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 1211. Tygor:


Oh sweet, only the 5th time this Fox News article was posted today.

Grothar leaves and everything goes to hell...
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Quoting 1239. ndscott50:
I live at 119 and I-25 about five miles east of longmont colorado. The St. Vrain river is about a mile away and normally is 15 feet across and a foot deep. This morning it was just out of its banks and about a foot short of the bridge. It is just amazing that that small river is over a mile wide and in my neighborhood. All I can do is wait to see what the morning brings.


15 ft to a mile wide, wow! Too close of a call. Hhhmm. Sounds like EM was hard at work. Rough, feel for you and everyone there!
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1247. scott39
TD 10 is less organized than it was earlier today due to 20nts of wind shear. Shear should become more favorable over the next 48 hours. An anticyclone should be in place also. Look for the ridge to weaken on about day 4. This should allow TD 10 to track farther N. I wouldnt be suprised to see a TX/LA landfall.
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The CIMSS maps indicate 30-40 knots of wind shear over Humberto:



Though this doesn't look like 30-40 knots of shear to me (also note the wave south of the Cape Verde Islands....down the road maybe?):

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1245. yoboi
Quoting 1239. ndscott50:
I live at 119 and I-25 about five miles east of longmont colorado. The St. Vrain river is about a mile away and normally is 15 feet across and a foot deep. This morning it was just out of its banks and about a foot short of the bridge. By 10:30am they closed 119 due to the threat off the bridge being overtopped. The water was still a mile from the house. I did some work and then went to leave my house at 3pm. As I walked out a state trooper pulled up and said we had to leave. I asked how long we had and he said you need to leave now. His tone indicated he was series.

In 15 minutes we packed up two kids, two dogs and some clothes and headed out. At that point the fire trucks had arrived and they were just starting to go door to door. When I got to the only road out of the neighborhoods it was flooded and impassable. After turning around I found the state PD. They knocked down a fence at the back of the neighborhood so we could drive out. We still went through over a foot of water.

Latest update from the HOA indicated all ways out of the neighborhood were cut off. Those who stayed were instructed to fill their bath tubs, conserve cell power and shelter on the second floor of their homes. I am glad we acted quickly and the family is now safe with my inlaws in Greeley.

No idea on the status of my house. It was not on a federal flood plain and I was told flood insurance was not needed when I purchased it. My house sits on a high lot a good four or five feet above street level. They are calling this a 500 year flood up stream in Longmont. I am certain the area where my house sits has not flooded in recorded history. It is just amazing that that small river is over a mile wide and in my neighborhood. All I can do is wait to see what the morning brings.



I hope everything will be ok...
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1244. Thrawst
.
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1243. GatorWX


Stan rainfall totals.
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Quoting 1070. beell:
.


Same trampoline????
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25 years ago today this bad boy was churning up the waters of the Western Caribbean passing through Jamaica. Thanks for the reminder, Nigel.

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Quoting 1207. unknowncomic:
Ex 98l starting to convect a bit. ANY ONE THINK IT HAS A CHANCE TO REGENERATE.
[RATE...ATE... ate...]

No need to shout... the blog is so quiet right now even a whisper is audible... lol

To answer the question... I know models yesterday were suggesting something off to our east [N of Hispaniola, I think] in about 5 or so days... but I dunno if that's as likely today as it seemed yesterday....
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I live at 119 and I-25 about five miles east of longmont colorado. The St. Vrain river is about a mile away and normally is 15 feet across and a foot deep. This morning it was just out of its banks and about a foot short of the bridge. By 10:30am they closed 119 due to the threat off the bridge being overtopped. The water was still a mile from the house. I did some work and then went to leave my house at 3pm. As I walked out a state trooper pulled up and said we had to leave. I asked how long we had and he said you need to leave now. His tone indicated he was series.

In 15 minutes we packed up two kids, two dogs and some clothes and headed out. At that point the fire trucks had arrived and they were just starting to go door to door. When I got to the only road out of the neighborhoods it was flooded and impassable. After turning around I found the state PD. They knocked down a fence at the back of the neighborhood so we could drive out. We still went through over a foot of water.

Latest update from the HOA indicated all ways out of the neighborhood were cut off. Those who stayed were instructed to fill their bath tubs, conserve cell power and shelter on the second floor of their homes. I am glad we acted quickly and the family is now safe with my inlaws in Greeley.

