A summary of the typhoon situation as things sit this morning, 8 October.
Typhoon 27 is in the record books, but what's up with the other two cyclones in the western Pacific?
The far outside cloud band of T27 is over NekoDash Weather HQ in Yokohama
And this is legit physics, not science fiction.
There are three typhoons out the Pacific now. Typhoon 27 (“Choi-Wan”) is one of the strongest storms we have seen in the Pacific so far this season. Typhoon 28, which also goes by its former name of Nolo, is a trans-Pacific traveler which started in the waters off Mexico and has made the rare journey to our side of the world. Typhoon 29 (“Koguma”) is an up-and-coming new storm with the potential to grow significantly in the next 48 hours.
They are all headed toward us, yet, the way surrounding systems are set up, it looks we have a very good chance to get lucky and avoid a direct hit from any of them.
Family portrait, T27, T28 and T29. Sat movie from 4 Oct 22:00 - 6 Oct 08:00
Surface Pressure prediction, 8 Oct, 06:00 JST (Data as of 6 Oct, 06:00)
First off, the stats of each storm, as of this morning’s 6:00 JMA data run:
Typhoon 27 Location: 29.1N, 145.6E, about 800km SE of Tokyo, moving N at 20kph. Central core pressure of 950hPa. Sustained winds over water of 150kph, gusts of 210kph. Gale force winds extend out 850km east, and 560km west of the storm.
T27 is forecast to continue moving northward, pivoting to a northeast bearing by the morning of 7 Oct, and the storm will continue to edge away from the Japanese mainland. While there will be no landfall from T27, coastal areas of Chiba and Ibaraki prefecture may get some gusts as an effect of the extreme outer wind bands of the storm.
Typhoon 28 Location: 25.7N, 173.9E, about 3,300km ESE of Tokyo, moving W at 25kph. Central core pressure of 960hPa. Sustained winds over water of 165kph, gusts of 240kph. The first tropical cyclone to cross the International Date Line since Dora in 2023. This remarkable storm first formed as a disturbance about 1,000 SW of Baja California in the eastern Pacific Ocean. It strengthened, became a hurricane, moved west toward Hawaii and caused some flooding on the Big Island around 25-26 Sep, and then continued on its long ocean voyage, transiting the IDL yesterday (5 Oct) around 9:00, JST, where it became designated as Typhoon 28. While still a very strong storm, T28 has passed its peak, and will gradually degrade as it moves west, encountering additional wind shear.
For all its efforts, though, T28 will not make it to Japan, forecast to turn north about 1,000 or km offshore and move into colder waters.
Typhoon 29 Location: 12.8N, 167.4E, about 3,700km SE of Tokyo, moving NNW at around 5-10kph. Central core pressure of 1000hPa, with sustained winds of 65kph. This is the new entry into the mix, just graduating to JMA typhoon status yesterday. It is still a disorganized storm with no eye and no defined cyclonic movement on satellite. It is projected to strengthen and mature over the next 48 hours, maintaining movement northwest and, by Sunday, 11 Oct, it may threaten the Mariana Islands, although its exact course through the tropics at this point is far from certain.
A little on the mechanics of what's going on here, and this will get a little deep, but stay with me: Checking the ECMWF chart Thursday, 8 Oct @ 06:00 JST, and you will probably go straight to that strong high sitting over the Korean Peninsula, with a long ridge of high pressure stretching east across Japan. While it is tempting to say "Oi, there's the shield keeping the typhoons away!” keep in mind that surface highs don't steer typhoons.
Storms are carried along by a "deep-layer" flow through the atmosphere, mainly the subtropical ridge and the troughs in the mid-latitude westerlies. The surface map just shows us where that ridge lives. Think of it like this: a typhoon is a tower of rotating air reaching well up into the atmosphere, and it gets carried along by the average wind through that whole tower, mostly set by large high-pressure areas (commonly called, “ridges”) and the jet stream-level troughs, operating about 10,000m or so up. The surface map shows only our ground-level view of the story. It gets pushed along, much as a tall tree leans with the average wind rather than just the breeze at its roots.
So what does the ridge actually do? T27 is the easy one. It's already pivoting up north, steered by the westerlies, and by Thursday, it should well away Japan, moving up north. Nothing to write home about here.
While current data suggest that T28 and T29 will not make landfall, to be fair, they are still way out at sea and a lot can change in the meantime. It will be between 3-4 days before we can get a definitive read on them. T28 and T29 both sit on the southern flank of the ridge, and that's the key. Storms riding south of a ridge get pushed westward and they only turn poleward when they reach the ridge's western edge or a competing trough breaks it down.
At this moment, most major models agree on this assessment for T28 (Nolo): a building ridge to its northwest keeps it tracking generally west until about 72 hours out, then it curves northwest as it rounds the ridge axis, with the big question being how far west each storm travels before it turns. It will turn and head north; it’s just a matter of when.
And that's where the uncertainty lies with T28 and T29 at the moment. A stronger ride or one which spans out further east than forecast means a longer westward run and a turn closer to Japan. On the other hand, a trough arriving sooner means an earlier turn and a safe pass out at sea. Models right now, although in general agreement on the course of the storms, disagree on the timing. NAVGEM and JGSM show a sharp pivot north, while GFS, ECMWF and the ensembles curve wider and slower. T29 carries the widest spread: some runs have it passing east of Honshu, others bring it toward the Izu Islands. We’ll get a firm grip on these tracks in a few days.
