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 1145. daddyjames:


LOL - I just got it!


Haha, I am old!

Come on TD 10, momma needs rain! (on topic comment)
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Quoting 1144. GatorWX:


I just found out he was Canadian, lol. So much for him being prez.


Apparently, he still qualifies as his mother was a US citizen when he was born . . . H

He's the male version of Sarah Palin. But should not necessarily be underestimated.
Member Since: June 25, 2011 Posts: 2 Comments: 3733
1147. GatorWX
Quoting 1142. GatorWX:



Feeling some tug from the epac. Vorticiy, 850-500 anyway, is all stretch that direction. If there wasn't as much mid level vorticity going on down there, I'd imagine this would be moving much slower. I haven't even looked at its speed yet. Until that vorticity dissipates are becomes far enough way, It may take while to really strengthen and also have less time over water.


4 mph, k, nm on that.
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1146. HadesGodWyvern (Mod)
Japan Meteorological Agency
Tropical Cyclone Advisory #17
Gale Warning
TROPICAL STORM MAN-YI (T1318)
9:00 AM JST September 13 2013
======================================

Ogasawara Waters

At 0:00 AM UTC, Tropical Storm Man-yi (1000 hPa) located at 21.0N 144.0E has 10 minute sustained winds of 35 knots with gusts of 50 knots. The cyclone is reported as moving west northwest at 8 knots.

Gale Force Winds
================
150 NM from the center

Dvorak intensity: T2.5

Forecast and Intensity
=======================
24 HRS: 24.1N 139.7E - 45 knots (CAT 1/Tropical Storm) Sea South Of Japan
48 HRS: 28.6N 137.1E - 55 knots (CAT 2/Severe Tropical Storm) Sea South Of Japan
72 HRS: 34.4N 140.4E - 55 knots (CAT 2/Severe Tropical Storm) Izu Islands Waters
Member Since: May 24, 2006 Posts: 51 Comments: 45738
Quoting 1143. ihave27windows:


No man, I Am Dave! Open up! I got the stuff!


LOL - I just got it!
Member Since: June 25, 2011 Posts: 2 Comments: 3733
1144. GatorWX
Quoting 1120. HurricaneHunterJoe:


I got 100 different ways Ted Cruz can pull his head.........................!


I just found out he was Canadian, lol. So much for him being prez.
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Quoting 1123. HurricaneHunterJoe:


Things are good LAbonbon! weatherwise 92 and low humidity, monsoon has left :) I dont have to shower 4 times a day.....LOL.........Don't know if I am allowed friendly salutations anymore....don't want to piss off the powers that be. Hope today finds you well! And things going good!............Daves not here man!


No man, I Am Dave! Open up! I got the stuff!
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1142. GatorWX
Quoting 1128. beell:


Interesting vort pattern around 93L TD10. Strongest vorticity well removed (more or less) from the "center".


Feeling some tug from the epac. Vorticiy, 850-500 anyway, is all stretch that direction. If there wasn't as much mid level vorticity going on down there, I'd imagine this would be moving much slower. I haven't even looked at its speed yet. Until that spin dissipates or becomes far enough way, It may take while to really strengthen and also have less time over water.
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1141. FOREX
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


Take this to your own blog please. thanks.
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1140. nash36
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


That's only because we have active storms in the basin. Once they are gone, it'll be all GW ALL the time! Along with the bickering that comes with it. In other words, I will be elsewhere. Lol.
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Quoting 1135. BahaHurican:
Be careful. Looks like it is getting dark there.


Hi Baha...you can watch live coverage here...after the commercial break...

Link
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1137. nash36
Quoting 1125. MississippiWx:
I made a blog about yesterday's debacle (an apology) if anyone would like to read it. I posted it earlier this morning, but realize some of you weren't around to notice. Please keep any comments about it off the main blog so you don't get "in trouble". :-)

Anyway, it's about time hurricane season showed up.



Yep, it showed up JUST in time for the MJO to exit stage left. We will then be heading into October, so Cape Verde season is just about over. It'll be homegrown systems from here on out. When it all ends, it appears it will be one of the, if not THE weakest seasons on record.
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Quoting 1134. redwagon:


I think she is growing right now... sucking up all that EPAC moisture.. she really has no impediments. Barring a center reloc upon strengthening - which could be a good or bad thing for TX - when she spins up won't she naturally be repelled from land? And inch a bit more Nrly? I am hoping against hope for a Hermine-type landfall, with a lucky humungous rain tail that whips straight up TX from CC to Waco.


