Unseasonably warm temperatures have hovered over northern Arizona for the past two months with no end in sight, according to the National Weather Service, as high pressure dominates the weather system with no precipitation in the forecast.
The average temperatures (averaged between the highs and lows) are typically around 51.6 degrees in October. This year, the average temperature was 54.5 degrees, almost three degrees above normal and 17th warmest in history. The warmest October was in 1950 at 59.5 degrees.
The average high temperature for October was 71.1 degrees. The typical average high for October is 66.4 degrees, almost four degrees cooler.
The average low for October was 37.9 degrees. The typical average low is 35.7 degrees, a 2.8-degree difference.
The precipitation in September and October totaled 1.32 inches. All of the rain fell in September, with no precipitation since Sept. 14.
The average precipitation for September and October is 1.82 inches and 1.60 inches respectively.
According to meteorologist Brian Klimowski with the National Weather Service in Bellemont, the unusual weather is a product of a persistent ridge of high pressure over much of the Western United States which has kept the area warm and dry.
With no measurable precipitation, Klimowski said this October ties with eight other years for the driest October on record. These years include 1999, 1995, 1964, 1952, 1950, 1937, 1934 and 1898.
September was the 51st driest year out of 120 years of data recorded.
“There is no identifiable reason for the lingering warmth and dryness,” Klimowski said. “It’s not that unusual for us to have a dry fall.”
The NWS said a long-wave high pressure setup over the southern Rocky Mountains with a trough off the Pacific coast made for a stable system that remained stationary over the area. As the air flowed into the ridge, the clouds evaporated, leaving the area with the clear skies, allowing the region to stay warm through this period.
Klimowski said La Nina is forecasted for the winter which could lead to a greater chance of drier than normal conditions and a significant chance of warmer than normal temperatures. Long range predictions show abundant precipitation in the Rocky Mountains and the Northeast and drier conditions in the southwest.
La Nina occurs when waters in the southern Pacific are cooler than normal. Variances in ocean temperatures often affect weather in other areas of the world by influencing the jet stream, the upper-level winds that direct storm systems.