Typhoon Lan, currently east of the Philippines, may rapidly intensify into a super typhoon and could eventually pose a threat to Okinawa and mainland Japan beginning this weekend.
Lan is currently about 500 miles east of the Philippines, to the north-northwest of Palau, and is about to curl north-northwestward.
Thunderstorm clusters are persisting near the center of Lan, and several outer spiral bands are now present in infrared satellite imagery from the Himawari-8 satellite.
Upper-level winds are favorable for development, featuring prominent outflow channels both to the northeast and southwest of Lan's center. Ample ocean-heat content is also in play.
Therefore, Lan is expected to rapidly intensify into a super typhoon – with maximum sustained winds of at least 150 mph – in the next couple of days, according to the U.S. Joint Typhoon Warning Center forecast.
Lan will track generally toward the north, before beginning a northeast turn due to the steering effects of high pressure to its east and the increasing influence of the jet stream as it gains latitude this weekend.
Lan is not a threat to the Philippines, Taiwan or eastern China, but by this weekend, it may pass close to Okinawa, then mainland Japan.
According to the latest forecast, Lan will make its closest approach to Okinawa Sunday, but winds will already begin picking up Saturday, and may linger a bit into early Monday.
However, it remains too soon to determine exactly what impacts Lan may have in Okinawa, including Kadena Air Base.
Lan will be a formidably strong typhoon by the time it reaches the latitude of Okinawa.
However, Lan's exact path – specifically, when and how sharply it turns toward the northeast – will hold keys to the degree of impact there.
A sooner northeast turn would lessen the threat of an eyewall strike. A later, less-sharp turn would increase that threat.
Despite this, Lan may have a large wind field, so even if Okinawa avoids the eyewall, tropical-storm-force winds, along with heavy rain and pounding surf, are possible impacts this weekend.
For now, all interests in Okinawa should monitor closely the progress of Lan.
Interestingly, despite the western Pacific Basin's deserved reputation as the most active tropical cyclone corridor on Earth, intense typhoons near Okinawa aren't as frequent as one may think.
According to NOAA's best track database, only seven Category 4 or stronger equivalent typhoons have tracked within 75 miles of Kadena Air Base in reliable records dating to 1971. The last to do so was Danas just over four years ago, in early October 2013.
Outlook: Japan Mainland
Lan should lose some of its intensity and transition to an extratropical storm - one featuring warm and cold fronts typical of the mid-latitudes - by the time it makes its nearest pass to Japan Monday.
But the size of Lan's wind field is likely to expand as it gains latitude and makes this transition by Monday.
The sharpness of the northeast turn near Japan is still in some question and will have some determination on the severity of impacts in Honshu, Shikoku and Kyushu.
A later or less-sharp northeast turn would allow Lan's large wind field to rake across much of these areas with damaging winds and power outages.
Heavy rain, flash flooding and mudslides are a more certain threat, unless the northeast turn of Lan is very sharp and occurs much sooner. Battering waves and coastal flooding are likely along the Pacific coasts of Honshu, Shikoku and Kyushu.
While the Atlantic Basin has seen one of its most active hurricane seasons on record, the western Pacific Basin, prior to Lan, had been in a relative slumber.
Through Oct. 16, roughly only half of the average activity – number, intensity, longevity – of tropical cyclones had occurred in the year-to-date in the western Pacific Basin, according to data compiled by Dr. Phil Klotzbach, tropical scientist at Colorado State University.
This included only one super typhoon: Noru, in late July.
Check back with us at weather.com for the latest on this potential typhoon threat ahead.
Jonathan Erdman is a senior meteorologist at weather.com and has been an incurable weather geek since a tornado narrowly missed his childhood home in Wisconsin at age 7. Follow him on Facebook and Twitter.