Bottom line: The high moving over the Asian mainland now will bestow gorgeous weather upon Japan this week, and it looks unlikely that we will get any landfall from all the storms out at sea now. That said, while the data certainly looks that way as things sit today, things can change. Keep your eyes on the skies.
Good morning. First off, I was out almost all last week on day job matters, so sorry about that. Some folks in the head office overseas decided they needed some stuff from Japan due immediately if not sooner, and that pretty much nuked my week. With that mess done, now I have a bit of time to see what’s happening in the skies over Japan
Trying to catch up on all that’s gone on in the weather. I was able to look outside once or twice and noticed the rain had stopped. The tenacious autumn rain front (秋雨前線) that messed with the weather here for the past four weeks has finally let up, leaving behind a very saturated September. Tokyo ran up a streak of 36 consecutive days with measurable rain, a record which stood since 2019 that nobody really wanted to beat.
T27 24 hr Satellite Loop: 3 Oct 22:00 - 4 Oct 22:00
The JMA's read on T27 as of 9am this morning
JMA's surface analysis of the weather buzz in and around Japan.
Glamor shot of T27. 5 Oct, 09:30 JST
Can October be a bit better? Certainly, we have a chance. A weak low pressure system trailing a front is working its way through the northern parts of the Sea of Japan and on into Hokkaido today and tomorrow, so we're not entirely clear yet. Cloud covers much of the nation this morning, but there is sunshine across parts of western Kyushu, the Sea of Japan coast, Hokkaido and some dots of sun in Okinawa.
Tuesday's front will bring rain from Hokkaido through the Sea of Japan coast of Tohoku and Hokuriku, along with a chance of locally heavy short downpours and gusty winds. Eastern Kanto, specifically the along the seaboard of Chiba and Ibaraki, could see some spotty rain as well.
After that, a high will take over and begin to dominate the country’s weather. Building in from the west, Japan should see broad sunshine with sunny to partly-cloudy skies nationwide from Wednesday onward. Temperatures will run normal to a bit above normal for early October, warming further toward the weekend.
Guys, we've got sunshine in store. Y’all remember sunshine, right? You know, the hot ball in the sky? Ring a bell?
Wednesday will still have some clouds hanging around on the Sea of Japan coast, but from Thursday it's going to be splendid, and the upcoming three-day weekend (10-12 Oct) is shaping up very nicely indeed, much different than the half sloppy/half really humid Silver Week we recently had.
But first, we need to get through T27. Typhoon 27 (aka, “Choi-wan”) is a very powerful storm, and we should take a moment to whisper a little prayer of thanks to whatever deity or celestial weather being you worship [or pass a beer and pizza to your favorite weather sub!] that this brute of a system will stay well offshore. Without employing my usual profanity-laced metaphors, Typhoon 27 is a monster of a storm, one of the strongest typhoons to pop up so far this season. As of JMA’s 6:00 data run, it was near 24.8N 146.6E, roughly 1,400km SSE of Tokyo, moving north-northwest at 20kph. Central pressure is 925 hPa, with sustained winds over water of about 180kph, and gusts to a breathtaking 250kph. It is a large, powerful storm. The area of storm force winds (defined by the JMA as that parcel of ocean where sustained winds hit 90kph or greater) extends 220km to the east and 165km to the west of center, while the gale force winds (54kph +) reach out in a lopsided 850km to the east and 560km to the west of storm center. Satellite imagery shows a clear, beautiful, well-defined eye, the mark of a mature storm.
T27 is peaking today, with the 925 hPa mark reached around 3am. The path downward from here will be slow, but definite. The storm should stay "very strong" (非常に強い、ひじょうにつよい) through Tuesday, then ease to "strong" and turn extratropical around the 7-8 Oct.
The good news here is the track. All major models, including the JTWC, JMA and ECMWF has the T27 continuing north near the Ogasawara Islands, then bending northeast keeping the storm well out over the open Pacific. The tempest, staying far offshore, well east of the Japanese islands, means no landfall. And, for a rain-and-storm-weary country, we can take solace in that.
There will be some impact, however, in the form of surf and winds. Waves up to 8m are forecast for Ogasawara through Tuesday, around 5m for the Izu Islands, and rough seas will reach the Pacific coast of Kanto and Tohoku from Tuesday into Wednesday. Winds too will pick up over the Izu Islands and Kanto on Tuesday and Pacific Tohoku on Wednesday, with forecasts estimating up to 40kph winds along the coast. Stay away from the coast and skip the fishing. Surfers, on the other hand, well, you guys are a different breed. Go do what you do best if you want. I wouldn’t and you shouldn’t, but, surfers gonna do the nami thing.
Any rain on the mainland Tuesday will come from the low and trailing front system and not directly from the typhoon.
Kanto will see a warm spike Tuesday as the typhoon's circulation pulls warm air north, standard for post-typhoon patterns, but still surprising as T27 has the power to bring in all this tropical air while still being so remote. Highs in Kanto and parts of coastal Tohoku should jump from today's 20–21c to somewhere in the 24–29c range, and then ease back toward normal by Wednesday–Thursday.
