Predicting the weather around Mt.Fuji by examining the clouds

Let’s go and see Mt.Fuji！But how will the weather be?

When the weather is clear, you can even see Mt.Fuji from Tokyo. If you have time, you might want to take a short trip closer Mt.Fuji to see it. It is easy to travel to the Mt.Fuji area from Tokyo. However, it’s much better to get there when the weather is perfect!

You might want to check the weather forecast before travelling. However, if you are already on the way to the Mt.Fuji area, why don’t you look at the clouds above Mt.Fuji instead? You can predict the weather to some extent by the types of clouds you see.

What are the most common types of clouds around Mt.Fuji?

Here we will introduce some types of cloud so you can predict the weather around Mt.Fuji.

Cap cloud (Kasagumo)

The Cap cloud a.k.a Kasagumo is a kind of lenticular or lens-shaped cloud covering the summit of Mt.Fuji. When warm air containing a lot of moisture comes strongly from windward and upward on the mountain slope, moisture starts to condense to form clouds when the air temperature drops under the dew point. However, the descending air current will travel along the mountain’s leeward side. At this point the clouds will start to warm up and evaporate again. That’s why you can only see a cap cloud covering the summit. According to the “weather lore” of the area, there is a saying about this “When Kasagumo appears, it will rain soon”. In fact, some meteorological statistics claim that when a cap cloud appears, there is a 70~75% probability that it will starts raining within 24 hours, no matter what the time of year. The following photograph was taken one day in autumn. Sure enough, it rained the next day.

Double cap clouds is also rarely appear. The saying goes “in that case, a storm is coming”.

Roll cloud (Tsurushigumo)

The roll cloud is quite similar to the cap cloud. First, warm moist air gets on the updraft. In cases where there are strong air flows along the top or side of the mountain, a kind of wind vortex called a “mountain wave” will sometimes form and cool on the leeward side. The weather lore of the area states, “when this cloud appears, be ready for bad weather”.

Other types of clouds

Other types of clouds, such as the “Banner cloud” which looks like fluttering flags extending from the middle to the top of the mountain, and the “band cloud” which resembles a belt going around the middle of the mountain, can be also observed at Mt.Fuji.

Summary

Many come to this area hoping to see not only Mt.Fuji but the lakes, forests and other landscape features surrounding it.  We must not forget that clouds are also an important factor to consider when discussing the beautiful scenery of Mt.Fuji. On this occasion we introduced just two types of clouds and how they can help you to predict the weather. We hope that one day you can see these clouds for yourself and see how they complete the many picturesque views of Mt.Fuji!