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 1547. SLU:
My early-April ACE forecast for 2013 of 130 - 190 units is going to BUST.

ACE to date (2013): 16.785

ACE to date (1981-2010 Climatology): 56

September 28th.



This year, well... I have so many bad thoughts about it. And ex98L won't do anything to improve the picture...

B-U-S-T NEUTRAL YEAR
2014 : B-U-S-T ELNINO YEAR

The future is not pretty lol
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Quoting 1548. beell:
Well after TD 10 moves ashore, the moisture should continue to wrap around the western periphery of the steering ridge.


09/13 06Z GFS Accumulated Precipitation @ 120 hrs.


Yes but us in East Texas get nothing :(
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Quoting 1593. ihave27windows:


.
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Lets go back to sleep.
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Quoting 1591. beell:


Next week, M. Always next week!


But I want an Oompa Loompa NOW!
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1592. GatorWX
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1591. beell
Quoting 1584. ihave27windows:




Today, it seems TD 10 could be sending rain our way?
Anyone?


Next week, M. Always next week!
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1590. GatorWX
Quoting 1587. SouthernIllinois:

Joe B, the excellent forecaster as he is, does not fully endorse GW with an agenda. Others on here do.

Do the math: The envy and disdain runs rampant. It's quite simple.


Mornin Puff,

Gumbo?



; )
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Just a quick post on thoughts I've had over the last couple of days: Regardless of some attitudes on the blog (the minority) everyone has an absolute right to view and posts weather related comments or graphics on the blog unless banned by those in charge; Most are not on this sight as a way to make friends or enemies; most do not come on the sight to hear the minorities drama; like when you go to work, "leave the Drama at the Front Door" No one person or select few bloggers make this site worth coming to; the people that disagree with the popular posts regarding storms, tracks, or development are not usually trolls, they are just fellow bloggers with their own ideas even if their thoughts are somewhat ridiculous at times, after all sharing ideas regarding weather is what the sight is all about and we all have a right to do that here. The only people credible and educated enough to discredit a fellow blogger harshly is someone with a weather/science related PHD. These are just my thoughts, whoever doesn't like them has that right, but the sun is coming up tomorrow for us all and we all still have our personal lives to live regardless of this blogs few who act superior and criticize others without warrant. Poof away, but doing so will have you only reading posts from a narrow point of view, and you might miss something important or that could make you laugh. At the end of the day this is just weather, weather has always been around and always will, before and after you; doesn't matter what you want it to do, or how many agree with you, for the weather is going to be ultimately controlled by forces that we are all somewhat ignorant on. Back to the tropics now.
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1585. FL1980
Quoting 1549. Neapolitan:
Yes, Joey, it looks like it should have been downgraded. Seriously. As the NHC noted, that "monster blowup" exhibits no telltale banding, and ASCAT found no winds above about 30 knots. IOW, it was downgraded from a tropical storm because it no longer is a tropical storm, not because the NHC isn't aware of things that Bastardi believes himself to know.

As has been said before, JB should leave the heavy duty meteorological analyses to the educated and experienced grownups, and stick to forecasting daytime highs in State College...


Why do people on this blog continue to mock Joe Bastardi? Is it because you disagree with his views? For people who don't like Joe Bastardi you certainly follow what he says a lot. He has his views and you have yours.
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Five years ago today, at about this time, I was out in the rain and wind looking for my St. Bernard Kalli. Ike had, for the most part moved through, and there was finally enough of a break to let the dog out. We weren't alone though; it seems a lot of dogs in the neighborhood bolted out when the doors opened. Along with all the people looking for their dogs, and dogs looking for the perfect spot, there were egrets in the street. Dazed and confused, literally...and I worried about them, but I knew I couldn't help.

We found Kalli, thankfully she was fine =) and we went home and began cleaning up our yard. We lost a maple tree and our chimney topper. That was it. The neighborhood immediately to our east lost their roofs, and sustained a great deal of damage. Crazy, but could be a custom homes vs. cookie cutters.