Beyond the Kanto spike, highs will be uneven across the country. Expect around 30c in Kagoshima and Naha, high 20s in Fukuoka, and much cooler air in Hokkaido and inland Tohoku, where lows drop into single digits. Under the migratory high, temperatures edge upward toward the weekend, with Kanto commonly topping 25c.
And, yes, we do have a couple of other little squirrels darting around in the Pacific now. We'll keep an eye on those and see if they're worth reporting on.
Have a great week, everyone.
Twenty-six numbered storms this year. Aren’t we on a streak out here in the western Pacific? Let’s have a quick quiz before we begin: Going back to 1960, what year produced the greatest amount of numbered storms?
While your mental microchips are grinding on that problem, let’s talk about T26. At the moment, T26 is a very disorganized blob of a system. No discernible eyewall, no real cyclonic movement, but with cloud tops of 15,800m, it is it is supporting a crazy intense rain footprint packed into a fairly localized cell. It is sitting at 20.5N 128.2E, making it about 1,200km south-southeast of Kagoshima, moving west-northwest at a solid 30kph. Central pressure logged in this afternoon at an even 1000hPa, and sustained winds of 72kph were measured over open water, with gusts of 108kph. Wave height over open water is 5.5 meters, so if surfing is your thing, then cowabunga!
24 hour satellite movie of T26, from 24 Sep, 21:30 to 25 Sep, 21:00
Glamor shot of T26. 25 Sep 2026, 17:00 JST
The JMA's forecast for T26 on 30 Sep 2026, 15:00 JST
The ECMWF forecast for the almost the same time: 30 Sep 2026, 18:00 JST
The ensemble model (also called, more deliciously, the spaghetti model), as derived by Weathernews.
A glitch on the ECMWF model. But just imagine...
T26, while a typhoon in the eyes of the Japan Meteorological Agency, is still defined as a Tropical Storm by other agencies.
The modeling for what we can expect from T26 is, for the moment, wildly split. Ultimately there will be consensus, and with each data run, the models are slowly finding common ground and agreeing on where the storm is heading, but they still disagree on the storm's exact position beyond 3-4 days out. All models agree that the typhoon will approach Okinawa, running along the south end of a large high pressure area centered in the northern Pacific. The models are also mostly agreeing that the storm will curve away from its current heading toward Okinawa, and chart a course to the northeast. But exactly where it will curve and what course it will take after the pivot is still a matter of electronic and numerical debate.
The primary European model (ECMWF), predicts the storm will move accelerate and move faster up the Pacific coast than the AI models are forecasting, starting from around 29 Sep at 18:00 JST. The American GFS model, meanwhile, is still thinking the typhoon will slow down and stall out. However, with each data run, the GFS has been gradually shifting that stall point farther northeast, meaning it's drifting closer to what the other models say.
So, while there is high confidence that T26 will pivot and turn to northeast, exactly where and when is the subject of much digital bickering. At this point, the forecasts for 30 Sep, evening (around 18:00, JST) disagree violently, by as much as 1,500 km. One model, NAVGEM, the Naval Global Environmental Model, places the storm southwest of Okinawa - you know, like near Taiwan, while two AI models (from Google DeepMind and Windborne) place it far to the east, southeast of Tokyo. The remainder fall within that vast ocean scape in between.
Intensity is a little easier to work with. Predictions for peak wind speed have become more consistent over the last day, with most models now clustering around 92–120 mph sustained wind over open water. Two models, the experimental HAFS-A and CTCX (an acronym for the very busy full name: Coupled Ocean/Atmosphere Mesoscale Prediction System for Tropical Cyclones), are the most aggressive, predicting a stronger storm, but they also predict the storm will peak about a day later than other models expect. The Joint Typhoon Warning Center, meanwhile, is tracking closely with Google DeepMind's AI model through 28 Sep, but after that, the two models begin to branch apart. The JMA and the ECMWF, too, who frequently agree on storm tracks and intensity, are also split on this one. For the 30 Sep, 18:00 JST forecast, the JMA is forecasting a still very robust storm with 125kph sustained winds over water, about 500km south of Osaka. The ECMWF forecasts a milder iteration of the storm about 400km southwest of Osaka, with more unenthusiastic winds of 40-50kph southeast of storm center.
The predictions for this one are all over the map, quite literally. Really, the only thing that all (well, most) models agree with at the moment is that T26 will turn toward the northeast after a close brush with Okinawa, and that the storm will not make landfall.
Quiz answer on the next post. Actually, I need to look that up myself.
I knew it would be cloudy, but didn’t expect rain today.
Kanto is getting a little post-typhoon wetness. As if we haven’t had enough lately.
BTW - only place in Japan where it’s raining now.
I was leaning very strongly toward a bias of it being cloudy, but no precipitation for today. There is so much drier air over the country, post-typhoon, I really thought we'd get away with it. My apologies, guys. I bungled this one.
Quick morning read on Typhoon 25
As of 6am this morning, T25 is at 25.2N 146.0E, about 1,100km SSE of Tokyo. Central barometric pressure is 980hPa with sustained winds of 108kph and gusts of 144kph. The typhoon is moving northwest at a very rapid 45kph.
The anticipated course has shifted a little west overnight, and the system is expected to make a closer approach to the central Honshu coast (Kanto) than anticipated yesterday, but the typhoon should still stay offshore, with the closest approach being around 3am on the 21st, when the eyeball approaches within 100km of Chiba's Pacific coast. No landfall is expected.