Well, not that far north, but isn't that currently indicated on the GFS?

Or are you further north than that?
Member Since: June 25, 2011 Posts: 2 Comments: 3733
Quoting 1122. MrMixon:
I don't see any dry slots soon. Going to suit up and walk around the house and vicinity to make sure nothing is taking on water...

Be careful. Looks like it is getting dark there.
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Quoting 1110. 1900hurricane:

Still pretty neutral on rain, but if I had to pick, I'd say I'm slightly more pessimistic than I am optimistic at this point. Hopefully 10L grows quite large in size in order to make up for the Mexican landfall. Something similar to what we saw with Alex in 2010 would be considered a success to me.


I think she is growing right now... sucking up all that EPAC moisture.. she really has no impediments. Barring a center reloc upon strengthening - which could be a good or bad thing for TX - when she spins up won't she naturally be repelled from land? And inch a bit more Nrly? I am hoping against hope for a Hermine-type landfall, with a lucky humungous rain tail that whips straight up TX from CC to Waco.
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This blog is so dead right now...
Member Since: September 6, 2012 Posts: 0 Comments: 304
Quoting 1123. HurricaneHunterJoe:


Things are good LAbonbon! weatherwise 92 and low humidity, monsoon has left :) I dont have to shower 4 times a day.....LOL.........Don't know if I am allowed friendly salutations anymore....don't want to piss off the powers that be. Hope today finds you well! And things going good!............Daves not here man!


Nice to know you kept up w/ hygiene during the inclement weather!

You're one of the consummately friendly people on here. Keep up the good work!

Anywho, who's Dave??
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00z Best Track for TD TEN.

AL, 10, 2013091300, , BEST, 0, 197N, 938W, 30, 1005, TD
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Quoting 1125. MississippiWx:
I made a blog about yesterday's debacle (an apology) if anyone would like to read it. I posted it earlier this morning, but realize some of you weren't around to notice. Please keep any comments about it off the main blog so you don't get "in trouble". :-)

Anyway, it's about time hurricane season showed up.



Funny how they have a big yellow circle around one tiny dot, and a small red circle within a larger, visible circulation :)
Member Since: June 25, 2011 Posts: 2 Comments: 3733
Quoting 1124. daddyjames:


Yup, puffing away


LOL
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1128. beell
Quoting 1119. GatorWX:
Anyone else notice that little surface swirl se of Gabs? Just thought it was interesting. 98 is still there, pretty dry.




Interesting vort pattern around 93L TD10. Strongest vorticity well removed (more or less) from the "center".
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This is from this morning

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Quoting 1107. FOREX:


Your thoughts on ex 98L?


Is that mess NE of the islands formerly 98L? I really haven't been watching it since we have a hurricane and TD/Poss TS going on......NHC says 10-20%....surface plot said dissipating low and that cold front coming off the US east Coast........
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I made a blog about yesterday's debacle (an apology) if anyone would like to read it. I posted it earlier this morning, but realize some of you weren't around to notice. Please keep any comments about it off the main blog so you don't get "in trouble". :-)

Anyway, it's about time hurricane season showed up.

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Quoting 1113. GeoffreyWPB:
Is that little dot on the right ex-98L?



Yup, puffing away
Member Since: June 25, 2011 Posts: 2 Comments: 3733
Quoting 1109. LAbonbon:


Joe, today's the first day I've been on in a while, and have missed your friendly salutations :)

How are things in SoCal?


Things are good LAbonbon! weatherwise 92 and low humidity, monsoon has left :) I dont have to shower 4 times a day.....LOL.........Don't know if I am allowed friendly salutations anymore....don't want to piss off the powers that be. Hope today finds you well! And things going good!............Daves not here man!
Member Since: Posts: Comments:
1122. MrMixon
I don't see any dry slots soon. Going to suit up and walk around the house and vicinity to make sure nothing is taking on water...

Member Since: March 26, 2006 Posts: 44 Comments: 1520
Link

What a mess....
Member Since: September 6, 2012 Posts: 0 Comments: 304
Quoting 1113. GeoffreyWPB:


Like this guy...

Texas Sen. Ted Cruz wishes there were ‘100 more’ people like the late Jesse Helms in today’s Senate.


I got 100 different ways Ted Cruz can pull his head.........................!
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1119. GatorWX
Anyone else notice that little surface swirl se of Gabs? Just thought it was interesting. 98 is still there, pretty dry.


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Not much SAL, I think Humberto ate it all!

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1117. 62901IL
Quoting 1116. rudyinpompano:
And back here in Florida, Lake O is getting quite a soaking...it's been looking like this for several hours...

