Live typhoon information for Japan, in English. This page shows the current situation straight from the Japan Meteorological Agency (JMA), an auto-generated map comparing JMA, JTWC (U.S. military) and international ensemble forecasts, live JTWC bulletins on developing disturbances, and a satellite loop — plus a plain-English guide to how typhoon information works in Japan. Everything updates automatically.
🌀 Current typhoon status (auto-loaded from JMA)
Source: JMA. Times are JST. For official warnings always check JMA English.
Track forecast at a glance — auto-generated comparison map
This map is generated automatically for the typhoon most likely to affect Japan. Red thick line = JMA official forecast. Blue = JTWC official forecast. Other colors are ensemble means from GFS (U.S.), CMC (Canada) and the U.S. Navy. When the lines bundle together, confidence is high; when they fan out, the track is genuinely uncertain — plan for the whole envelope, not one line.
Updates about every 30 minutes. Base map © GSI Japan. Tracks: JMA, JTWC, ATCF a-deck (NCAR/RAL, NCEP). The interactive version below lets you toggle each model.
Tool: Interactive track map — JMA, JTWC and global models on one screen
日本の気象庁・米軍JTWCの公式予報に、イギリス・カナダ・アメリカ海軍などの数値予報モデルやアンサンブル（集団）平均・総合予報まで、その時点で入手できる各国モデルの最新の進路予想を1枚の地図に重ねて描きます。凡例で表示のオン・オフを切り替えでき、各モデルの最新初期時刻（計算した時刻）と説明もその場で確認できます。時刻スライダーを動かせば、各機関が同じ時刻にどこを予想しているかを並べて比較でき、予報のばらつき（＝不確実性）が一目で分かります。ヨーロッパECMWF・アメリカGFS・ドイツICONは地図に線を引けないため、下のWindyの地図で確認できます。
地図はドラッグで移動、スマホは2本指でピンチ、ダブルタップ／ダブルクリックで拡大できます。⤢で最初の表示に戻ります。
青＝気象庁（10分平均風速・予報円つき）、橙＝米軍JTWC（1分平均風速）。風速の平均時間の定義が違うため、強さの数字は米軍のほうが大きく出ます。位置の比較には影響しません。地図：国土地理院タイル。
ECMWF・GFS・ICONは進路の座標を公開していないため、上の地図に線として重ねることができません。代わりに3モデルの計算結果を横並びで表示します。各地図下のタイムバーを同じ日時に合わせて、渦の位置のズレを見てください。
Windyのハリケーントラッカーで各国モデルの進路線を見る →
ECMWF・GFS・ICONなどの進路線を1枚で比較できます（Windyのサイトが新しいタブで開きます）
気象庁（日本）
日本の防災の基準。予報円つきで不確実性まで発表するのが特徴。避難や運休の判断は必ずこちらを基準にしてください。
米軍JTWC（アメリカ）
米軍の艦船・基地を守るための機関。発生前の「たまご」段階から番号を付けて追うのが強みで、気象庁より早く動きます。日本向けの公式警報ではありません。
ECMWF（ヨーロッパ）
解像度およそ9km・137層。中期予報の総合精度は世界最高水準とされ、SNSでいう「ヨーロッパの予想」はほぼこれ。
GFS（アメリカ）／ICON（ドイツ）
GFSはNOAAの全球モデルで最大16日先まで。遠い将来では台風を発達させすぎる傾向。ICONはECMWFとGFSが割れたときの3本目の票。
地図提供：Windy.com。データ：気象庁／JTWC／各国モデル（UKMET・CMC・NAVGEM・GEFS 等）はNCAR/UCAR公開データ。
Which model should you trust? (ECMWF vs GFS vs JMA)
There is no permanent winner. The European model (ECMWF) has the best average global scores, the American GFS updates more frequently, and JMA’s own guidance is tuned for storms near Japan — but for any individual typhoon, any of them can be best. What actually works:
Look at agreement, not at one line. If JMA, JTWC and the ensembles all point the same way, the forecast is stable. If they split (for example, ECMWF recurves the storm east while GFS takes it into the continent), the honest answer is “not decided yet” — prepare for the possibilities on both sides. And never anchor on a single run of a single model: each model recalculates every 6–12 hours, and a dramatic single-run track that no other model shows usually disappears in the next run. Watch the trend across runs instead.
