ATL: HARVEY - Post-Tropical - Discussion

[tolakram]

Harris County monitors numerous gauges.

Addicks Reservoir is about to hit the spillway elevation. A spillway is generally a concrete structure that sits below the height of the dam (the ones I'm familiar with look like giant stepping stones) to allow water to flow out and not overtop the dam, which would lead to catastrophic failure. They started to do controlled water releases to try and avoid this but unfortunately the water levels have continued to rise.

https://www.harriscountyfws.org/GageDetail/Index/2110?R=1



2109 8/29/2017 6:47 AM 107.94' Spillway is 108'

[PTPatrick]

Wow, good to see the system is really drying out to the west still this morning. Looks like west Houston could start to taper off soon if trends continue. Rain shutting off west of loops too which will help with the reservoirs out west. Looking for silver linings...I know they are already full and the situation worsened for some areas overnight, like Beaumont. Sooner we can get the axis of precipitation past the Sabine the better!

I just say twc was saying buffalo bayou was going down. But then they came back and said it would rise again where stef is due to the reservoir. That's what so hard about his...Houston is so big and it's not total underwater. Lots of hoods are high and dry and when you add the sprawling metro, there seems to be quite a lot of variation in effects. Either way it's one for records!

I should add...despite drying trend. Both nam and gfs swing another axis around the Houston metro later this evening and overnight...hopefully that is just model as I think they haven't done an amazing job predicting precip bullseyes so far.

[nutkin517]

Just saw pics on the Beaumont Enterprise Facebook page showing the Neches River at Pt Neches Park overflowing at the boat docks area.

Greg Bostwick says he sees some strengthening in Harvey and says we are going to get this all over again tonight.

My boss just texted me and said not to come in today unless you're basically across the street.

[tgenius]

Harris County monitors numerous gauges.

Addicks Reservoir is about to hit the spillway elevation. A spillway is generally a concrete structure that sits below the height of the dam (the ones I'm familiar with look like giant stepping stones) to allow water to flow out and not overtop the dam, which would lead to catastrophic failure. They started to do controlled water releases to try and avoid this but unfortunately the water levels have continued to rise.

https://www.harriscountyfws.org/GageDetail/Index/2110?R=1



2109 8/29/2017 6:47 AM 107.94' Spillway is 108'

Mark, does that mean when it goes over the spillway that the entire reservoir would breach and all that water would spill out or just the top-off?

[Hurricane Andrew]

I can't imagine hiw much rain Beaumont has gotten. Does anyone know?

You can go to http://www.dd6.org and click on their interactive maps under rainfall and see the rain gauges since midnight. It has been anywhere from 3-15 inches depending on where you are. Almost 10" in my area.

Thanks, man, I appreciate that. Be safe, keep checking in!

[tolakram]

Mark, does that mean when it goes over the spillway that the entire reservoir would breach and all that water would spill out or just the top-off?

No, but keep in mind I can only speak to what I'm familiar with. Generally these are called retention basins, they are designed to retain water when more than normal flow enters the basin and release at a constant amount, thereby preventing most flooding downstream. In emergencies authorities can increase water release above normal levels to try and ease height levels and, as a safety precaution, spillways are engineered to prevent overtopping. So once the spillway level is reached any water that goes into the basin comes back out and is not retained (so to speak) which will exacerbate the flooding.

Here's a the sat view of the dam and the outlet that allows normal flow to make it through.

https://www.google.com/maps/place/Addicks+Reservoir/@29.7907802,-95.6226615,909m/data=!3m1!1e3!4m5!3m4!1s0x8640dbbf4a2478d9:0x2bf28e4143fe0904!8m2!3d29.7907839!4d-95.6235563?hl=en&authuser=1

[tolakram]

Above spillway level now.

2109 8/29/2017 7:19 AM 108.01'

[Extratropical94]

I found this neat graphic on twitter showing the various heights of the dams and spillways of Addicks Reservoir. Don't know if they are correct, but it gives a good overview how the uncontrolled water flow from the 108'-spillway will increase flooding along the BW8 corridor.

 https://twitter.com/cjmoose/status/902431264535437312

[tolakram]

Pic from above

[Nimbus]

Mark, does that mean when it goes over the spillway that the entire reservoir would breach and all that water would spill out or just the top-off?