Link

storms are stationary over your area.
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And back here in Florida, Lake O is getting quite a soaking...it's been looking like this for several hours...

Link
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Front Mid Conus will keep 93L away from Texas...

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CV may take a break until that wave E Africa enters the Atl...

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Is that little dot on the right ex-98L?

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Interesting... RTD Denver is tweeting messages on its website regarding localized flooding in the Denver area, and has notified customers that Boulder bus routes are not running...
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Is there any chance of some sort of Fujiwhara effect if 90E develops as expected. I realise that this usually occurs in the open ocean but can it apply across land - the two systems are definitely close enough.
It would appear that the steering patterns for TD10 are likely to be pretty weak, so perhaps more scope for 90E to influence TD10's track?
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Quoting 1105. redwagon:


1900, do you have a dull thud sense of hope, after how many times we've been burned? - figuratively and literally - about pre-Ingrid?

Still pretty neutral on rain, but if I had to pick, I'd say I'm slightly more pessimistic than I am optimistic at this point. Hopefully 10L grows quite large in size in order to make up for the Mexican landfall. Something similar to what we saw with Alex in 2010 would be considered a success to me.
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Quoting 1076. HurricaneHunterJoe:
Good Evening Class!


Joe, today's the first day I've been on in a while, and have missed your friendly salutations :)

How are things in SoCal?
Member Since: Posts: Comments:
Flooding assault on both sides of Mexico.

1. SHOWERS AND THUNDERSTORMS ACCOMPANYING A BROAD AREA OF LOW PRESSURE
LOCATED JUST SOUTH OF ACAPULCO MEXICO HAVE BECOME MORE ORGANIZED
THIS AFTERNOON. ENVIRONMENTAL CONDITIONS APPEAR CONDUCIVE FOR
FURTHER DEVELOPMENT DURING THE NEXT COUPLE OF DAYS AS THE SYSTEM
MOVES SLOWLY TOWARD THE NORTHWEST OR NORTH. THIS SYSTEM HAS A
MEDIUM CHANCE...50 PERCENT...OF BECOMING A TROPICAL CYCLONE DURING
THE NEXT 48 HOURS...AND A HIGH CHANCE...60 PERCENT...OF BECOMING A
TROPICAL CYCLONE DURING THE NEXT 5 DAYS. REGARDLESS OF
DEVELOPMENT...THIS SYSTEM...IN COMBINATION WITH TROPICAL DEPRESSION
TEN IN THE BAY OF CAMPECHE...COULD BRING HEAVY RAINS TO PORTIONS OF
SOUTHERN AND EASTERN MEXICO FOR THE NEXT SEVERAL DAYS. THESE RAINS
COULD CAUSE LIFE-THREATENING FLASH FLOODS AND MUD SLIDES.
Member Since: July 6, 2010 Posts: 113 Comments: 32338
1107. FOREX
Quoting 1104. HurricaneHunterJoe:
A lot of things going on



Your thoughts on ex 98L?
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00z Best Track for 90E.

EP, 90, 2013091218, , BEST, 0, 144N, 990W, 30, 1002, DB
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Quoting 1093. 1900hurricane:

Getting really picky here, but with KDP values generally between zero and one, it would be incorrect to call it heavy rain at this point. However, what it is is persistent and unwelcome at this point, and any little bit more is going to aggravate the flooding concerns that already exist. With the moist orographic upslope continuing, it's a pretty bad situation along the Front Range right now.

*EDIT to correct Specific Differential Phase acronym.


1900, do you have a dull thud sense of hope, after how many times we've been burned? - figuratively and literally - about pre-Ingrid?
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A lot of things going on

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Quoting 1096. barbamz:


Zicoille and Caribboy, don't stay on this flooded blog for a while or you're constantly suffering the pains of Tantalos:

Tantalus (Greek: Τάνταλος, Tántalos) was a Greek mythological figure, most famous for his eternal punishment in Tartarus. He was made to stand in a pool of water beneath a fruit tree with low branches, with the fruit ever eluding his grasp, and the water always receding before he could take a drink.
(From Wiki)


lolllll we want very heavy rain, that's only what we want, GOD (IF IT EXISTS) can help us...
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Is Humberto moving to the NE?
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luck...
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Quoting 1057. VAbeachhurricanes:


I don't think "luck" is a term scientists should be using.


Some discoveries are just luck, the scientist part is figuring out the meaning of the discovery.
Member Since: June 25, 2011 Posts: 2 Comments: 3733

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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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