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 146. Tazmanian:



reported


plzs take that suff too your own blog


I think a mod came on not too long ago and said so


Taz, we've had it with you... STOP POLICING!
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Quoting 106. RitaEvac:




Quoting 97. SouthernIllinois:
Of course crapping out. Should have known better than to ever think this had a chance to make it into Cypress in the first place. :(

*** END QUOTES***

Just a reminder that Cumulonimbus_missingus is one of
the most frustratingly common cloud formations of summer.
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12Z GFS at 102 hours. not very impressive for 93L
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Quoting 136. FunnelVortex:
Ex-98L is back.

Gabby is back to TS status.

Humberto still a hurricane.

Recon is going to go out to 93L.



recon is still on the runway
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The only satisfaction I can get from 93L right now is that changes for it to approach the MS. Gulfcoast are slim to none. Other than that I'm very concerned for the people in Mexico and I can only hope that it will start moving faster.
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Is the area of disturbed weather east of the Leewards remnants of 98L? A low looks like it trying to form in South Texas looking at the Water Vapor Sat You can clearly see the CCW spin. Could this possibly pull Soon to be Ingrid northward into South Texas or even further up the coast?
Living here 90 miles in land from Galveston we are remembering Ike from 5 years ago today.
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As a tribute to Grothar, we have the Blobfish:




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Once there is some "clearance" between 93L and the E-pac disturbance in around 24-36 hours, and 93 is able to fully control the large-scale environment in the BOC, we should see some intensification. While the dirty side is going to remain off-shore until landfall the greatest threat from this system will be inland (flooding and mudslides) as noted by Dr. Masters well into late next week.

The current Colorado situation is pretty unbelievable as well......... Wind speed is the least of these folks problems at the moment in Mexico and Colorado.
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Quoting 124. will40:
Hanna it did show them up to 50ft then started descending not sure what is going on

oh ok.... possible problem with the airplane.
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The ADT finally found the eye of Humberto, so the Raw #s are high.



UW - CIMSS
ADVANCED DVORAK TECHNIQUE
ADT-Version 8.1.5
Tropical Cyclone Intensity Algorithm

----- Current Analysis -----
Date : 12 SEP 2013 Time : 151500 UTC
Lat : 21:50:35 N Lon : 29:00:31 W


CI# /Pressure/ Vmax
4.0 / 986.8mb/ 65.0kt


Final T# Adj T# Raw T#
3.7 4.1 5.0

Estimated radius of max. wind based on IR :N/A km

Center Temp : -31.7C Cloud Region Temp : -62.1C

Scene Type : EYE

Positioning Method : FORECAST INTERPOLATION

Ocean Basin : ATLANTIC
Dvorak CI > MSLP Conversion Used : ATLANTIC

Tno/CI Rules : Constraint Limits : 0.5T/hour
Weakening Flag : ON
Rapid Dissipation Flag : OFF

C/K/Z MSLP Estimate Inputs :
- Average 34 knot radii : 100km
- Environmental MSLP : 1013mb

Satellite Name : MSG3
Satellite Viewing Angle : 41.4 degrees

************************************************* ***
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Ex-98L is back.

Gabby is back to TS status.

Humberto still a hurricane.

Recon is going to go out to 93L.

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Quoting 120. Tropicsweatherpr:
93L moving faster than forecast?

Looks on schedule to me.
Member Since: July 6, 2010 Posts: 113 Comments: 32250
Quoting 67. AussieStorm:



Goodnight
The home of Carl Perkins, (Mr. Blue Suede Shoes)
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Quoting 111. MrMixon:
Biblical, eh? Don't I feel lucky...

Area forecast discussion
National Weather Service Denver/Boulder Colorado
941 am MDT Thursday Sep 12 2013


Update...major flooding/flash flooding event underway at this time with biblical rainfall amounts reported in many areas in/near the foothills. Precipitable water values in excess of an inch and a quarter on GPS sensors certainly support lots more rain today and tonight. 13z hrrr run has another 1-3 inches of rain predicted in the foothills through 04z so things are not looking good. Will extend the area of the Flash Flood Watch to include zone 43 and also extend it in time through 12z tomorrow morning.


wow....I have never seen that used. Stay safe. Unbelievable to see what is happening.
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Looks relatively benign on sat imagery, but that can be very deceiving with warm rain processes.

