Summer 2013 Colorado Weather, Rain, Monsoon, Thunderstorms, Hail, El Nino, La Nina, etc (Denver: hotel, theater)

[Colorado Rambler]

As of this writing, we are experiencing a hard down pour here in Cortez along with a few dramatic pyrotechnics involving lightening and thunder. The Weather Channel is running a banner with flash flood warnings for NE Montezuma County and the east part of Dolores County, along with the San Miguel River drainage among others. I encountered a man in the City Market tonight who works on the Navajo Rez. He just drove in from there and he said there's several inches of standing water in more than a few places and people were stranded on rooftops due to flooding in Chinle Wash. Apparently the mountains north of Flagstaff are getting hammered too. No where near as extreme as Boulder of course, but still unusual for us. I've seldom heard of the folks on the rez directly to the southwest of us getting stranded by floods from a desert wash - an hour or two of torrential stream flow after a thunder-storm, yes. Being stranded because a desert wash has decided to turn itself into a lake is cause for considerable comment around here.

The meteorologist on the Weather Channel just called the Boulder floods a thousand year event, BTW.

Reporting in from the far SW quadrant,

- Rambler

[jazzlover]

Originally Posted by Colorado Rambler

The meteorologist on the Weather Channel just called the Boulder floods a thousand year event, BTW.

- Rambler

The "weather babes" and "weather hunks" on the Weather Channel might be meteorologists, but they are pretty lousy historians. The Weather Channel has sunk to being the "National Enquirer" of weather reporting. "Never let the truth get in the way of a good story" is their mantra. A "thousand year event?" I don't think so.

[wanneroo]

Originally Posted by jazzlover

The "weather babes" and "weather hunks" on the Weather Channel might be meteorologists, but they are pretty lousy historians. The Weather Channel has sunk to being the "National Enquirer" of weather reporting. "Never let the truth get in the way of a good story" is their mantra. A "thousand year event?" I don't think so.

When NBC came in they purged most of the serious meteorologists and those that were not into the drama and hysteria of 24 hour news. Sadly the Weather Channel is a far cry from what it used to be.

My family goes back 100 years in Colorado and they had plenty of flood stories to tell. I remember growing up when the Big Thompson flood had happened not long before and there was much talk about that.

As you say, it's a big issue now because some of these places have been built on in recent decades where nothing existed before or nothing much. It is just part and parcel of living. Nothing lasts forever. When you live on a flood plain, someday your home might be gone. It's like with the Atlantic hurricanes. People act like hurricanes have never been so powerful, but they have been, just that there were not millions of homes existing on sand spits next to the ocean.

I've seen some bad flooding before, fortunately lived on some of the highest ground around in these places.

[Colorado Rambler]

Originally Posted by jazzlover

The "weather babes" and "weather hunks" on the Weather Channel might be meteorologists, but they are pretty lousy historians. The Weather Channel has sunk to being the "National Enquirer" of weather reporting. "Never let the truth get in the way of a good story" is their mantra. A "thousand year event?" I don't think so.

Eh, I don't know. I agree that the media adores hyping EVERYTHING to attract audience ratings. On the other hand, I think we may have slightly different working definitions of "100 year" floods or "incidents." Back in the day when I took hydrology in college, the prof would be speaking of the history of a rather specific area of the flood plain when describing 100 year or whatever events. For example, the homes in Colorado Springs built in the flood plain of Fountain Creek near the UCCS campus could statistically expect a flood of X no. CFS every 100 years or so.

In your previous post about the subject, you seemed to be including much wider areas for your point of reference when discussing such occurences. I went ahead and googled the US Geological Survey (USGS) to see how THEY defined a "100 year event." Here's their explanation for anybody who might be interested in the subject:

Possibly you can remember when a really big rain, be it from a hurricane or a large frontal system, hit your town. If flood conditions occurred because of the rain then you might have heard the radio or TV weatherman say something like "This storm has resulted in a 100-year flood on Soandso River, which crested at a stage of 20 feet." Obviously, this means that the river reached a peak stage (height) that happens only once every 100 years, right? A hydrologist would answer "Well, not exactly." Hydrologists don't like to hear a term like "100-year flood" because, scientifically, it is a misinterpretation of terminology that leads to a misconception of what a 100-year flood really is.

Instead of the term "100-year flood" a hydrologist would rather describe this extreme hydrologic event as a flood having a 100-year recurrence interval. What this means is described in detail below, but a short explanation is that, according to historical data about rainfall and stream stage, the probability of Soandso River reaching a stage of 20 feet is once in 100 years. In other words, a flood of that magnitude has a 1 percent chance of happening in any year.

What is a recurrence interval?

