Summary of Information on Typhoons in 2004
We updated the AMeDAS Statistics for 2004 data, so this is a good chance to reanalyze typhoons that approached Japan during 2004 by searching Typhoon Disaster Information Database. Here we compare heavy rains and strong winds of 2004 typhoons with past typhoons using Typhoon Impact Index. Precipitation Impact Index Typhoons in 2004 with an especially large precipitation impact index is Typhoon 200423, and it ranks third in history following Typhoon 197617 and Typhoon 199019. The most interesting point is the large precipitation impact index in spite of the relatively moderate total precipitation amount of 500mm observed at top-ranking stations during Typhoon 200423. The reason is that rainfall became large evenly across Japan, so the sum of precipitation amount of many points resulted in a large number; hence it is a symbolic number that represents the extent of disasters across Japan. Typhoon 200421 appears next, but the order is just as low as 22th. Of course it is because the heavy rain of this typhoon was localized and it does not mean that the amount of rain was small. But we can conclude that the year 2004 was not the year of many large rainy typhoons. Wind Impact Index In contrast to the precipitation impact index, the wind impact index has three typhoons within top 10 typhoons, such as Typhoon 200418 (1st), Typhoon 200416 (3rd), and Typhoon 200423 (8th). Comparing the impact of heavy rains and strong winds, we can say that "the year 2004 was the year of windy typhoons." The largest damage in 2004 was recorded by Typhoon 200418, and the primary reason of the largest damage lies in the strong winds of this typhoon which was one of the strongest in these 30 years. The disasters of storm surge, which is another frequent type of disasters in 2004, was also caused by the successive approach of such powerful windy typhoons. In short, in a historical context, the year 2004 can be characterized as the year of especially strong winds. Composite Impact Index As many as three typhoons ranked within top 5 typhoons in history, namely Typhoon 200423 (2nd), Typhoon 200418 (4th), Typhoon 200416 (5th). This ranking of the composite impact index illustrates that the year 2004 was the year of unprecedentedly frequent strike of powerful typhoons against Japan. If we classify the higher ranking typhoons, Typhoon 200423 is an almighty-type typhoon with large indices of both heavy rains and strong winds, while Typhoon 200418 and Typhoon 200416 are windy-type typhoons with a larger wind impact index.
According to the General Insurance Association of Japan, the total amount of claim due to wind and flood disasters in 2004 reached 727.4 billion yen, which is the largest in history over the previous record of 621.7 billion yen in 1991. Among many natural disasters, the claim on Typhoon 200418 is the largest claim of 382.3 billion yen, and Typhoon 200423, Typhoon 200416 follows. These numbers show that the year 2004 is the year of natural diasters, one after another.
The number of typhoons in the year 2004 was 29, a little larger than the average number of 27. For Japanese people, however, this year may be remembered as "the year of disasters" because of the unprecedented number of typhoon strikes against Japan and subsequent disasters. The positive result of this phenomenon is that people can now understand the fact that every typhoon has its own unique character because they could compare many typhoons while keeping their clear memory about what happened, and that the analysis of typhoon characters in advance may be effective for disaster mitigation and prevention. The following statistics partially came from Japan Meteorological Agency.
Philippines The number of casualties exceeded 1500 due to the subsequent attacks of three typhoons, Typhoon 200425 (MUIFA), Typhoon 200426 (MERBOK), Typhoon 200427 (NANMADOL) and another tropical storm Winnie (Philippine name). China Zhejian Province suffered from the largest damage in these several years by Typhoon 200413 (RANANIM). Taiwan Large-scale damage includes that in southern and mountainous areas by Typhoon 200407 (MINDULLE), and that in northern and mountainous areas by Typhoon 200417 (AERE). Countries and regions in the Pacific Large-scale damage includes that in Yap Island by Typhoon 200401 (SUDAL), and that in Saipan Rota Island by TYphoon 200416 (CHABA).
This year people often referred to the record-breaking number of landfall typhoons on Japan in the context of abnormal weather. It seems that there are growing interests about a possible connection between unusual weather and so-called "global warming." To be honest, that relationship may exist, but we haven't seen the evidence. This year's phenomena should be thoroughly examined from the scientific point of view, but it is also true that atmospheric conditions in a global scale happened to fall into a state in which Japan had many typhoons in a local scale. Hence it may be a leap of logic to say that "the climate of the earth is abnormal because Japan had many typhoon landfalls this year." More meaningful question is how the long-term trend of the characteristics and tracks of typhoons changes in relation to climate change such as global warming. A noteworthy fact is that we had many typhoons that reached the 30N line around Japan (120E-150E) keeping the "strong typhoon" category. Does this suggest that northern areas such as Japan are likely to have more strong typhoons in the future? If this is true, we need to rethink current measures against typhoons. It is generally agreed that the trend is still not observed (or to put it more correctly, we still cannot say that the trend is observed). We however have to pay attention to the activity of typhoons after 2005 to check whether the trend can be observed or not. In the world, the repeated strikes of hurricanes in 2004 also raised people's attention to severe weather. Hurricane Charley, Frances, Ivan, Jeanne have left severe damage over the United States and Caribbean countries, and Hurricane Jeanne was the most catastrophic that killed more than 2000 people in Haiti. It has been pointed out that we may have more severe weather in the future if the warming of the earth continues. Year 2004 was the year that this warning was taken seriously with our real experience.
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