Weather Tables

[Edgewood]

Hey all,

I'm looking for either a program or a method to come up with realisitic weather tables for my homebrew. Preferrably, the program would be campaign neutral and would offer a wide variety of weather types, everything from clear sunny days, to torrential rainstorms or thick blinding coastal fog, and would also take into account thngs such as different zones such as arctic, temperate, tropical, etc...

I've been searching the internet but I'm finding only scant programs that only do so much or are very specific to a gameworld. Any ideas??

 

[Lanefan]

I dreamed up my own a long time ago; it's not that difficult.

Instead of plugging a bunch of numbers in here, I'll just give the basic ideas and you can then design your own.

First thing is, you need to know what is about "normal" for the location and season; you should quasi-build this in during world design, because without it any weather table becomes meaningless. A vague idea is all you need...OK, it's a west coast in the fall; normal is going to be rain to the north, cloudy to the south, low-high temp's about 5-15C, winds probable.

Next, come up with a series of % tables for each general climate zone (arctic, temperate forest, plains, desert, coast rainforest, desert, etc.) to determine the general conditions for a given day. This might be all you need if weather is not important, except:

You'll need - more often than you might expect - a table for windspeed and direction. Direction's easy - a d8 will do. But if you want to get accurate with windspeed you have to fudge a bit to suit your conditions roll. Example: if your conditions roll says "fog" and your windspeed roll says 35 mph, you've got something that cannot usually exist...try again.

Between those two, you should be mostly set. However, if you're a weather geek like me and want to get really carried away:

Next, come up with a table (very small one) to determine if conditions are improving, remaining the same, or deteriorating.

And one to determine if the wind is increasing, staying the same, or decreasing.

Then, come up with a % table for temperature vs. normal (very hot, hot, warm, normal, cool, etc.); oh, and you'll need to know if the temp. is rising, falling, or staying put in relation to what you've decided is "normal".

You'll find, after doing this the long way for a while, you get pretty adept at coming up with weather conditions on the fly without going through all the rolls...just a few key ones backed by whatever scene you want to set.

Oh, and don't forget to factor in corner cases like dust storms (where appropriate), ash falls from distant volcanic activity, even eclipses if you haven't figured out their frequency in other ways...

Lanefan

 

[Olaf the Stout]

I have used WeatherMaster before for my campaigns when I wanted weather to be important. It costs $19.95 but you can get a free 30-day trial (using the full version with all the features) to see what you think of it first.

It is totally campaign neutral and even supports worlds with different axis tilts or multiple suns. Give it a go.

Olaf the Stout

P.S. I'm not associated with the company at all, just a happy customer.

 

[Aus_Snow]

Campaign Planner 3, from Ronin Arts, has a neat system for this, among other things. It's got a separate page with charts and forms for 'Hot', 'Temperate' and 'Cold' climates.

I've found them all to be pretty useful, actually. They have forms that can be filled in Acrobat Pro [and some other programs], or they can be printed.


But yes, of course, with a bit of work, you can put together your own weather charts for d20.

 

[Edgewood]

Here's a website I found with a pretty good online program. It's free to use. Check it out. I might start to use this and use some of the ideas from above. Thanks guys.

http://direpress.bin.sh/tools/weather.html

 

[philreed]

I've found them all to be pretty useful, actually.

Always good to hear. The Campaign Planners can be found here.

 

[The Lost Muse]

I just use real-world weather reports for various locations, and keep campaign time roughly analogous with irl claendar time.

 

[Edena_of_Neith]

If your campaign is set in the Temperate Zone, remember that the area doesn't really have it's own weather: it's always importing Someone Else's weather.
This Someone Else's Weather is brought in through Fronts. Think of Battle Fronts, because that's where the idea of weather fronts comes from.
A warm front comes up from the southwest or south or rarely, from the southeast. A cold front comes from the west or northwest, but can come from the north, northeast, or even southwest (chasing the warm front.) A warm front brings temperatures warmer than normal for the area, the cold front brings temperatures colder than normal for the area, and everyone grumbles constantly about it being either too hot or too cold.
This push and pull of fronts is endless and inexorable and most annoying. Winds howl and roar from the south after a warm front passes, then howl even faster after the cold front passes. Great soaking rains occur ahead of the warm front, then severe thunderstorms occur ahead of the cold front. After the cold front passes, grey skies and drizzle are followed by cold clear nights.
In the winter, rain (or worse, icestorms) and rain and snow occur north of the warm front, rain occurs ahead of the cold front, and arctic blasts follow the cold front. If the area is north of the low pressure center (where the warm front and cold front start) then a snow storm occurs.

Low pressure centers are the places where, as noted, cold fronts and warm fronts start and extend away. Think of them as anchors.
Where do low pressure centers go?
This is dictated by roaring winds aloft known as the jet stream. The jet stream carries low pressure centers along it, slowly in the summer, and swiftly in the winter. The jet stream is further north in the summer, further south in the winter. And the warm air is warmer, the cold air less cold, in the summer. In winter, the warm air is less warm ('hey, it's up to 0 Celsius! How nice!') and the cold air much colder.

