TCCOR Explained: The US Military Typhoon Alert System on Okinawa, What TCCOR 1-E Actually Means, and Why Civilians Should Watch It Too

If you are on Okinawa and searching in English during a typhoon, the number you keep seeing is not a category. It is a TCCOR level.

A tropical cyclone seen from the International Space Station. Archive image, shown for illustration. It is not live imagery of any current storm.

TCCOR stands for Tropical Cyclone Condition of Readiness. It is the alert system used by US military installations on Okinawa, in mainland Japan, in Guam and elsewhere in the western Pacific, and it runs on a completely different logic from the Japanese warning system next to it.

During Typhoon Dolphin this week, installations across Okinawa went to TCCOR 1 at seven in the morning on Thursday. Japan Airlines and All Nippon Airways cancelled all Friday flights to and from Naha.

Those two things happened for the same reason, and the TCCOR number is the more precise description of it.

This guide covers what the levels mean, what happens on the ground at each one, and why it is worth watching even if you have nothing to do with the military.

What the levels actually mean

The whole system is built on one threshold: sustained winds of 50 knots, which is about 58 mph or 93 km/h. Every level is a statement about how many hours away that wind is.

TCCOR 5 — destructive winds of 50 knots or greater possible within 96 hours. Only used outside the established typhoon season.

TCCOR 4 — possible within 72 hours. This is the default state from 1 June to 30 November. If nothing is happening in the Pacific in September, Okinawa is still at TCCOR 4.

TCCOR 3 — possible within 48 hours. This is when general cleanup starts: securing loose objects around homes and offices, checking supplies.

TCCOR 2 — anticipated within 24 hours.

TCCOR 1 — anticipated within 12 hours. This is the level Okinawa reached on Thursday morning for Dolphin.

TCCOR 1-E, Emergency — destructive winds of at least 58 mph are occurring now. Outdoor activity is prohibited except for lifesaving measures.

TCCOR 1-R, Recovery — winds of 50 knots or greater are no longer forecast. Damage assessment begins, but the all clear has not been given.

All Clear — the storm is over and not forecast to return.

Two things about that list are worth noticing.

The first is that it is a forecast system, not an observation system. TCCOR 1 does not mean the wind has arrived. It means someone has decided the wind is twelve hours out. The decision is made in advance, on purpose, so that preparation happens while it is still safe to be outside.

The second is that the numbers go down as the danger goes up, which is the opposite of a hurricane category and catches people out constantly.

What TCCOR 1-E means on the ground

This is the level that actually changes life on the island.

At 1-E, outdoor activity is prohibited except for lifesaving measures. That is not a recommendation. Bases close, gates restrict movement, and personnel are expected to be inside and stay inside.

For Dolphin, reporting ahead of the storm noted that 1-E conditions could persist longer than in previous storms this season, because the system was large and slow. A wide wind field means the 58 mph threshold is exceeded for longer, even if the peak is lower.

That is the part civilians most often get wrong. A weaker storm that is physically enormous can hold an island in 1-E for many more hours than a compact, violent one passing quickly.

The practical effects extend well past the fence line. On-base shops, schools, medical facilities and food services close. Contractors and Japanese national employees who work on the installations do not go in. Anyone whose accommodation or travel plan assumed base access loses it.

A spokeswoman for Fleet Activities Okinawa put the reasoning plainly this week: "The safety of our Sailors, civilian personnel, their families, and our ships and aircraft are our top priority."

Ships leave. Aircraft leave. That is a routine part of the sequence, and it happens days early — which is one reason military aircraft movements can look strange in the days before a storm.

Why civilians should watch it anyway

Three reasons, and the first is the practical one.

TCCOR is published in English, updated on a fixed schedule, and stated in plain hours. Japanese warning information is more precise and more locally specific, but if your Japanese is limited, the TCCOR level is the fastest way to know roughly how much time is left.

Kadena Air Base and the other installations publish the current level publicly, and it is not restricted information.

Second, it is a good proxy for when the island stops working. Okinawa's civilian infrastructure does not follow TCCOR, but it responds to the same storm on a similar timetable. When bases go to TCCOR 1, that is the twelve-hour mark for everybody, and it lines up closely with when ferries stop, when shops close, and when flights get cancelled.

Third, and this is the honest limitation: TCCOR is a readiness system for installations, not a public safety instruction for you. If you are a resident or a visitor, the binding guidance is the Japan Meteorological Agency warning for your municipality and whatever your local government issues. TCCOR is a useful English-language clock, not a substitute for that.

Use it as timing information. Use JMA for what to actually do.

One more practical note. If you are a visitor with a flight and you see TCCOR 1 declared, treat that as your signal to check your airline immediately rather than waiting for the storm. Twelve hours ahead of destructive winds is already after most cancellation decisions have been made.

Where to check this yourself

Kadena Air Base and other installations publish current TCCOR status on their official pages and social channels.

For the weather itself, use the responsible national agency:

Japan Meteorological Agency: https://www.jma.go.jp/en/typh/

Joint Typhoon Warning Center: https://www.metoc.navy.mil/jtwc/jtwc.html

Korea Meteorological Administration: https://www.kma.go.kr/eng/weather/typoon/typhoon_05.jsp

Hong Kong Observatory: https://www.hko.gov.hk/en/index.html

JTWC is the US military forecast centre for this basin, so its bulletins are the input the TCCOR decisions are built on. JMA is the official Japanese source and the one that governs warnings for the civilian population.

The short version

TCCOR is a countdown to 50-knot winds, not a measure of storm strength.

5 is 96 hours, 4 is 72, 3 is 48, 2 is 24, 1 is 12. Okinawa sits at 4 all season by default.

1-E means the wind is here and nobody goes outside. 1-R means it is leaving. All Clear means it is done.

The numbers go down as the danger goes up.

And if you are a civilian, TCCOR is the clearest English-language clock available for how much time is left — but the instruction you actually follow comes from JMA and your local municipality.

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