Massive, historic, “biblical” rainfall cascaded through much of Colorado Thursday, leaving three people dead and one missing as of Thursday night as a result of the flooding.
Up to 8 inches of rain fell across a hundred-mile expanse of Colorado’s Front Range, causing thousands to be evacuated as local streams turned into rampaging torrents. The heavy rains returned to the foothills region Thursday night, with more precipitation forecast for Friday.
The National Weather Service issued constantly-updated versions of a local area forecast, and one at 9:41 a.m. MDT reported a dire warning:
MAJOR FLOODING/FLASH FLOODING EVENT UNDERWAY AT THIS TIME WITH BIBLICAL RAINFALL AMOUNTS REPORTED IN MANY AREAS IN/NEAR THE FOOTHILLS
There’s no scientific definition of “biblical” but the flooding has been unlike anything local residents have ever seen before.
Boulder County Sheriff Joe Pelle, after facing 20-foot walls of water racing down canyons already stripped bare by wildfires and drought, said, “This is not an ordinary day. It is not an ordinary disaster.’’
A dozen dams overflowed and six actually blew out, while officials were keeping their eyes on several high-hazard dams whose failure would seriously endanger lives.
This week started rainy for Boulder, which has seen 14 inches of rain fall since Monday. Boulder Creek’s flow rate usually measures at 100–300 cubic feet per second. On Thursday, it hit 4,500, more than double the previous record. NWS issued a flash flood warning “until further notice.”
Boulder’s Office of Emergency Management evacuated the area around the creek, issuing a statement saying, “All residents are warned to go to higher ground immediately due to the potential for flash flooding along the creek.”
Three towns, Lyons, Estes Park and Jamestown, were totally isolated by water and cascading rivers. Lyons lost power and Estes Park lost telephone lines and cell tower service. The only way residents could speak with the outside world was through ham radio.
“There’s no way out of town. There’s no way into town. So, basically, now we’re just on an island,” Lyons resident Jason Stillman told the Weather Channel after he had to evacuate his home at 3 a.m. due to a river flooding into the street. On Thursday night, the National Guard began trucking people out of the trapped town.
Eleven counties received flash flood warnings. Governor John Hickenlooper called on the National Guard and President Barack Obama declared a state of emergency in Colorado.
Starting on Thursday, and as of press time, the National Snow and Ice Data Center in Boulder was closed, meaning that a visit to their website yielded this disconcerting message:
The National Center for Atmospheric Research in Boulder, was also closed Friday.
Though there have been severe storms in the past, the amount of rain that has fallen in so short a time is unprecedented. One graph should suffice to put this event in perspective.
This is daily precipitation data from a weather station in Boulder over the last 120 years. Each red cross is the amount that fell in one 24-hour period, and each point is plotted against the “return period,” or how often on average that amount can be expected every 1, 2, 5, 10, 100, 1,000, or 10,000 years. The vast majority of readings fall below 10 years, or about 80 millimeters in one day.
After that it’s easy to pick out individual days. So the big outlier on the graph in the upper right is one day where about 120 millimeters (4.8 inches) of rain fell on this station, expected to happen once every 100 years.
On Wednesday and Thursday in just one 15-hour period, 183 millimeters fell on Boulder, which is 7.21 inches — literally off the chart. The previous wettest September day was in 1909, with just over 3 inches.
What’s happening in Colorado is that unprecedented. Rain totals in other areas could be even higher — Northwest Boulder reported 8.62 inches since the storm began on Wednesday. Aurora, a suburb of Denver, reporter 11.5 inches of rain from the storm. Denver’s average annual precipitation is 14.92 inches.
Weather.com meteorologist Chris Dolce said, “A slow-moving area of low pressure over the Rockies combined with a moist, southerly flow at all levels of the atmosphere will keep the threat of locally heavy rain and flooding in place into the weekend.”
And it’s not just Colorado. Historic, “unbelievable” rainfall in New Mexico on Thursday caused flooding in areas that typically have little to no flow at this time of year. An area in the Guadalupe Mountains received 11 inches in a 24-hour period. The state has been grappling with intense drought in 2013, and riverbeds that are usually dry have become treacherous. Carlsbad Caverns National Park closed on Thursday because of the flooding.
On Wednesday, Energy Secretary Moniz visited the National Renewable Energy Laboratory around 20 miles south of Boulder to help open a clean energy technology development facility. The Energy Department announcement of this visit noted climate change is the reason to support clean energy technology: “In order to face the challenges of a changing climate, we’ll need the smartest scientists, brightest engineers and the most innovative policy makers working toward clean energy solutions.”
One single event cannot definitively be said to be caused by climate change. But a study last year found that as the Earth gets warmer, precipitation patterns shift and we will see more intense downpours as storms become stronger because they have more energy.
According to Weather Underground, there won’t be many records left by the time the waters recede:
Other locations in the Boulder and Rocky Mountain Front Range have picked up over 11″ of precipitation in just the past 24 hours. The official Colorado state record of 11.08″ for a 24-hour period set at Holly on June 17, 1965 might be in jeopardy. UPDATE: A site near Eldorado Springs in Jefferson County has reported 14.60″ of rainfall as of 9:40 p.m. MT on Thursday evening. It is not clear if this is a storm total or 24-hour total. … The full extent of the damage and number of storm-related fatalities has yet to be determined (the rain continues to fall heavily in many locations) but the flooding, at least in Boulder, will be of historic proportions.