Flash Floods Kill 3 in Colorado; Dangerous 93L Developing in Gulf of Mexico

By: Dr. Jeff Masters , 3:06 PM GMT on September 12, 2013

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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 two people. The floods were triggered by widespread torrential rains of 4 - 6" that fell in less than twelve hours, thanks to a flow of extremely moist air from the southeast that pushed up against the mountains. These sort of upslope rain events are so-named because as the air flows uphill, it expands and cools, forcing the moisture in it to fall as rain. Balloon soundings from Denver last night and this morning recorded the highest levels of September moisture on record for the station. 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, was 1.33" at 12Z (8 am EDT) on September 12, and 1.31" at 00Z September 12. The previous September record was 1.23", set on September 10, 1980. Balloon soundings began in 1948. Wednesday night's rainfall was heaviest near Boulder, Colorado, where a flash flood watch continues through Thursday evening. Though rainfall amounts today are not expected to be as great as on Wednesday, the soils are saturated, and additional flash flooding will occur today as an upper-level low centered over the southern Great Basin continues to pull a moist southeasterly surface flow of air across Eastern Colorado. A map of Boulder flood zones and detailed history of previous floods in the area may be found here.


Figure 1. Flooding in Boulder, Colorado on Wednesday evening, September 11, 2013. Photo posted by brandish on Instagram @photogjake.


Figure 2. Radar-estimated rainfall for the Colorado's Front Range from the September 11 - 12 flash flood event. Rainfall amounts of 6 - 8" (dark rad colors) were indicated near Boulder (circle with a "+" symbol), and confirmed by rain gauge measurements.


Video 1. Flooding in Boulder, Colorado at 36th and Colorado Street on Wednesday night, September 11, 2013.

Dangerous 93L developing in the Gulf of Mexico
A low pressure system (Invest 93L) over the Southwestern Gulf of Mexico's Bay of Campeche is generating heavy rains over the Yucatan Peninsula and adjacent waters as it moves west-northwest at about 5 mph. Radar loops from Mexico show that 93L has a pronounced rotation and is developing low-level spiral bands, and there is a strong possibility that the Air Force hurricane hunter plane scheduled to investigate 93L Thursday afternoon will find that a tropical depression has formed. Satellite loops show only a modest area of heavy thunderstorms, but these are steadily growing in intensity and areal coverage. The atmosphere is unusually moist, ocean temperatures are a very warm 29 - 29.5°C (84 - 85°F), and wind shear is a moderate 10 - 15 knots. These favorable conditions for development are expected to continue through Monday, according to the latest SHIPS model forecast. The computer models predict a landfall location along the Mexican coast between Veracruz and a location a few hundred miles south of the Texas/Mexico border by early next week. The storm is expected to maintain a forward speed of about 5 mph during the coming five days, and this slow motion will potentially allow 93L enough time to intensify into a hurricane before landfall. The high levels of moisture and slow motion of 93L make it a very dangerous rainfall threat, and I expect rainfall amounts of 5 - 10 inches will affect portions of the Mexican coast between Veracruz and Brownsville, Texas over the next five days. An added danger is the presence of tropical disturbance 90E in the Eastern Pacific Ocean, on the other side of Mexico. If 93L 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. In their 8 am EDT Thursday Tropical Weather Outlook, NHC gave 2-day odds of development of 60% and 5-day odds of 80%.


Figure 3. Latest satellite image of Tropical Depression Ten.

Humberto peaks in intensity
Hurricane Humberto is headed northwards over the far Eastern Atlantic, and has likely peaked in strength, with 85 mph winds. Humberto is listed in NHC's preliminary Best-Track data repository as having achieved hurricane strength at 8 am EDT on September 11, which would tie it with Hurricane Gustav of 2002 for latest appearance of the season's first hurricane since 1941. Satellite loops show that Humberto is well-organized hurricane with a distinct eye, but the storm has moved over waters cooler than 26°C, and wind shear has risen to 20 knots, which will likely cause weakening over the next few days. Humberto is not expected to be a threat to any land areas.

