Weather

What Is Weather?

Weather is a corridor 460 m tall and 2,000 m long, full of storm cells drifting north on a 7 m/s wind. Each cell swells at 3.4 m/s until it is 88 m in radius, and two cells that touch become one cell with the area of both. The aeroplane covers ground at 40 m/s whatever the nose is pointing at, so the heading you choose decides which weather you meet and nothing else.

Two resources are spent at once. The tanks hold 100 and burn 1.2 every second, whether the aeroplane is flying at the destination or across the corridor. The airframe holds 100 as well and is charged only in weather: 44 per cent a second at the dead centre of a cell, less the nearer the rim your track passes. Fuel is the clock that runs out on a cautious flight. The airframe is the clock that runs out on a bold one.

How to Play

1. Press play. The flight begins at the western edge of the corridor with nine cells already in the band, the nearest of them about 250 m ahead.
2. Hold the up key, or the top pad, to swing the nose north, and the down key or the bottom pad to swing it south. The nose arrives at 1.45 radians a second, so a heading change is something you start early.
3. Read the chart well ahead of the aeroplane rather than the cell beside it. The picture is about 800 m wide on a laptop, twenty seconds of flying, and every cell in it is drifting while you close on it.
4. Cross a cell only when the alternatives are worse than the price. A grown cell taken through the middle costs more airframe than the flight has, and a graze at four fifths of its radius costs about a seventh of what you hold.
5. Watch the fuel gauge as closely as the airframe meter. A straight crossing is fifty seconds of flying and the tanks hold eighty-three, so every detour comes out of a fixed allowance.
6. Fly the 2,000 m to the dashed line. The run ends there, whatever is left in the tanks.

What the Chart Shows

• The band edges. Two heavy ink lines mark the 460 m of corridor the aeroplane can use. Cells are held inside them too, which is why even the largest of them leaves a lane open.
• The cells. Each one is drawn as rings that darken toward the middle, and the darkness is the charge you would be paying there. Tight black rings mean a cell to go around.
• The destination. A dashed line in mint, 2,000 m from the start of the run.
• Your own track. The thin line behind the aeroplane is where the flight has actually been, and its distance from a straight line is what the weather has cost.
• The meters along the top. Distance made good is the score, and the airframe bar is what ends most flights. The fuel gauge is the one people stop looking at until it matters.

The Route Round a Cell

A cell grown to its ceiling has a radius of 88 m, so a line through the middle of it is 176 m of weather. That is 4.4 seconds at 40 m/s, and the charge averages half the core rate across the chord, which comes to 96.80 per cent of the airframe. The airframe holds 100. A crossing of a grown cell is the whole flight.

Offset the line and the price falls away quickly. Half a radius off the centre costs 51.96 per cent, four fifths off costs 15.14, and a cell that misses the track entirely costs nothing. The airframe absorbs six grazes at four fifths of a radius. Two at half a radius will finish it.

Two Clocks Running

The fuel arithmetic is worth doing once. The tanks hold 100 and burn 1.2 a second, so the aeroplane has eighty-three seconds of air in it. A straight crossing of 2,000 m at 40 m/s takes fifty seconds. The thirty-three seconds in between are what the detours have to fit inside, which works out at an average track efficiency of about sixty per cent: the route can be two-thirds longer than the straight line and no longer.

The airframe arithmetic is harsher. A hundred points will pay for one full crossing of an ordinary cell, or for six grazes along a rim. The field only fills up as the flight goes on, so the weather near the destination is the expensive weather, and the fuel saved by cutting a corner early is fuel the flight wants for the detour it cannot avoid late.

Reading the Sky Ahead

The wind is what makes the field hard to read. Cells cross the corridor at 7 m/s while the aeroplane covers ground at 40 m/s, so a cell 400 m ahead has moved seventy metres north by the time the aeroplane gets there. Aim at where the gap will be rather than where it is now.

Growth does the same thing more slowly. A cell of 40 m becomes a cell of 88 m in fourteen seconds and then stops, so the small cell on the right of the chart is a large one on arrival, and a merge can drop a 130 m cell where a gap used to be. Some lane always exists. The work is finding it before the tanks run down.

Weather on a Phone

The corridor is scaled to the height of the window rather than to a fixed pixel size, so the whole 460 m band stays on screen and a metre of sky is a metre of sky on any device. A tall narrow window shows less of the corridor ahead, which sharpens the aiming problem on a phone, and the fuel allowance does not change to match.

Steering is by two pads in the bottom corners of the picture, one for north and one for south. The turn is a rate rather than a position, so a pad is held down and not tapped: hold it and the nose swings at 1.45 radians a second, release and it keeps the heading it has. Nothing here needs a second finger or a hover.