Like people, air quality forecasts aren’t perfect

In California’s San Joaquin Valley, yesterday (May 7, 2018) was one of the more interesting days. When I awoke, what I noticed immediately upon looking out my front window was a blue-colored sky. And upon my noticing that, I decided what I would do was to work in the yard outside.

The temperature for much of the day was on the cool side, or, what I deemed to be cool. Although yesterday in Fresno, according to the local weather reporting on television, Fresno did reach a high of 89.

What was interesting was that the air in Fresno County based on San Joaquin Valley Air Pollution Control District (SJVAPCD) air-quality forecasting data, forecasted was an Air Quality Index of 108 which would put the air in the “Unhealthy for Sensitive Individuals” range. In other words, air that is unhealthy to breathe for people with “sensitivity” to air quality in that range such as children, the elderly and people with existing health issues.

After I retired and retreated to the indoors from my yard-working activities at around 4 p.m. I cleaned up, had a bite to eat and then waited for the local news broadcast to try to learn about both the weather and air quality related info.

I heard more than once how blue the sky was. I then heard the air quality forecast for tomorrow which was expected to be in the “Moderate” range.

But, what I was really after was the quality of yesterday’s air. So, I went online, visited the SJVAPCD Web site (, clicked on “Fresno County” on the “Air Quality Forecast” over on the right-hand side of the page and what was displayed was a color bar with a black arrow pointing to the orange color, which is indicative of a range of air that, for “sensitive individuals,” is unhealthy to breathe.

The next step was to move my cursor pointer over to the left-hand side of the page and click on the “Air Quality Forecasts & Data” provision, and when doing this, a list of options is displayed. The provision I opened was “Daily Forecast.”

To my surprise …

Lo and behold what I discovered was surprising: Fresno along with the Valley portion of Kern County showed orange with Fresno’s accompanied by the number “108” and Kern’s accompanied by the number “119.”

Using my mouse pointer and positioning it over Fresno opened up a corresponding box with the following wording: “Fresno, Forecast: Unhealthy for Sensitive Groups; Pollutant: O3 [ozone] (73 ppb) [parts per billion].

Ordinarily, this tells me what I want to know. But not in the case of yesterday. So, I performed a more specific search using “RAAN” a provision known as the “Real-time Air Advisory Network” which provides air quality information in real-time. This “RAAN” can be accessed on the page in at least two places: On the left and right.

Once there, I scrolled down to the “Fresno” section. Clicking on the “North Fresno (Ozone only)” list item which provides air-quality data for North Fresno, in fact, not only did I find for May 7, 2018 air that for most of the day was in the range of “Good,” but it was only between the hours of 6 and 7 p.m. that ozone in the air was outside of that range reaching a high of 62 ppb or air of “Moderate” quality. Data, meanwhile, for 5 a.m. is missing but presumably air during this time for North Fresno was good also.

So, I continued to search the various Fresno County monitor-location selections: Clovis, Southeast Fresno, Central Fresno, Parlier, and Tranquility. Not one place did I find air that was in the orange zone. Nowhere could I find indications for any of the Fresno County-based monitor stations where a spike was in that “Unhealthy-for-Sensitive-Individuals” range. The highest was Parlier which registered 67 ppb and that was at 6 p.m. and also in the “Moderate” range.

The forecasts 411 

I am thinking: wow! amazing! The forecast was wrong?!

When you think about such though, this should not be all that surprising.

That said, however, I suppose that is the nature of forecasts. That forecasts do provide reasonable predictive data, whether for weather, air quality, economic or financial data, a forecast is nevertheless still a forecast, and bottom line, that piece of information should at all times be kept first and foremost in mind.

I guess in my choosing to work outside, the determining factor was the color of the sky, blue, along with, of course, the light northwesterly breezes.

Less sophisticated, I’ll admit, but a “good” indication – in this instance – nonetheless.

Image above: National Oceanic and Atmospheric Administration

– Alan Kandel