Gabrielle heads towards Canada
Tropical Storm Gabrielle is headed northwards to Canada after bringing 40 mph winds and just over an inch of rain to Bermuda on Tuesday night. Satellite loops show that wind shear has ripped up Gabrielle, leaving the storm with almost no heavy thunderstorms, and exposing the low level circulation to view. Wind shear is expected to rise to an extremely high 45 - 70 knots on Friday as Gabrielle encounters a trough of low pressure, which will likely destroy the storm. Gabrielle's remnants will likely bring heavy rain to the Canadian Maritime Provinces on Friday and Saturday.

Jeff Masters

After the Rain (mtnwoman67)
Lots of rain in Colorado for weeks. Last evening's setting sun gave us a great show east of us.
After the Rain

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Quoting 894. Ameister12:

Wow! Very ominous looking shelf cloud? What kind of conditions did you get as the storm passed through?

It rained. Lol It did rain pretty hard, it was VERY windy and there were a few power flashes. Alot of wires are down around tho, and it hailed a little
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Quoting 893. Mexicanguy:
I don't think the BOC's TCHP is enough to support a hurricane so many days...She will need to move in order to grow


Its not really going to matter if it makes hurricane strength, really, for the main impact it'll have. If it significantly taps into the moisture from the Pacific, rain is the main threat - regardless of how strong the winds get.
Member Since: June 25, 2011 Posts: 2 Comments: 3733
You folks in hurricane alley can probably relate to this one:



Not such a common scene for Colorado...

Member Since: March 26, 2006 Posts: 44 Comments: 1520
Quoting 879. wxgeek723:


Beat me to it. Local news panicking about it right now...

Is that wall cloud from today?

Yes, from not even an hour ago. Its still thundering quite alot.

Quoting 891. Bluestorm5:


Remind me of June 2013 derecho that hit my area... this is by far the best picture I've taken of storms.




Wow. That's beautiful. I don't think i'll ever see a storm that nice here in SE PA but you never know
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Quoting 867. CybrTeddy:


Whoa, take it easy man. I am not after you, nor have I shown anything less than the utmost respect to you. Matter of fact, I can't think of a time in the last few years when you've made a post I didn't agree with. However you really shouldn't call a BoC system "trash" when it has opportunity to strengthen into a significant storm. You just made a rather crass statement that I found disagreeable. BoC systems are actually I dare say some of the most impressive.

Let's keep this drama free.
Okay Teddy :).Just had to make sure we were still on good terms.
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Quoting 877. Doppler22:
img src="Image and video hosting by TinyPic">

This is the storm that hit me. It may not look like too much to some people but this is the best structured storm I have ever seen.

Wow! Very ominous looking shelf cloud! What kind of conditions did you get as the storm passed through?
Member Since: August 9, 2009 Posts: 10 Comments: 5027
I don´t think the BOC´s TCHP is enough to support a hurricane so many days...She will need to move in order to grow
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Quoting 868. HurricaneAndre:
In the last 5 years,each I name storm was a hurricane
2012 Isaac
2011 Irene
2010 Igor
2009 Ida
2008 Ike

It would be a crying shame if it didn't reach hurricane strength.
Odds are it will. In the past 5 years the I storm was a hurricane. In the past 15 years only 1 I storm WAS NOT a hurricane.
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Quoting 877. Doppler22:
img src="Image and video hosting by TinyPic">

This is the storm that hit me. It may not look like too much to some people but this is the best structured storm I have ever seen.


Remind me of June 2013 derecho that hit my area... this is by far the best picture I've taken of storms.


Member Since: August 1, 2011 Posts: 28 Comments: 8031
Quoting 877. Doppler22:
img src="Image and video hosting by TinyPic">

This is the storm that hit me. It may not look like too much to some people but this is the best structured storm I have ever seen.


It's looking threatening. Thanks.

