Typhoon "Lan" made landfall as forecast this Tuesday morning (local time) south of Shingu, Japan. In addition to the strong winds, it's the intense rainfall that's the problem, especially as the storm system is moving relatively slowly.
Typhoon "Lan" reaches Japan
On Tuesday morning (local time), typhoon "Lan" hit Shingu in Wakayama prefecture (Honshu). Previously, it had weakened somewhat, with winds of just over 100 km/h near the coast. But the wind shouldn't be the biggest problem, as "Lan" is moving rather slowly, bringing plenty of rain locally. Some stations have already announced new precipitation records, notably in Iwate, where 576 mm of rain fell in 24 hours. There are also reports of a tornado in the Shizuoka region.
Fig. 1; Source: Japan Meteorological Agency
Extreme precipitation
In the northern hemisphere, a tropical storm is generally stronger on its right-hand side, as seen in the direction of motion, due to its cyclonic (counter-clockwise) rotation. This is also where the greatest quantities of precipitation are normally concentrated. The same is true of "Lan", as the following representation of 24-hour rainfall sums shows. The prefectures of Wakayama, Nara and Mie are particularly hard hit. In Miyagawa, more than 600 mm were accumulated in the space of a day. This corresponds to a 60 cm column of water falling from the sky. The confluence of the waters quickly causes water levels to rise by several metres. To put things in perspective, the driest place in Switzerland(Ackersand in Valais) receives an average of just 543 mm of precipitation per year!
Fig. 2; Source: Japan Meteorological Agency
Evolution and classification
While continuing to weaken, "Lan" will continue its trajectory over the Sea of Japan. The north-western coast of Honshu, in particular, will continue to experience heavy rainfall in the hours ahead, but accumulations are likely to be slightly lower than on the southern coast.
In principle, tropical storms can occur all year round in the Pacific, but the peak season is between May and October. On average, around 25 named storm systems form in the Pacific Northwest, of which around 17 reach typhoon status. "Lan" is the eighth to appear on this year's list of names. Other typhoons that have already made headlines this year are "Mawar", "Doksuri" and "Khanun". The 2023 typhoon season has so far been slightly above average.
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