Boulder's 1-in-100 Year Flood Diminishing; Ingrid a Dangerous Flood Threat for Mexico

By: Dr. Jeff Masters , 3:43 PM GMT on September 13, 2013

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Colorado's epic deluge is finally winding down, as a trough of low pressure moves across the state and pushes out the moist, tropical airmass that has brought record-breaking rainfall amounts and flooding. Devastating flash floods swept though numerous canyons along the Front Range of Colorado's Rocky Mountains Wednesday night and Thursday morning, washing out roads, collapsing houses, and killing at least three people. The flood that swept down Boulder Creek into Boulder, Colorado was a 1-in-100 year event, said the U.S. Geological Survey. A flash flood watch continues through noon Friday in Boulder. According to the National Weather Service, Boulder's total 3-day rainfall as of Thursday night was 12.30". Based on data from the NWS Precipitation Frequency Data Server, this was a greater than 1-in-1000 year rainfall event. The city's previous record rainfall for any month, going back to 1897, was 9.59", set in May 1995. Some other rainfall totals through Thursday night include 14.60" at Eldorado Springs, 11.88" at Aurora, and 9.08" at Colorado Springs. These are the sort of rains one expects on the coast in a tropical storm, not in the interior of North America! The rains were due to a strong, slow-moving upper level low pressure system to the west of Colorado that got trapped to the south of an unusually strong ridge of high pressure over Western Canada. This is the same sort of odd atmospheric flow pattern that led to the most expensive flood disaster in Canadian history, the $5.3 billion Calgary flood of mid-June this summer. The upper-level low responsible for this week's Colorado flood drove a southeasterly flow of extremely moist tropical air from Mexico that pushed up against the mountains and was lifted over a stationary front draped over the mountains. As the air flowed uphill and over the front, it expanded and cooled, forcing the moisture in it to fall as rain. Balloon soundings from Denver this morning continued to show levels of September moisture among the highest on record for the station, as measured by the total Precipitable Water (PW), which is how much water would fall at the ground if the entire amount of water vapor through the depth of the atmosphere was condensed. Four of the top eight all-time September highs for Precipitable Water since records began in 1948 have been recorded over the past two days:

1.33" 12Z September 12, 2013
1.31" 00Z September 12, 2013
1.24" 12Z September 13, 2013
1.23" 12Z September 10, 1980
1.22" 00Z September 2, 1997
1.21" 00Z September 7, 2002
1.20" 00Z September 13, 2013

Wunderground weather historian Christopher C. Burt discusses how this year's flood compares to previous Colorado floods in his latest post.

A map of Boulder flood zones and detailed history of previous floods in the area may be found here.


Figure 1. A torrent of water rushes alongside a swamped house following flash flooding near Left Hand Canyon, south of Lyons, Colo., Sept 12, 2013. (AP Photo/Brennan Linsley)



Figure 2. Observed rainfall for the Colorado's Front Range from the September 11 - 13 rain event. Rainfall amounts greater than 10" (pink colors) were indicated near Boulder. Image credit: NWS Denver.

Tropical Storm Ingrid a Dangerous Rainfall Threat for Mexico
Tropical Storm Ingrid, the ninth named storm of the 2013 Atlantic hurricane season, has formed in the Southwestern Gulf of Mexico's Bay of Campeche. Ingrid is the most dangerous Atlantic tropical cyclone of 2013 thus far, due to its rainfall potential. Ingrid is embedded in an exceptionally moist environment, and is already bringing heavy rains to the Mexican coast in Veracruz state, as seen on Mexican radar. Satellite loops show that Ingrid is not well-organized, and has only a modest area of heavy thunderstorms. However, the Friday morning hurricane hunter mission found 45 mph winds, prompting NHC to upgrade Ingrid. Moderate wind shear of 15 - 20 knots is interfering with development, but ocean temperatures are a very warm 29 - 29.5°C (84 - 85°F).


Figure 3. Percent chance of receiving more than 16" of rain during a five day period, from the Friday 2 am EDT run of the experimental GFDL ensemble model for Tropical Storm Ingrid. More than 16" of rain are predicted for the Oaxaca and Tampico areas of Mexico. Image credit: NOAA/GFDL.