More later...
Posted a video about what effects meteorologists think the current El Niño will have on the upcoming autumn and winter seasons in Japan. If things set up the way they're going now, we can look forward to a warmer than normal autumn season, and a milder than normal winter.
It's a bit of a long video, clocking in at 13 minutes plus change, but there is a lot of ground to cover here. The El Niño we have going now is not a simple topic.
if you have some time, give it a watch.
Thanks!
- NekoDash
Although still designated as Tropical Storm (TS) 24W elsewhere, Typhoon 25 (aka "Dujuan") graduated to a typhoon last night, as per the JMA's definitions.
As of 06:00 JST this morning, the storm was located at 17.6N 149.7E, about 670km northeast of Anderson AFB on Guam. T25 has sustained winds of 72kph with gusts of 100kph and a relative high central pressure of 996hPa, and is trucking along north-northwest at fairly energetic 25kph. Still steadily intensifying in a very favorable developmental environment, with warm sea surface temperatures and low wind shear, the system has grown cloud tops of over 16,000 meters.
The storm structure is still quite disorganized, as seen on satellite images, but is expected to coalesce over the next 24 hours.
JMA's track of typhoon 25, as of 06:00 this morning.
Himawari Satellite Map of T25. 17 Sep 2026; 09:00 JST
Infrared image at the same time as the image above, showing strong development.
T25 is expected to maintain its growth for the next 48 hours, but then increased wind shear as it moves into more northerly waters will restrain further growth.
All major models are aligned on the path of the storm. T25 will start to turn more northwestward this evening, and will trace a curving west-northwest path for about a day. By the 20th, high level winds will pivot the typhoon northeast, and that will turn will take it on a run up the central Pacific coast of Honshu, where it will dump precipitation and bring moderately heavy winds from the afternoon of the 20th into the late afternoon of the 21st. While T25 will bring strong weather to the coastal and some more inland areas of central Honshu, actual landfall is not expected by any of the models at this time.
Rain and wind intensity estimates on the Japanese mainland are still up for grabs at the moment, although we should get a clearer picture of that as we head into the weekend.
More data and updates as the storm develops.
After a few days of indecision, models have come into agreement on the path of a small tropical depression which will soon become typhoon 25.
This new storm first popped up on the long range models around last Thursday or Friday. Between Friday and Monday, potential courses changed several times, with predicted paths showing a direct hit to Tokyo, to a course more southward toward Okinawa, then over to Korea, then over Kyushu and out into the Sea of Japan. You get the idea. Overnight, though, there has been broad consolidation on all the major models that I use when scanning the skies: the European-based ECMWF, the US-run GFS, Japan’s own JMA and the JTWC - the Joint Typhoon Warning Center - operated by the US military out of Pearl Harbor, but they are separate from the GFS. Some of the other B-team models I check here and there, notably the AI-driven Fengwu and Fuxi models, operated by the Hong Kong Observatory are also in agreement.
4 models and their thoughts on the position of typhoon 25 on 20 Sep@21:00
Tracking from the Joint Typhoon Warning Center, based on the data run from 16 Sep; 06:00 JST.
I say broad consolidation because while there is overall agreement now about the projected path of the storm through Monday, there are also some minute differences in projected tracks and strength of the storm. There is also some uncertainty about the timing and course of the storm as it pivots to the northwest, toward Honshu, and models also disagree on whether or not there will be landfall. Those questions will suss out over the next 24-48 hours and I anticipate firmer cohesion among the models by Thursday evening.
For now, the system is still a depression, designated as TD24W by the JTWC. In JMA terms, the storm is set to graduate to a typhoon by 21:00 tonight. There is still not a lot of structure in the storm, as you can see from the satellite images here, but significant development is expected in the next 24 hours. As of 6am this morning, it was sitting at 14.8N 148.8E, about 2,400 km SSE of Yokohama, with sustained winds of 55kph.
Let’s see what the next 24 hours brings. The only thing I can say with confidence right now is that there is a very strong chance that the storm, as a typhoon, will make a very close approach to the Kanto area. As general path and speed projections sit at the moment, it will mess with outdoor Silver Week plans on Sunday and Monday. I will definitely be keeping an eye out on this storm, and the next 24-48 hours will be crucial in seeing where the system will go from here.
Just to note, while I do my best to deliver accurate, reliable, transparent weather information, please check with the JMA, weathernews.jp, tenki.jp, or the Joint Typhoon Warning Center for the latest updates on the course and strength and expected impact of T25.
This is one of those days where it is hard to begin. Heavy rain in some areas, blazing sunshine in others, muggy in the middle, and all because of a persistently little front, doggedly separating two distinct masses of air fighting for dominance as we move…or, really, try to move…away from summer and into the cooler months of autumn.
So, let’s try to untangle the spaghetti and see what’s happening. First off, rain. With storms forming an arc over Japan, from Akita in the north, holding over Tohoku toward the Sea of Japan then turning south from Ishikawa and going on in to Kyoto and Mie, areas under the line of rain today got pounded relentlessly. Nibetsu (仁別) in Akita got 128mm of rain as of 20:20 tonight, and it was still falling as I try to rush this post out the door at 21:00. Ishikawa’s Wajima (輪島) clocked a little better at 139.5mm at the same time with drops still falling. Kameyama (亀山) in Mie had a relatively tamer day, accumulating 92.5mm of wetness, while Miyazu (宮津) in Kyoto saw 43mm, with a good chance of rain to fall overnight to add to the total. Many other places along the arc have received between 8-16mm over the past 24 hours.