Really severe action:
Member Since: October 25, 2008 Posts: 55 Comments: 6078
I think we could very well see 4-5 more named storms by November 30th. I wouldn't consider 14-15 total named storms this season to be a bust.
Member Since: August 9, 2009 Posts: 10 Comments: 5027
Quoting 857. CybrTeddy:
NHC probably still recalling Nate in 2011, so it's good to be conservative after that with these slow moving systems.

Nate literally stalled in the same spot for days while encountering dry air from the Texas Death Ridge and shear from a nearby upper-level low. Don't think TD Ten will have quite as many issues. :P
Member Since: July 6, 2010 Posts: 113 Comments: 32338
Boulder Creek dropped for a few hours, but is rising again:


(Click image for gage page)
Member Since: March 26, 2006 Posts: 44 Comments: 1520
Organizing quickly.
Member Since: July 8, 2005 Posts: 259 Comments: 24248
Whether it intensifies or not, having a system just sit and spin in the BOC is going to cause some epic rainfall amounts, on an even larger scale than what's going on in CO right now. I only hope the people there are prepared and have an evacuation plan.
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Quoting 875. VAbeachhurricanes:


Season is still a bust


Yup.
Member Since: July 8, 2005 Posts: 259 Comments: 24248


I know this is a similar view to civicane49 but look at the area south of Haiti. It looks like some spin going on there.
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Ah, Nate...
The first troll storm that I ever tracked. :P Predicted to quickly become a hurricane, go north then west, and hit Mexico...
It turned west, went quasistationary and upwelled itself, only turning into a 75mph Cat 1 for like what?? 12 hours??
Member Since: July 19, 2011 Posts: 12 Comments: 2459
And of course, the estimate from the GFS does not include what has already fallen.

Comisión Nacional del Agua
Comunicado de Prensa No. 612-13
México, D.F., septiembre 12 de 2013

Las lluvias máximas de las últimas 24 horas, medidas en milímetros, se registraron en Banco Chinchorro, Q. Roo, (264.9); Amaconite, Tab., (142.4); Requetemu, S..L.P. (98.8); Sta. Ma. Chimalapa, Oax., (96.6); Alvarado, Ver., (89.8); Paraíso,Tab., (55.0); Usila, Pue., (53.0); y Chihuahua, Chih., (49.6).

Translation:

The maximum rainfall in the last 24 hours, measured in millimeters, were recorded in . . .
Member Since: June 25, 2011 Posts: 2 Comments: 3733
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Quoting 869. Doppler22:
Seaside Heights, a beach community in New Jersey, lost its boardwalk during Hurricane Sandy. They rebuilt it and it reopened Memorial Day. Now, a huge section is up in flames.


Beat me to it. Local news panicking about it right now...

Is that wall cloud from today?
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Quoting 870. IKE:
Nothing coming around here anytime soon....from Mobile,AL.....

.MARINE...AN AREA OF HIGH PRESSURE ACROSS THE SOUTHEAST STATES WILL
CONTINUE TO WEAKEN AS A COLD FRONT APPROACHES FROM THE NORTH ON
FRIDAY...AND THEN STALLS ALONG THE COAST OVER THE WEEKEND. THIS
FRONT IS THEN EXPECTED TO DISSIPATE THE EARLY PART OF NEXT WEEK AS A
STRONG SURFACE RIDGE REBUILDS ACROSS THE SOUTHEAST STATES AND
NORTHEASTERN GULF.
THIS WILL BRING A RETURN OF LIGHT TO MODERATE
EASTERLY WINDS.
That will give TD10/Ingrid enough time to plow us. Lol J/K
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img src="Image and video hosting by TinyPic">

This is the storm that hit me. It may not look like too much to some people but this is the best structured storm I have ever seen.
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No one has posted a steering map lately. This is for systems > 1000mb



and the steering layer for Humberto

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Quoting 854. Relix:
So, where are the season is a bust idiots?


