By: MrMixon, 4:20 PM GMT on July 20, 2011
Flooding in our area has been happening faster than I can post about it. In the past two weeks, Denver, Boulder, Fourmile Canyon, Nederland, and Wondervu have all had very significant precipitation events, each of them the result of different afternoon monsoonal thunderstorms.
I've been trying to gather some info about the monsoonal thunderstorm that nailed Nederland this past Sunday (July 17th). We listened to this storm thunder across the mountains to our west and I could tell it was bad from the radar, but we only got a few drops here on Pinon Way (coincidentally, it was one of our lowest daily rain totals for the past two weeks...).
Several gauges in Nederland, however, showed significant precipitation in just a short time:
The Big Springs weather station reported 2.37" of precipitation, most of which fell between 3:30 and 4:30pm, an impressive rainfall rate for this area (1 inch per hour is considered a hard rain, so 2.37" per hour is darn near biblical).
In roughly the same one hour period, two gauges just northeast of Barker Reservoir showed totals of 1.31" and 1.34". Again, both of these gauges show the precipitation occurring in roughly the same 3:30-4:30pm window. These lower totals aren't surprising, since it seemed like (from the radar) the brunt of the storm hit more of the western part of town.
One commenter on the Boulder Daily Camera, who said they live "outside Nederland" reported almost 4" from this storm, which gels with some third-party rumors I heard today.
This storm caused widespread damage to roads and properties in the town of Nederland. In addition to damage caused to several private residences along North Beaver Creek (also called Caribou Creek), the Community Center and Blue Owl Books were both hit particularly hard by the flooding.
Though the total precipitation varied widely across the Nederland area, certainly parts of Nederland got 2.5" or more of precipitation in just an hour. For reference - average precipitation for the entire month of July is about 2.3". The Big Springs station is already at 4.76" for the month... it's only the 18th... and we have a 30-40% chance of storms every day through at least Thursday of this week.
I've done a little digging into how frequently Ned gets storms of this magnitude, but there aren't too many long-term precipitation records for our part of the mountains. I did find some info and I'll post more details when I've got some time. The quick answer is that a daily precipitation total of 2.5" or greater is not unprecedented for Nederland... I found at least a couple examples of 2.5" or more in a given day, but only a couple... I'd say daily totals of greater than 2" are fairly rare - maybe once every 10-20 years. Getting 2.5" is even more rare... and getting all 2.5" in less than an hour is exceedingly rare (happening only once or twice in a lifetime). I'll try to make time to get up the actual data on previous storms of this size as time allows...
Note - the average July precipitation value is based on the data available here:
UPDATE - Yet ANOTHER monsoonal storm hit the foothills near Nederland last night... this one nailed our place, giving us 1.54" of rain in less than an hour (our biggest single-storm total so far, though less than the monster storm which ravaged Ned on Sunday). It also dumped a TON of hail on Wondervu, which I photographed on my way home last night. Some of the hail was still piled up in shady spots when I drove into work this morning...
Updated: 5:08 PM GMT on July 20, 2011
By: MrMixon, 2:43 AM GMT on July 13, 2011
Our monsoonal thunderstorms have been impressive as of late. On Monday my rain gauge had 0.75" and we'd had about 0.30" the day before.
Update: We got another 0.15" of rain Tuesday, though we only caught the edge of the big cells moving through. Some parts of Denver got over an inch of rain from a single storm cell Tuesday night!
Update 2: We got a mere 0.08" last night, though it came down in a hurry. That storm cell went on to drop significant rain in Fourmile and Boulder Canyons (over 1.0" in some spots). The USGS stream gauge at Fourmile displayed an impressive spike last night:
Flooding and debris flows in the Fourmile Canyon area lead to several roads being closed last night. One car in Sunshine Canyon was reported to have been "washed away" by the flood waters. Daily Camera Article.
Update 3: 0.64" on Thursday
Here are some links about the North American Monsoon:
And here's a nice link for examining precipitation patterns around Boulder and the foothills:
Middle Boulder Creek at Nederland, CO
South Boulder Creek at Pinecliff, CO
Updated: 4:23 PM GMT on July 15, 2011
Big Springs Subdivision
|Dew Point:||26.7 °F|
|Wind:||3.0 mph from the West|
|Wind Gust:||10.0 mph|
Updated: 5:16 AM MDT on October 26, 2016