the same amount of water as about 10,000 25-meter swimming pools.
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You don't want all of that coming down on you!
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Are there any signs that we can watch out for that indicate a cumulonimbus cloud is approaching?
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Yes, a certain type of cloud may be a sign.
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So here's the second question!
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Which of these two types of clouds could be an indication that a cumulonimbus cloud is approaching?
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No.1, Mammatus, and No.2, Cirrostratus.
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Which one do you think?
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Uh... No.2.
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Cirrostratus? Well, the correct answer is...
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Mammatus!
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I can't even hit a 50-50 chance!
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Mammatus clouds can be formed at the base of clouds spread in the direction cumulonimbus clouds are traveling.
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So, when the sky darkens and you see mammatus clouds, that's a sign of cumulonimbus clouds approaching.
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You should check the radar forecast screen for confirmation, with the question "Is a cumulonimbus cloud approaching?"
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Then you may be able to reduce the risk.
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So what should I watch out for when a cumulonimbus cloud approaches?
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One cumulonimbus cloud is not so big.
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You may get a downpour as the cloud passes by and then it's over.
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But there are times when a number of well-developed cumulonimbus clouds form in a row.
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In that case, what do you think will happen?
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Instead of having one cumulonimbus at a time, the clouds are connected in succession?
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So then, the rain will keep falling.
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Yes. It's called "Bands of heavy rain clouds."
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Cumulonimbus clouds form one after another on the windward side.
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They extend linearly to create a band of heavy rain clouds.
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Each one causes a torrential downpour at the same location.
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And that can lead to disasters, so they are very dangerous.
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In recent years, torrential rain caused by a band of heavy rain clouds has caused flooding disasters every year.
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For this reason, since June 2022, weather reports have started forecasting bands of heavy rain clouds as early as six to twelve hours in advance.
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So, once you hear that, you have a little bit of time to prepare.
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That's right.
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If you get this information, you may need to evacuate yourself.
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I think it's good to check if your evacuation bags are OK, which shelter you should go to if necessary, things like that, and then take action.
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You need to act fast, especially at night.
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However, the prediction accuracy of bands of heavy rain clouds is still not perfect.
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Just because the information is announced doesn't necessarily mean they will form, and, conversely, they can form even if no alert is announced.
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Also, remember that heavy rain doesn't necessarily happen only when there is a band of heavy rain clouds.
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The best way to be prepared is to listen carefully to all the weather information issued, especially advisories and warnings.
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The second of the dangerous weather phenomena brought about by cumulonimbus clouds is lightning strikes.
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Cumulonimbus clouds are thunderclouds, so there are lightning strikes.
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Now, here's another question.
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Lightning only strikes right below a cumulonimbus cloud.
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True or false?
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I think it would be seen lightning spreading in many directions at once, so I'll say "False."
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Correct! Please look at this.
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- Oh, wow! Yeah...
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That... that's crazy! It shoots out sideways and falls straight down.
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Lighting falls right below a cumulonimbus cloud, where rain is pouring as a matter of course.
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However, it doesn't necessarily mean you're safe because it's not raining where you are.
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Lightning strikes fall sideways like this.
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So, if you hear thunder, you should think there is the possibility of a lightning strike, and immediately take shelter inside a building.
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The energy of one bolt of lightning is about 1,800 kWh.
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That's the equivalent of six months' worth of electricity for an average household.
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Never shelter from the rain under a tree.
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That's very dangerous because of the possibility of side lightning strikes.
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Also, prepare flashlights and cell phone batteries in advance ready for power outages.
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The third of the dangerous weather phenomena is hailstorms.
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Next question! Which season is most prone to hailstorms?
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- Hail is ice, right?
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No.1, Winter, No.2, Summer.
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I mean, I only imagine hail falling when it's cold, so it's Winter, right?
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- The correct answer is...Summer!
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Hail is blocks of ice that grow in cumulonimbus clouds.
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I had no idea!
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Developed cumulonimbus clouds can produce large amounts of hail or even huge hailstorms.
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Before hail starts falling, take shelter in a sturdy building!
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Number four is tornadoes, especially when the cumulonimbus become very large.
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Have you heard of "supercell?"
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Yeah, like when stores have big discounts, like 70% or 80% off?
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Well, yes... But that's not the same thing!
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Oh, sorry, I meant a "super sale!"
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Wow, you're not enjoying being a part of that!
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Not a ”super sale” but a ”supercell” is a cumulonimbus cloud that is much larger than ordinary.
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When they get this huge, they can cause disaster-level waterspouts and tornadoes!
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Regular cumulonimbus clouds can also produce tornadoes, but supercells tend to bring very powerful ones, like this one.
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They are extremely dangerous.
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A supercell tornado observed in Ibaraki Prefecture in May 2012 was so powerful, it toppled entire houses to their foundations.
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If you see funnel-shaped clouds like this or flying debris soaring in a tubular shape under a cumulonimbus cloud, a tornado outbreak is possible.
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Immediately evacuate to a sturdy building or go underground.
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Check out weather information in English on sites such as Nowcasts of the Japan Meteorological Agency.
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Disaster prevention measures really can take many forms, but I think just being aware of the weather information counts for a lot.
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Yes. And I think it's fun to look up at the sky and understand what you see.
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I hope that an extension of that feeling of enjoyment will be your ability to ensure safety and secure evacuation.