Forecast for Ingrid
The soils along the Mexican Gulf Coast are already saturated from the rains of Tropical Depression Eight and Tropical Storm Fernand, and it won't take much additional rain to generate dangerous flash floods and mudslides. An added danger is the presence of tropical disturbance 90E in the Eastern Pacific Ocean, on the other side of Mexico. If Ingrid intensifies sufficiently, it could draw in the moisture from 90E across Southern Mexico, resulting in torrential rains on both the Pacific and Atlantic sides of Southern Mexico. Ninety-E represents a threat to develop into a tropical depression in its own right; in their 8 am EDT Friday Tropical Weather Outlook, NHC gave 2-day odds of development of 70% for the disturbance, and predicted a north to northwest motion of the storm towards the coast. This morning's 2 am EDT run of the experimental GFDL ensemble model predicted that a some areas of Mexico are at high risk of 16+ inches of rain due to the combined effects of Ingrid and 90E. The greatest danger is on the Pacific side in Oaxaca state, where the combined effects of the circulations of Ingrid and 90E will pull a flow of very moist air upwards over the mountains, creating torrential rains. All of the models predict a west-northwest to northwest track for Ingrid into Mexico, but heavy rains of 2 - 4" may also affect extreme South Texas by early next week.

Today is the 25th anniversary of the intensification of Hurricane Gilbert into the strongest hurricane ever observed in the Atlantic (at the time.) I was on the hurricane hunter flight into Gilbert that day, and will be posted an account of the mission later today.

Jeff Masters

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frost warnings for north central Ontario tonight

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Quoting 70. SouthernIllinois:

That's why I'm allergic to them. haha.


That could be your ironic nickname. Everyone should have one.

From puff to peanut??
Member Since: January 1, 2008 Posts: 0 Comments: 3804
Quoting 69. Tazmanian:
hmmm


EL nino forming ??


here the map from 9/2/2013




here the map from 9/12/2013



I think that's not out of the question.
Member Since: July 8, 2005 Posts: 259 Comments: 24976
Quoting 66. HCW:



Just because it's over the water doesn't mean that it's a waterspout. From some of the images I saw it looks like a rare tornado over the water


I was having an issue with this. I watched a couple meteorologists call those "waterspouts" waterspouts just this morning.
But when I looked at the video, I was like "those are tornaodos" to me.

But I also thought, while a "tornado" is over water, it's called a waterspout dispite its size or strength.
Member Since: September 16, 2007 Posts: 0 Comments: 11228
We drove into town the same day as Frederick stormed in. Boarded up the relatives house & headed for the Piney wood Hills. We hunkered down in an A frame cabin and it was so eerie to see the lightning looking as if it was smeared across the sky.  Had to chainsaw our way back into town after the storm.
Quoting 55. scott39:
Today is the 34th anniversary of Hurricane Fredric. It made landfall as a strong Cat 3( some would argue Cat 4) in Mobile Al.

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Tropical Storm Ingrid Forms in Gulf
Tropical Storm Ingrid has formed in the western Gulf of Mexico and is forecast to move gradually northwestward over the next few days. Landfall is expected Sunday along the west coast of Mexico near Tampico.
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Quoting 66. HCW:



Just because it's over the water doesn't mean that it's a waterspout. From some of the images I saw it looks like a rare tornado over the water


They're referred to as tornadic waterspouts when they form from a supercell thunderstorm.
Member Since: January 1, 2008 Posts: 0 Comments: 3804
Quoting 66. HCW:



Just because it's over the water doesn't mean that it's a waterspout. From some of the images I saw it looks like a rare tornado over the water
normally this time of year ya get lots of them out over great lakes as the colder air rotates over the warmer water cold vortex showers forms
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Quoting 59. calkevin77:


Well so now she's officially Ingrid huh. She sure does look raggedy atm. I have a feeling that except for deep South Texas the only thing she's going to bring up here is a 90% chance of mosquitos.


Keep checking your 10-day. If it drops off, we'll cry together on each other's shoulders. Most important thing, Avila sees Ingrid going N.. with that EPAC TD spinning huge amounts of moisture into her the whole trip up the coast.
Member Since: August 4, 2007 Posts: 0 Comments: 3383
Quoting 50. ricderr:
Living in el paso the same storm system affected us as colorado but to a much lesser degree....what most don't understand is the lands south of colordao.....the high desserts...the 4 to 5 inches of rain we had were as devastating.....el paso and similar cities are suffering from flooding.....broken aroyos and sinkholes.....it's nothing to the point of a federal disaster area....don't get me wrong...but to someone who is witnessing this type of event first hand and for the first time it is awe inspiring the power of flowing water


Used to live in El Paso remember those floods well. Couldn't live farther from there now and still live in Texas. Our floods here are quite different.
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Quoting 75. daddyjames:


N at 0. Direction not very useful in this case ;)
Your right. Time will tell.
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Member Since: May 21, 2006 Posts: 5095 Comments: 116137



Scary for that boat....
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Quoting 71. scott39:
Per Tropical Atlantic 12Z has Ingrid heading N at 0mph.


