Sep 10, 2013

When Big Rain Days strike

When do Big Rain Days (BRDs) occur in south Florida?

We've had four of them so far this year.

The bar chart above shows the monthly distribution of South Florida's Big Rain Days (BRDs) from 1992 to present. Definitions: A Big Rain Day is formally defined as any day in which an average of an inch or more of rain fall across all of south Florida. That may not sound like much at first, as any single rain gage could record multiple inches during a really good local downpour, but to have an average of an inch fall across the entire south Florida peninsula is a regionally significant (and rare) rainfall event.

The long-term annual average is five.

Does that mean we're due?

The above calendar chart shows the full history of South Florida's Big Rain Days (BRDs), from 1992 to present.  BRDs are shown as big rain drops and scaled according to the size of the event. Also shown are Intermediate Rain Days (IRDs), i.e. the smaller blue circles, and No Rain Days (NRDs). NRDs are any day in which an average of under 0.05 inches of rain fell across all of south Florida.  Not surprisingly, NRDs are the norm during the winter and spring dry season and IRDs are the norm during the summer.  BRDs are rare in comparison.


September and October have reputations for being BRD Months.

But October is also the month that we can expect a pretty good string, i.e. multi-month span, of No Rain Days (NRDs) to begin.

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