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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Just a little OT topic here:

Voyager 1 has left the solar system!
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Quoting 392. SomeRandomTexan:



I am not holding my breath, but hopefully it will get far enough North so that central Texas will see some H2O
We can hope, but next couple of days is hot and dry for sure. Glad I have a pool.
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If you actually read the study Fox News quoted you'll find that Fox didnt quite report it right....I know, shocking, huh?
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Quoting 394. clwstmchasr:


Clearly moving much faster than the models or NHC forecasted. I don't see anyway this gets up near Texas.
I think after it makes landfall the moisture will try and stream up that way.
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Quoting 380. EricSpittle:
You mis-spelled "doesn't understand" :)
Also "intentionally misrepresents". ;-)
Member Since: November 8, 2009 Posts: 4 Comments: 13508
Quoting 389. MississippiWx:
Step aside, Sharknado. We have smokenadoes in Mississippi. This is amazing.



Woah...
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Quoting 391. FunnelVortex:


And Texas needs rain!



I am not holding my breath, but hopefully it will get far enough North so that central Texas will see some H2O
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Quoting 388. SomeRandomTexan:
If 93L doesn't put on the breaks soon, it will never gain any latitude and will slam into Mexico soon. She is running out of real estate and needs to really slow down.


And Texas needs rain!
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Anyone able to access that Boulder Creek webcam? I'm getting error messages trying to access it now.

MrMixon any updates?
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Step aside, Sharknado. We have smokenadoes in Mississippi. This is amazing.

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If 93L doesn't put on the brakes soon, it will never gain any latitude and will slam into Mexico soon. She is running out of real estate and needs to really slow down.
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Quoting 352. MississippiWx:


If it is already that far into the Bay of Campeche, I don't see it moving much farther to the north. It has to start putting on the brakes, like now.


to be honest it seems to have slowed down a lot since earlier
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Quoting 380. EricSpittle:
You mis-spelled "doesn't understand" :)

So I did. :)
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Quoting 377. CaneHunter031472:
WHO IN THE HECK TURNED ON THE HAARP DEVICE HUH?


I guess they finally got enough funding. lol
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Invest 93L and Hurricane Humberto are going strong. And a blob alert in the Carribean.

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Quoting 321. TimSoCal:
Days like today are a little bit heartbreaking for me. I work in insurance, and I keep having to tell people in CO that their homeowners insurance doesn't cover floods. It's sad, because I can hear the desperation in their voices, and I wish there was something else I could do.


Mines does. I have a all perils policy which includes flood. It does not go thru national flood.
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Quoting 355. Birthmark:

The headline should be "Fox News wildly overestimates result of study."
You mis-spelled "doesn't understand" :)
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Torrential storms for US and Mexico
BBC weather video, 12 September 2013 Last updated at 12:27
Some torrential storms are in the forecast for parts of the United States and Mexico.
As BBC Weather's Ben Rich reports, some areas of Mexico could see more than a month's worth of rain in just three days.


First Autumn storm heads to UK
BBC weather video, 12 September 2013 Last updated at 10:57
The first storm of Autumn 2013 is set to sweep across the UK on Sunday with severe gales and heavy rain. BBC Weather's Alex Deakin reports.

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WHO IN THE HECK TURNED ON THE HAARP DEVICE HUH?
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Quoting 360. RGVtropicalWx13:

NHC forecasted to do so in the latest TWO


Forecasted it to so - move N?
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375. xcool
ya imo
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Quoting 370. xcool:
93L is td now
really.
Member Since: June 11, 2013 Posts: 20 Comments: 2697
Quoting 350. hurricanehanna:


looks like upper level winds moving to the west but system staying almost stationary ?


System is near the surface, not 35,000 feet tall
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That's what some can't grasp seems, there are no sides.


There's the data,the consensus and observed trends Globally

All else, is jus noise.


Fresca?
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Quoting 365. Patrap:



Wow, shear or not, that is starting to take on an UGLY disposition!
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370. xcool
93L is td now
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Quoting 357. FEMAroadwarrior:


I worked for FEMA after Katrina, and some of the folks out of the 500 year floodplain were told they didn't need flood insurance by their brokers. Absolutely tragic.


