Random Weather Generator

What the random weather generator does

Press the button and it hands you a sky. Not just rain, but Light Freezing Drizzle. Not just cloud, but Mostly Cloudy with Haze. Not just a storm, but Thunderstorm Heavy Rain Hail in Vicinity.

Those are real phrases, and they are not written the way a novelist would write weather. They are built the way an engineer would, and that is the interesting part. Every entry in this list is a piece of one of the most precise and least poetic languages ever invented, a language spoken by machines at airports and read by pilots who need the sky described the same way every single time.

How to use it

1. Choose how many you want. One for a single condition, more if you are browsing the range.
2. Press Generate. A fresh draw every time.
3. Press Copy to take the set with you.

These are not descriptions. They are code.

Ordinary weather words are hopeless for aviation. If a pilot in Tokyo and a forecaster in Chicago and an automatic station in the desert all describe the sky in their own words, in their own language, with their own sense of what counts as heavy, then nobody can be sure they mean the same thing, and in aviation being unsure about the weather gets people killed.

So there is a system, and it is one of the quiet triumphs of standardisation. It is called METAR, it is governed by international aviation and meteorological bodies, and it fixes exactly how the sky may be described. Not roughly. Exactly. There is a defined list of weather types, a defined list of ways to qualify them, and strict rules about how they combine, and every airport on Earth uses the same one.

The phrases in this list are that system, turned back into readable English. In its native form a line like Heavy Thunderstorm Rain is not written in words at all. It is written +TSRA: a plus sign for heavy, TS for thunderstorm, RA for rain, three symbols carrying what would otherwise be a sentence. A pilot reads that the way you read a word, at a glance, without unpacking it, because it always means precisely one thing.

Every apparently clunky entry here is doing that job. "Fog in Vicinity" is not a mood. It is a statement, accurate to within a defined distance, about where the fog is relative to the runway. The clunkiness is the precision. There is no room for a nicer word, because a nicer word might be understood two ways, and the entire point is that this cannot be.

The grammar of a sky

Once you know the system is a language, you can read its grammar off the list, and it turns out to have parts of speech.

There is intensity, which works like the volume knob: light, moderate or heavy, written as a minus sign, nothing, or a plus sign. Every precipitation can be turned up or down, which is why the list holds Light Rain, Rain and Heavy Rain as three separate official states rather than one vague one.

There are descriptors, which modify the weather like adjectives. Freezing. Blowing. Shallow. Patches of. Showers of. These attach to the main phenomenon and change its character: Fog becomes Freezing Fog becomes Shallow Fog becomes Patches of Fog, each a genuinely different thing to fly into.

There are the phenomena themselves, the nouns: rain, snow, drizzle, hail, fog, mist, dust, sand, smoke, and the rare violent ones, the funnel cloud and the tornado.

And there is proximity, which places the weather in space relative to the observer.

The system then combines these under firm rules, up to three phenomena in a single report, stacked in a fixed order of importance. And the order is not arbitrary. The rules say that when several things are happening at once, the most dangerous is named first, which is why anything tornadic jumps to the front of the line ahead of the rain and the hail. The grammar has a sense of priority built into it, because it was written by people for whom the priority was a matter of survival.

What looks like a pile of weather words is a sentence with a strict syntax, and once you can parse it, a string like Thunderstorm Heavy Rain Hail in Vicinity reads cleanly: a thunderstorm, with heavy rain and hail, occurring near the airport but not directly over it. Every word is load-bearing.

The strangest word in the list

Read down the entries and one phrase keeps recurring in a way no ordinary weather report would ever use. In Vicinity. Fog in Vicinity. Showers in Vicinity. Thunderstorm in Vicinity.

It sounds oddly formal, almost legalistic, and that is exactly what it is, because it is answering a question ordinary weather never has to answer: not just what is the weather, but precisely where is it relative to me right now.

In the METAR system, "in the vicinity" is not a vague gesture at nearby. It has a defined meaning: the phenomenon is happening between roughly five and ten miles from the point of observation. Not at the airport, which would be reported differently, and not far away, which would be reported differently again, but in that specific ring around it. There is even a separate term for weather beyond that ring, out at a distance.

This is the detail that reveals what the whole language is for. An ordinary person looking out of a window cares whether it is raining on them. A pilot approaching a runway needs to know that a thunderstorm is sitting seven miles off the approach, not overhead and not gone, because in the time it takes to land, seven miles is nothing and that storm may arrive. The weather that is near is a different operational fact from the weather that is here, and the language has a precise word for the difference.

Which is the whole character of the thing in one phrase. Where you or I would say it looks a bit stormy over there, the system says Thunderstorm in Vicinity and means a bounded, defined, unambiguous fact about a ring of sky between five and ten miles out. It is weather described by people who cannot afford to be misunderstood, and the list this generator draws from is a small piece of that impossible, admirable precision.

Where these come from

The conditions are drawn from the standardised set of aviation weather phenomena, translated into plain English and curated by hand, so these are real reportable states rather than invented ones. Your browser picks from them at random. Nothing you do here leaves your device.

Questions people ask

What does METAR actually stand for?

It comes from the French for an aviation routine weather report, and the name is now used worldwide regardless of language. A METAR is the standard hourly observation issued at an airport, covering wind, visibility, weather, cloud, temperature and pressure in a fixed coded format that every pilot is trained to read.

Why not just write the weather in normal words?

Because normal words vary by person and language and leave room for being understood two ways, and aviation cannot tolerate either. A fixed code means a report generated automatically in one country is read identically by a pilot from another, with no translation and no ambiguity. The oddly rigid phrasing is the price of that certainty, and it is a price worth paying at altitude.

What exactly does "in the vicinity" mean?

In this system it is a defined distance, not a vague one: the phenomenon is occurring roughly five to ten miles from the point of observation, near but not overhead. There are separate ways of reporting weather that is directly at the station and weather that is farther off, so the single phrase carries a precise spatial fact.

Why are some of these so long and specific?

Because the system lets several conditions combine, up to three at once, each with its own intensity and descriptors, stacked in order of importance. A long entry like a thunderstorm with heavy rain and hail nearby is simply the grammar doing its job, packing a full and unambiguous picture of a complicated sky into one ordered line.

Are these real weather conditions?

Every one is a genuine reportable state in the international aviation weather system. Some of the combinations are rare, and a few, like the tornado and funnel cloud entries, are the ones a pilot most hopes never to file, but all of them are real phenomena with defined codes rather than invented descriptions.

References

1. Meteorological Aerodrome Report (METAR). SKYbrary Aviation Safety. https://skybrary.aero/articles/meteorological-aerodrome-report-metar
2. METAR product information. Aviation Weather Center, NOAA. https://aviationweather.gov/help/data/
3. Aviation Routine Weather Report. CFI Notebook. https://www.cfinotebook.net/notebook/weather-and-atmosphere/aviation-routine-weather-report