N at 0. Direction not very useful in this case ;)
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Quoting 72. ricderr:
flooding in socorro


what a mess

mud pie anyone
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flooding in socorro


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Per Tropical Atlantic 12Z has Ingrid heading N at 0mph.
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hmmm


EL nino forming ??


here the map from 9/2/2013




here the map from 9/12/2013

Member Since: May 21, 2006 Posts: 5095 Comments: 116137
Typical Florida waterspout:

Member Since: January 1, 2008 Posts: 0 Comments: 3804
Quoting 54. bappit:

The shear will have to relax first. From the forecast discussion.

ASSUMING THAT THE SHEAR DECREASES DURING THE NEXT 48
HOURS OR SO...THE NHC FORECAST CALLS FOR GRADUAL STRENGTHENING.

There's no reason to assume it won't.
Member Since: July 6, 2010 Posts: 113 Comments: 34217
66. HCW
Quoting 60. SouthernIllinois:

I know. Most of those are really skinny and ropey. I guess this spout agrees that it IS really all about the thickness. ;)



Just because it's over the water doesn't mean that it's a waterspout. From some of the images I saw it looks like a rare tornado over the water
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Quoting 50. ricderr:
Living in el paso the same storm system affected us as colorado but to a much lesser degree....what most don't understand is the lands south of colordao.....the high desserts...the 4 to 5 inches of rain we had were as devastating.....el paso and similar cities are suffering from flooding.....broken aroyos and sinkholes.....it's nothing to the point of a federal disaster area....don't get me wrong...but to someone who is witnessing this type of event first hand and for the first time it is awe inspiring the power of flowing water


I knew there was a blogger from El Paso, but couldn't remember who. I was following the flooding in southern NM & extreme west Texas yesterday, as well as the flooding in CO. NWS listed the Guadalupe Mts, as of yesterday noon or so, as having gotten 10-12 inches between 9/11 and midday yesterday. That is a LOT of water in a short time. Glad to hear you're 'high and dry'.
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Quoting 1875. daddyjames:


Mr. M

How are things by you? Still ok - relatively speaking?
Quoting 1879. hurricanehanna:
1871. MrMixon

How are you doing this am ? What are things like in your area ?




Well, I can't say I've ventured too far yet, but I imagine the image above is indicative of what I'd find if I did venture out. In our immediate vicinity it is foggy/cloudy and has been raining off and on since I got up.

The family (wife and dogs) are home safe and we have no plans to leave - wife's workplace is closed and I had already arranged to be off today. According to email, of the 25 people who work in my office, only 2 made it in (I think they're crazy for trying, but they do live quite close).

For some odd reason we still have power. We've heard that Nederland has lost and regained power several times. Last word (as of about an hour ago) was that Nederland does NOT have power and may not get it again until midday Saturday.

The hummingbirds seem a bit grumpy, but otherwise unfazed. The ground squirrels appear to be in suspiciously good spirits... I wonder about them.


Quoting 1881. Neapolitan:
...it's no more "balanced" than a guy whose left leg swells to twice its normal size due to elephantiasis, and who simultaneously loses his right leg in an accident....


I hear that elephantiasis stuff is all hype...
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Quoting 39. SouthernIllinois:

Why yes, they are. Although there are a lot of just plain nutty people out there nowadays. We like to keep nuts associated JUST with trees, or we hope to. haha.

Trees that produce nuts are from the Beech Family, and include, Beech, Buckeye, Chestnut, and all indigenous species of oaks to North America.


Peanuts aren't from trees! ;p

jk
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62. 7544
its hurricane season for mexico usa may get its turn in oct .
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Toronto Pearson Int'l Airport
Date: 12:00 PM EDT Friday 13 September 2013
Condition:Mostly Cloudy
Pressure:30.0 inches
Tendency:rising
Visibility:15 miles
Temperature:52.2°F
Dewpoint:42.1°F
Humidity:68%
Wind:N 17 gust 26 mph

refreshing day after a couple of extreme heat days

58 degree temp change over 36 hr period
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Quoting 40. redwagon:


But it looks like Ingrid is going to be big enough to pass that moisture all around. If we time in on a huge raintail as she makes landfall - and look at that convection band she already threw off! - some of those GFS rain fcsts could verify.


Well so now she's officially Ingrid huh. She sure does look raggedy atm. I have a feeling that except for deep South Texas the only thing she's going to bring up here is a 90% chance of mosquitos.
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Quoting 40. redwagon:


But it looks like Ingrid is going to be big enough to pass that moisture all around. If we time in on a huge raintail as she makes landfall - and look at that convection band she already threw off! - some of those GFS rain fcsts could verify.


