By John Simpson
January 2020 was slightly below average in rainfall and slightly above average in temperature. I recorded 0.87″ of rain in Central Del Lago and my nine-year average is 1.01.” The Tucson airport recorded 0.65″ and its 30-year average is 0.94.” Most places in the Vail Voice readership area reported between 0.8″ and 1.0.” Much of Tucson to our West and Mescal to our East reported lower 0.5″ to 0.7″ amounts.
On the temperature side, The Tucson airport had day time highs about 1.8 degrees above average and night time lows about 0.3 degrees below average for the month. January 2020 was the 30th warmest since records began in the 1880s. Nothing too exciting, unlike last year when we had two different snow events at the first of the month.
I want take time to discuss how the National Weather Service (NWS) determines rainfall and temperature averages or “normals.” They use the most recent 30-year averages. A quote from the Tucson NWS site states “Climatic normals describe the average of a meteorological value, like temperature and precipitation, over a 30-year period. The United Nations World Meteorological Organization (WMO) established guidelines that climatic normals be calculated using three consecutive 10-year periods ending in the most recent year that ends with the digit 0.” Right now, we are using the 1981 to 2010 normals or averages. After this year is over, early next year will be used to calculate the new 1991 to 2020 normals world-wide. These will be released during Summer of 2021 and will go into effect soon after. The 1980s will “go away” and the 20-teens will replace them in the new 30-year normals. Since the 1980s was the wettest decade in Tucson history and the 20-teens was the warmest decade, the new 30-year average temperatures will be warmer and the new 30-year average rainfalls will be lower, for the most part. This could vary somewhat by month. The Tucson NWS has a great deal of statistics for the past decade and does compare it to previous decades of the 20th century. You can find this data at https://www.wrh.noaa.gov/twc/climate/decadal/Year2010-2019.php.
