Storms, in saves founded with Moderate or Harsh storms. They form in their real basins and seasons by the calendar, each with a name used in turn: Atlantic and East Pacific hurricanes (Jun-Nov, peak Aug-Oct), West Pacific typhoons (all year, peak Jul-Oct), North Indian cyclones (Bay of Bengal and Arabian Sea, around the monsoon), South Indian, Australian and South Pacific cyclones (Nov-Apr), and winter gales in the North Atlantic and North Pacific (Oct-Mar) and the Southern Ocean (all year, worst in the austral winter). About 120 a year at Moderate (Harsh: half as many again), up to 8 or so at once.
Tropical storms drift west and poleward at about 10-12 knots, then curve away east (and speed up) past their recurve latitude; gales run east at about 25 knots. Each builds up over the first half of its life (3-12 calendar days, a day being 72 s of play) and fades over the rest; its strength at a point is that times how near its core it is (full within 35% of its radius, about 200-500 nm, fading to nothing at the edge).
From company level 6 (with breakdowns), a ship in a storm sails slower (by up to 40% at the core at Moderate, 60% at Harsh) and wears faster (up to 2x / 3x), and its breakdown chance rises the same way. Fuel per mile stays the same (the engines just make less way), so a storm alone never strands a ship that set off with enough fuel. A hurricane, typhoon or cyclone strong enough over a port (85% of full strength at Moderate, 70% at Harsh) closes it: ships there wait in port, and ships bound for it wait 25 nm off it with engines off, until it passes ("Waiting off Charleston for Hurricane Ana to pass"). These waits aren't holds: no red dot, nothing for the player to do, and no random breakdowns while waiting (nor in an icebreaker's convoy). Recovery boats go in regardless.
Warnings in the activity log, for the HQ, hubs and every port a ship is at, bound for or has on its route: a tropical storm heading for one (about 2 calendar days ahead), one closing and reopening, and each ship sailing into a storm.
Wind: everywhere, all the time, following the real prevailing winds by latitude: the north-east (south-east) trade winds in the tropics, the westerlies of the middle latitudes (strongest in the Southern Ocean's roaring forties), the polar easterlies, and near calm in the doldrums and horse latitudes, wandering in direction (up to about 45 degrees) and strength with slow gusty variation over thousands of miles and minutes of play, and wound round every storm (anticlockwise in the north, clockwise in the south), strongest at its core. The same for every player. On the World map it shows as gusts: short pale streaks blowing its way, drifting and fading, none in a calm, more, longer and brighter the stronger it blows. Ships at anchor face into it.
Clouds: drifting cloud over the globe, thicker along the equator and the middle latitudes' storm tracks and thinner over the subtropics, clearing as the map zooms in (from 7 to 24 px a degree) so ships show.
Night and day: the side of the globe turned from the sun is dark, with dusk and dawn a soft band between (a terminator, so one side of the world is in its night while the other has its day). The sun stands over the sub-solar point of the calendar's moment, tilted with the seasons (23.44 degrees); the calendar runs on Greenwich time, so the sun is over Greenwich at 12:00 GMT, the rest of the world an hour on for every 15 degrees east (the birds' nights and the deck crews' watches go by each place's own hour); the top bar shows London time, GMT in winter and BST (an hour ahead) from the last Sunday in March to the last Sunday in October, marked GMT or BST. Two darkenings: 90% of the map art, land drawings, marinas and weather is lost at the darkest, and 60% more of the lanes, ports, labels, birds and ships over them (so the names still read), and over it all the lights: ships' navigation lights (red to port, green to starboard, white at the masthead and stern, each with a halo) and the warm glow of their decks with a few deck lamps, each marina's entrance lights (red and green, haloed), lamps along its quay (a warm glow over the HQ and the industry), a lamp every 5 dock units down each pier (white at its tip), along the basin's walls and round the jetty's arms, its HQ lit (a glow in its company's colour and warm light, its windows lit, more and cooler the bigger it has grown, a few dark; red aircraft lights on its corners from level 6) and each industry building under an orange sodium floodlight with a lamp at each corner of its yard and a few lit windows (all drawn once into the marina's lights item, again when the HQ or industry changes), its town's windows lit over a glow across the town, and its lighthouse sweeping two opposite beams round once every 6 s of play, and, zoomed out past the marinas, the ports' towns as warm glows (7 to 18 px by size band). The ships' and the marinas' lights (lighthouse, entrance, quay) come on under a storm's cloud by day as well, as dark as the cloud is thick; the towns' glow is night's only. Birds already sleep by their port's night. Nothing else changes with the dark.
Ships at anchor in a storm (waiting for a berth, idle, tugs, recovery boats and other service ships) swing and pitch about their anchors, more the stronger the storm there; one over 50% of its strength at the port batters each ship there once, taking 20% of its maintenance ("Sea Otter was battered at anchor off Rome by Storm Ciaran: maintenance down to 64%").
On the World map each storm is part of the sky's cloud, thick and dark (thinned a little as the map zooms in, so the ships under it show): a hurricane, typhoon or cyclone a dense core wound round with dark spiral bands (turning anticlockwise in the north and clockwise in the south, stopping when paused) and a clear eye once strong; a gale a ragged mass of dark rain cloud, longer east-west, with no spiral; lightning flickering in hurricanes, typhoons and cyclones (jagged forked bolts in the eyewall and bands, more often the stronger the storm; gales have none), and its name ("Hurricane Ana", "Typhoon Yagi", "Storm Ciaran") under it when big enough on screen. Before level 6 storms are drawn but harmless. Storms are saved with the game.
Each storm's track shows as a thick grey dashed line (30% opaque): where it has been since it formed (a point every 10 s of play, saved with it; storms from older saves start theirs where they were) and where it will go until it blows out (storms keep a fixed course, so this is exact). Hovering a storm (within half its radius) shows a pointer, makes its track stronger and rings its edge and core with dashed circles; clicking it opens its popup, which follows it and closes when it blows out: Strength (at the center, the core's edge, halfway out and the edge, building up or fading), what it does to ships at its center, whether it closes ports (tropical storms), its Cloud (rings, spiral bands, eye), Size (radius and across), Course (heading and speed), the ships In it now (yours named), Time (how long it has been going and has left, in calendar and play time), where it Formed, and where its basin's storms spawn and when. In multiplayer, joined games keep their own copy of each track (updates leave tracks out).
The Tutorial's Storms tip explains them the first time they act on ships.
Maritime Empire