Yes I am really hoping for an Alex (2010) type thing to happen. Only this time give Central Texas more rain than Alex did. I know us in Houston had some severe flooding from Alex.


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Member Since: March 1, 2012 Posts: 0 Comments: 7100
Today is the 34th anniversary of Hurricane Fredric. It made landfall as a strong Cat 3( some would argue Cat 4) in Mobile Al.
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Quoting 32. CybrTeddy:
12z GFS back with the hurricane idea from Ingrid, a solution that cannot be discounted.


The shear will have to relax first. From the forecast discussion.

ASSUMING THAT THE SHEAR DECREASES DURING THE NEXT 48
HOURS OR SO...THE NHC FORECAST CALLS FOR GRADUAL STRENGTHENING.
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Quoting 30. SouthernIllinois:
Thank you for a fresh clean slate!! Began I NEW blog about waterspouts. Check it out if you want. Beginning in October, gonna be featuring my "weekly tree" blog that will entail a different species of trees every Saturday. Writings, pictures, and research will be derived from HUNDREDS of legit sources. For tree nuts out there, you will LUV this!! I will even include my own pictures I will take with my NEW CAMERA!!! <3

This was yesterday over Lake Michigan. Friggin' AWESOME!!!!!! :)

Natalie



Heckuva water spout!
Member Since: January 1, 2008 Posts: 0 Comments: 3804
bye bye ULL

shear decrease now maybe Ingrid actually do something for once
Member Since: September 6, 2012 Posts: 0 Comments: 304
Quoting 20. AussieStorm:
Big Thompson Canyon Flooding of 1976

On July 31, 1976, during the celebration of Colorado's centennial, the Big Thompson Canyon was the site of a devastating flash flood that swept down the steep and narrow canyon, claiming the lives of 143 people, 5 of whom were never found. This flood was triggered by a nearly stationary thunderstorm near the upper section of the canyon that dumped 300 millimeters (12 inches) of rain in less than 4 hours (more than 3/4 of the average annual rainfall for the area). Little rain fell over the lower section of the canyon, where many of the victims were.
Around 9 p.m., a wall of water more than 6 meters (20 ft) high raced down the canyon at about 6 m/s (14 mph), destroying 400 cars, 418 houses and 52 businesses and washing out most of U.S. Route 34. This flood was more than 4 times as strong as any in the 112-year record available in 1976, with a discharge of 1,000 cubic meters per second (35,000 ft3/s).


I was living in Denver at the time. I remember the rain that night. It was epic even down in Denver. My next door neighbor and his girlfriend were camping beside the Big Thompson that night and both were killed. For people in Colorado who were there, it was one of those events that is burned into your memory forever. I've been thinking about it this week a lot. Prayers go out to the people affected in Colorado right now.
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Living in el paso the same storm system affected us as colorado but to a much lesser degree....what most don't understand is the lands south of colordao.....the high desserts...the 4 to 5 inches of rain we had were as devastating.....el paso and similar cities are suffering from flooding.....broken aroyos and sinkholes.....it's nothing to the point of a federal disaster area....don't get me wrong...but to someone who is witnessing this type of event first hand and for the first time it is awe inspiring the power of flowing water
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Ingrid is 24-36 hours ahead of where it should be per the intensity models.
Member Since: July 8, 2005 Posts: 259 Comments: 24976
nice lunch time read thanks doc

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GFS 132 hours - starting to get some rain up in S. Texas.
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Good consensus that Humberto will become a hurricane again, perhaps a Category 2.
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43. josF
Thank you,Dr Masters.
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Quoting 26. Tazmanian:



why do you keep calling it TD 10 when its a TS


Ok, changing the D to S.... thanks Taz.... my bad...
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Quoting 27. DavidHOUTX:


Yes it is, it really feels the ridge around 78 hours and goes due west into Mexico though


But it looks like Ingrid is going to be big enough to pass that moisture all around. If we time in on a huge raintail as she makes landfall - and look at that convection band she already threw off! - some of those GFS rain fcsts could verify.
Member Since: August 4, 2007 Posts: 0 Comments: 3383
Quoting 30. SouthernIllinois:
Thank you for a fresh clean slate!! Began I NEW blog about waterspouts. Check it out if you want. Beginning in October, gonna be featuring my "weekly tree" blog that will entail a different species of trees every Saturday. Writings, pictures, and research will be derived from HUNDRED of legit sources. For tree nuts out there, you will LUV this!!

Natalie


Cool, looking forward to the tree blog.
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Dr. Masters co-founded wunderground in 1995. He flew with the NOAA Hurricane Hunters from 1986-1990. Co-blogging with him: Bob Henson, @bhensonweather

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