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Hazard: Storm!

This article originally appeared in the April/May 2015 issue.

“It was a dark and stormy night...”

So begins Edward Bulwer-Lytton’s novel Paul Clifford. The line has been roundly mocked for its banality, but it sets an immediate scene in the reader’s mind, one of raw, primal forces, darkness and gloom, and nature’s power. Storms occupy outsized places in popular literature and in the human zeitgeist. Their place in role-playing games, Traveller in particular, are no exception. But while a common and necessary part of nature, storms rarely make appearances in games.

Why should the referee include a storm? Storms add drama and another complication to the heroes’ mission. They serve as wild, natural counterpoints to the shiny, well-behaved environments that often accompany Imperial technology. They add a dimension of unpredictability, turmoil, and a sense of urgency. Additionally, a storm can make for a great adventure or series of adventures in its own right. In short, storms bring excitement, which is the meat and drink of every gamer.

That said, Traveller lacks rules for creating and gaming storms. We shall set out to correct this oversight. The rules set down here will focus mostly on the effects storms have on the PCs and their activities, with only as much discussion of the mechanics behind storm formation and propagation as necessary.

Author’s Note: while based on real-world meteorological science, the concepts presented here are part of a game. Nothing written here is intended to be used in real-life weather situations. Readers are directed to their respective national weather organizations or meteorological institutes for more information.

The Making of Storms

A storm is an atmospheric disturbance which affects both air and ground. They can be violent. Regardless of the type of storm, the mechanisms behind its creation can be boiled down to a few common items: low barometric pressure; atmospheric lift; atmospheric instability; and usually moisture. Other factors include season (dictated by the world’s axial tilt), overall world climate, the prevailing atmospheric pressure (thin, standard, or dense); and the world’s hydrographics percentage.

Every planet possessing an environment other than hard vacuum has some type of weather; storms are a common element. For example, Mars, in the Terra system (Solomani Rim 1827), has suffered planetwide dust storms, despite having a very thin atmosphere.

Worlds with exotic atmospheres (Atmosphere type A+) have similar storm ingredients, except their clouds are not composed of water, but far more exotic compounds. These compounds are almost always toxic. The most common are ammonia, methane, carbon dioxide, hydrogen and sulfur. If water is present, it's usually in very small quantities. Storms on such worlds—especially large ones—generally take the form of ferocious winds, chemical sleet, and lightning. Such storms can be very long-lived; Jupiter’s Great Red Spot has been raging since before Gian Domenico Cassini first observed it in a.d.1665 (-2803 TI).

Creating the Storm

The following storm creation system is designed to be simple and quick. Rather than go into detailed meteorological details, we will use common storm characteristics and their effect on the heroes, combining the results creatively to describe various types of storm. Several common conditions can affect PCs: strong winds, poor visibility, hindrances to movement, and debris. Duration is also a factor.

To begin, throw 2D-2 (optional DMs: -1 for Atmosphere 5-; +1 for Atmosphere 8+; the world’s Size/5, dropping fractions). Treat 0 as 1 for purposes of calculation in the formulae below. The result represents all of the following:

Example: the referee wants to create a storm. She throws 2D-2 and gets 8; the storm is quite powerful (perhaps the equivalent of a Severe Thunderstorm on Terra) and since the world is similar to Terra, she simply rules that it is indeed a thunderstorm. She throws 3 (on 2D) for the storm’s duration and plugs it into the above equation: 2D(i + 10), resulting in 3(8+10) = 54 minutes. She rules that this will be one large, slow-moving tempest. The winds clock in at 72 kph (12 kph8); the referee decides that these are gusts, not sustained winds. Those same winds make the DM to fly -8 (-2 for a fully streamlined vehicle, or -16 for anyone foolish enough to try flying exposed). The penalty for visibility, movement and each team member’s DEX are all -4. Finally, the referee rules that hits come from flying debris; any PC leaving their vehicle has an 80% chance (a throw of 5+) every combat round of being hit for Foil damage.

The referee may “fine-tune” the storm by determining each value separately, beginning with the Intensity throw and applying the applicable formulae for each throw.

The referee should describe the storm based on the die results, the world’s climate, and common sense. For example, the storm in the above illustration could be a blizzard on a frozen world. The same modifiers (Intensity, wind speed, movement and visibility penalties (from blowing snow), hits risk (perhaps manifesting as exposure and hypothermia) and DEX penalties (slippery ground, or hidden obstacles) would apply.

The accompanying table may be useful in helping provide a description.