That arc will continue overnight and move slightly tomorrow, and another band of showers are set to fire up off the nation’s Pacific coast tomorrow, bringing the increased chance of more precipitation from around Nagoya on up to Tokyo.
The engine for all this rain is the little front that could. This front, called the Autumn Rain Front (秋雨前線、あきさめぜんせん) locally has been messing with Japan’s weather for the past week and a half. Slowly moving north and south as the air masses behind it tussle for dominance like sumo wrestlers on a Japan-sized dohyo, the front has been the delineation line for epic amounts of rain. From the south, constant inflow of warm, moist air has provided the moisture, while cooler air behind the front provides the catalyst for the storms we have seen.
The first blip of what may become Typhoon 25
National rain radar, 14 Sep @ 20:35 JST
This high was one of the major catalysts of today's summer-like highs across the country.
Tomorrow's weather map, thanks to our good friends over at Weathernews
And, as long as this front remains the battleground between two vastly different types of air (Maritime Tropical vs Continental Polar), the elevated chances of rain nationwide will continue. The Million-Yen question everyone is asking: How long will it last? I can see the front hanging out at least through the 20th of the month. That’s when we may get some typhoonery coming in from the Northwest Pacific which may disrupt the integrity of the front, but more about that later.
Today, temperatures south of the front were almost summer-like, with 282 stations across the country reporting high temperatures north of 30c. The hotspot today was in Kagoshima, where a high of 34.1 was registered at Kanoya (鹿屋). Kanto’s own Hell’s Valley, in Saitama’s Kumagaya and Kuki area, hit 33.2 and 33.9, respectively.
A powerful high up north way off the Pacific coast created a clean sweep of huge amounts of warm air from the tropics up into Japan, creating today’s unseasonably warm temperatures. Tomorrow, however, the front - the Autumn Rain Front - is due to drift a bit more toward the Pacific, and that will bring some cooler temperatures to much of the country. The Pacific side of Tohoku and northern Kanto will see the biggest drops, of up to 8c lower than today, but most of the nation from Akita on down to near Hiroshima will see some degree of lower temps tomorrow.
For the rest of the week, temperatures will yo-yo, going from near summer to near seasonal. Hokkaido will see highs in the lower 20s this week, while Tohoku careens from highs of close to 30 today on the Pacific Coast to 21 tomorrow. Kanto, too, will cool down to the mid-20s through Wednesday before things get a little warmer as we close out the week. Nagoya, and the Chubu area as a whole, will see little relief, with highs coming down around 2-3c over the area from yesterday. Kansai, Chugoku, Shikoku, Kyushu and Okinawa will see very little change from today through Friday.
Nationwide, mostly cloudy with high chances of rain for the week. A few areas may get a break in the clouds and see a few hours of sunshine here and there, but that’s going to be more of an exception rather than a rule. Only Hokkaido, which shamelessly flaunts its drier, calmer skies, will see nicer weather this week.
Now, what’s this I said about a typhoon? Well, a little invest - an embryonic storm - has bubbled up at around N13 / E156. This has been on the long-range models for a few days. Last Friday, the ECMWF thought it was going to head right into Kanto. Then by Saturday evening, that was revised to a track down toward Okinawa. Sunday evening’s data had the storm moving toward Korea, then turning up toward Japan. The GFS model has been similarly adventurous. The two models, and a couple of others I reference for storm tracks, are nowhere in agreement yet. The only thing we know is that a storm will develop and it will grow into a typhoon. Beyond that, getting to the “where” and “when” and “how strong” of the question, still remains to be seen. Current tracks suggest the system will keep a southerly heading toward Okinawa through to around Monday, 21 Sep, but from there, it’s anyone’s guess at this point. Will it go straight and move into the Chinese mainland? Will it recurve northeast toward Japan? Will it decide to pay Korea a visit? At this point, Monday evening, 14 Sep, we just don’t know. In the next 48-72 hours, I imagine the models will consolidate, and we can put a kind of definite path on the storm. Stay tuned.
Have a great week, everyone.
Tonight's weather chart (9 Sep, 21:00 JST) [from Weathernews]
If you are anywhere in Japan right now, you have probably noticed the air has been especially heavy and damp lately. I mean, torrential rains in various parts of the country aside, it is just absolutely insane humidity pretty much nationwide.
With the Tokyo/Yokohama area hitting 89% humidity today, and similar levels from Tohoku on down, the air feels oppressive, heavy and downright hard to breathe. So, what’s up and why are we in a sauna today?
First, let’s be thankful it isn’t mid-summer. With temperatures on the Pacific coast ranging from 26-30c, and cooler, low-to-mid 20s along the Sea of Japan coast up into Hokkaido, things could be a lot worse if we had this level of humidity with late-July and August level high temps. Little comfort, yes, but let’s take what we can get.
We have several causes fueling our humidity index today. In no particular order, they are:
Got a little academic on you there, but that’s the mechanics behind our high humidities.
Today's heat stress advisories from the Ministry for the Environment
Surface level humidity profile. Hot and sticky out there.
