JJ 41 gives us the Weather Modifiers by Climate and Season table. I’m using it to generate the next year’s weather on Gabor Lux’s Fomalhaut map, which includes a region called Kushala that looks to me like a good candidate for the Weather Modifier’s Af Koppen Code category, Tropical Rainforest.
While entering Precipitation values I noticed that the modifiers are all negative. Is this correct for Tropical Rainforest? Maybe I am misunderstanding how to use the table. If you read this, thanks for your time and consideration!
1 Like
Rainforest generally corresponds to Koppen code Af or Am. Af has precipitation modifiers ranging from -1 to -3 by season, and is defined (elsewhere) as receiving at least 2.4” of precipitation per month. If you compare to the Precipitation table, results of 10+ are “Rainy”, with at least 1” of precipitation per day; 7-9 are “Drizzly” with at least 1/4” of precipitation per day.
With the average -2 modifier, there is thus a 25% chance each day of Drizzly weather, and a 2.78% chance of Rainy weather. Taken across a 30 day month, that yields an expected 2.7” of precipitation at the minimum rainfalls; the actual value could be considerably higher if it trends above the minimums.
So yes, the modifiers being mostly negative is intentional – the table is calibrated such that a 0 adjustment ends up with quite a lot of rain in practice. There is one notable exception, in that Am has a +4 modifier in summer, which will lead to constant and torrential downpours (appropriate for tropical monsoons).
Thank you so much for your response! I half expected I just did not appreciate the reality reflected in the numbers and your explanation restores my confidence in the table. It is a privilege to be able to interact with game designers in this way. Thanks again!