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Member Since: July 3, 2005 Posts: 426 Comments: 128626

299
WGUS55 KBOU 121551
FFWBOU
COC069-121845-
/O.NEW.KBOU.FF.W.0052.130912T1551Z-130912T1845Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000 Z.OO/

BULLETIN - EAS ACTIVATION REQUESTED
FLASH FLOOD WARNING
NATIONAL WEATHER SERVICE DENVER CO
951 AM MDT THU SEP 12 2013

THE NATIONAL WEATHER SERVICE IN DENVER HAS ISSUED A

* FLASH FLOOD WARNING FOR...
LARIMER COUNTY IN NORTH CENTRAL COLORADO...

* UNTIL 1245 PM MDT

* AT 949 AM MDT...DOPPLER RADAR INDICATED HEAVY RAIN CONTINUING
ACROSS THE WARNED AREA. ADDITIONAL RAINFALL AMOUNTS OF 1 TO 2
INCHES WILL BE POSSIBLE THE NEXT TWO HOURS. ADDITIONAL FLASH
FLOODING WILL CONTINUE.

* SOME LOCATIONS THAT WILL EXPERIENCE FLOODING INCLUDE...HIGH PARK
BURN AREA...ESTES PARK...PINGREE PARK...BUCKHORN MOUNTAIN...GLEN
HAVEN AND DRAKE.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

HEAVY RAINFALL WILL CAUSE FLASH FLOODING OF CREEKS...STREAMS...ROADS
AND CULVERTS IN THE HIGH PARK BURN AREA. SOME AREAS AFFECTED INCLUDE
RIST CANYON...BUCKHORN CREEK...REDSTONE CANYON...STOVE PRAIRIE...AND
GULCHES DRAINING INTO THE POUDRE CANYON ALONG HIGHWAY 14. ROCK
SLIDES OR DEBRIS FLOWS CAN ALSO BE EXPECTED ACROSS ROADS IN THE BURN
AREA.

EXCESSIVE RUNOFF FROM THIS STORM WILL CAUSE FLASH FLOODING OF CREEKS
AND STREAMS...ROADS AND ROADSIDE CULVERTS. THE HEAVY RAINS COULD
ALSO TRIGGER ROCK SLIDES OR DEBRIS FLOWS IN STEEP TERRAIN.

MOVE TO HIGHER GROUND NOW. ACT QUICKLY TO PROTECT YOUR LIFE.

STAY AWAY OR BE SWEPT AWAY. RIVER BANKS AND CULVERTS CAN BECOME
UNSTABLE AND UNSAFE.



LAT...LON 4027 10517 4026 10566 4065 10582 4066 10526



RPK

CLICK HERE TO GO TO PREVIOUS BULLETINS.
Member Since: July 3, 2005 Posts: 426 Comments: 128626
12z GFS isn't all that impressed with 93L?
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Quoting 81. Thundercloud01221991:
I am hoping that after 93L hits Mexico that it turns north and heads into central Texas. I am now living in Southeast Texas and we really need the rain. So if 93L can come here I would be very happy

Noooooooo, I have plans for the weekend of the 20th in Port A-no high tides and no storms!
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Behold the waters, and deliver to parched lands

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I think 93L may have some issues with that feature in S Texas .
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Hanna it did show them up to 50ft then started descending not sure what is going on
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The U.S. is certainly not experiencing the unprecedented heat that we saw last year. Matter of fact, the lows just slightly outnumber the highs this year.


Hi Max Hi Mi Low Max Low Min
YTD 7,960 12,684 12,495 8,726
LYTD 29,176 25,999 5,350 4,045

YTD Highs = 20,644
LY Highs = 55,175
YTD Lows = 21,221
LY Lows = 9,995
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Product: Air Force High Density (HDOB) Message (URNT15 KNHC)
Transmitted: 12th day of the month at 15:33Z
Date: September 12, 2013
Aircraft: Air Force Aircraft (Last 3 digits of the tail number are 301)
Mission Purpose: Investigate fifth suspect area (flight in the North Atlantic basin)

Mission Number: 1

Observation Number: 03

15:33:30Z 30.400N 88.917W 1017.0 mb*
(~ 30.03 inHg*) - 1017.1 mb*
(~ 30.03 inHg*) - No Wind 29.5°C
(~ 85.1°F) 23.0°C
(~ 73.4°F) No Wind - - - -
Time Coordinates Aircraft
Static Air Pressure Aircraft
Geopotential Height Extrapolated
Surface Pressure D-value Flight Level Wind (30 sec. Avg.) Air Temp. Dew Point Peak (10 sec. Avg.)
Flight Level Wind SFMR
Peak (10s Avg.) Sfc. Wind SFMR
Rain Rate Estimated Surface Wind (30 sec. Avg.)
Using Estimated Reduction Factor Peak Wind at Flight Level to
Est. Surface Reduction Factor

HDOB Observations

Independent Calculations from Tropical Atlantic

At 15:24:00Z (first observation), the observation was 9 miles (15 km) to the E (91°) from Gulfport, MS, USA.

