Goni and Atsani both became typhoons over the weekend and will strengthen further in the coming days, as one or both could become super typhoons.
After battering the Mariana Islands with flooding and damaging winds, Goni continues to strengthen as it tracks westward over the open Pacific Ocean.
Atsani also continues to strengthen as it moves over the open ocean to the east of the Mariana Islands. While Goni tracked through the Mariana Islands, Atsani will track northwest passing north of the islands this week.
This track will keep Atsani from impacting any landmasses this week; however, Goni will eventually reach Taiwan by this weekend as a powerful typhoon.
A much weaker Goni brought more than 250 mm (10 inches) of rain to Guam over the weekend.
The strongest winds passed to the north of Guam. Saipan, which sustained structural, tree and power pole damage during once-Super Typhoon Soudelor, had wind gusts to 90 kph (56 mph).
This week, the stage is set for both Goni and Atsani to become major typhoons due to the combination of very warm water and low wind shear. There is high confidence that at least one of these cyclones will become a super typhoon and the potential exists for both to achieve this status.
Multiple tropical systems roaming the western Pacific is far from unusual. “What is uncommon is the fact that there could be two super typhoons at the same time,” said AccuWeather Meteorologist Anthony Sagliani. The last time that occurred was October 1997 with Ivan and Joan.
“The track of these two storms will keep them far enough apart from each other to prevent their wind fields from disrupting one another,” Sagliani continued. Typically, the strong winds outflowing from one super typhoon will disrupt the circulation of another and inhibit it from becoming as strong.
Goni began to rapidly strengthen as the storm tracked across the Philippines Sea on Monday and additional strengthening will continue through at least the middle of the week.
Sagliani expects Goni to be past its peak intensity before taking aim at the corridor from Taiwan to South Korea and Japan from this weekend into next week.
“Wind shear will increase in the path of Goni late this week, causing it to weaken some,” he said. “While it may not be a monster that it could become over the open water, the system should still be very impactive regardless of whether or not landfall occurs in Taiwan.”
Destructive winds, flooding rain and inundating storm surge should still be accompanying Goni when it passes near or over Taiwan.
One scenario for Goni’s track is for it to plow into Taiwan, where cleanup operations in the wake of Soudelor continue, before tracking up the far-eastern China coast.
Another possibility is for Goni to turn to the north quicker, barreling through Japan’s Ryukyu Islands and then targeting the Korean Peninsula.
All residents from Taiwan to South Korea and Japan should continue to monitor the cyclone and check back with AccuWeather as more precise details to the track and impacts become available.
Meanwhile, the more northward track of Atsani will keep the future super typhoon over the open ocean through this weekend with only shipping interests at risk.
Even though no impacts [other than to shipping] are expected this week, there remains a threat that the cyclone could turn westward next week and eventually impact Japan.
Atsani could eye Honshu with a possible landfall during the first half of next week; however, many factors will determine if the powerful typhoon makes a direct landfall or turns northeast away from Japan.
A direct landfall would bring life-threatening impacts such as destructive winds, flooding rainfall and mudslides.
Even if Atsani curves out to sea prior to reaching Japan it could still lash eastern Honshu, including Tokyo with strong winds and rain.
“There have been five super typhoons during the 2015 West Pacific Tropical Season thus far, which already surpassed the normal seasonal average of four,” continued Sagliani.
If both storms were to become super typhoons, that would be seven for the season, making it the seventh-highest total in any single season since 1959.
The latest Accuweather Tropical Forecast calls for nine super typhoons through the end of the year, which would stand as the third-highest total on record behind 1965 and 1997 with 11 super typhoons each year.