No idea on the status of my house. It was not on a federal flood plain and I was told flood insurance was not needed when I purchased it. My house sits on a high lot a good four or five feet above street level. They are calling this a 500 year flood up stream in Longmont. I am certain the area where my house sits has not flooded in recorded history. It is just amazing that that small river is over a mile wide and in my neighborhood. All I can do is wait to see what the morning brings.
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Quoting 1234. GatorWX:
2005's Hurricane Stan

Click for article.



Due to Stan's position within a large area of convective activity and thunderstorms, the hurricane's effects were far-reaching and widespread across Central America. Flash floods generated by the hurricane caused severe crop losses, particularly to coffee crops. Overall, Stan caused at least 1,668 deaths across six countries, with many others unaccounted for. Most of these fatalities occurred in Guatemala, and were mostly caused by mudslides triggered by torrential rainfall. The floods in Guatemala destroyed entire towns and disrupted exportation of petroleum. In Mexico, the heavy rains triggered additional mudslides and caused rivers to overflow, flooding nearby villages. Despite being relatively far from Stan as opposed to other countries, El Salvador was also severely affected by the hurricane. The Santa Ana Volcano erupted while Stan was producing heavy rains in the country, which contributed to the damage already wrought by mudslides. Transportation in the country was disrupted. Across the region, Stan caused $3.9 billion in damages, primarily due to torrential rainfall.


Here are the top 10 storms that 10L compares with based on rainfall. TD11 (1999) dumped 43 inches at one location.

TEN

Results ranked from best match to worst match, with ties being won by the earlier storm.
ELEVEN 1999
DORA 1956: No graphic available.
LORENZO 2007: No graphic available.
ROXANNE 1995
DOLLY 1996
NATE 2011: No graphic available.
HENRI 1979
MITCH 1998
INEZ 1966
BRENDA 1973:

A link to the page that provides this.
LINK
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1237. GatorWX
Know what I mean?

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1236. yoboi
Quoting 1211. Tygor:


Oh sweet, only the 5th time this Fox News article was posted today.


Just wait until Dr M has the blog about this yr artic ice he said he would be posting it soon....
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1235. GatorWX
See ya Pott!
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1234. GatorWX
2005's Hurricane Stan

Click for article.



Due to Stan's position within a large area of convective activity and thunderstorms, the hurricane's effects were far-reaching and widespread across Central America. Flash floods generated by the hurricane caused severe crop losses, particularly to coffee crops. Overall, Stan caused at least 1,668 deaths across six countries, with many others unaccounted for. Most of these fatalities occurred in Guatemala, and were mostly caused by mudslides triggered by torrential rainfall. The floods in Guatemala destroyed entire towns and disrupted exportation of petroleum. In Mexico, the heavy rains triggered additional mudslides and caused rivers to overflow, flooding nearby villages. Despite being relatively far from Stan as opposed to other countries, El Salvador was also severely affected by the hurricane. The Santa Ana Volcano erupted while Stan was producing heavy rains in the country, which contributed to the damage already wrought by mudslides. Transportation in the country was disrupted. Across the region, Stan caused $3.9 billion in damages, primarily due to torrential rainfall.
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Quoting 1229. pottery:


That would be a catastrophe if that happens.

40'' in 5 days? WOW !


unfreaking believeable - yes, that would be devastating. Concerned for folks I know on the east coast near Puebla. Even if tthey only get a smattering of that, would not be good.

And the same story on the Pacific side as well, pretty much.
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1232. pottery
I'm out.
Stay safe, all.
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Member Since: May 12, 2012 Posts: 11 Comments: 2541
Quoting 1222. Catherdr:


Hopefully, he has lost only his internet connection....


Most likely that is the reason.
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1229. pottery
Quoting daddyjames:


Yes it was.

The international desk has stated that - from the combined BOC, EPAC, and Monsoonal flow some regions may receive up to a meter of rain (40 inches) as predicted by the models.

