Typhoon Noru May Bring High Winds, Storm Surge, Flooding Rain to Ryukyu Islands, Western Japan This Weekend

Jon Erdman, Brian Donegan and Chris Dolce
Published: August 2,2017
Typhoon Noru is marching toward a potentially destructive strike in the Ryukyu Islands and southwestern Japan this weekend, concluding a long, strange journey that the tropical cyclone has already made through the western Pacific Ocean.
Noru was equivalent in strength to a Category 2 hurricane as of Wednesday evening U.S. time (Japan is 13 hours ahead of U.S. EDT) and was centered over 400 miles east of Kadena Air Base in Okinawa, Japan.

Current Storm Status

Large swells generated from Noru are already affecting parts of the Japanese coast. The Japan Meteorological Agency has already issued advisories for high waves in the Ryukyu Islands, as well as the Pacific coasts of Kyushu, Shikoku and Honshu, to the east of Tokyo.
Noru will bend on a west-northwest track through Friday, thanks to blocking high pressure to its north over South Korea and the Sea of Japan. Eventually, later in the weekend, a southward dip of the jet stream will approach from Manchuria, which will force Noru to take a sharp turn to the north. Unfortunately, that jet-stream dip won't arrive in time to protect Japan from a typhoon strike.
Noru may first weaken a tad in the next day or so, as it battles a little wind shear and some dry air ahead of it. However, Noru may undergo yet another strengthening phase near the Ryukyu Islands Friday or Saturday, due to a maximum of oceanic heat content near the islands and less wind shear as the aforementioned high builds.

Noru Path History and Forecast Path

While it is still too soon to definitively forecast where the center will track, here are the general threat levels for where the eyewall of Noru may track – where the strongest winds and storm-surge potential are:

• High risk: Amami, Tokara, Osumi Islands; Kyushu (especially southern and western)
• More uncertain risk: Okinawa (including Kadena AB), Shikoku, western Honshu, southern South Korea

Noru may lose some intensity after being bent northward, due to land interaction, but it's not yet clear how much. Typically, when tropical cyclones interact with jet-stream dips, their wind field enlarges, even if their peak winds diminish. This means high winds may spread into parts of South Korea and western Honshu by later in the weekend.
In addition to the threats from high winds, storm surge and battering waves, heavy rainfall is likely to trigger dangerous flash flooding and mudslides in much of western Japan with the passage of Noru.
Residents and visitors in southern Japan should monitor the progress of Noru closely. Preparations for a potentially destructive typhoon should be made in the days ahead.
(MORE: Hurricane Central)
While typhoons recurving toward Japan are rather common every year, there have been only four that have been the equivalent of a Category 4 near Japan's Kyushu Island since 1971, according to NOAA's best tracks database.
Noru has been a tropical cyclone for 13 days since first becoming a tropical depression on July 20. Here's a recap of what's happened so far.

Noru's Rapid Intensification Last Weekend

Noru strengthened from a tropical storm with estimated 70-mph winds (60 knots) to a Category 5 super typhoon with estimated 160-mph winds (140 knots) in just 18 hours from 8 p.m. EDT July 29 to 2 p.m. EDT July 30, according to the U.S. Joint Typhoon Warning Center.
It's stint as a Category 5 equivalent didn't last long as Noru weakened on Monday, July 31.
(MORE: Stunning Images of Noru)

Last Week's Fujiwhara Effect

Last week, Noru teamed up with another tropical cyclone named Kulap in a meteorological dance called the Fujiwhara effect.
Named after a Japanese researcher who discovered this in experiments with water in the early 1920s, the Fujiwhara effect details how two tropical cyclones less than 900 miles apart rotate counter-clockwise about one another.
Think of the teacup ride at Disney or the Tilt-a-Whirl at your local county fair, but with tropical systems instead. In the teacup ride, adjacent teacups can not only spin, but revolve about each other.
(MORE: Weirdest Hurricane and Tropical Storm Paths)
While Kulap had degenerated to a remnant, one could still pick out its leftover circulation in Himawari-8 visible satellite imagery July 27 south-southwest of Noru.

Typhoon Noru and the remnant of former Tropical Storm Kulap are shown in this visible satellite image from the Himawari-8 satellite on July 27, 2017.
(Japan Meteorological Agency)

Last Tuesday, thanks in part to the Fujiwhara interaction, Noru crossed its path from the previous week completing an oval-shaped loop.
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