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“Never Before Experienced” Rains Hammer Japan During Early July

“We’ve never experienced this kind of rain before. This is a situation of extreme danger.” — The Japan Meteorological Agency

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During recent days as much as 25 inches of rain has fallen over parts of Japan shattering previous all time precipitation records for parts of the island nation. The resulting floods have spurred a major emergency response by 54,000 personnel, taken the lives of more than 125 people, and forced more than 2.8 million to evacuate.

(Rising global surface temperatures increase atmospheric water vapor levels — providing liquid fuel that spikes the most powerful rainfall events to even greater extremes.)

On July 3, Typhoon Prapiroon swept over southwestern Japan bringing with it a spate of heavy rains. Over the following days, Prapiroon got caught up in stationary front even as a high pressure system to the east continued to circulate tropical moisture into the region. Beneath that eastern high, sea surface temperatures ranged between 2 and 3.5 degrees Celsius above normal. Meanwhile, warmer than normal ocean surfaces dominated a region east of the Philippines. These large, abnormally warm zones produced excess evaporation which helped to feed even more moisture into the region.

The result was a historic and devastating rain event for Japan. Isolated locations received more than 39 inches (1000 mm) of rain over a three day period. With one hour rainfall exceeding 3 inches in a number of locations. Motoyami received one day rains of 23 inches. With Mount Ontake seeing more than 25 inches over three days.

(Warmer than normal ocean surfaces, as shown in yellow and red in this sea surface temperature anomaly map, helped to fuel Japan’s recent extreme rainfall event. Image source: Earth Nullschool.)

Rising global temperatures increase overall atmospheric moisture loading by approximately 8 percent for each degree Celsius of global temperature increase. Water vapor provides fuel for storms both through enhancing convection and by engorging clouds with moisture. Recent scientific studies have found that climate change can greatly enhance the peak intensity of the most severe storms in this way. And the U.S. National Climate Assessment has identified a historical trend of increasing instances of heavy precipitation.

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Very Hot Pacific Hurls Super Typhoon Vongfong Toward Japan

Vongfong

(Perfect Storm Vongfong churns on a course toward a weekend collision with Japan. Image source: NOAA.)

Bombification…

On Monday afternoon, Typhoon Vongfong was a moderate strength category 2 storm churning through the open waters of the Western Pacific. These waters, warmed to 1-2 degrees Celsius above the 20th Century average by a merciless human heating of the world’s atmospheres and oceans provided extra fuel upon which the still growing storm could feed.

In the airs above, conditions grew more and more favorable, wind shear dropped and an upper level high pressure system built over the strengthening storm. These conditions allowed Vongfong to draw deep from the newly heightened pool of potential storm energy of the hotter than normal Western Pacific. The result was that Vongfong’s pressure rapidly dropped to 900 mb, just 5 mb shy of super typhoon Haiyan’s peak strength. Wind speeds surged by nearly 80 mph inflating Vongfong to a powerful 180 mph monster.

Vongfong is now the 6th Western Pacific storm to reach extreme category 5 intensity this year — the strongest tropical cyclone on record for all of 2014 thus far.

Forecast Track Brings Vongfong’s Heavy Rains Over Japan

Thankfully, this human-warming amplified monster storm still remains well away from the densely populated land masses of the Philippines and Japan as it explores the absolute upper limits of maximum storm intensity. But, by this weekend, Vongfong is expected to come slamming into the island chain near Okinawa as a strong category 3 storm and then to ride into Japan as a category 2 storm, bearing strong winds and dumping copious amounts of rain over the already water-logged archipelago.

Vongfong forecast strength and track

(Vongfong forecast strength and track. Image source: Joint Typhoon Warning Center.)

Japan, during the month of September, received extraordinary rainfall totals, in some places breaking all-time records. Now, during October, a 1-2 punch of Western Pacific storms threatens to bring more flooding to already saturated regions. As of today, official forecasts for locations along Vongfong’s track could receive more than 10 inches of rain by this weekend. A heavy addition to already record fall totals for the archipelago nation.

Conditions in Context

Overall, the Pacific Ocean has been far warmer and stormier than is typical. Today shows the broader Northern Pacific at an extraordinary +1.18 degrees Celsius above the already hotter than normal 1979 to 2000 average. And this extra heat seems to be heightening storm formation in regions where storm-feeding atmospheric instability and moist air abound. In total, the North Pacific Basin has seen 38 tropical cyclones this year, just shy of the annual average of 40-45 and with nearly three months left to go in the year. Some of these storms have been among the most intense on record with fully six super typhoons spawning in the Western Pacific and with the Eastern Pacific seeing its 4th strongest storm ever to form for that basin — category 5 Hurricane Marie.

NOAA sea surface temperature anomaly

(NOAA sea surface temperature anomaly for the Pacific Ocean between 40 N and 40 S Latitudes. Image source: NOAA/Ocean Surface Observation.)

Though most of the intense heat anomalies are to the north and east, almost all regions show above average water temperatures. The waters along the typical typhoon track running toward Japan, for example, range from 0.5 to 1.5 C above average just east of the Philippines to 1 to 3 C above average in a zone east of Taiwan and just south of Japan.

Links:

NOAA

Joint Typhoon Warning Center

NOAA/Ocean Surface Observation

Hurricane Marie

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