Yes I was one of them.
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My little barometer said 1008 mb here in Guadeloupe. Very impressive,for ex invest 98L
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Quoting 352. MississippiWx:


If it is already that far into the Bay of Campeche, I don't see it moving much farther to the north. It has to start putting on the brakes, like now.


I suppose if it drifts further North, it might simply get all cut up by the, er,...shears.
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Looks like Humberto is heading into high shear and cooler waters.

Should be downgraded to 75-80 MPH next advisory.
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364. BA
Quoting 206. cctxshirl:


no hurricanes in CC please-maybe a few little storms, but no hurricanes. Apartments I live in have no windstorm certificate therefore my contents are not covered in the event of a hurricane.


no windstorm insurance? it is required by law...and obviously the comment about CC will gladly eat a storm like "Ingrid to be" to fill the lake levels...no, first off, our water shed is far inland, second, in order to get such a thing it would wipe us out on the island
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Member Since: June 11, 2013 Posts: 20 Comments: 2697
Quoting 351. Hou77083:


do not get started again of GW Please!


I agree, and this time I will try to not even make peace between the sides, lest I get accused or it be implied that I was doing anything bad. lol.
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We should have TD 10 at 5 pm AST.
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Quoting 352. MississippiWx:


If it is already that far into the Bay of Campeche, I don't see it moving much farther to the north. It has to start putting on the brakes, like now.

NHC forecasted to do so in the latest TWO
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Quoting 348. GTstormChaserCaleb:
Humberto on the RGB Airmass:



That wave to the SSW of Humby looks healthy.
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Dang, those are some nasty floods. When I first saw this, I was like "It could happen tomorrow?". Thankfully, the death toll was only 3 and not hundreds. I bet 93L will become Ingrid tonight, if not tomorrow.
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Quoting 321. TimSoCal:
Days like today are a little bit heartbreaking for me. I work in insurance, and I keep having to tell people in CO that their homeowners insurance doesn't cover floods. It's sad, because I can hear the desperation in their voices, and I wish there was something else I could do.


I worked for FEMA after Katrina, and some of the folks out of the 500 year floodplain were told they didn't need flood insurance by their brokers. Absolutely tragic.
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Wow, there has been so much windshear squashing storms right & left, "out of the blue" this year that it could almost make someone believe in a Supreme Being of some kind!
I wonder if CaribBoy has gotten any rain yet.  Well, anyway, shear is cropping up again even in front of 93L, like on the storm before it.

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Quoting 344. Patrap:



Note the default from the er, "author"..

But people should still be concerned about global warming, Fitzpatrick says.
"The paper in no way diminishes the extensive body of observations that global warming is happening and that it is largely due to human activity," she added.
"Global surface temperature is still rising ... 2012 was in the top ten warmest years on record. The period 2001-2010 was the warmest on record since instrumental measurements began," she added.


Magine dat?

The headline should be "Fox News wildly overestimates result of study."
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Member Since: July 21, 2011 Posts: 83 Comments: 7167
Quoting 327. unknowncomic:
This is bound to get a few comment on TWU

Climate models wildly overestimated global warming, study finds



Link


Thanks for sharing.
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Quoting 330. Stormchaser2007:


If it is already that far into the Bay of Campeche, I don't see it moving much farther to the north. It has to start putting on the brakes, like now.
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Quoting 241. SouthernIllinois:
Climate models wildly overestimated global warming, study finds

Can you rely on the weather forecast? Maybe not, at least when it comes to global warming predictions over short time periods.

That’s the upshot of a new study in the journal Nature Climate Change that compared 117 climate predictions made in the 1990's to the actual amount of warming. Out of 117 predictions, the study’s author told FoxNews.com, three were roughly accurate and 114 overestimated the amount of warming. On average, the predictions forecasted two times more global warming than actually occurred.

Some scientists say the study shows that climate modelers need to go back to the drawing board.

Read More



do not get started again of GW Please!
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Quoting 349. Patrap:


looks like upper level winds moving to the west but system staying almost stationary ?
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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.