Tri-Cities drier and warmer in updated NOAA weather averages being released

When discussing weather, there is a lot of comparison to “average” or “normal” conditions in a given place. These represent an expected temperature, precipitation, or other value averaged over a 30-year period for stations around the world. The National Oceanic and Atmospheric Administration (NOAA), parent agency of the National Weather Service (NWS), calculates these averages for nearly 10,000 stations around the United States. Averages are updated once per decade, with the previous dataset covering 1981 to 2010. On May 4, NOAA will formally release new numbers for 1991 to 2020. A discussion of why the climate is changing lies outside the scope of this article.

CHANGES FOR THE TRI-CITIES

The general trend for the Tri-Cities is drier and somewhat normal, but the change varies seasonally. This section will focus on averages for the Tri-Cities Airport in Pasco. Averages for other sites around the United States can be found at this link.

The biggest temperature change comes during the summer, with both the average low and average high in July raising by more than a full degree. Interestingly, while annual average temperatures have increased some winter averages have decreased. Both lows and highs for January, February, and March are slightly cooler, but this cool down is smaller than the warming trend found in other months.

Nine out of twelve months saw a decrease in average precipitation. Previously the Tri-Cities had three months with average rainfall above one inch. That has been cut down to two. During the 1981-2010 period, the driest month was August with 0.27 inches of rain. The August average for 1991-2020 didn’t change, but August is no longer the driest month in the Tri-Cities. July’s average dropped from 0.28 to 0.15 inches. The two months that experienced an increase in average precipitation only did so by a hundredth of an inch.

The Tri-Cities gets a lot less rainfall during the winter than in previous years. Given the nature of weather disturbances coming off the Pacific Ocean, the wettest months fall in late autumn and winter. With many of these months losing around 0.20 inches with the new update, annual precipitation at the airport has dropped over an inch from 8.83 to 7.62 inches. At face value, an inch of rain does not seem like a lot of water, but when the region is working with less that 10 inches to start off every drop counts.

The Tri-Cities is often referred to as a desert region, and by some measures it is. Arguably the most common climate classification scheme is the Köppen climate classification. Under Köppen calculations, the Tri-Cities previously came in as cold semi-arid with small areas of cold desert around Mattawa. Much of the Columbia Basin was close to the cold desert classification, however, and with slightly drier and warmer average conditions the cold desert zone has expanded to reach from the Tri-Cities to near Mattawa with small (but larger than before) sections of desert near George.

Looking at things from a layman’s perspective, a difference of less than a degree of warmth can seem minimal. It’s true that it’s nearly impossible for an individual to perceive a one degree change in temperature. That said, small differences can mean a lot for energy usage, growing season length, and irrigation needs.

With the old dataset, the Tri-Cities averaged 8 days above 100 degrees per year. In the decadal update, that value is now 10. The number of days reaching at above 85 degrees increased by five per year. Again these values seem minimal, but this means more electrical usage for air conditioning and other things that utility companies that serve tens of thousands of homes need to account for in their planning.

Slightly warmer average temperatures provide a growing season that’s a few days longer. If farmers are planting earlier, irrigation districts need to have their systems up and running earlier. Furthermore, with less rain to depend on irrigation districts need to be prepared for higher water consumption. These are just a few of the effects of a drier and slightly warmer climate. Not all effects are bad, of course, but all of them need to be considered to keep the economy functioning efficiently.

HISTORY AND METHODOLOGY

Global use of 30-year averages began in the 1930s when the predecessor to the UN’s World Meteorological Organization instructed member agencies to construct the dataset. Later it was determined that these should be updated every 10 years. Doing so allows agencies to add new stations to the database. Furthermore, decadal updates allow scientists, government leaders, and the general public to adapt to changes in the climate over time. There are numerous ways to construct weather averages, but in this pre-computer era this was likely one of the simplest. Having one standard way of calculating averages that’s agreed upon by every weather agency is important.

Without this standard, different countries might use vastly different methods which could come up with numbers that aren’t comparable across international boundaries. This wouldn’t matter much in settings like the American heartland, but consider what would happen if the United States and Canada used a different calculation standard for their averages. If that were the case Bellingham, Washington and Vancouver, British Columbia could have official normals that are several degrees apart, despite only being about 40 miles from each other.

With modern technology, it is certainly possible to calculate averages in a different way, but doing so would require all 193 members of the World Meteorological Organization to agree on a new method. This would take years and probably isn’t worth the trouble.