Tool: Latest JTWC bulletins — tropical disturbances (Invests), decoded automatically
気象庁がまだ何も発表していない段階の「たまご」を、公式に公表している唯一の機関が米軍JTWCです。その公式発表文を自動で解析して「いま、たまごが何個あるか」を文字で表示し、同じ位置を監視マップ上にも重ねます。米軍サイトを開く必要はありません。
水色の点と地名が日本の位置です。大きな丸印は、米軍の発表文から読み取った「たまご（擾乱）」と台風の位置に、当ページが重ねて描いたものです（緑＝LOW / 黄＝MEDIUM / 赤＝HIGH、濃赤＝すでに台風）。インド洋・アフリカ・オーストラリアまで入った元の画像は「全体（元画像のまま）」で見られます。
緑の丸 ＝ LOW
監視はしているが、24時間以内に発達する可能性は低い。日本の記事で「たまごが発生」と書かれるものの多くがこの段階で、そのまま消えることも珍しくありません。まだ動く必要はありません。
黄の丸 ＝ MEDIUM
発達の可能性は高まっているが、台風になるのは24時間より先になりそう。「なるかどうか」から「いつなるか」に話が移った段階です。予定があるなら、ここから毎日チェックを。
赤の丸 ＝ HIGH
24時間以内に発達する見込み、または既に発達し始めている。同時にTCFA（熱帯低気圧形成警報）が出されます。たまご段階で出る最も強いシグナルで、台風番号が付くのは時間の問題です。
図の中の記号の読み方
90W〜99W | 調査領域（Invest）の通し番号。これが「たまご」の正体。90〜99を使い回すので、番号の若さに意味はありません。末尾のWは北西太平洋＝日本に来る海域。 |
TCFA | 熱帯低気圧形成警報。「まもなく台風級が生まれる」という速報で、HIGHと同時に出ます。 |
TD / TS / TY / STY | 熱帯低気圧／熱帯暴風（＝日本の台風）／台風／スーパー台風。TSから日本でいう「台風」です。 |
◯◯Z | 協定世界時。日本時間は＋9時間。301200Z＝30日21時。18Zは翌日3時になるので日付に注意。 |
更新タイミング（日本時間）
JTWCは00/06/12/18UTC（日本時間9時・15時・21時・翌3時）を基準に解析し、サイトへの掲載はそこから2〜3時間後です。9時ちょうどに見ても前の回のままのことがあります。
画像出典：Joint Typhoon Warning Center（米海軍・空軍合同台風警報センター）。JTWCは米軍の艦船・基地を守るための機関で、日本国民向けの公式警報ではありません。日本での最終判断は気象庁の発表を基準にしてください。
What is a “typhoon egg” (taifū no tamago)?
If you follow Japanese news during typhoon season you will constantly hear about a taifū no tamago — literally a “typhoon egg”. It is not an official meteorological term. Neither JMA nor JTWC uses it. It was popularized by Japanese TV weather segments, and depending on who is speaking it refers to one of three quite different things:
| What people call an “egg” | What it actually is | Where to see it |
|---|---|---|
| Egg (loose usage) | A low-pressure area or a cluster of tropical thunderstorms with no defined center | JMA surface charts |
| Egg (most common) | An Invest (90W–99W) — a numbered suspect area being tracked by JTWC | The JTWC bulletin tool below (green / yellow / red markers) |
| Egg (Japanese media) | A tropical depression officially analyzed by JMA (labelled a/b/c) | JMA charts; becomes “Typhoon No. X” if it intensifies |
In JTWC documents the same things are called a tropical disturbance, suspect area, or invest. The catch: a single Japanese headline saying “an egg has appeared” can mean anything from “a cloud cluster that will probably dissolve tomorrow” to “a system one day away from becoming a typhoon”. The tools on this page let you tell which one it is.
The five ingredients an egg needs to become a typhoon
Of the many tropical vortices that form, only a fraction grow into typhoons. The classic requirements (based on Gray’s tropical cyclogenesis conditions) are:
| Condition | Threshold | Why it matters |
|---|---|---|
| Warm sea surface | ≥26.5°C down to ~50 m depth | A typhoon’s fuel is heat released when evaporated seawater condenses. Over cool water it cannot develop, and it weakens when it reaches cooler seas near Japan. |
| Latitude | Roughly ≥5°N | Without the Coriolis effect the air cannot start rotating — typhoons do not form on the equator. |
| Weak vertical wind shear | Small difference between upper and lower winds | Strong shear tears a developing vortex apart. Many “promising” eggs die this way. |
| Moist mid-troposphere | No dry-air intrusion | Dry air chokes off the thunderstorms that sustain the vortex. |
| A seed disturbance | Monsoon trough, easterly wave, etc. | Vortices do not appear from nothing — some low-level convergence must start it. |
When JTWC raises an area from LOW to MEDIUM to HIGH, it is judging that these ingredients are coming together. In reality, far more invests fade away at green than ever reach red.