"100-year floods can happen 2 years in a row"

Statistical techniques, through a process called frequency analysis, are used to estimate the probability of the occurrence of a given precipitation event. The recurrence interval is based on the probability that the given event will be equalled or exceeded in any given year. For example, assume there is a 1 in 50 chance that 6.60 inches of rain will fall in a certain area in a 24-hour period during any given year. Thus, a rainfall total of 6.60 inches in a consecutive 24-hour period is said to have a 50-year recurrence interval.

Likewise, using a frequency analysis (Interagency Advisory Committee on Water Data, 1982) there is a 1 in 100 chance that a streamflow of 15,000 cubic feet per second (ft3/s) will occur during any year at a certain streamflow-measurement site. Thus, a peak flow of 15,000 ft3/s at the site is said to have a 100-year recurrence interval. Rainfall recurrence intervals are based on both the magnitude and the duration of a rainfall event, whereas streamflow recurrence intervals are based solely on the magnitude of the annual peak flow.

Ten or more years of data are required to perform a frequency analysis for the determination of recurrence intervals. Of course, the more years of historical data the better—a hydrologist will have more confidence on an analysis of a river with 30 years of record than one based on 10 years of record.
Recurrence intervals for the annual peak streamflow at a given location change if there are significant changes in the flow patterns at that location, possibly caused by an impoundment or diversion of flow. The effects of development (conversion of land from forested or agricultural uses to commercial, residential, or industrial uses) on peak flows is generally much greater for low-recurrence interval floods than for high-recurrence interval floods, such as 25- 50- or 100-year floods. During these larger floods, the soil is saturated and does not have the capacity to absorb additional rainfall. Under these conditions, essentially all of the rain that falls, whether on paved surfaces or on saturated soil, runs off and becomes streamflow.

In other words, an urban area that has experienced a high rate of growth will have stream flow events that can vary significantly from previous historical norms. I think this is also clouding the understanding of the discussion. So, THEN I looked up a record of peak hydrological discharges for the Boulder area and discovered the recent (2008) South Boulder Creek - major drainage plan - a gold mine of statistics and information about Boulder area hydrology for those with a scientific bent and the inclination to wade through it all (280 pages plus of info!). For example:

100 Year Thunderstorm Peak Hydrologic Discharges vs. Routed Hydraulic Peak Discharges (cfs)
Taken from Table 2, Hydraulic Modeling Report,( HDR December 30, 2008)

[the first value uses the MIKE11 Hydrological Model and the second value given uses MIKE21]

Location

Eldorado Springs 4520, 4520
HWY‐93 7120, 6630
US‐36 7690, 7250
Baseline Road 8770, 5010
Confluence 8910, 4570

OK, you take Eldorado and Highway 93, and find out what the discharge values are for THIS storm and I'll take Baseline and US 36 and do the same. We'll split the difference with Confluence. Once we've both collected our respective data for those locations we can meet at high noon and have a shoot-out at the OK Corral to determine if we're gonna use the MIKE11 vs the MIKE21 model.

Nah, I'm not real up for that either.

Sooner or later, a faculty member from the geology or climatology department at CU will emerge to explain the recorded data, and then we'll have a better idea. I'll take their findings over those of the Weather Channel myself.

Perhaps for now, we could just settle on "one hell of a lot of water," and let it go at that.

[suzco]

Platteville, Morgan County is flooding; Ft Morgan's flooding; the South Platte is still rising; and it's raining there. The Big Thompson has cut Loveland in half. The St. Vrain has cut Longmont in half. (All of the Front Range flood water is flowing to the South Platte.) Just heard that I-76 east of ft morgan is flooding (exit 82 is closed).

Stay safe everyone.

[jim9251]

.56" of rain in Ridgway in the past 24 hours.


The low pressure system centered over northern Utah will rotate through western Colorado today with plenty of moisture in place and embedded disturbances to provide the trigger for numerous showers and thunderstorms. Storms will produce heavy rain with potential for flash flooding and mud and debris flows possible. The low will lift out to the northeast on Monday with drier air moving in on the back side. This will result in less coverage of showers and storms through the work week with enough lingering moisture to produce afternoon thunderstorms mainly anchored to the higher terrain. Temperatures will be on a warming trend back to near normal levels through the week.

[MtnJam]

Oh, just a little collateral damage...

Is there a media blackout on the fracking flood disaster in Colorado?

[CosmicWizard]

^^^^^Shhhh.....don't let the truth get out.

[mountainrose]

Originally Posted by MtnJam

Oh, just a little collateral damage...

Is there a media blackout on the fracking flood disaster in Colorado?

This needs its own thread.

[Colorado Rambler]

Originally Posted by mountainrose

This needs its own thread.

Yes, it really, really does. Too bad Idunn doesn't seem to be around at the moment. He'd be the perfect forum member to start it. My IRL is kind of chaotic right now, but if I get the chance, I'll post a new thread about it later on this evening if no one else hasn't already started one. This is serious stuff, the flood has the potential to spread those fracking chemicals everywhere and cause Lord knows how many people to come down sick for some mysterious reason. We need to spread the word.