Storm Type Storm Component
  Wind Rain Hail Lightning Sleet Snow Particulates Flooding
Dust storm/Sandstorm     ()      
Thunderstorm       ()
Electrical Storm   ()        
Ice Storm*       ()      
Rainstorm             ()
Exotic (Size/Atmosphere A)     --      
* Precipitation falls as rain, but freezes on contact with a surface
** Indicates a storm that must be specially imposed by the referee
() Indicates an uncommon or rare component
-- Indicates sleet is not composed of water, but other—possibly toxic—compounds

Special Storms

Some storms should be specially imposed by the referee: tornadoes and cyclones (tropical storms, hurricanes, and typhoons.)

Tornadoes: If the referee rules that an Intensity 10+ storm is tornadic, (s)he should throw an additional 1D-1, which represents all of the following:

As with the process above, the referee can determine the tornado’s characteristics separately. This may be desirable anyway, as tornadoes are notoriously unpredictable storms that often violate established meteorological conventions.

Example: It’s the heroes’ unlucky day; the storm has spawned a tornado! The referee—after calculating the parent storm’s base characteristics—throws 1D for a 4. The twister is an EF3, quite capable of tossing the PCs’ ATV like a toy. (If she needs a wind speed, consulting a published Enhanced Fujita scale shows the tornado packs winds of 218-265 kph.) She multiplies 4275 and gets the funnel’s width: 1,100 meters. Finally, she multiplies 422.4 and finds that it is moving at 67 kph and will be on the ground for 4 minutes (16 combat rounds.)

Cyclones (tropical systems, hurricanes, etc.): For these disturbances, the procedure is similar. Throw an additional 1D-1, representing all of the following (0 becomes 1 for purposes of calculation):

The duration of a cyclone is always 12 hours, divided into 2 periods of 6 hours bookending a calm interval (the storm's “eye”) of 6D minutes. Note that ordinary storms do not become cyclones; these disturbances build during several days at sea and last 2D+5 days.

After the Storm

Storms usually have socioeconomic impact out of proportion to their area of direct effect. Besides the physical devastation they bring, they affect an area’s economy, society, and environment.

The economic impact can be devastating and long-term. Smashed businesses mean fewer places for citizens to shop or work. Destroyed dwellings mean homelessness and refugees. Particularly bad storms can wipe out entire communities, forcing migrations. Local governments and Imperial agencies struggle to reestablish communications, commerce, and order. Outside aid is commonly required.

Social disruption is frequent. Looters and con artists find storm-ravaged areas easy pickings. Accepted mores go out the window as desperate victims do whatever is necessary to survive. Aid workers may, subtly or not, try to influence storm victims to their own views. Such workers may in fact be composed of organizations or troops loyal to the local government. Oppressive regimes may deny relief to victims they deem rebellious as a tool of control or punishment.

Disease is also frequent. Devastated and strained medical services usually find themselves combating hard-to-stop epidemics. Parasitic and bacteriological contamination of food and water also takes a toll. Psychologically, survivors may suffer Post-Traumatic Stress Disorder, thus overwhelming any remaining mental heath services.


There are many ways in which the referee can include a storm in the adventure. The easiest decision is when to include it; either during the group’s current mission, or before. This determines whether the group is struggling for survival or helping pick up the pieces.

The referee also decides whether the storm is a random encounter, mere background color; or the main thrust of the adventure. Featuring the tempest as the focus of the adventure almost always puts the adventurers amidst the violence. The aftermath can be almost as dangerous, for the reasons stated above.

Some adventure themes lend themselves well to stormy action:

Ship’s Locker

Besides the cold weather clothing and filter mask mentioned in Book 3, other gear is useful during stormy weather:

Conductive Suit:
(TL 8) Cr300. An insulated garment with a metallic mesh covering its exterior. Provides protection against electric currents, including lightning strikes; against lightning, however, the suit is only equivalent to Ablat (Book 1). Weighs 1.5 kg.
De-Icing Spray:
(TL 6) Cr25. A canister of chemical de-icing agent. Each application melts one square meter of ice up to 25cm thick. Ten applications. Weight negligible.
(TL 4) Cr25+. A waterproof outer garment made of cloth coated with rubber or other waterproof materials. May come with a hat made of the same material. Weighs 0.1 kg.
Weather Station:
(TL 6) Cr1,200. A dedicated package of equipment for measuring and forecasting weather and storms. Typically includes an anemometer, a barometer, a thermometer, a precipitation gauge, and a hygrometer, Advanced models include radar and can be linked to a computer. Fully portable at tech level 8+. May also be mounted on a starship at no weight or cost. Weighs 3 kg (portable).
(TL 7) Computer software that allows for detailed analysis and prediction of weather systems. Typically found aboard IISS Donosev survey vessels. 1 space, Cr300,000.