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 246. Torito:


I didn't say recon in the first place?...



nop

Quoting 236. Torito:


That's right off the NHC site, and it says it is possible. Don't assume that it is out of the question dude



that's what you said above
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Member Since: June 11, 2013 Posts: 20 Comments: 2737
Boulder Creek Camera (static shot. Click image for live view):

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Quoting 242. Tazmanian:



you are reading it worng they wont send a recon out that out that far they olny go too 55W if they where too send some in out there it would be the Global Hawk not the recon


I didn't say recon in the first place?...
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Product: Air Force High Density (HDOB) Message (URNT15 KNHC)
Transmitted: 12th day of the month at 16:49Z
Date: September 12, 2013
Aircraft: Air Force Aircraft (Last 3 digits of the tail number are 302)
Mission Purpose: Investigate fifth suspect area (flight in the North Atlantic basin)

Mission Number: 1

Observation Number: 01

16:49:00Z 30.417N 88.917W 1016.6 mb
(~ 30.02 inHg) 12 meters
(~ 39 feet) 1018.0 mb
(~ 30.06 inHg) - No Wind 39.4°C
(~ 102.9°F) 21.9°C
(~ 71.4°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 16:39:30Z (first observation), the observation was 10 miles (15 km) to the E (84°) from Gulfport, MS, USA.

At 16:49:00Z (last observation), the observation was 10 miles (15 km) to the E (84°) from Gulfport, MS, USA.
Member Since: July 3, 2005 Posts: 423 Comments: 127810
Quoting 239. will40:


Global Hawk will go that far



yes that is so ture
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243. FOREX
Quoting 240. Patrap:
55W is the Iimit for Manned recon, the Global Hawk Drone can reach Humberto and stay aloft for 24 hours for a Mission.

Relax


lol
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Quoting 236. Torito:


That's right off the NHC site, and it says it is possible. Don't assume that it is out of the question dude.



you are reading it worng they wont send a recon out that out that far they olny go too 55W if they where too send some in out there it would be the Global Hawk not the recon
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55W is the Iimit for Manned recon, the Global Hawk Drone can reach Humberto and stay aloft for 24 hours for a Mission.

Relax
Member Since: July 3, 2005 Posts: 423 Comments: 127810
Quoting 233. Tazmanian:



they wont send a recon that far out they olny go out too 55W


Global Hawk will go that far
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Quoting 215. Bluestorm5:
Today is the day I turn in my resume and my letter of intent to my meteorology professors for opportunities in undergraduate research at UNCA. I can't believe it's finally time to be professional on a real deal. Wish me a luck to get into undergraduate research at UNCA!


Awesome, best of luck!
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Quoting 233. Tazmanian:



they wont send a recon that far out they olny go out too 55W
Global Hawk can...
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Quoting 233. Tazmanian:



they wont send a recon that far out they olny go out too 55W


That's right off the NHC site, and it says it is possible. Don't assume that it is out of the question dude. Besides, they aren't using recon, it is global hawk.
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Quoting 233. Tazmanian:



they wont send a recon that far out they olny go out too 55W


Global Hawk can reach Humberto, P-3 cannot.
Member Since: July 8, 2005 Posts: 259 Comments: 23892
98L remains dry ... TIRED!
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Quoting 232. Torito:
YES! SEND ONE INTO HUMBERTO!

I. ATLANTIC REQUIREMENTS
1. SUSPECT AREA (BAY OF CAMPECHE)
FLIGHT ONE --TEAL 70-- FLIGHT TWO --TEAL 71--
A. 12/1800Z A. 13/1200Z
B. AFXXX 01FFA INVEST B. AFXXX 0210A CYCLONE
C. 12/1515Z C. 13/0900Z
D. 19.5N 93.0W D. 19.5N 94.0W
E. 12/1745Z TO 12/2100Z E. 13/1130Z TO 13/1530
F. SFC TO 10,000 FT F. SFC TO 10,000 FT

2. SUCCEEDING DAY OUTLOOK: CONTINUE 12-HRLY FIXES AS
LONG AS SYSTEM REMAINS A THREAT.
3. REMARKS: POSSIBLE GLOBAL HAWK MISSION FOR 13/1100Z INTO
HURRICANE HUMBERTO OR BAY OF CAMPECHE SYSTEM.
II. PACIFIC REQUIREMENTS
1. NEGATIVE RECONNAISSANCE REQUIREMENTS.
2. OUTLOOK FOR SUCCEEDING DAY.....NEGATIVE.




they wont send a recon that far out they olny go out too 55W
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YES! SEND ONE INTO HUMBERTO!

