BLOG: Is that what normal means? - | WBTV Charlotte

BLOG: Is that what normal means?

CHARLOTTE, NC (WBTV) -

Saturday, we finally got rain at the airport – a little over half an inch, in fact! However, we’re still below normal on precipitation for the year. We all know that.

The question is – what is normal? Not the number – but what does “normal” really mean? It may not be what you think.

“Normal precipitation” is the average of the precipitation values over a 30-year period. It goes back to math class. Remember how to take averages? Add up how much rain we’ve gotten from January 1 – August 16… for each of the past 30 years. Then divide by 30. Seems easy enough – but I find it easier to take the National Weather Service’s word for it. If it says we’re 6.78” behind on rainfall, that means that we’re that much below the average. It doesn’t mean that every year we should get a certain amount of rain and we haven’t gotten enough this year.

Each year can be quite variable. Some years we get a lot more rain and other years we get a lot less. The average takes out the extremes and gives us a middle of the road value, rather than a target.

A better indicator of where we stand is the Drought Index. At this point, most of us in the WBTV viewing area range from “Abnormally Dry” to “Severe Drought” level. There is a team of actual humans who asses these things that you will find on the US Drought Monitor’s website:

Short-term drought indicator blends focus on 1-3 month precipitation. Additional indices used, mainly during the growing season, include the USDA/NASS Topsoil Moisture, Keetch-Byram Drought Index (KBDI), and NOAA/NESDIS satellite Vegetation Health Indices. Other indicators include groundwater levels, reservoir storage, and pasture/range conditions.

This should be more worrisome than being below average since it indicates our topsoil moisture, groundwater and reservoir storage levels are low. Those are real reasons to conserve water.

The good news is that in the extended forecast, most days have at least a chance for rain. It doesn’t mean we will all get rain every day – but we have a chance. At this point, that’s a step in the right direction!

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