In 40 years tracking the vagaries & eccentricities of the weather I've never seen the National Weather Service refer to a flood as "biblical". That's how the Denver office described it late last week. 15 inches of rain, falling on drought-hardened, wildfire-scarred soil, which made run-off even worse.
It wasn't the result of stalled T-storms, but a much-larger scale storm marooned over the Intermountain West, stuck in place for 6 days, forcing tropical moisture up against the Front Range. When assessing the potential for disaster don't just look at the intensity of a storm. The forward speed is just as critical.
When weather systems stall bad things often result: more intense heat, drought or flooding.
The 1991 Halloween Superstorm that dumped over 30 inches of snow on MSP will be forever tattooed on my psyche. That storm stalled too, and the models didn't pick it up.
No drama for us, just a warming trend, the best chance of rain & T-storms Thursday, before we cool down again late week.
.5 - 1 inch of rain fell Saturday night, the most in 5 weeks. Long-range models hint at a potential for more heavy rain late next week as we transition from shirtsleeves to light jackets.
Photo credit above: "A truck and car is washed away by a flash flood that hit Manitou Springs, Colo., Friday sits in a drainage, covered in rocks, Saturday, Aug. 10, 2013. Friday’s torrential rains swept mud, boulders and other debris from the burn scar down U.S. 24, washing away vehicles and damaging several homes and businesses in the area." (AP Photo/The Colorado Springs Gazette, Michael Ciaglo).
Photo credit above: "Reuters/John Wark. "An aerial view of a farm house surrounded by flood waters along the South Platte River near Greenley, Colorado September 14, 2013. Farming communities along the South Platte River were ordered to evacuate ahead of a predicted surge in the flooding which may have claimed a fifth life and has left many still unaccounted for, according to authorities."
* "Flash Flood Products: What Do They Mean?" Here's a good recap and reminder from NOAA.
Summer 2013 Weather Extremes Tied To Extraordinarily Unusual Polar Jet Stream. Here's an excerpt of a good article from Steve Tracton at The Capital Weather Gang that explains the "split" polar jet, a shift in the pattern that may be at least partially responsible for some of the odd weather we've witnessed in 2013, including the historic floods near Boulder. Here's an excerpt: "For at least the past one or two decades the adjective extreme has increasingly become used in describing unusual weather. It’s virtually impossible now to escape news of extreme drought, excessive rainfall and floods, record breaking heat waves, cool spells and severe weather outbreaks, etc. which seem to recur year after year around the Northern Hemisphere. This summer was no different except that the behavior and configuration of the polar jet stream, the river of high altitude winds marking the divide between warm and cool air, were rare and mind-boggling. Instead of meandering as a single stream like it normally does, it transformed into a “dual” jet stream configuration, sometimes transitioning from this dual setup back into a single more coherent stream, back and forth..."
Photo credit above: "In this image made with a slow shutter speed which blurred the rushing water, flood waters course through a small park in Boulder, Colo., Thursday morning, Sept. 12, 2013. Heavy rains and scarring from recent wildfires sent walls of water crashing down mountainsides in the area." (AP Photo/Jud Valeski).
Image credit above: "Water vapor satellite loop from Sept. 12, 2013 showing the plume of moisture directed at Colorado." Credit: CIMSS.
Amid Drought, Explaining Colorado's Extreme Floods. Yes, climate change was probably a large contributing factor, superimposed on otherwise random storm cycles. Here's an excerpt from National Geographic: "....Sandra Postel, National Geographic’s Freshwater Fellow, said that the long-term drought that has parched the area and gripped much of the Colorado River Basin over the past 14 years may be partly to blame for the severity of the floods. Drought tends to harden the soil, she said. When rains do come, less of the water can absorb into the ground, so it quickly runs off the land. Similarly, fires can lead to worse flooding, because they remove vegetation that can slow down and trap rainfall, Postel said. (See “Fire and Rain: The One-Two Punch of Flooding After Blazes.”) In 2012, the Boulder area was afflicted by the Flagstaff Fire. In 2010, the Fourmile Canyon fire caused damage to Boulder County worth $217 million. Scientists have warned that increasing frequency and severity of wildfires and droughts may be symptoms of climate change, as much of the planet warms. That, in turn, can lead to more floods..."
Photo credit above: "A home and car are stranded after a flash flood in Coal Creek destroyed the bridge near Golden, Colorado, September 12, 2013. Scientists say drought, fires, and global warming may have helped spur the flood." Photograph by Rick Wilking, Reuters