Today, it seems TD 10 could be sending rain our way?
Anyone?
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1583. beell
Quoting 1577. Neapolitan:
AL, 10, 2013091312, , BEST, 0, 194N, 951W, 30, 1000, TD, 34, NEQ, 0, 0, 0, 0, 1008, 180, 90, 0, 0, L, 0, , 0, 0, TEN, M,


60 nm ENE of Veracruz.

Station SACV4 - Sacrifice Island, Mexico
19.174 N 96.093 W



5 day pressure plot


5 day wind speed plot
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1581. VR46L
World weather in one image

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Found Ts winds.
Member Since: June 11, 2013 Posts: 20 Comments: 2871
Quoting 1577. Neapolitan:
AL, 10, 2013091312, , BEST, 0, 194N, 951W, 30, 1000, TD, 34, NEQ, 0, 0, 0, 0, 1008, 180, 90, 0, 0, L, 0, , 0, 0, TEN, M,
I believe shear from 90E may be affect it plus that is close to land.
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1578. beell
Quoting 1572. GatorWX:


It definitely is monsoonal in nature. I don't see this coming together instantly, but if it does, with time to spare, then it could do big things.


Edited comment to monsoon depression.
(monomania runs rampant)
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AL, 10, 2013091312, , BEST, 0, 194N, 951W, 30, 1000, TD, 34, NEQ, 0, 0, 0, 0, 1008, 180, 90, 0, 0, L, 0, , 0, 0, TEN, M,
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Quoting 1574. GatorWX:


Good morning to you Cane. Still a lot of moisture in the ground here. The mower kept bogging down and stalling yesterday. The ditches are finally empty! The grass was lush and long though. I doubt we're anywhere near our "dry" season yet.



That winter of 09-10 was brutal here. Relative! It killed a lot of trees and fish though, so it was cold, period. Lows in the mid-20's and highs in the upper 40's, bleh! This is swFL darnit!


I know. Used to work at the USDA station in Miami. Specializing in tropical/sub-tropical tree crops. For the first time they had ice - it was horrible for the germplasm they maintain.
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GFS shows Humberto becoming more shallow rapidly, and possibly redeveloping into a weak TS when it gets further west, if it can survive the trip.

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1574. GatorWX
Quoting 1570. CaneHunter031472:


Good morning Gator. A whole 2 weeks without any significant rain here on th MS Gulf Coast and enjoying the Dry air. Best of all. My grass is starting to go dormant so less mowing required. Either that or it's about to die.


Good morning to you Cane. Still a lot of moisture in the ground here. The mower kept bogging down and stalling yesterday. The ditches are finally empty! The grass was lush and long though. I doubt we're anywhere near our "dry" season yet.

Quoting 1566. daddyjames:



Good morning Gator.

I miss that - along with the coast. Being a SoFLian for the vast majority of my life, cold is not something I have grown accustomed to - yet. The weather is fantastic now, but in a four to five months . . . sigh.


That winter of 09-10 was brutal here. Relative! It killed a lot of trees and fish though, so it was cold, period. Lows in the mid-20's and highs in the upper 40's, bleh! This is swFL darnit!
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Good morning folks. Currently it's 73° with 100% humidity and light fog. 30% chance of rain today. I received a weeks woth of rain yesterday evening.
2.86" in two hours.
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1572. GatorWX
Quoting 1564. beell:


Perhaps indicative of stronger boundary layer winds well removed from the center. A hallmark of the monsoon.

Ok, I'll give the whole monsoon thing a rest for now.
(not)
:)


It definitely is monsoonal in nature. I don't see this coming together instantly, but if it does, with time to spare, then it could do big things.
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Good morning Blog!!
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Quoting 1560. GatorWX:
Morning James,

Same old, same old here.

73 F, 98% RH, 72 F DP, 20% Chance of Rain, Forecasted temps in the low 90's. Just another summer day.

No rain in the last two days, so that's been a plus.


Good morning Gator. A whole 2 weeks without any significant rain here on th MS Gulf Coast and enjoying the Dry air. Best of all. My grass is starting to go dormant so less mowing required. Either that or it's about to die.
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Quoting 1562. islander101010:
characters spent 1000s of post writing about the high pressure was going to force the systems west this yr. only problem while the high was strong there were no cyclones.