At 15:33:30Z (last observation), the observation was 9 miles (15 km) to the E (91°) from Gulfport, MS, USA.
Member Since: July 3, 2005 Posts: 426 Comments: 128626
121. VR46L
Quoting 70. yoboi:



Yeah I have figured out that pattern that goes on over there.....it took some time but I had to look at the right maps....


Its just rainy drizzly days most of the time !
Member Since: March 1, 2012 Posts: 0 Comments: 6927
93L moving faster than forecast?
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Quoting 93. SouthernIllinois:
>Unacceptable. ;)

Well, from the current discussion going on I guess I have to run to the liquor store for breakfast?


Maybe possibly strong storms headed my way, hopefully not as bad as last night. House got hit by lightning last night, everyone is okay but my brand new TV and a few other things are toast. Hopefully insurance replaces the things, just happy there was no fire and that my son and fiance weren't upstairs because our bedrooms are right where the lightning hit.
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Quoting 104. MississippiWx:
Apology to the Community

Yesterday seemed to find every raw nerve this community had. Relax, you are human.
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Quoting 113. SouthernIllinois:

Don't even know what the hell you did, but don't have to. I never hold grudges....am forgiving. You have nothing to worry about over here friend. Just you better not go ANYWHERE since I love the insight you bring. You hear me. THAT IS AN ORDER.

lol


Lol. I'm going nowhere.

Btw. Everyone try to keep comments about this on my blog. That is what it is there for and I don't want you getting banned for commenting about this here.

Now, back to the topic. :-)
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Quoting 108. will40:
according to tropicatlantic recon is still on runway

it does appear that way...here too

Link
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Quoting 106. RitaEvac:





I can't even count how many times that has happened to me and I am sure others in Houston LOL
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Biblical, eh? Don't I feel lucky...

Area forecast discussion
National Weather Service Denver/Boulder Colorado
941 am MDT Thursday Sep 12 2013


Update...major flooding/flash flooding event underway at this time with biblical rainfall amounts reported in many areas in/near the foothills. Precipitable water values in excess of an inch and a quarter on GPS sensors certainly support lots more rain today and tonight. 13z hrrr run has another 1-3 inches of rain predicted in the foothills through 04z so things are not looking good. Will extend the area of the Flash Flood Watch to include zone 43 and also extend it in time through 12z tomorrow morning.
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Quoting 104. MississippiWx:
Apology to the Community


No worries man some people on here can really push that nerve. Some say just ignore but that's not so easy sometimes.
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Quoting 101. SouthernIllinois:

Seabreeze time means seabreeze time....my speciality bartending drink. Vodka....a lil grapefruit juice with a splash of cranberry juice. Ahhhhhhhh.


How bout Ruby Red Vodka
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according to tropicatlantic recon is still on runway
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Quoting 101. SouthernIllinois:

Seabreeze time means seabreeze time....my speciality bartending drink. Vodka....a lil grapefruit juice with a splash of cranberry juice. Ahhhhhhhh.


Still here and no answer yet??? I thought it was an easy question for someone of your expertise!
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Quoting 97. SouthernIllinois:
Of course crapping out. Should have known better than to ever think this had a chance to make it into Cypress in the first place. :(




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Summary of Flooding in the Colorado Front Range
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Apology to the Community
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Quoting 98. GatorWX:


I didn't mention that, but that's just another piece of the puzzle. It's really incredible. It could be quite historic for that area.


I have been watching this in the models for sometime that if 93L makes landfall in Mexico the Colorado better get ready as the steering flow suggest 93L will move toward El Paso then up the Front Range causing an epic flood event.
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Large rock slide in Boulder Canyon near Magnolia is blocking both lanes, according to scanner.
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Denver
NEXRAD Radar

Storm Total Surface Rainfall Accumulation ° Elevation
Range 124 NMI

Member Since: July 3, 2005 Posts: 426 Comments: 128626
Firehose...

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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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