Talk about no rest for the weary. Super Typhoon Trami, the third western Pacific storm this month to reach Category 5-equivalent status, is packing a punch with winds sustained at nearly 150 mph. It may slam into southern Japan this weekend as a weaker, though still formidable, typhoon.
Since achieving elusive Category 5 status Monday, Trami has since fluctuated in intensity as a shortwave trough approaches from the northwest. This dip in the jet stream has siphoned drier air into the northwestern limb of the storm, eroding some of its “fuel” and knocking it down a peg to a Category 4-equivalent. Still, Trami remains a force.
On the forecast track, the Joint Typhoon Warning Center (JTWC) is calling for a general curve to the northeast in the days ahead. That would bring the center of circulation into southern Kyushu, Japan, sometime late this weekend into early next week. With a “gradual weakening trend through seventy-two hours” expected, Trami may end up as a strong Category 2 or low-end Category 3-equivalent when it potentially makes landfall.
The Japanese Meteorological Agency has already hoisted gale advisories for the southernmost prefectures of the nation. In addition to winds sustained around 100 mph and gusting well over 125 mph, Trami has residents of southern areas bracing for a five- to seven-foot storm surge and excessive rainfall. While uncertainty looms large, this forecast still has considerable “wiggle room” to switch things up.
In the meantime, Trami is in no hurry to go anywhere. The JTWC reports that the storm “has tracked northward at 01 knots over the past six hours.” That’s a mere 1.15 mph. The average New Yorker in Manhattan walks two-and-a-half times as fast.
Why is Trami meandering so slowly? The answer lies in steering currents. The winds aloft in the atmosphere are weak. That means there’s nothing to push and pull a storm. While these sluggish winds are conducive to cyclone growth without the threat of being torn apart, they also pose a challenge. Every subtle shift of wind can have enormous implications on which way the typhoon drifts. That’s why the JTWC has cautioned that they have “low confidence . . . due to high uncertainty in the weak steering environment.”
Forecasting typhoons is challenging, much as is predicting any weather occurrence. Because the JTWC generally doesn’t dispatch airplanes into the storm, there are “holes” in the data that meteorologists have to work around. That means no in situ observations from inside the storm. Instead, intensity estimates are made using satellites, which lend themselves handily to the Dvorak technique. It’s a form of particle tracking that can be used to derive wind speed and direction at different levels based on the motion of clouds below.
If it seems to you that the western Pacific has been cranking storms out lately, you’re not wrong. To begin September, Typhoon Jebi reached Category 5. Although it weakened by the time it collided with Japan, it killed at least 11 people and brought a 10.8-foot storm surge to Osaka Bay. Later, Typhoon Mangkhut achieved Category 5 equivalency before ravaging the northern Philippines and ultimately Hong Kong.
Trami comes on the heels of an exceptionally active period in the tropics when at least seven cyclones spun simultaneously worldwide. Something called the Walker circulation generally prevents both basins — Atlantic and Pacific — from being active simultaneously. When air rises over one ocean, it condenses and forms clouds. Then it snakes around the world parallel to the equator, where it eventually sinks. This falling air ordinarily should cut off storm growth. But for uncertain reasons, that wasn’t the case.
Trami has arisen during a relative lull in tropical cyclone activity.
Some exceptional images of this storm have been captured from space, which we share below.