Season is still a bust
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Quoting 860. zicoille:


The flash floods don't cause death...
Human irresponsability cause death!
Look for example the picture illustrating the Dr Masters post. Do you think the guy on the bicycle is responsable?
When you see flash floods, you stay home, or you stay where you are. You don't go outside to realise picture just to have THE PICTURE !


I've been listening to the Boulder County Sheriff and Fire Live Audio Feed for the last few hours. The folks being rescued, evacuated, sheltering in place, etc., are not all irresponsible. Many are in a situation where the water is coming to them, not the other way around.
Member Since: June 26, 2013 Posts: 0 Comments: 1817
I noted earlier today that our well water had changed colors abruptly today. Then I saw this on twitter...



We got a brief break from the rain (maybe 30 minutes). It has started again...

Member Since: March 26, 2006 Posts: 44 Comments: 1520
Quoting 85. rmbjoe1954:


And that would be a good thing for our Mexican neighbors.


Racing? Supposed to meander in the BOC for three days at least. No good steering currents yet. We could use the rain here in the middle Rio Grande Valley but not a hurricane or even a strong ts. However there is a low on the Pacific coast of Mexico that may move inland about the same time. It could be interesting here in Texas and way too interesting in Mexico
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Excerpts from Hurricane Bret 1999:

"The depression did not strengthen right away due to vertical shear caused by an upper-level trough over the extreme western Gulf of Mexico. But the trough moved away and Bret reached tropical storm strength late on the 19th while beginning to move slowly northward. The vertical shear decreased. Bret rapidly became more organized and then steadily strengthened to a 125-knot category four hurricane on the Saffir/Simpson scale on the morning of the 22nd, while appproaching south Texas coast near Brownsville. Responding to the presence of a weak mid-tropospheric ridge over the northwest Gulf of Mexico and to a mid-tropospheric cyclonic circulation over the Rio Grande valley, Bret turned northwestward and slowed its forward speed down to about 5 knots."

Forecast and Warning Critique:

"The average forecast track errors for Bret are as follows: 65 n mi at 24 hours, 155 n mi at 48 hours, and 255 n mi (5 cases) at 72 hours. These values are just slightly below the previous 10-year averages. The GFDL model had a left bias and brought the hurricane inland over Mexico on a northwest to westward track for several forecasts as Bret moved northward. It has been suggested that the use of high-resolution topography with 18,000-feet mountains over Mexico in the GFDL model is the reason for the left bias.

The official forecast issued at 1800 UTC on the 19th, when Bret first became a tropical storm, had a 72-hour wind speed error of -85 knots. This was caused by the GFDL bias and resultant official forecast which placed the storm inland in 72 hours, rather than strengthening in the Gulf of Mexico."



Link
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870. IKE
Nothing coming around here anytime soon....from Mobile,AL.....

.MARINE...AN AREA OF HIGH PRESSURE ACROSS THE SOUTHEAST STATES WILL
CONTINUE TO WEAKEN AS A COLD FRONT APPROACHES FROM THE NORTH ON
FRIDAY...AND THEN STALLS ALONG THE COAST OVER THE WEEKEND. THIS
FRONT IS THEN EXPECTED TO DISSIPATE THE EARLY PART OF NEXT WEEK AS A
STRONG SURFACE RIDGE REBUILDS ACROSS THE SOUTHEAST STATES AND
NORTHEASTERN GULF.
THIS WILL BRING A RETURN OF LIGHT TO MODERATE
EASTERLY WINDS.
Member Since: Posts: Comments:
Seaside Heights, a beach community in New Jersey, lost its boardwalk during Hurricane Sandy. They rebuilt it and it reopened Memorial Day. Now, a huge section is up in flames.
Member Since: Posts: Comments:
In the last 5 years,each I name storm was a hurricane
2012 Isaac
2011 Irene
2010 Igor
2009 Ida
2008 Ike

It would be a crying shame if it didn't reach hurricane strength.
Member Since: Posts: Comments:
Quoting 863. washingtonian115:
Don't rile his head up/instigate please.Only decided to attack because he has back up from his Pal's.Teddy has been after me now for what ever stupid reason.But don't worry.I have a gift for them and every other person..
Link

Scroll down to post 22 please..