TROPICAL DISCUSSION - INTERNATIONAL DESKS
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
242 PM EDT THU SEP 12 2013

A PROLONGED PERIOD OF HEAVY RAINS IS EXPECTED OVER EASTERN
AND SOUTHERN MEXICO INTO NORTHERN CENTRAL AMERICA. HEAVIEST RAINS
ARE EXPECTED ESPECIALLY ACROSS THE GULF OF MEXICO BASIN/SIERRA
MADRE ORIENTAL. MODELS ARE AGREEING ON SOME OF THESE AREAS
RECEIVING AMOUNTS OF 40 INCHES OR 1000MM DURING THE NEXT 05
DAYS...IN PARTICULAR DURING THE WEEKEND. THIS IS A VERY DANGEROUS
SITUATION WITH A HIGH RISK FOR FLASH FLOODS AND MUDSLIDES.


That would be a catastrophe if that happens.

40'' in 5 days? WOW !
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Quoting 1220. moonlightcowboy:


Is all that mess se of them headed their way too?


Think it is forecast to rain throughout the night into the morning - some areas predicted to receive another 2-3 inches.
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1227. GatorWX
Quoting 1220. moonlightcowboy:


Is all that mess se of them headed their way too?


It certainly appears there's a lot of moisture flowing towards them. They're stuck in the middle of the flow which is conveniently placed over the front range.

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1226. txjac
Quoting 1217. daddyjames:


Come to think of it, Mr. Mixon (a blogger in that area) went to go outside and check on things, and never came back . . .

Not joking.


I was just thinking the same thing.
Hopefully he rejoins us soon and gives us an update
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Quoting 1207. unknowncomic:
Ex 98l starting to convect a bit. ANY ONE THINK IT HAS A CHANCE TO REGENERATE.

I'm with you! I'm thinking that this could really be a problem if it develops because it's so far south that it could threaten more areas once it has moved farther west. I think it dodged being pulled out to sea by literally "playing dead!" And because it's so weak now, it will keep on moving west more than if it were stronger.

Member Since: May 12, 2012 Posts: 11 Comments: 2541
Quoting 1210. pottery:

Not enough time for it to do much else.
But the rainfall could be very heavy.

I was watching some UTube of flood damage after Mitch in Honduras.
Terrible.


Yes it was.

The international desk has stated that - from the combined BOC, EPAC, and Monsoonal flow some regions may receive up to a meter of rain (40 inches) as predicted by the models.

TROPICAL DISCUSSION - INTERNATIONAL DESKS
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
242 PM EDT THU SEP 12 2013

A PROLONGED PERIOD OF HEAVY RAINS IS EXPECTED OVER EASTERN
AND SOUTHERN MEXICO INTO NORTHERN CENTRAL AMERICA. HEAVIEST RAINS
ARE EXPECTED ESPECIALLY ACROSS THE GULF OF MEXICO BASIN/SIERRA
MADRE ORIENTAL. MODELS ARE AGREEING ON SOME OF THESE AREAS
RECEIVING AMOUNTS OF 40 INCHES OR 1000MM DURING THE NEXT 05
DAYS...IN PARTICULAR DURING THE WEEKEND. THIS IS A VERY DANGEROUS
SITUATION WITH A HIGH RISK FOR FLASH FLOODS AND MUDSLIDES.
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Quoting 1221. CaneHunter031472:


Interesting
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Quoting 1217. daddyjames:


Come to think of it, Mr. Mixon (a blogger in that area) went to go outside and check on things, and never came back . . .

Not joking.


Hopefully, he has lost only his internet connection....
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Quoting 1216. GatorWX:


It's going to be a very long night for them I'm afraid.



Is all that mess se of them headed their way too?
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TD TEN isn't looking good because of shear from the upper level TUTT low dropping SSW out of TX.
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Quoting 1199. BahaHurican:
I disagree... I am sure I read a few sighs of satisfaction at the rain u got before Gabrielle fell apart the first time.... lol


Considering how ominous the TW east of Pre-Gabrielle was... I really thought we would get plenty of rain, but it wasn't the case. However we had a very decent lightning show, bringing some excitement and satisfaction with it :-)
Member Since: October 6, 2007 Posts: 0 Comments: 6161
Quoting 1213. AussieStorm:


@denverpost of a road washed out near Lyons, Colorado.


Come to think of it, Mr. Mixon (a blogger in that area) went to go outside and check on things, and never came back . . .

Not joking.
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1216. GatorWX
Quoting 1213. AussieStorm:


@denverpost of a road washed out near Lyons, Colorado.


It's going to be a very long night for them I'm afraid.