Not just characters - who knew the tropics would take a vacation throughout the entire month of August?
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1568. GatorWX
CMC is back on board developing 98L.
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Humberto is now severely sheared

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Quoting 1560. GatorWX:
Morning James,

Same old, same old here.

73 F, 98% RH, 72 F DP, 20% Chance of Rain, Forecasted temps in the low 90's. Just another summer day.

No rain in the last two days, so that's been a plus.



Good morning Gator.

I miss that - along with the coast. Being a SoFLian for the vast majority of my life, cold is not something I have grown accustomed to - yet. The weather is fantastic now, but in a four to five months . . . sigh.
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DMAX didn't help 10 much for what I see. Too close to land I guess.

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1564. beell
Quoting 1559. GatorWX:


It doesn't look ideal and there still seems to be quite a lot of influence between 90E and 10. Needs distance.


Perhaps indicative of stronger boundary layer winds well removed from the center. A hallmark of the monsoon.

Ok, I'll give the whole monsoon depression thing a rest for now.
(not)
:)
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1563. GatorWX
Some stragglers might move ashore this morning, maybe...

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characters spent 1000s of post writing about the high pressure was going to force the systems west this yr. only problem while the high was strong there were no cyclones.
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Models remain quite consistent with Humberto strengthening into at least a Category 2 hurricane as it recurves.


ECMWF seems to have the best handle of both TD10 and Humberto overall.
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1560. GatorWX
Morning James,

Same old, same old here.

73 F, 98% RH, 72 F DP, 20% Chance of Rain, Forecasted temps in the low 90's. Just another summer day.

No rain in the last two days, so that's been a plus.
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1559. GatorWX
Quoting 1551. beell:
Still a little bit of a doughnut vort around TD10.



It doesn't look ideal and there still seems to be quite a lot of influence between 90E and 10. Needs distance.
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Pressures are 1000mb in a TD? Impressive.
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1557. SLU
000
WTNT35 KNHC 131157
TCPAT5

BULLETIN
TROPICAL DEPRESSION TEN INTERMEDIATE ADVISORY NUMBER 3A
NWS NATIONAL HURRICANE CENTER MIAMI FL AL102013
700 AM CDT FRI SEP 13 2013

...LIFE-THREATENING FLOODING EXPECTED OVER PORTIONS OF EASTERN
MEXICO...


SUMMARY OF 700 AM CDT...1200 UTC...INFORMATION
----------------------------------------------
LOCATION...19.5N 95.0W
ABOUT 75 MI...120 KM ENE OF VERACRUZ MEXICO
MAXIMUM SUSTAINED WINDS...35 MPH...55 KM/H
PRESENT MOVEMENT...WSW OR 250 DEGREES AT 3 MPH...6 KM/H
MINIMUM CENTRAL PRESSURE...1000 MB...29.53 INCHES


WATCHES AND WARNINGS
--------------------
CHANGES WITH THIS ADVISORY...

NONE

SUMMARY OF WATCHES AND WARNINGS IN EFFECT...

A TROPICAL STORM WARNING IS IN EFFECT FOR...
* COATZACOALCOS TO BARRA DE NAUTLA

A TROPICAL STORM WARNING MEANS THAT TROPICAL STORM CONDITIONS ARE
EXPECTED SOMEWHERE WITHIN THE WARNING AREA WITHIN 36 HOURS.

INTERESTS ELSEWHERE ALONG THE COAST OF EASTERN MEXICO SHOULD MONITOR
THE PROGRESS OF THIS SYSTEM.

FOR STORM INFORMATION SPECIFIC TO YOUR AREA...PLEASE MONITOR
PRODUCTS ISSUED BY YOUR NATIONAL METEOROLOGICAL SERVICE.



DISCUSSION AND 48-HOUR OUTLOOK
------------------------------
AT 700 AM CDT...1200 UTC...THE CENTER OF TROPICAL DEPRESSION TEN WAS
LOCATED NEAR LATITUDE 19.5 NORTH...LONGITUDE 95.0 WEST. THE
DEPRESSION IS MOVING TOWARD THE WEST-SOUTHWEST NEAR 3 MPH...6 KM/H.
A SLOW AND ERRATIC MOTION IS EXPECTED TODAY AND TONIGHT...FOLLOWED
BY A SLOW MOTION TOWARD THE NORTH-NORTHWEST ON SATURDAY.