Whoa, take it easy. I am not after you, nor have I shown anything less than the utmost respect to you. Matter of fact, I can't think of a time in the last few years when you've made a post I didn't agree with. However you really shouldn't call a BoC system "trash" when it has opportunity to strengthen into a significant storm. You just made a rather crass statement that I found disagreeable. BoC systems are actually I dare say some of the most impressive.

Let's keep this drama free.
Member Since: July 8, 2005 Posts: 259 Comments: 24248
The trough from the N is going to BUST that ridge!
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Quoting 802. Doppler22:
I have never seen storm clouds like the ones outside my window right now...


please take pics and share if safe and possible.
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864. Ed22
Quoting 828. washingtonian115:
Well server thunderstorm outside.But after last year these are like kittens being compared to lions.

More BOC trash?.Getting sick of these storms.Don't care for it.See ya's.
sorry to say its not a BOC trash, it has a tight low level circulation but the convection associated with the system it not all that organized, this system could reach hurricane strength in the next 36 to 48 hours from now.
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Quoting 855. PalmBeachWeather:
Oh My
Don't rile his head up/instigate please.Only decided to attack because he has back up from his Pal's.Teddy has been after me now for what ever stupid reason.But don't worry.I have a gift for them and every other person..
Link

Scroll down to post 22 please..
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The cone is unusually wide for such a short distance. Unlike most of the season's previous packages, I guess this one is expected to crawl rather than sprint, though it looks like it is moving pretty well.

Plus some shear is effecting it making it shallow on the west. Looks as though it might jog south of west but don't know if that is a rotational illusion.

Any thought?
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too early to say td 10 wont be a wind event
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Quoting 849. LurknLearn:


How is flash flooding that is causing deaths lucky?


The flash floods don't cause death...
Human irresponsability cause death!
Look for example the picture illustrating the Dr Masters post. Do you think the guy on the bicycle is responsable?
When you see flash floods, you stay home, or you stay where you are. You don't go outside to realise picture just to have THE PICTURE !
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Td 10 will show the nhc who's boss at intensity!! LOL!!
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NHC probably still recalling Nate in 2011, so it's good to be conservative after that with these slow moving systems.
Member Since: July 8, 2005 Posts: 259 Comments: 24248
Quoting 852. TropicalAnalystwx13:

TD 10 helped form the costliest hurricane in recorded US history in 2005.
That still don`t count it need to be upgrade from the system that was td 10,even though Katrina form from little remains it was a new circulation so td 12 applies in this not 10.
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Quoting 850. MiamiHurricanes09:
See ya'.

Don't come back. ;)
Oh My
Member Since: October 3, 2008 Posts: 0 Comments: 5897
HERE WE GO
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Quoting 845. Tazmanian:
TD 10 can be a hard TD when it be comes in getting names out of it in past years when it comes too TD 10 they all ways go poof after getting forming

TD 10 helped form the costliest hurricane in recorded US history in 2005.
Member Since: July 6, 2010 Posts: 113 Comments: 32338
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Quoting 828. washingtonian115:
Well server thunderstorm outside.But after last year these are like kittens being compared to lions.

More BOC trash?.Getting sick of these storms.Don't care for it.See ya's.
See ya'.

Don't come back. ;)
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Quoting 786. zicoille:
They are so lucky in Colorado: 6 inches of rain, WOW!
RAIN, That's what we want in the northern leewards islands. And to be egoist, that's what we want in St Barth's!
So long time without good and heavy rain!
I don't understand why, again, 98L is gone....in the south!
They don't need in Martinique !
WE NEED RAIN HERE !


How is flash flooding that is causing deaths lucky?
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Jeff co-founded the Weather Underground in 1995 while working on his Ph.D. He flew with the NOAA Hurricane Hunters from 1986-1990.

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