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The west pacific looks to have two or three cyclones in the next couple of weeks impacting land.
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Just terrible...flooding in Boulder, CO which has taken the lives of 3 people.



Cool Dual Waterspouts over Lake Michigan:

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@denverpost of a road washed out near Lyons, Colorado.
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RESIDENTS ORDERED TO EVACUATE IRONDALE NEIGHBORHOOD

Residents are ordered to immediately evacuate from Commerce City's Irondale neighborhood in the following area:
. North Border: E. 88th Avenue
. South Border: E. 80th Avenue
. East Border: Monaco Street
. West Border: Highway 2

Everyone in this area needs to leave now. Do not stay.

The evacuation is due to a dam failure on the Rocky Mountain Arsenal National Wildlife Refuge. There is an embankment currently holding back a significant amount of water which is 300 yards wide, three-quarters of a mile long and about 15-20 feet deep. That is equivalent to three football fields in width and 12 football fields in length. The embankment is expected to fail within the next hour and water will begin flowing in the neighborhood.


If residents do not have a place to evacuate to, they can seek shelter at Adams City High School, 7200 Quebec Parkway. Highway 2 is closed north of E. 80th Avenue so evacuees can take Highway 2 south at E. 80th Avenue or Quebec Parkway to Adams City High School. Interstate 76 is still open for travel. Check the Colorado Department of Transportation for current road and weather conditions, call 511 or visit www.cotrip.org.

Emergency Responders are in the neighborhood now notifying residents and monitoring the situation. FirstCall is being deployed through ADCOM for community notification. Red Cross is assisting at the shelter.

Residents can call 911 for emergencies or 303-288-1535 for assistance.
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1211. Tygor
Quoting 1139. tramp96:
More evidence that GW is a crock heck even the good doctor has slowed waaaay down on the amount of GW articles.

Link


Oh sweet, only the 5th time this Fox News article was posted today.
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1210. pottery
Quoting BahaHurican:
Nobody believes TD 10 will be more than a weak TS hitting MX... either that or they're watching the breaking news on flood and fire...

Not enough time for it to do much else.
But the rainfall could be very heavy.

I was watching some UTube of flood damage after Mitch in Honduras.
Terrible.
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Quoting 1207. unknowncomic:
Ex 98l starting to convect a bit. ANY ONE THINK IT HAS A CHANCE TO REGENERATE.


Looks like me from google earth - puffing away. (I know)
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Quoting 1133. HurricaneCamille:
This blog is so dead right now...


Look where the 3 active storms are, then you will understand why the blog is dead.
Member Since: October 6, 2007 Posts: 0 Comments: 6161
Ex 98l starting to convect a bit. ANY ONE THINK IT HAS A CHANCE TO REGENERATE.
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Quoting 1203. SuperStorm093:
this place is dead it seems
Nobody believes TD 10 will be more than a weak TS hitting MX... either that or they're watching the breaking news on flood and fire...
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Quoting 1114. sunlinepr:
CV may take a break until that wave E Africa enters the Atl...



And of course this one too will be a Fishland visitor.... SIGH
Member Since: October 6, 2007 Posts: 0 Comments: 6161
this place is dead it seems
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1202. GatorWX
Quoting 1198. daddyjames:


The NHC agrees. Can't get any more blunt than this:

000
WTNT35 KNHC 122335
TCPAT5

BULLETIN
TROPICAL DEPRESSION TEN INTERMEDIATE ADVISORY NUMBER 1A
NWS NATIONAL HURRICANE CENTER MIAMI FL AL102013
700 PM CDT THU SEP 12 2013

...TROPICAL DEPRESSION MOVING SLOWLY WESTWARD...
...LIFE-THREATENING FLOODING EXPECTED OVER PARTS OF EASTERN
MEXICO...



Looking at that and the wv, yeah.
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Quoting 1194. pottery:

Just the usual. :):))

But I have to admit to doing ''a Baha'' earlier.
Lager & Ice? Why not ?

heheheheh
There are days when I wish it were possible to plus the really good posts more than the meager once....
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1200. pottery
1197

True that !
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Quoting 1195. CaribBoy:


I would say.... no.

XD
I disagree... I am sure I read a few sighs of satisfaction at the rain u got before Gabrielle fell apart the first time.... lol
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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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