TUCSON, Ariz. — With Monsoon now in full swing in Arizona, many are wondering: What's monsoon going to look like this year?
There's no exact science to figure out how monsoon will perform year-to-year, but we do have some good ways of getting a rough estimate of what monsoon will look like in Tucson in 2020.
One of the best ways of figuring out the monsoon forecast is looking back at historical trends. It's an important time of year for the desert -- monsoon produces over half our average annual rainfall each year. August is the month that produces the most rain in Tucson -- about 2.39 inches on average.
On average, Tucson sees about six inches in monsoon rainfall each year. The wettest monsoon ever recorded was in 1964 with 13.84 inches, and the driest was in 1924 with 1.59 inches. There have been five times since the year 2000 that we've seen less than five inches of rain during monsoon.
Many will remember 2019 as a dry year for monsoon -- we barely made it over five inches of rain last year. That may have been partially due to our cool, wet spring.
Look at the tropics
Some say that an El Nino year produces a better monsoon, but the truth is that it doesn't have much of a direct effect. Indirectly, however, it can create an increased number of tropical storms that make their way from the eastern Pacific into Arizona.
This year, sea surface temperatures are close to average and we're expecting neutral conditions through monsoon in Arizona.
Heating can be a factor in creating monsoon conditions, and we've had plenty of that in our early summer days. Tucson saw an early start to our 100-degree days this year.
Wind conditions can also play a role. Southerly wind conditions make for a stronger monsoon, while north or northwest winds quell monsoon activity.
Cloud cover is another factor. If cloud cover prevents temperatures from climbing high enough, we just won't see much thunderstorm monsoon activity.
When we add all these factors together, we're likely looking at average monsoon conditions for 2020. It may not be very exciting, but we'll likely see more intense monsoon activity than last year's below-average conditions.