How likely is an egg to become a typhoon — and to reach Japan?
Neither JMA nor JTWC publishes an official “egg-to-typhoon” probability. But three things can be said with confidence from how the agencies operate: (1) JMA attaches a forecast track (forecast circle) to a tropical depression only when it expects it to become a typhoon within 24 hours — once you see a forecast circle, typhoon formation is close to certain. (2) JTWC’s HIGH (red) means development is expected within 24 hours (or already beginning) and comes with a TCFA — Tropical Cyclone Formation Alert — also a high-confidence signal. (3) Formation does not mean arrival: in an average year about 25 typhoons form, roughly 12 come within 300 km of Japan, and only about 3 make landfall (JMA 1991–2020 normals).
The official definition: 34 knots, not “17.2 m/s”
JMA defines a typhoon as a tropical cyclone over the northwest Pacific or South China Sea whose maximum 10-minute sustained wind is about 17 m/s = 34 knots (Beaufort force 8) or more. The “17.2 m/s” you sometimes see is a derived figure from the Beaufort scale boundary; the operational threshold is 34 kt (≈17.5 m/s). Note this is a lower bar than the word “typhoon” suggests to English speakers: a JMA “typhoon” starts at tropical-storm strength. JTWC, meanwhile, measures winds as 1-minute averages, which read roughly 10–15% higher for the same storm — one common reason the two agencies’ numbers differ.
Tool: Himawari satellite loop (up to 72 hours) — spot the “egg” yourself
気象庁のひまわり画像を直近24時間ぶん自動で読み込み、そのまま再生します。台風・熱帯低気圧の位置と進路予報も重ねて描くので、渦がどれなのか迷いません。
はじめの数コマがそろうと自動で再生を開始します
黄色い線が海岸線です（気象庁の海岸線タイル）。日本列島・朝鮮半島・台湾・中国大陸・フィリピンなどの位置は、この線と主要都市の地名で確認できます。水色の線は台風がこれまで実際に通ってきた経路、黄色い破線は気象庁の進路予想です。それぞれチェックを外せば非表示にできます。渦を巻いた白い雲のかたまりが「たまご」の候補です。時間を進めても形が崩れず、渦の中心が締まっていくものほど発達しています。逆に、24時間のあいだに形が崩れて散らばっていくものは発達しません。画像：気象庁 ひまわり8号/9号。
Reading JMA’s typhoon chart — circles, categories, timing
The forecast circle is not the size of the storm. It is the area where the typhoon’s center is expected to be with about 70% probability at that time. A bigger circle means a less certain forecast, not a bigger typhoon.
Intensity and size are separate scales
| JMA label | Criterion |
|---|---|
| Strong (強い) | Max 10-min wind 33–44 m/s |
| Very strong (非常に強い) | 44–54 m/s |
| Violent (猛烈な) | ≥54 m/s |
| Large (大型) | Radius of 15 m/s winds 500–800 km |
| Very large (超大型) | Radius of 15 m/s winds ≥800 km |
JMA updates typhoon information every 3 hours as standard, and every hour when a typhoon is close to Japan. New model runs arrive roughly every 6 hours, so checking a few times a day is enough — refreshing every 30 minutes will not give you new information, only new anxiety.
Typhoon numbers and names
Japan refers to typhoons by number: “Typhoon No. 16” means the 16th typhoon of the calendar year (JMA’s internal code 2616 = year 2026, storm 16). International names (like PEILOU or CHAN-HOM) come from a fixed list of 140 names contributed by 14 Asia-Pacific countries and regions, used in rotation. Japanese media rarely use the names — if you are matching Japanese and international news, match by number and date.
If a typhoon is approaching — practical notes for visitors
Japanese railways announce keikaku unkyū (planned suspensions) up to a day or more in advance; airlines usually decide cancellations the day the storm passes closest. Once the track firms up (2–3 days out), check your airline and rail operator directly. For official English information: JMA English typhoon page, NHK WORLD-JAPAN (English broadcasts during disasters), and JNTO for traveler guidance. Power-outage and river-camera information is linked (in Japanese) from the Japanese version of this page.
