'Once-in-decades' Super Typhoon Neoguri makes an early impact on Japan

Tuesday, July 8, 2014, 5:46 PM - As Super Typhoon Neoguri sweeps past Okinawa and heads towards landfall in southern Japan today, news sources such as The Guardian, and JapanToday.com have quoted a Miyako fisherman who, in speaking to NHK television, said: "It's rare that we brace for a typhoon (as early as) July." So, what's behind Neoguri's early and powerful appearance?

Neoguri (Korean for 'raccoon') spun up over warm tropical Pacific Ocean waters east of the Philippines, starting on June 30. Within days it had advanced not only in strength - becoming a Tropical Depression and then a full-fledged Tropical Storm by July 4 - but it had also advanced to the west, tracking over even more warm ocean water as it veered northward, towards Japan. By end of the day on Friday, July 4, forecasters with the Joint Typhoon Warning Center (JTWC) had upgraded Neoguri to Typhoon status, and as it was still out over open water, it continued to intensify, becoming a Super Typhoon on July 6. It has weakened since then, after passing by the island of Okinawa and moving over the East China Sea, and it is expected to continue to weaken before it makes landfall on the island of Kyushu, and then tracks along the east coast of Japan, past Tokyo and off to the north by Sunday.

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With all tropical cyclones - tropical storms, hurricanes, typhoons, etc - their strength depends on two main factors: 1) how much warm ocean water they have access to as their energy source (specifically water above 27 C, which extends down to a depth of at least 50 metres or so), and 2) how strong the winds are at the top of the storm compared to those at the bottom of the storm (ie: the wind shear).

The basic 'engine' of a hurricane is fairly simple. Warm water evaporates from the ocean surface and is taken up by the air just above the water, increasing the humidity and warming that air as well. In turn, that warmed, moist air rises up, cooling as it does, and releasing energy as the water it picked up evaporates, forming clouds and rain. When the now-cooled and dry air reaches the top of the storm, it is cycled back downwards in the core of the storm and at its edges, where it warms up, gathers more moisture, is sucked back into the storm clouds and the process repeats. The warmer the water, the more energy that can be passed on into the storm, the faster the whole process goes, and the stronger the storm can grow. However, for this 'engine' to run most efficiently, the circulation of air inside the storm has to be as straight up-and-down is it can. If the orientation of the eye and clouds is tilted in any way, such as when the wind speeds get stronger as you go higher up in the storm (ie: strong wind shear), this slows and limits all the processes of releasing and gathering energy in the storm. It can't grow as powerful and if the shear is strong enough, it might tear apart the storm before it can develop.

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The fisherman from Miyako is right about Neoguri. While it's not unheard of to have a typhoon this early, as they can (and do) happen at any time of the year, it is a little unusual for Japan to see one make landfall in early July. According to the Japan Meteorological Agency, the country sees most of their typhoon landfalls in August, and they list ten tropical cyclones over the past 60 years or so as making landfall in Japan earlier than normal. The latest of those was in late June (2004), s Neoguri isn't too far off from making that top-ten list. Forecasters had already been expecting an above-average Pacific Typhoon Season, roughly the opposite of predictions for the Atlantic Hurricane Season, and a big reason for both of these forecasts was the expected development of an El Niño - the 'warm phase' of the El Nino Southern Oscillation (ENSO) - in the equatorial Pacific Ocean.

NEXT PAGE: How El Niño affects storms, and could it be responsible for Neoguri's early arrival?