MAXIMUM SUSTAINED WINDS REMAIN NEAR 35 MPH...55 KM/H...WITH HIGHER
GUSTS. SOME STRENGTHENING IS FORECAST DURING THE NEXT 48 HOURS...
AND THE DEPRESSION IS EXPECTED TO BECOME A TROPICAL STORM LATER
TODAY. AN AIR FORCE RESERVE HURRICANE HUNTER AIRCRAFT IS CURRENTLY
INVESTIGATING THE DEPRESSION.

THE ESTIMATED MINIMUM CENTRAL PRESSURE IS 1000 MB...29.53 INCHES.


HAZARDS AFFECTING LAND
----------------------
RAINFALL...THE DEPRESSION IS EXPECTED TO PRODUCE 10 TO 15 INCHES OF
RAIN OVER A LARGE PART OF EASTERN MEXICO...WITH ISOLATED AMOUNTS
AROUND 25 INCHES POSSIBLE...ESPECIALLY IN AREAS OF MOUNTAINOUS
TERRAIN. THESE RAINS ARE LIKELY TO RESULT IN LIFE-THREATENING FLASH
FLOODS AND MUD SLIDES.

WIND...TROPICAL STORM CONDITIONS ARE EXPECTED TO FIRST REACH THE
COAST WITHIN THE WARNING AREA LATER TODAY.


NEXT ADVISORY
-------------
NEXT COMPLETE ADVISORY...1000 AM CDT.

$$
FORECASTER AVILA
Member Since: July 13, 2006 Posts: 12 Comments: 5104
Quoting 1554. beell:


As long as it is stretched out over a few days...we'll take it.

NHC says 20 knots of SW shear near TD 10 this morning.
:)


I'm burnishing my apple as we speak ;). (We all get lucky sometimes, gotta savor the moment). :D
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Good morning from Central OK,

Well, the front has pushed through - and brought with it wonderful temps - mid-80's through the weekend. Fantastic timing as the state fair is in full swing in OKC.

Locally - the SI story is causing quite a storm, but not of the weather related kind.

Nationally, themes of fire and flood dominate - ironically in regions that have suffered both in the past year. Thoughts and prayers for everyone in CO, and for those in NJ affected by the fire yesterday.

Gear those same thoughts and prayers for folks in Mexico, and potentially Texas. If the model forecasts for precipitation pan out, it matters little if TD10 ever spins up to a named storm.

Gabby is going out with a bang. Humberto continues its tour of the central ATL. 10L is being sheered, and appears will take its time getting its act together. But that is not what is important with this storm.

Again, a reminder, there are folks here from Mexico - and some of us have family and friends there. Please take this into consideration before posting anything "dismissive" of 10L and where it'll impact. Thanks.

Have a fantastic morning.
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1554. beell
Quoting 1550. daddyjames:


Well, Texas' prayers are going to be answered - maybe more so than they wanted.


As long as it is stretched out over a few days...we'll take it.

NHC says 20 knots of SW shear near TD 10 this morning.
:)
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1553. VR46L
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This is gonna be a lot of rain for me! :/
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1551. beell
Still a little bit of a doughnut vort around TD10.

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Quoting 1548. beell:
Well after TD 10 moves ashore, the moisture should continue to wrap around the western periphery of the steering ridge.


09/13 06Z GFS Accumulated Precipitation @ 120 hrs.


Well, Texas' prayers are going to be answered - maybe more so than they wanted.
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Quoting 1540. IKE:

2m
Does this look like it should have been downgraded? Seriously, center under monster blowup. I wouldnt have
Yes, Joey, it looks like it should have been downgraded. Seriously. As the NHC noted, that "monster blowup" exhibits no telltale banding, and ASCAT found no winds above about 30 knots. IOW, it was downgraded from a tropical storm because it no longer is a tropical storm, not because the NHC isn't aware of things that Bastardi believes himself to know.

As has been said before, JB should leave the heavy duty meteorological analyses to the educated and experienced grownups, and stick to forecasting daytime highs in State College...
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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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