In Lexington, Kentucky, a typical temperate climate occurs. Here are averages for that area:

January: highs in the 30s, lows in the 20s, average (varies greatly)
February: highs in the 30s, lows in the 20s, average (varies greatly)
March: highs in the 40s, lows in the 20s, average (varies greatly)
April: highs in the 60s, lows in the 40s, average (varies considerably)
May: highs in the 70s, lows in the 50s, average (varies some)
June: highs in the 80s, lows in the 60s, average (varies little)
July: highs in the 90s, lows in the 70s, average (varies little)
August: highs in the 90s, lows in the 70s, average (varies little)
September: highs in the 80s, lows in the 60s, average (varies some)
October: highs in the 70s, lows in the 50s, average (varies considerably)
November: highs in the 60s, lows in the 40s, average (varies greatly)
December: highs in the 40s, lows in the 20s, average (varies greatly)

In Minneapolis, a harsh temperate climate occurs:

January: highs in the 1s, lows in the -10s, average (varies tremendously)
February: highs in the 1s, lows in the -10s, average (varies tremendously)
March: highs in the 20s, lows in the 1s, average (varies tremendously)
April: highs in the 40s, lows in the 20s, average (varies greatly)
May: highs in the 60s, lows in the 40s, average (varies greatly)
June: highs in the 80s, lows in the 60s, average (varies considerably)
July: highs in the 80s, lows in the 60s, average (varies considerably)
August: highs in the 80s, lows in the 60s, average (varies considerably)
September: highs in the 70s, lows in the 50s, average (varies greatly)
October: highs in the 50s, lows in the 30s, average (varies greatly)
November: highs in the 30s, lows in the 10s, average (varies greatly)
December: highs in the 10s, lows in the -1s, average (varies tremendously)

In Atlanta, a warm temperate climate exists:

January: highs in the 50s, lows in the 30s, average (varies greatly)
February: highs in the 50s, lows in the 30ss, average (varies greatly)
March: highs in the 60s, lows in the 40s, average (varies greatly)
April: highs in the 70s, lows in the 50s, average (varies considerably)
May: highs in the 80s, lows in the 60s, average (varies slightly)
June: highs in the 90s, lows in the 70s, average (little variation)
July: highs in the 90s, lows in the 70s, average (little variation)
August: highs in the 90s, lows in the 70s, average (little variation)
September: highs in the 80s, lows in the 60s, average (varies slightly)
October: highs in the 70s, lows in the 50s, average (varies considerably)
November: highs in the 60s, lows in the 40s, average (varies considerably)
December: highs in the 50s, lows in the 30s, average (varies greatly)

 

[Edena_of_Neith]

Thus, you don't need weather tables. You can simply declare to yourself:

- A warm front has pushed through the area, or:
- A cold front has pushed through the area.

Consider these additional things:

The jet stream, 5 miles high, roars along at hurricane force, is 100 miles wide or wider, and flows around the entire planet. It writhes and coils and alters it's course like a snake trying to slither across pavement.
Sometimes the jet stream will go way north in a curve, and that's known as a ridge. Sometimes the jet stream will go way south in a curve, and that's known as a trough.
* As a general rule, it is always colder north of where the jet stream happens to be at the moment, regardless of any other factors. *

I said the Temperate Zone got Someone Else's Climate. To the north is the subarctic and the arctic, and the cold air over those regions comes south. To the south are the tropics and subtropics, and warm air over those regions comes north. In the winter, the cold air is colder and the warm air less warm, and in the summer the cold air is less cold and the warm air is warmer, but the two great regions of air - cold and warm - are always there.
Caught between them, the jet stream writhes and twists and bows, creating ridges and troughs (and thus heat waves and cold waves), with warm air masses (led by warm fronts) and cold air masses (led by cold fronts) following each other in mad succession, like armies of dragons fighting in a constant running battle around and around the globe, the war never ending (this mad succession of air masses would do credit to Lord Foul's Sunbane, if you've read the books of Stephen Donaldson.)

Sometimes, the jet stream is blowing one way (from west to east), cold air is coming from the northwest towards the southeast, and warm air is roaring from the southwest to northeast. The spring sun is shining down strongly, producing intense warm updrafts.
The result is that calamnity we know as the tornado. All those winds blowing in different directions at different altitudes start a thunderstorm cloud rotating, and then Bad Things happen.
Add in a chinook effect - strong drafts of warm dry air roaring down the slopes of a mountain range, the chinook blast crashing into the mess of conflicting winds I just described, and you have a Tornado Alley. Such an area has mass outbreaks of tornadoes, with tornadoes possible every month of the year.