The equation for finding the relative humidity!
Surface level frontal position as of 9am this morning
Today's sea surface temperatures, captured by JAXA.
Surface wind analysis for 10am this morning
Now, this front…As noted, it has been around for a week and a half, retaining its integrity between cooler air up north, and tropical air down south. The line - the front - delineates a clash between these two air masses. That clash is helping generate the heavy rains we have seen across the country lately. Today, the front is sitting along the Pacific Coast of the country, and the ghost of T24, embodied as a low pressure system, is moving north-northeast, and is offshore from the Kansai area today. The rotation of the low is pulling down some cooler air, giving Kansai a brief (today only), if very rainy, spell of cooler weather.
North of the front, we have cooler temps, but humid air and rain patterns extend up to Aomori prefecture. South of the front, warmer temperatures make for oppressive, heavy weather. Clouds cover most of the country today, and that pattern will continue through the rest of the week. The stationary front will also hang around through the week, moving around some, bisecting the country and bringing higher chances of rainfall along with it.
Today’s rainfall will be along a line from the Kansai area up to Hokuriku, with some scattered bands out toward the Pacific coastline. Rain is expected to move further east during the day, with rain again approaching Chubu (Gifu, Aichi and thereabouts) and the central Honshu interior highlands.
If you notice any inclement or severe weather activity, please go to the JMA, weathernews.jp or tenki.jp for the latest detailed information.
Stay safe and stay dry.
Oh, never mind. Pretty much the entire country is also going to be under cloud cover, so the 3 passes visible tonight will go unnoticed by those of us locked on the ground. If you happen to be airborne - even a commercial craft cruising at 8,000 meters will do - you may be lucky enough to catch a glimpse of the space station as it whizzes by at about 420km above.
Lots of places in Japan are going to get this stuff over the next few days.
No, seriously, there is an ISS flyby tonight. We just won't see it from the ground.
For those of us on the ground, get ready for a gray and dreary, but warm, week as the former T24 makes its way north and feeds precipitation forming along that very persistent stationary front parked midway over the country. The 秋雨戦前 (あきさめぜんせん, Aki Same Zen Sen), the first autumn front of the year bringing cooler rains (or similar such clumsy translations) will move a little north and back a little south over the next four days, but will retain its integrity at least through Friday. Chances of rain remain high throughout the week, with only some areas of Hokkaido getting a pass with fair to partly cloudy skies.
High temperatures for the week will depend on which side of the front you are on. North of the front, you can expect low-20s for daytime highs, while those south of the line can expect to feel peak temperatures in the upper-20s, with a few places touching 30 here and there. Kanto will be a bit of a battleground between the warm and cooler air, with highs today and tomorrow in the 28-30 range, but plunging down to 21c by Thursday, only to see a rebound to the mid-20s by the close of the week.
Not much sun to be seen in most of the nation through the week, at least.
Just a quick weather update. I won’t take you long on this pleasant Sunday morning.
Well, “pleasant” is subjective. I like having a hot cup of coffee listening to the sound of autumn rain, so today’s weather in Yokohama fits pretty square in my definition, for sure.
The stationary front has begun a slight drift northward. Coupled with the warm, tropical flow powered by the weakening T24, large areas of heavy precipitation have come ashore along the central Pacific coast, from Kanto on down to Wakayama’s Kii Peninsula. This blob of rain will continue to drift slowly north over the next 24 hours, bringing anywhere from 100-250mm of rain to those in the path of the system.
T24's Okinawa Tour is coming to an end, as is T24 itself.
National radar as of 11:05 today. Rain along the Pacific Coast, from Kanto to Kansai.
The players in Japan's weather transposed on the 9:00 Himawari satellite image
T24, meanwhile, is finishing its counter-clockwise pirouette around Okinawa and will start to head toward the Japanese mainland from tomorrow. It is encountering cooler ocean temps and outflow has weakened. This less favorable environment will lead to T24 to be demoted to a simple tropical cyclone by Tuesday. It will still have plenty of rain to give, but winds will be weaker as it moves closer to the islands of Kyushu and Shikoku.
Rain all day today and into tomorrow, making for a sloppy Monday commute for the central Pacific coast. Rain will move into parts of Tohoku and Hokuriku from late today into tomorrow. High temperatures on the south side of the front will pop up to the upper-20s to low-30s, while those on the northern side of the front will still get low-20 daytime temps.
A very rainy 19.2c at NekoDash Weather HQ in glorious northwestern Yokohama as of 11:30am. Need to get more coffee. Have an awesome Sunday, wherever you may be.
So, yesterday I described Japan’s weather scene as an “atmospheric box of cats”. Which it truly was. It took a while to figure out how what was behind T24 and the “autumn rain front” (translating directly from 熱帯低気圧, as it is noted in local media), and where things were going. I also love to employ the phrase “box of cats” to describe any sort of chaotic or disorderly system.
Although the crystal ball of weather mysticism looked kind of haze, today we’re getting a little clarity as to what we can expect from the intricate dance between T24 and the persistent stationary front. Again, let’s get to T24 first.
The projected loopy, drunken path of T24
T24 and its interaction with our persistent stationary front will be the catalyst for LOTS of rain.
The 5-day temperature average shows the effect the autumn front had on daily highs this past week.
