NewsLocal News


Remembering the 2013 northern Colorado flood: the weather pattern that produced such a devastating storm

Posted: 2:07 PM, Sep 11, 2023
Updated: 2023-11-08 11:22:47-05
2013 colorado floods look back2.png
Mike Nelson 2013 flood 10 year anniversary.jpg

DENVER — It's hard to believe it's been a decade since devastating floods ravaged parts of the Front Range in September of 2013.

Normally, we have stormy weather every month of the year except for the month of September.

For years, Denver7's Chief Meteorologist Mike Nelson used to tell brides "if you're having an outdoor wedding, get married in September. It's the quietest month."

But in September of 2013, it was a different story. The floods that hit the Front Range and northeast plains were unprecedented.

Here's what happened.

A weather front stalled across the state from about the 10th to the 15th of September 2013. That front combined with a monsoon flow of moisture coming in from the south. That tropical moisture produced high amounts of thunderstorm activity and heavy rainfall.

Will Pitner
Will Pitner is rescued by emergency workers after a night trapped sheltering outside on high ground above his home as it filled with water from a surge of water, after days of record rain and flooding, at the base of Boulder Canyon, Colo., Friday Sept. 13, 2013. People in Boulder were ordered to evacuate as water rose to dangerous levels amid a storm system that has been dropping rain for a week. Rescuers struggled to reach dozens of people cut off by flooding in mountain communities, while residents in the Denver area and other areas were warned to stay off flooded streets. (AP Photo/Brennan Linsley)

The heaviest rainfall totals were seen in parts of Larimer County, Boulder County, and another band that went through Aurora and extended up to the Firestone and Dacono area. That rainfall then drained into the South Platte River Basin. That's why we had such terrible flooding all the way along the South Platte and out to Sterling and beyond.

Some areas received more than a foot of rain. Parts of Boulder County saw 15 inches of rain, other areas got up to 18 inches.

More than a foot of rain dropped on Bellvue with Estes Park receiving nearly a foot of rain. Jamestown's rain gauge recorded 13.47 inches during the historic event.

Southeast Boulder got a whopping 21 inches, and Nederland saw over a foot, all flowing downhill to the rivers in Boulder County.

The flow patterns on the South Platte River reached 13 feet. Normally, the South Platte levels only reach between 2.5-3 feet. The flood stage starts at 10 feet.

Downtown Denver didn't see quite that much, but at City Park, there was still over 7 inches of rain.

Finally, the monsoon flow weakened, and the front moved to the east on the 15th of September, letting up on the intense rain and flooding.

But the damage was left behind.

To many, it was reminiscent of the Big Thompson floodthat occurred at the end of July 1976.

big thompson d7 coverage-AGAIN.png

Local News

Remembering the 1976 Big Thompson Canyon flood

Robert Garrison
2:48 PM, Jul 31, 2022

David Barjenbruch, senior meteorologist at the National Weather Service in Boulder, described the Big Thompson flood as a more localized, heavy rain-producing thunderstorm that spurred the 1976 catastrophic flash flood. But that event mostly affected just the Big Thompson Canyon.

In comparison, the 2013 northern Colorado flood was more widespread, over a larger area. And this heavy rain event lasted over a longer duration of time- approximately 30 hours, Barjenbruch explained.

Typically, we don't see more than an inch of rain in the entire month of September. The monsoon moisture was more typical of what we would see in the middle to late part of the summer in July and August.

Colorado Flooding
Homes in residential neighborhood in Longmont, Colo., are submerged as flooding continues to devastate the Front Range and thousands are forced to evacuate with an unconfirmed number of structures destroyed, Friday, Sept. 13, 2013. The dayslong rush of water from higher ground has killed four people and turned towns on Colorado's expansive eastern plains into muddy swamps. (AP Photo/John Wark)

"We had various sources of moisture, one of those being the Gulf of Mexico. Rich low-level moisture was available in the atmosphere in combination with some subtropical moisture that was coming off of the Baja," Barjenbruch said.

Another important feature of this storm was what Barjenbruch called a mesoscale convective vortex. He described it as "turning winds into the foothills, which created or enhanced the upslope in the region." The National Weather Service defines upslope as an "increased chance of thunderstorm development if the air is unstable."

Those conditions fueled the persistent, heavy rainfall in Boulder and Larimer Counties, the evening of the 11th through the 12th of September 2013.


Local News

Town of Lyons hosts official flood remembrance ceremony

Claire Lavezzorio
5:06 PM, Sep 10, 2023

While some people ask Nelson if the 2013 flood happened because of climate change, he said it could be attributed more so to a bad combination of weather.

Many of the studies that were done in the wake of the 2013 storm found climate change was not really the driver of that flood. Nelson said there's an awful lot of things we can attribute to global warming and climate change, but this might have just been one of those rare weather events.

"Perhaps it's just once in a lifetime event. Let's hope it is. But the time to be prepared for flooding is anytime during those spring to summer, to late into the fall, months here. We're getting toward the tail end of our of our flash flood season, but it's never too early to prepare for that next flood," Barjenbruch said.

Colorado Flooding
An abandoned car lies off a road devastated by flood waters along the South Platte River east of Greeley, Colo, Tuesday, Sept. 17, 2013. Northern Colorado's broad agricultural expanses are especially affected, with more than 400 lane-miles of state highway and more than 30 bridges destroyed or impassable. (AP Photo/John Wark)

We all know how unpredictable Colorado weather can be, so there's no way to know for sure if we could see another storm of this kind in our lifetime.

But "that said," Barjenbruch told Denver7, "We are continuing to make advances in the meteorological world in the forecast business, where we have higher resolution modeling available that allows us to capture some of these local, what we would call orthographic- or storms that produce locally heavy rains against the Front Range."

WEATHER LINKS: Hourly forecast | Radars | Traffic | Weather Page | 24/7 Weather Stream

Click here to watch the Denver7 live weather stream.

Denver7 Weather