From The Grand Junction Daily Sentinel (Dennis Webb):
With the continuing dry conditions, the local National Weather Service is starting to be asked the annual seasonal question: Are we seeing any signs of the imminent arrival of monsoon season with its welcome rainfall?
“There’s hope. Let’s just put it that way. There’s some hope,” said Tom Renwick, a forecaster with the agency’s Grand Junction office.
The National Weather Service in Tucson says in an online forecast discussion for that Arizona city that the monsoon season there “finally looks to be getting into the swing,” and cites the anticipated moisture levels with storms expected into next week. The Arizona Daily Star in Tucson reported Sunday that the monsoon season’s first storm helped lead to 92% containment of a major wildfire in that part of the state. In Albuquerque, New Mexico, the National Weather Service is forecasting “wetting storms” this week as monsoon moisture increases there.
And so monsoon season has made its way to the Southwest. But Renwick adds, “It’s just not reaching here.”
But he takes some heart in a shift in the local weather pattern that could presage the monsoon season’s arrival.
The season occurs in mid to later summer as a high pressure system sets up with winds circulating around it clockwise to funnel moisture up into the region from the Gulf of Mexico. Renwick said high pressure is moving into Texas, but not yet far enough east for the monsoon to reach Colorado.
Renwick said the region is seeing typical summer convection activity over higher terrain where rising air and the presence of some moisture can produce brief thunderstorms of the kind weather forecasters call “pop-and-drop” storms. Monsoon season by contrast is marked by a persistent pattern of sometimes moisture-laden storms. Renwick said those storms can contain enough water to cause flash flooding.
Monsoonal moisture would be welcomed by area agricultural producers, municipal water providers worried about water supplies, and firefighting agencies dealing with tinder-dry conditions and a growing number of wildfires in the region. Mesa County is currently in severe drought, according to the federal U.S. Drought Monitor.
Renwick said precipitation in Grand Junction for the year so far has totaled 2.85 inches, compared to 4.5 inches on average.
June is typically the driest month of the year in the city, averaging 0.44 inches based on historical National Weather Service data from 1900-2006. This June brought 0.51 inches of precipitation, still less than the average amount that falls locally any other month than June.
In July average precipitation locally inches up to 0.61 inches, and in August it reaches 0.99 inches. Much of that jump is due to monsoon rain.
Renwick said the monsoon can arrive by mid-July or earlier locally, but usually shows up in force by later July into August…
Just 0.1 inches of measurable rain has fallen in Grand Junction so far this month, being recorded on Sunday. Renwick said that compares to just 0.21 inches on average by this point in July.