Typhoon 24: Around 24 hours ago, most models were split between two scenarios: 1) That the typhoon would do a bit of a loop around Okinawa, regain a bit of strength, then launch back up toward Japan, or 2) That T24 would take a bit of a southward turn, fizzle out, become part of an upper-level flow, then drift up toward Japan. In either event, T24 was destined to make it up this way. The only question was whether it would be as its own entity or integrated with another system.
Models are now in broad agreement that the answer to the question is A. T24 will make a bit of a loop in near Okinawa over the next two days, steered by high pressure systems near the Yellow Sea. It will retain its form, get a small yet notable second wind [Note…see what I did there? Second wind…for a typhoon…that was good, you got to admit.], and make a run for the Japanese mainland. The refresh won’t last long, though, as a wind shear, drier air and lack of convection will slowly choke off energy for the storm, and it is expected to be downgraded, in domestic JMA terms, from a typhoon to a tropical storm/cyclone (熱帯低気圧, nettai tekiatsu) by the early morning hours of the 9th. It will still pack a fair amount of wind and rain. So, hold that thought. Let’s look at the action the stationary front brings to the table now.
熱帯低気圧, the persistent autumn stationary front. You could argue this is something like a mirror rainy season front. Same mechanisms are at play here: vast seasonal air masses bumping up against each other with rain and weather events playing out for days along a front which doesn’t move anywhere fast. It’s the classic cool air vs warm air scuffle we see when seasons are changing. The front, which drenched Aomori on Monday, deluged Hokuriku on Wednesday and saturated Kyushu and western Japan yesterday has drifted a little south to off the Pacific coast of the country and it is the major contributor to our sub-30 degree lows today.
Over the next couple of days, the front is predicted to retain its integrity and move back up north. At the same time, T24 will be warm, moist tropical air into the frontal boundary, fueling even more rain. As it moves north, the rain with move along with it, and, from Sunday through Wednesday, large areas of the nation will get precipitation, in places locally heavy, as the front moves back through followed by the stormy remains of T24. Rainfall along Kyushu will reach up to 200mm through Sept 8, Kansai can see between 100-180mm. Chubu (Nagoya) will get off easy and get between 10-35mm from the system while Kanto can expect to see anywhere from 10-65mm. Unsettled conditions persist through at least Wednesday.
The sole exception to this hot, wet mess is Hokkaido, which will shamelessly clock in with sunny, gorgeous skies and highs in the low-to-mid 20s through the period. Enjoy it if you’re up in that area.
In Honshu and points south, daily high temperatures will remain in the high 20s over the weekend, but are set rebound some as the front retreats north and warmer air fills the void. Kyushu and west Japan will see highs at 30 and slightly above from Monday, 7 Sep, while Nagoya and Kanto will hit the 30 degree mark from Tuesday.
That’s the weather recap. Have yourselves a wonderful Saturday evening.
I have sat at my keyboard for most of the morning trying to figure out how to approach the narrative of the weather situation in Japan, and this is the best I’ve got.
Good morning, Japanweather community. It has been a few days since I’ve posted, and all the while, we have had some wild weather events. I do apologize, but sometimes the day job (you know, the thing that actually pays the bills around here) gets intense. I had to give that my full attention this week, and I missed out on some of the major events of the week, such as the flooding in Aomori.
So, I mentioned a box of cats. Let’s untangle the skies and see what we have. At the moment, all the carnage up there boils down to two major players: Typhoon 24, and a stubbornly persistent stationary front. Let’s break down these two.
T24's weak structure is obvious in this Himawari image from this morning.
Today's 21:00 weather map from the fine folks over at Weathernews. Y'all rock. I mean that. Thanks!
First up, T24. We have some typhoonery going on in the form of a little storm named Typhoon 24 (aka, “Krovanh”) . T24 is weak, as cyclones go. It is barely a typhoon, even by JMA standards. Checking in this morning with winds of around 64kph, it is still just a tropical storm in the eyes of the Joint Typhoon Warning Center. Central pressure in T24 is 990hPa which, also, doesn’t suggest a strong storm. There T24 does have some structure, as satellite pics show, the storm is not robust by any means.
What is unique about T24 is that the system is not being moved by a normal steering mechanism, and the storm has wobbled around aimlessly like a partygoer returning home after a spectacularly festive evening. Typhoons, as I’ve mentioned here before, for all their awesome power, are really just low pressure cells on steroids and can be pushed around by surrounding systems with relative ease. Right now, the steering currents aren't carrying the storm along a normal path. Most prominently, a wall of high pressure building over the Yellow Sea has set up a roadblock directly in front of T24, halting any forward movement and forcing it into a sharp southward dip and, possibly, a U-turn.
Trying to unbox what may happen over the next 5 days is little more than a Hail Mary pass at the moment. Usually, when steering is obvious on a typhoon and you get an idea of system motion, you can get a better, more confident read on where things will be, but T24 is just sitting there, being churned around in circles and a little southward movement. Models do not agree on the fate of T24 over the next 120 hours, so let’s summarize quickly each of the two major potential tracks that may happen here.
> Scenario 1: Movement over Okinawa, a loop south, rebuilding and movement to Japan. This depends on system movement coming in from Mainland China, but the upshot of this plot is that T24 will approach Okinawa over the next 24-48 hours, where strong wind shear and dry, cool northern air will drop it below tropical storm strength. But once it turns northeast and accelerates toward mainland Japan, some models show its core surviving, firing up new thunderstorm activity, and re-intensifying as it approaches the Pacific coast.