No, but keep in mind I can only speak to what I'm familiar with. Generally these are called retention basins, they are designed to retain water when more than normal flow enters the basin and release at a constant amount, thereby preventing most flooding downstream. In emergencies authorities can increase water release above normal levels to try and ease height levels and, as a safety precaution, spillways are engineered to prevent overtopping. So once the spillway level is reached any water that goes into the basin comes back out and is not retained (so to speak) which will exacerbate the flooding.

Here's a the sat view of the dam and the outlet that allows normal flow to make it through.

https://www.google.com/maps/place/Addicks+Reservoir/@29.7907802,-95.6226615,909m/data=!3m1!1e3!4m5!3m4!1s0x8640dbbf4a2478d9:0x2bf28e4143fe0904!8m2!3d29.7907839!4d-95.6235563?hl=en&authuser=1

So this probably means looking at a couple inches less of sheetrock for a few months VS heading for the attic with a hatchet.

[nutkin517]

20+ active water rescues in Jefferson County.

[BobHarlem]

Pic from above

http://www.ustream.tv/channel/SPvAJLUahk2 is a stream video looking at where the left most red arrow is pointing

[NDG]

It has that subtropical/hybrid look this morning.

[Frank P]

still looks east to me, or perhaps just north of due east on the limited vis loops... should have been making that NE turn per all the model runs... not sure if any take it this far to the east... perhaps inland near south central LA coast? who knows

[nutkin517]

still looks east to me, or perhaps just north of due east on the limited vis loops... should have been making that NE turn per all the model runs... not sure if any take it this far to the east... perhaps inland near south central LA coast? who knows

Local meteorologist says Cameron Parish.

[NDG]

I agree with wxman57, the worst of the heavy rains might be over for the Houston area, especially western side of the city. The GFS keeps shifting east towards the Euro. So not unless the converging rains shift to the NW quadrant of the COC the heaviest rains might be over for the city, keeping my fingers crossed my forecast comes through. IMO.

[ace]

I apologize for asking it here, but I don't know where else to ask (so please feel free to point me to the right forum). I'm in NW Harris County (Spring), and I'm hearing of another system in the Western Gulf. The GEFS Ensemble is showing a Middle to Upper Texas Gulf landfall...next week? Is that just an outlier model?

[RL3AO]

I apologize for asking it here, but I don't know where else to ask (so please feel free to point me to the right forum). I'm in NW Harris County (Spring), and I'm hearing of another system in the Western Gulf. The GEFS Ensemble is showing a Middle to Upper Texas Gulf landfall...next week? Is that just an outlier model?

It can't be ruled out. The Euro also hints at a weak low in the western Gulf. I don't think it will become a named storm at this time, but more rain looks very possible.

[flamingosun]

From televised news conf -
Dallas mayor reports that school aged children in the shelters there can immediately start attending Dallas public schools. He named the elementary, Jr high and High schools that will be taking them, All they have to do is walk in, register, and go to class. Bus transport provided, as well, I think.

Phenomenal move by Dallas to provide these children with some immediate sense of normalcy and to relieve parents of that particular worry.

[KBBOCA]

I apologize for asking it here, but I don't know where else to ask (so please feel free to point me to the right forum). I'm in NW Harris County (Spring), and I'm hearing of another system in the Western Gulf. The GEFS Ensemble is showing a Middle to Upper Texas Gulf landfall...next week? Is that just an outlier model?

I'm not an expert on the models, but to my knowledge the NHC is only showing likely potential development of Invest 93L which is WAY WAY WAY out in the far eastern Atlantic. Any talk of it coming to the Gulf are just insane. There's no way anyone can accurately predict where it will go in relation to the US mainland at this point!

http://www.nhc.noaa.gov/gtwo.php?basin=atlc&fdays=2



Praying for all of you affected by Harvey. Stay safe, and may you find unbelievable support from family, neighbors and even total strangers at this time. Many of us far away are standing with you all and will do all we can to help.

And keep asking questions here as needed. It's a great forum full of many people who have MUCH experience in hurricanes and their aftermath.