Digital Typhoon: Summary of Typhoons in 2006

The number of typhoons in 2006 was 23, which is the same number as 2005, and is still smaller than the average number of about 27. The number of typhoons that made landfall at Japan is also as small as two, but this year had other events not apparent in those numbers, such as extensive disasters caused by extra-tropical cyclones that absorbed typhoons. The following is the typhoon that gave the largest direct impact on Japan. Typhoon 200613 (SHANSHAN) This typhoon first passed across Sakishima Islands recording very strong winds, and then made landfall at Kyushu with keeping most of its intensity. This typhoon was strong as a typhoon that makes landfall at northern Kyushu, so the damage was extensive especially at Nagasaki, Saga, and Fukuoka on buildings and agriculture. In addition, a few tornadoes were formed in Miyazaki Prefecture, which was far from the center of the typhoon, and the accident of derailment at Nobeoka City was picked up as one of the symbol of the disaster.

The following typhoons did not give direct impact on Japan, but can be said as characteristic typhoons of this year. Typhoon 200612 (IOKE) A hurricane formed near Hawaiian Islands moved all the way to the west passing the International Date Line, and kept a very strong intensity for several days. All the people in Wake Island and Minamitorishima Island were evacuated to prepare for the direct hit of the typhoon, but those low-lying islands were severely damaged due to the storm surge. Another interesting hypothesis is that the formation of such a strong hurricane (typhoon) near Hawaiian Islands may be related to El Nino events, and in fact it was observed that El Nino event has already started since this autumn (in Japanese), according to Japan Meteorological Agency. Typhoon 200616 (BEBINCA) + Typhoon 200617 (RUMBIA) One of the characteristic events of this year is the frequent formation of twin or triplet typhoons, and the most problematic event was the twin typhoons of Typhoon 200616 (BEBINCA) and Typhoon 200617 (RUMBIA). Those typhoons are far from strong ones, but Typhoon 200216 was difficult to predict due to its irregular shape and movement. The event turned to more serious when an extra-tropical cyclone showed rapid intensification in east of Honshu after it absorbed the warm air of those two typhoons. Strong winds caused by the cyclone lead to a series of accidents occurred in the sea and in the mountains, resulted in the total of about 40 people who were killed or missing. This disaster reminds us the issue of how we can raise attention to extra-tropical cyclones of rapid intensification, and some media seems to have decided to use the word "bomb cyclone" to raise attention.

Typhoons in Other Regions

In East and South East Asia Region, the damage of typhoons were concentrated in China in the first half, and Philippines in the last half. In the first place, a gigantic rainy clouds of Typhoon 200604 (BILIS) caused heavy rainfall in the inland China which killed about 1000 people. Then Typhoon 200608 (SAOMAI), which was acknowledged as the strongest typhoon that made landfall at the mainland China in these 50 years, gave extensive damage on Zhejiang Province, killing about 450 people in the coastal areas of China. These typhoons also cast light on the cover-up of the scale of disasters by the local government of China, and the credibility of official announcements on those disasters was questioned. In the last half of this year, there were a series of typhoons that made rapid intensification in east of Philippines, and especially Typhoon 200621 (DURIAN) caused the largest disaster due to mudslides in the slope of Mayon Volcano. This disaster can be said as an unfortunate disaster because the cause of the disaster was the ash and rock produced by the eruption of Mayon Volcano started just a few months before the attack of the typhoon. The record-breaking amount of rainfall turned those ash and rocks to mudslides that buried villages in the slope. But another aspect of this disaster is the delayed implementation of disaster reduction in Philippines. The number of people who were killed or missing reached about 1500, and still about 110,000 people were in evacuation, but the recovery process remained to be slow.

Hurricanes

On the other hand, the activity of hurricanes in the north Atlantic was relatively calm, in comparison to very active seasons in 2004 and 2005. The 2005 season was especially the most active season in the recorded history, characterized by the series of formation of very strong hurricanes such as Hurricane Katrina and the first naming of Greek Alphabet on tropical storms. In this season, however, hurricanes that made landfall at the mainland USA is Ernesto and other small ones, and the hurricane name was used just to Issac. The named storms was 27 in the last year, while only 9 in this year.

Relationship between Global Warming and Typhoons (Hurricanes)

This change of activity may raise new interest in a dispute on the relationship between global warming and tropical cyclones, which was discussed actively since last year. One document was released in the end of November from the scientist side to give information to this dispute from the scientific point of view. A document named Statement on Tropical Cyclones and Climate Change describes the consensus reached at a workshop where many researchers on tropical cyclones worldwide gathered at one place. This document therefore can be said as the most reliable source of information, the latest and scientifically sound consensus on this issue. The following is an excerpt of "Consensus Statements" from the summary.

Consensus Statements by International Workshop on Tropical Cyclone-VI (IWTC-VI) Participants

Though there is evidence both for and against the existence of a detectable anthropogenic signal in the tropical cyclone climate record to date, no firm conclusion can be made on this point.
No individual tropical cyclone can be directly attributed to climate change.
The recent increase in societal impact from tropical cyclones has largely been caused by rising concentrations of population and infrastructure in coastal regions.
Tropical cyclone wind-speed monitoring has changed dramatically over the last few decades, leading to difficulties in determining accurate trends.
There is an observed multi-decadal variability of tropical cyclones in some regions whose causes, whether natural, anthropogenic or a combination, are currently being debated. This variability makes detecting any long-term trends in tropical cyclone activity difficult.
It is likely that some increase in tropical cyclone peak wind-speed and rainfall will occur if the climate continues to warm. Model studies and theory project a 3-5% increase in wind-speed per degree Celsius increase of tropical sea surface temperatures.
There is an inconsistency between the small changes in wind-speed projected by theory and modeling versus large changes reported by some observational studies.
Although recent climate model simulations project a decrease or no change in global tropical cyclone numbers in a warmer climate, there is low confidence in this projection. In addition, it is unknown how tropical cyclone tracks or areas of impact will change in the future.
Large regional variations exist in methods used to monitor tropical cyclones. Also, most regions have no measurements by instrumented aircraft. These significant limitations will continue to make detection of trends difficult.
If the projected rise in sea level due to global warming occurs, then the vulnerability to tropical cyclone storm surge flooding would increase.

Some facts and hypotheses have been proposed so far on the relationship between climate change (global warming) and tropical cyclones, but there is a problem of uncertainty in existing records, as commented in 2005 Summary, so there is still not enough evidence to conclude which one is correct from the scientific standpoint. It is not strange if tropical cyclones get stronger when the earth gets warmer, but more detail is still not clear at this moment. Another important point is that the recent increase of disasters by tropical cyclones is caused more by societal changes than by the changes of tropical cyclones themselves. In the United States, the important factor is that more people are beginning to live on coastal areas, and also in Japan, the danger is increased when houses and factories are built in areas that were previously considered dangerous (e.g. vulnerable to floods). Another big issue, that elderly people are killed more than other people, is definitely the change of society, not the change of nature. It is therefore important to study the change of society with the effect of global warming when we study the relationship between tropical cyclones and disasters. There are still many things yet to be understood about tropical cyclones, but there is also a growing motivation to study and analyze tropical cyclones. One direction is a study through organizing high-quality large databases of past records, and another direction is a study through high-resolution simulations using powerful computers. More knowledge on tropical cyclones will be acquired by the advancement and integration of those two approaches.

Digital Typhoon: Summary of Typhoons in 2006

Summary of Information on Typhoons in 2006

Typhoons in Other Regions

Hurricanes

Relationship between Global Warming and Typhoons (Hurricanes)

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