Typhoon FAQ
- When is typhoon season in Japan?
- Typhoons can form in any month, but most approach Japan between July and October, peaking in August and September. About 25 form per year, ~12 approach Japan, ~3 make landfall (JMA 1991–2020 normals).
- What is a TCFA?
- A Tropical Cyclone Formation Alert, issued by JTWC when it expects a watched disturbance to develop into a tropical cyclone within about 24 hours. It is one of the strongest early signals — typically half a day to a day ahead of JMA’s first announcement.
- Why do JMA and JTWC intensity numbers differ?
- JMA uses 10-minute average winds, JTWC uses 1-minute averages (which read higher), and they run independent analyses. Neither is “wrong” — compare trends, not absolute numbers.
- Will my flight be cancelled?
- Usually decided the day the typhoon passes closest to your airport. Wind direction matters as much as strength. Watch your airline’s operation page from 2 days out; morning flights sometimes escape before conditions worsen.
- Is the mountain of forecast lines on the map scary?
- The opposite — seeing many models honestly shows you the uncertainty that a single official line hides. Tight bundle = confident forecast. Wide fan = keep plans flexible.
Sources
Japan Meteorological Agency (typhoon analyses, forecasts, satellite imagery), JTWC (bulletins, TCFA), ATCF a-deck via NCAR/RAL and NCEP (model tracks), GSI Japan (base maps). All data loads directly from the agencies when you open this page; this site adds the decoding, comparison and Japanese–English explanation.
Typhoon FAQ for Travelers
Q. Will my flight be cancelled?
Airlines in Japan usually decide 1–2 days in advance and publish lists of affected flights on their websites (JAL/ANA have English pages). Domestic flights are cancelled more readily than international ones. Flights typically stop for the half-day around the typhoon’s closest approach and resume quickly — often the same evening or next morning. To see current conditions yourself, our live airport weather map colors 385 airports worldwide by flying conditions, updated every 5 minutes.
Q. Do trains stop?
Yes — and this is often the bigger issue for travelers. Japanese railways announce keikaku unkyū (計画運休, planned suspension) up to 1–2 days ahead: Shinkansen and local lines shut down before the storm arrives, then restart after track inspection. Check the JR company covering your route on the day before.
Q. Should I change my plans?
A typhoon disrupts any one location for roughly 12–24 hours. If your schedule has a buffer day, you usually just lose one day indoors. Move essential travel (airport transfers, cruise boarding) to before the storm, not after — the backlog on the first day after can be worse than the storm day.
Q. How dangerous is it, really?
Inside sturdy buildings (hotels are concrete), the main risks are flying debris near windows and going outside at the peak. Stay in during the worst hours, stock snacks and water beforehand, and charge your devices. Coasts and rivers are the truly dangerous places — do not go “wave watching.”
Q. What do the Japanese warning levels mean?
注意報 (chūihō) = advisory, 警報 (keihō) = warning, 特別警報 (tokubetsu keihō) = emergency warning, the highest level, issued only for exceptional storms — take it seriously. The JMA English site shows all current warnings: jma.go.jp (English).
Q. When is typhoon season, anyway?
May to October, peaking in August–September. Full month-by-month statistics and travel tips: Japan Typhoon Season by Month (30-year JMA data).
Why JMA and JTWC Forecasts Differ
If the U.S. JTWC map calls a storm “Category 4” while JMA calls it just “very strong,” neither is wrong — they measure differently:
1. Wind averaging. JMA reports winds averaged over 10 minutes; JTWC uses 1-minute averages, which come out roughly 10–15% higher for the same storm. JTWC numbers therefore always look stronger.
2. Different scales. “Category 1–5” is the U.S. Saffir–Simpson scale. JMA instead uses its own classes: strong (強い), very strong (非常に強い), violent (猛烈な). A JTWC “super typhoon” roughly corresponds to JMA’s top classes.
3. Different roles. JMA is the official WMO forecast center for this region (RSMC Tokyo) — its warnings are what Japanese authorities, airlines and railways act on. JTWC is a U.S. military forecast, useful as a second opinion. When they disagree on the track, the honest reading is “uncertainty is high” — which is exactly why this page overlays both plus ensemble models.