> Scenario 2: T24 moves slightly south, but encounters a much more hostile environment as it begins to bump up against the high pressure areas near the Chinese mainland. Harsh wind shear and cold, dry air work together to completely dismantle the storm. T24 then just washes out into a disorganized, broad monsoon depression that limps toward Japan as a weak remnant rainmaker. Timeframe for this scenario is 48-60 hours from now.
We will see which scenario plays out. Official forecasts currently split the difference between these two scenarios.
Now, on to the stationary front. This is the front which powered the storms which inundated Aomori earlier this week. After moving south this much of this week, sparking sometimes intense rainfall along its leading edge, it has come to a halt. Drier air is behind it, warmer air is in front. Depending on what T24 - or its remnants - decide to do, it will either stay down south, interact with the remnants of T24 and dissipate, or it will retain its frontal integrity and move up north, dragging the rain along with it.
In either event, in any of these scenarios, much of Japan from Tohoku on down will see a good chance of rain through next Thursday, 10 Sep. Aomori got hit on Monday, Hokuriku was deluged on Wednesday. Today, after missing out on a lot of the action recently, Kansai and Shikoku get their share of rain, while Kyushu gets saturated for the next few days.
Bottom Line: Through to Tuesday, 8 Sep, elevated rain chances in much of the nation from Tohoku on down to Okinawa, Hokuriku being the primary exception. Hokkaido can expect sunny to partly-cloudy skies for the period. Summertime temps have broken, and much of the country can expect daytime high temperatures in the upper 20s, while the interior highlands and parts of Hokkaido will see a brisker peak in the mid-to-high teens. Unsettled conditions largely present while what’s left of T24 and the stationary front do their dance.
Have a great weekend everyone!
Hi everyone. I have spent a couple of days working on a small side project and wanted to show it to the community.
Pulling data from the JMA, this page gives national high and low at the moment, plus weather stats for 30 locations around the country. You can get local weather conditions for each of the 30 locations, including 5 day forecasts. It is still primarily in Japanese at the moment, but I'm going to work on that.
It's not an app; just a basic web page. It's just in a pilot/prototype phase as of now, but first steps are the most important.
Swing over and give it a look if you have a couple of minutes. Let me know what you think either by DM or in the comments. I would like to expand this out and give it more functionality.
This summer has been nowhere near the absolute burner that last year was. We have had our warm spots, and western and southern parts of the country have had it worse than those in the north, but, on the whole, it has been more tolerable season than we had in 2025. Here we are, in the last days of August, and can we say summer is closing? Well, yes, and no. Mostly no.
The main player in the country’s weather today will be a front bisecting the nation along a line roughly coming in onshore from the Sea of Japan coast at Fukui prefecture, over Gifu prefecture, heading over Aichi prefecture then trailing out into the Pacific Ocean. This front has been slowly moving down the country from the north, after approaching Hokkaido on Tuesday.
Today's highs will cut closely along the lines of a front neatly bisecting the country.
Rainfall today will also move along the front.
Weather Map for today at 21:00 (from Weathernews)
Some domestic media has been calling this line the “first front of autumn” (初秋前線) and while it is fair to describe it as such, I feel that is also is misleading. Those areas behind the front will feel their first real break in summer temperatures today, but the relief will be short-lived, and those beyond the front will still be in full summer mode. Additionally, the front is set to dissipate by midday tomorrow, and temperatures from Tohoku on south will begin edging up again by the start of the week.
For today, those north of the front will feel the first true break of summer, with highs in the upper teens/low 20s in Hokkaido to the upper 20s in Kanto. South and west of the front, however, it is still summer. Nagoya, right on the edge of the front, will see 30 today, while Osaka/Kyoto onwards will still be in the low-to-mid 30s.
There is a strong chance for scattered showers along and behind the front, with some areas, especially in the Hokuriku area (Ishikawa, Toyama, parts of Gifu and Nagano), set to see heavy local rain storms through today. Rain will be scattered between Fukushima prefecture to Shizuoka prefecture along the Pacific side of the country.
Rain chances dissipate nationwide tomorrow as the front unravels. Tomorrow’s highs behind the former front will begin to edge up a bit, although not quite as intense as earlier this past week. No change for areas south and west of Chubu and Hokuriku (the line from around, say, Nagoya - Ishikawa), as summertime temps still dominate.
Elsewhere, two typhoons are bumbling around the central Pacific Ocean, but they are nowhere near Japan. Long range models do suggest some tropical storm players approaching Japan next weekend, but it is way too early to note anything. The two major models I deal with, the ECMWF and the GFS, are in wild disagreement over course, timing and intensity. The only thing they do agree on right now is that some tropical storms will begin to upwell in the next 5-7 days. Beyond that, we need to wait until around the middle of next week to give a definitive on how/where/if those storms will intersect the nation.
Have a chill weekend everyone. Take care and stay safe.
![Tonight's weather chart (9 Sep, 21:00 JST) [from Weathernews]](https://preview.redd.it/f1zo1qenzeoh1.png?width=850&format=png&auto=webp&s=73c0dd63dd06f1b0ab032c06bde4b7902f51b6a6){kind=link}
