Bar chart dynamics
How to read a monthly rain chart

South Florida has two distinct meteorologic seasons:

A 6-month wet season and a 6-month dry season.

How to read a rain chart

Things you should know: (1) The water year begins anew the start of May each year. But it’s not an exact science (i.e. precise point) when they start and end from one year to the next. For example, we classify October as a wet season month even though the afternoon rain showers usually end in early October. And the start of May is probably the swamp’s driest time, yet it’s also the same month, as it approaches June, that the summer rainfall pattern begins. (2) Most of my rainfall charts show background gray coding. That’s the historical statistics as counted from 1983 to present. Why 1983? It was a good year, and most of the SFWMD’s record by basin reaches back that far. Looking at the chart above, the dark gray band is the average range for each month (i.e. between the 25th and 75th %tile) and the light gray is the historic rang (i.e. between the max and min). The white bar in the middle is the normal or median monthly rain. (3) My charts are based on basin-wide rainfall, not local rainfall.

Newspapers calculated rainfall by calendar year. (They are wrong. How dare them!) They also calculate rainfall for an individual gage in Ft. Myers and Naples (The shame!).

In summary, numbers mean more if you can frame them against the expected values and ranges that came before. And its by water year, not calendar year, that we tally rainfall totals in south Florida.

Why 1993?
Statistics from 1993 to present

Most of my hydrographs …

Are based on historical stats starting in 1993.

Hydrographs pop when you add in the statistical record as a backdrop

The reason(s)?

For one I wanted to be consistent across the board with all the hydrographs I created. To do that I had to pick a date, and 1993 jumped out as coinciding with the modern era of water management. It also seemed to be a date that most stations had accurate data for. Many stations go back further in time, and I like looking at that data, too. But 1993 is a breakpoint beyond which quite a few index wells don’t have data.

Keep in mind I started created my hydrographs in the early 2000s (also called the “aughts.”) The data streams are now nearly twice as long as when I got started.

In summary, I picked 1993 to be consistent, and so that my observations were framed relative to a common statistical measuring stick. To be sure, I like slicing and dicing the data for decadal comparisons. But for my go-to charts, I also base them on the post-1993 record.