This has been one wet August | AspenTimes.com

This has been one wet August

Jeremy Heiman

Aspen’s weather for the last month or two has been better for mushrooms than for the typical recreation-loving Aspenite.

A monsoon weather phenomenon has been bringing us all the rain, and it’s actually common for a Colorado summer. And though last month wasn’t nearly as wet overall as July 1998, precipitation this month has already exceeded last August’s total.

As of yesterday, rain fell on 14 out of 23 days so far in August, said Charlie Bailey, who keeps weather data at the city of Aspen’s drinking water treatment plant. Some 1.53 inches of precipitation had fallen in August through yesterday, compared with .98 inches for the entire month of August 1998.

The weather system that has brought that moisture is still in place and can be expected to stick around for at least another week or so, said Todd Dankers, a forecaster with the National Weather Service in Boulder. In Colorado, a monsoon condition often sets up about the second week in July and lasts until some time in early September, Dankers said.

A monsoon condition last summer actually brought much more precipitation in July than this year, Bailey said. Aspen received a record 4.26 inches of rain in July 1998, compared with 2.63 inches last month.

Nolan Doesken, assistant state climatologist at the Colorado Climate Control Center in Fort Collins, said a monsoon, as it forms in this area, is a wind that drifts northward, bearing moisture northward from the Gulf of Mexico, the Gulf of California and the Pacific. The wind is brought about as summer heating over the southwestern states causes air to rise, drawing in air from areas of higher pressure to replace it. The wind brings plentiful moisture with it, moisture that is squeezed out when the air cools as it rises over the Rockies.

Bailey said though Colorado is known for having as many as 300 sunny days per year, last summer and this summer haven’t kept the state on course for that average. But better weather is around the corner, it appears.

As fall approaches, Dankers said, the jet stream drops down from the north to a position nearer to Colorado. Stronger weather systems move into the Western states from the Pacific, and break up the heating pattern. That bodes well for sunnier days.

“After you shut off the monsoon,” Dankers said, “if there’s no big weather systems bringing moisture, you get days that are dry through the afternoon, with cooler nights.” That’s typical fall weather here.

But Doesken said the pattern can change again and briefly bring back the monsoon conditions.

There’s no relationship between this summer’s monsoon rains and the La Nia phenomenon that is affecting weather in much of the world this year, Dankers said. “I think the two are independent,” he said.

All in all, Dankers said, it hasn’t been an extremely wet summer in Colorado. But the Western Slope looks greener than usual, because there’s been a bit of rain nearly every day, keeping the grasses and brush from drying out.

Another reason it may seem like a wet summer is that some of the rainstorms have been heavier than usual for Colorado. Some isolated heavy showers have hit areas with poor vegetation cover, causing mudslides like the ones that closed Interstate 70 near Gypsum and Bakerville and those that have blocked Highways 82 and 133 at times.

On the good side, the last two summers have seen few wildfires in Colorado, especially compared with 1994, when the Storm King fire near Glenwood Springs killed 14 firefighters.

The bad news, Dankers said, is there’s no chance a monsoon could bring bodacious amounts of snow to Aspen this winter. Monsoons are strictly a summer phenomenon.


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