I. ATLANTIC REQUIREMENTS
1. SUSPECT AREA (BAY OF CAMPECHE)
FLIGHT ONE --TEAL 70-- FLIGHT TWO --TEAL 71--
A. 12/1800Z A. 13/1200Z
B. AFXXX 01FFA INVEST B. AFXXX 0210A CYCLONE
C. 12/1515Z C. 13/0900Z
D. 19.5N 93.0W D. 19.5N 94.0W
E. 12/1745Z TO 12/2100Z E. 13/1130Z TO 13/1530
F. SFC TO 10,000 FT F. SFC TO 10,000 FT

2. SUCCEEDING DAY OUTLOOK: CONTINUE 12-HRLY FIXES AS
LONG AS SYSTEM REMAINS A THREAT.
3. REMARKS: POSSIBLE GLOBAL HAWK MISSION FOR 13/1100Z INTO
HURRICANE HUMBERTO OR BAY OF CAMPECHE SYSTEM.
II. PACIFIC REQUIREMENTS
1. NEGATIVE RECONNAISSANCE REQUIREMENTS.
2. OUTLOOK FOR SUCCEEDING DAY.....NEGATIVE.

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231. Tygor
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.


Bad choice in an area that has been known to get hurricanes. It reminds me of those in Florida and the Carolinas who are shocked when a hurricane hits...seems to be part of the risk.
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Member Since: July 3, 2005 Posts: 423 Comments: 127810
Member Since: July 3, 2005 Posts: 423 Comments: 127810
Quoting 222. weathermanwannabe:
Here are the current winds at the only buoy in the BOC due North of 93L. Not much in the nature of winds at the moment, and air pressure is currently rising at that location, but the winds are out of the E-NE at 15 knots; that is consistent with a developing low to the south of that location:

Station 42055
NDBC
Location: 22.203N 94W
Date: Thu, 12 Sep 2013 15:50:00 UTC
Winds: ENE (70°) at 15.5 kt gusting to 17.5 kt
Significant Wave Height: 5.2 ft
Dominant Wave Period: 7 sec
Mean Wave Direction: ENE (58°)
Atmospheric Pressure: 29.84 in and rising
Air Temperature: 84.0 F
Dew Point: 76.1 F
Water Temperature: 84.9 F


Also note the toasty water temps.



93L will like that



all so the recon airplane is back up


Link
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Quoting 215. Bluestorm5:
Today is the day I turn in my resume and my letter of intent to my meteorology professors for opportunities in undergraduate research at UNCA. I can't believe it's finally time to be professional on a real deal. Wish me a luck to get into undergraduate research at UNCA!


Good luck Blue! You have a promising future :)
Member Since: September 5, 2007 Posts: 0 Comments: 3481
wheels up on recon
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Colorado cannot catch a break with weather. Last summer it was the Waldo Canyon fire. This year it's flooding. Shows that CO deals with more than just snow.
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Quoting 215. Bluestorm5:
Today is the day I turn in my resume and my letter of intent to my meteorology professors for opportunities in undergraduate research at UNCA. I can't believe it's finally time to be professional on a real deal. Wish me a luck to get into undergraduate research at UNCA!


G/L!!!
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Quoting 220. FOREX:


B


Yea I'm thinking A or B right now as the most likely solution.
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Here are the current winds at the only buoy in the BOC due North of 93L. Not much in the nature of winds at the moment, and air pressure is currently rising at that location, but the winds are out of the E-NE at 15 knots; that is consistent with a developing low to the south of that location:

Station 42055
NDBC
Location: 22.203N 94W
Date: Thu, 12 Sep 2013 15:50:00 UTC
Winds: ENE (70°) at 15.5 kt gusting to 17.5 kt
Significant Wave Height: 5.2 ft
Dominant Wave Period: 7 sec
Mean Wave Direction: ENE (58°)
Atmospheric Pressure: 29.84 in and rising
Air Temperature: 84.0 F
Dew Point: 76.1 F
Water Temperature: 84.9 F


Also note the toasty water temps.
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221. Relix
Quoting 215. Bluestorm5:
Today is the day I turn in my resume and my letter of intent to my meteorology professors for opportunities in undergraduate research at UNCA. I can't believe it's finally time to be professional on a real deal. Wish me a luck to get into undergraduate research at UNCA!