If a cold front is passing over a desert area, the strong surface winds behind the cold front often produce sandstorms.
If cold air is blowing over warm lakes, it produces the Lake Effect: clouds downwind of the lake, along with rain ... or ungodly amounts of snow in the winter.
If there is a mountain range, it tends to rain on the windward side and produce temperate rainforests, while on the leeward side you have a desert.
If you have a deep valley amidst mountains on all sides, air coming down into that valley can compress and warm and produce astonishing heat. Or if there is moisture, icestorms as the air coming over the mountains is warm, but cold air is trapped down in the valley (during the cold months.) Or fog in the winter, as frost grips the valley during long winter nights.

If your setting is rich in mountain ranges - as the Forgotten Realms region of Faerun is - you could have drastic changes in the climate from one local area to another, due to the effect of the mountains.
The jet stream still roars overhead, high in the sky, but the mountains lower down mess up the climate in a big way for the locals.

 

[Edgewood]

If your campaign is set in the Temperate Zone, remember that the area doesn't really have it's own weather: it's always importing Someone Else's weather.
This Someone Else's Weather is brought in through Fronts. Think of Battle Fronts, because that's where the idea of weather fronts comes from.
A warm front comes up from the southwest or south or rarely, from the southeast. A cold front comes from the west or northwest, but can come from the north, northeast, or even southwest (chasing the warm front.) A warm front brings temperatures warmer than normal for the area, the cold front brings temperatures colder than normal for the area, and everyone grumbles constantly about it being either too hot or too cold.
This push and pull of fronts is endless and inexorable and most annoying. Winds howl and roar from the south after a warm front passes, then howl even faster after the cold front passes. Great soaking rains occur ahead of the warm front, then severe thunderstorms occur ahead of the cold front. After the cold front passes, grey skies and drizzle are followed by cold clear nights.
In the winter, rain (or worse, icestorms) and rain and snow occur north of the warm front, rain occurs ahead of the cold front, and arctic blasts follow the cold front. If the area is north of the low pressure center (where the warm front and cold front start) then a snow storm occurs.

Low pressure centers are the places where, as noted, cold fronts and warm fronts start and extend away. Think of them as anchors.
Where do low pressure centers go?
This is dictated by roaring winds aloft known as the jet stream. The jet stream carries low pressure centers along it, slowly in the summer, and swiftly in the winter. The jet stream is further north in the summer, further south in the winter. And the warm air is warmer, the cold air less cold, in the summer. In winter, the warm air is less warm ('hey, it's up to 0 Celsius! How nice!') and the cold air much colder.

In Lexington, Kentucky, a typical temperate climate occurs. Here are averages for that area:

January: highs in the 30s, lows in the 20s, average (varies greatly)
February: highs in the 30s, lows in the 20s, average (varies greatly)
March: highs in the 40s, lows in the 20s, average (varies greatly)
April: highs in the 60s, lows in the 40s, average (varies considerably)
May: highs in the 70s, lows in the 50s, average (varies some)
June: highs in the 80s, lows in the 60s, average (varies little)
July: highs in the 90s, lows in the 70s, average (varies little)
August: highs in the 90s, lows in the 70s, average (varies little)
September: highs in the 80s, lows in the 60s, average (varies some)
October: highs in the 70s, lows in the 50s, average (varies considerably)
November: highs in the 60s, lows in the 40s, average (varies greatly)
December: highs in the 40s, lows in the 20s, average (varies greatly)

In Minneapolis, a harsh temperate climate occurs:

January: highs in the 1s, lows in the -10s, average (varies tremendously)
February: highs in the 1s, lows in the -10s, average (varies tremendously)
March: highs in the 20s, lows in the 1s, average (varies tremendously)
April: highs in the 40s, lows in the 20s, average (varies greatly)
May: highs in the 60s, lows in the 40s, average (varies greatly)
June: highs in the 80s, lows in the 60s, average (varies considerably)
July: highs in the 80s, lows in the 60s, average (varies considerably)
August: highs in the 80s, lows in the 60s, average (varies considerably)
September: highs in the 70s, lows in the 50s, average (varies greatly)
October: highs in the 50s, lows in the 30s, average (varies greatly)
November: highs in the 30s, lows in the 10s, average (varies greatly)
December: highs in the 10s, lows in the -1s, average (varies tremendously)

In Atlanta, a warm temperate climate exists:

January: highs in the 50s, lows in the 30s, average (varies greatly)
February: highs in the 50s, lows in the 30ss, average (varies greatly)
March: highs in the 60s, lows in the 40s, average (varies greatly)
April: highs in the 70s, lows in the 50s, average (varies considerably)
May: highs in the 80s, lows in the 60s, average (varies slightly)
June: highs in the 90s, lows in the 70s, average (little variation)
July: highs in the 90s, lows in the 70s, average (little variation)
August: highs in the 90s, lows in the 70s, average (little variation)
September: highs in the 80s, lows in the 60s, average (varies slightly)
October: highs in the 70s, lows in the 50s, average (varies considerably)
November: highs in the 60s, lows in the 40s, average (varies considerably)
December: highs in the 50s, lows in the 30s, average (varies greatly)

Just for all of that info, I'm giving you 5,000,000 XP.