Twin Storms: Goni a Threat to Taiwan, Ryukyu Islands; Atsani Becomes Super Typhoon

Jon Erdman
Published: August 18,2015

Twin typhoons Goni and Atsani are churning through the tropical western Pacific Ocean. One is increasingly likely to affect typhoon-weary Taiwan and Japan's Ryukyu Islands later this week. The other's future is more uncertain.
(MORE: Record Year to Date in the Western Pacific)
Typhoon Goni, located about 800 miles east-southeast of Taipei, Taiwan, had maximum estimated sustained winds of 115 mph as of 8 p.m. EDT Tuesday, making it equivalent to a Category 3 hurricane on the Saffir Simpson Hurricane Wind Scale.
Goni began a period of rapid intensification Monday morning (Sunday evening mainland U.S. time) while moving west away from Guam and Saipan. Winds increased 60 mph in the 24 hours from 5 a.m. EDT Sunday to 5 a.m. EDT Monday, according to the U.S. military's Joint Typhoon Warning Center (JTWC). This includes an increase of 40 mph in just six hours late Sunday from 5 p.m. EDT to 11 p.m. EDT. This is the equivalent of jumping from Category 1 to Category 4.
Goni has since leveled off its intensity, as outflow winds aloft to its north are not optimal for strengthening, right now. However, the JTWC says these conditions should improve, allowing Goni to eventually strengthen yet again later this week.
Goni affected Guam and Saipan as a tropical storm with strong winds and heavy rain Friday through Sunday, and will likely threaten parts of East Asia late this week or this weekend.
Meanwhile, Super Typhoon Atsani, which has been steadily strengthening, is churning several hundred miles to the east of Goni. Atsani had maximum sustained winds of 150 mph as of 8 p.m. EDT Tuesday, equivalent to a strong Category 4 hurricane.
(SOUDELOR RECAPS: Impacts | Reports | Images | Rain Visualization)

Infrared Satellite: Twin Systems

Two Threats to Asia Ahead?

Forecast Path: Goni

Steered by high pressure aloft just south of mainland Japan, Goni may eventually bring at least some impacts to the northern Philippines, Taiwan or Japan's Ryukyu Islands, including Okinawa, late this week or this weekend.
As Goni approaches the Pacific waters in the general vicinity of those countries, it will begin to turn north over the western Pacific. Where this northward turn occurs will dictate exactly where and when we will see the worst impacts. While the forecast calls for Goni to begin weakening by that point, it will likely still remain a dangerous typhoon.
For now, the peak impacts in Taiwan and Japan's Ryukyu Islands looks to be Saturday and Sunday.
(FORECASTS: Taipei | Shanghai)
Of course, any scenario that takes the eye of Goni directly over Taiwan will mean significant impacts on Taiwan, but also a significantly weaker tropical cyclone for anyone affected by Goni after that. Uncertainty remains high with where Goni will head after this weekend. In recent days, some computer model runs have taken Goni near eastern China or the Korean Peninsula, while others have sharply turned it towards southern mainland Japan. It's far too early to know the ultimate outcome.
But that's just the first typhoon. What about its twin to the east, Typhoon Atsani?
Current indications suggest the eastern system, instead of following in the wake of the first system, will instead track more toward the northwest in the days ahead.

Twin Typhoons Outlook

This is expected to occur thanks to a weakening upper-atmospheric high pressure zone to its north. This will keep Atsani well northeast of Saipan and Guam.
However, Atsani may eventually pose a threat to mainland Japan early next week, if the jet stream doesn't curve it into the open waters of the north Pacific Ocean in time.
Monday evening's computer model forecasts continued to disagree on this point, with America's GFS model favoring a sharper recurvature and a lower risk for the Japanese mainland, and Europe's ECMWF model favoring a more ominous track that could bring a strong and slow-moving typhoon close to Tokyo in about a week.
(FORECAST: Tokyo | Osaka)
Both models indicate there is some risk of Typhoon Atsani having some impact on the small Izu and Ogasawara island chains lying south of Tokyo and north of the Northern Marianas.
(MORE: Expert Analysis | Hurricane Central)
Interests in the western Pacific, including Taiwan, Japan, the northern Philippines and eastern China should monitor closely the progress of each of these typhoons.

Saipan and Guam Impacted By Heavy Rain, Strong Winds

Over the past weekend, Goni affected Guam and the Northern Mariana Islands as a tropical storm.
Tropical storm-force winds (39 mph or greater) occurred as the center passed through the islands. Off Saipan, a sustained tropical storm-force wind of 43 mph was reported just before 11 p.m. local time (7 a.m. EDT) Saturday. A peak gust of 61 mph was recorded there at 10:23 p.m.
On Guam, Andersen Air Force Base clocked a 49-mph sustained wind at just before 5 a.m. local time Sunday (3 p.m. EDT Saturday), with gusts to 58 mph, as a heavy rain band lashed the northern end of Guam. Guam International Airport near Hagatna, Guam's capital, gusted as high as 46 mph at 5:28 a.m. local time Sunday.
Heavy rain arrived Saturday and continued Sunday, prompting flash flood warnings for Guam and Rota. Guam International Airport reported 13.86 inches of rain Friday through 4 p.m. local time Sunday. (Guam is 14 hours ahead of U.S. Eastern Daylight Time.)
This is the second tropical cyclone to affect Saipan in the last two weeks. The island is still struggling to recover from Typhoon Soudelor.
The Pacific News Center reported about 4,000 households in Saipan, or over 25 percent, have requested assistance from the Federal Emergency Management Agency.
Power outages and a lack of running water and food have plagued the 44-square-mile island about 135 miles northeast of Guam since an intensifying Soudelor hit the island square on Aug. 2.
(WATCH: Saipan Struggles After Soudelor)
Guam's main newspaper, the Pacific Daily News, says some families on Guam are also recovering from typhoon damage – in their case, damage from Typhoon Dolphin back in May. Dolphin's eyewall passed over Guam, delivering gusts as high as 106 mph to the northern end of the island.

Active Northwest Pacific Typhoon Season

Including the two current typhoons and Halola, which migrated westward from the central Pacific basin, there have already been 17 named storms (tropical storm strength or stronger) so far this year in the Northwest Pacific basin. Fourteen of those have become typhoons -- equivalent to hurricanes -- and five of those (Maysak, Noul, Dolphin, Nangka and Soudelor) became "super typhoons", packing sustained winds estimated of at least 150 mph.
According to Colorado State University scientist, Dr. Phil Klotzbach, the Northwest Pacific basin had seen record levels of year-to-date tropical cyclone activity through early August, as measured by the accumulated cyclone energy or ACE index.
Meteorologist Chris Dolce contributed to this report.

MORE: Typhoon Soudelor Photos