Wish you the best!
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220. FOREX
Quoting 219. Torito:


I think it will:

A. Get stuck in the GOM and head towards FL, striking as a moderate to strong TS.

B. Turn west over Mexico and die off, resulting in a TD to weak TS making landfall with heavy rain.

C. Head to TX, making landfall as a moderate TS, with a bit of rain soaking the state.


B
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Quoting 212. CaneHunter031472:


I can tell you one thing for sure. It is highly unlikely that it will make a turn to the north.


I think it will:

A. Get stuck in the GOM and head towards FL, striking as a moderate to strong TS, or possibly a cat 1 hurricane.

B. Turn west over Mexico and die off, resulting in a TD to weak TS making landfall with heavy rain.

C. Head to TX, making landfall as a moderate TS, with a bit of rain soaking the state.
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How long until we get numbers from RECON?
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Road closures in our area (the red circles with a white bar) continue to multiply.


(Click image for live, clickable data on current closures)
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Today is the day I turn in my resume and my letter of intent to my meteorology professors for opportunities in undergraduate research at UNCA. I can't believe it's finally time to be professional on a real deal. Wish me a luck to get into undergraduate research at UNCA!
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214. Relix
98L.... 98L you can do it!
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Member Since: January 1, 2008 Posts: 0 Comments: 2847
Quoting 195. CybrTeddy:


The answer lies on the other side of the Pacific if you want your answer for the GFS's consistency, you'll note the strength of the low to the south in the GoH was stronger than it was on the 06z, causing it to compete for energy and dragging it southwards.

Still though, the 00z showed almost no development, the 06z showed a hurricane, the 12z showed a moderate tropical storm, it's quite clear the GFS isn't sure what to do with 93L. It's obvious though the intensity will be determined of track.


I can tell you one thing for sure. It is highly unlikely that it will make a turn to the north.
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Quoting 210. hurricanes2018:
invest 93L stating to look like a tropical storm with winds 40 mph


Yea, looks like a strong TD or a minimal TS.
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invest 93L look like a tropical storm with winds 40 mph
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Quoting 185. Patrap:




Glad to see a bit of a dry slot working its way into the county, but the larger view shows there's still plenty of rain in our future. Rains are supposed to intensify this afternoon/evening.

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Quoting 185. Patrap:


Next batch coming. Not looking good!
Member Since: January 1, 2008 Posts: 0 Comments: 2847
Quoting 202. Patrap:
AFR HH C-130





cool - thanks.

I was teasing my brother, who is a pilot, and will be taking off shortly from IAH, to go and help them so we can start getting data ;) He thinks I have lost my mind. I said it's been gone for years!
Member Since: September 5, 2007 Posts: 0 Comments: 3481
Quoting 187. B183:
What will it take to get 93L to slide on a more northerly track towards the Texas coast or Mexico border? I think we will gladly eat a strong, slow moving tropical storm or Cat 1 just to get water back in our lakes. We're down to 30% capacity in Corpus Christi.


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.
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93L intensifying really slowly. When recon gets here, I would expect the NHC to declare it a td or a weak TS.

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Pressure still falling near Ex-98L.

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Quoting 125. weatherskink:
I think 93L may have some issues with that feature in S Texas .


I agree
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AFR HH C-130



I. ATLANTIC REQUIREMENTS
1. SUSPECT AREA (BAY OF CAMPECHE)
FLIGHT ONE --TEAL 70--
A. 12/1800Z
B. AFXXX 01FFA INVEST
C. 12/1515Z
D. 19.5N 93.0W
E. 12/1745Z TO 12/2100Z
F. SFC TO 10,000 FT
Member Since: July 3, 2005 Posts: 423 Comments: 127810
HWRF calling for slow-moving Ingrid.

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gabs is going back to TD AT THE 8pm advisory, most likely. Convection is diminishing once again.

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Quoting 197. HurricaneAndre:
--TEAL 70--


That's the call sign :)
Member Since: September 5, 2007 Posts: 0 Comments: 3481

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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.