Storm Warnings

Flood Education and Harvey Update 8/28/2017 10:30am

Posted by on Aug 28, 2017 in blog, Storm Warnings, storm water | 0 comments

Here is the update to the rainfall amounts as of 10:30am 8/28/2017:


As you can see, there have literally been 2′-3′ of rain that has fallen across the Greater Houston area. As a comparison, here are the rainfall totals from last year’s Tax Day Flood 2016:

tax day 2016.png

And here is the Memorial Day Flood of 2016:

Memorial Day 2016.png

Now, one thing to note is that the reason that these floods occurred was because of rainfall rate, or how much rain fell in 1 hour.  While Harvey has not been light on that, it is the primary reason for both of these floods.

If you pay attention to the totals, however, they are unprecedented.  Nothing comes close. While Tropical Storm Allison was devastating to Houston, it also meandered around Houston for almost 2 weeks dumping its rain on the area:

allison track.png

And these charts show the rainfall amounts for the Houston area because of Allison:

allison rainfall.png

While these would be mind-boggling during any year, they pale in comparison to the chart at the top of this post.  This should put this rain event into perspective.  As of noon yesterday enough rain had fallen across the Houston area to fill up a 2 mile by 2 mile by 2 mile cube! And rain is still falling…

water cube.png

Numerous people who are flooded, and have never before flooded, should not be surprised because of the immense amount of rain in such a short time period.  Houston is basically flat, and at over 2200 square miles, and when you put 2′-3′ of water on it, you have 2′-3′ of water on it.  No other way to explain it.  As a point of education, some of you have heard about 100 year flood event, 500 year flood event, etc.  These are a bit of a misnomer.  Here is the lowdown:

year flood events.png

Houston’s rain water flows into street, then into ditches or storm sewers, and then into creeks and bayous and then into rivers and then into Galveston Bay.  This system is called the watershed.  And each watershed acts differently to rain.  Some are slow to drain because they are long and windy, like Cypress Creek.  Some are quicker to drain but end up accumulating behind a levy, like Addicks and Barker Resevoirs. Here is a quick glance at the Greater Houston watersheds:


One thing to note.  Because Cypress Creek’s watershed is SO long and windy and so slow to evacuate rain water, the Harris County Flood Control District and Army Corps of Engineers installed a levy.  This levy doesn’t hold water back, but actually acts as a relief valve for the Cypress Creek watershed.  The waters in Cypress Creek, when they reach a certain level overtop the levy and allow some of the water to make its way down into the Addicks Reservoir.  This has happened with Harvey, and the Memorial Day 2016 and Tax Day 2016 flood events.  I hope this puts this flooding into perspective…even while rain still falls.


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Harvey’s Impact 48 Hours Later in Houston

Posted by on Aug 27, 2017 in blog, Storm Warnings, storm water | 0 comments

48 hours

48 hours in and rain is still coming…looks like the forecasters, unfortunately, got it right.  Houston, which already suffered 2 tremendous, historic floods in 2016 is now bracing itself to see even more record breaking flooding.  There isn’t much to say except for pray for Houston!

Attention: while those whose homes are not flooded and you’re basically safe but stir crazy, please be careful “playing” in the flood waters. While it may look, and could even be, innocent enough, please keep in mind that all of our storm sewers AND more importantly our sanitary sewers are underground. There is always a likelihood that when flood waters are present that there could be some bacteria and other yucky stuff that has been flushed out of overflowing sanitary sewers. Again, if you or your kiddos feel the need to “play” in the flood waters, keep it out of your eyes, ears, mouth and nose. And be sure to wash with anti-bacterial soap after coming into contact with flood waters.

For everyone else, please stay home if it is possible.  Once the rain lets up and waters begin to recede, do your part to help your neighbors for a few days to recover, in what will be months of effort before “normal” returns.

Below is a map of streams and bayous as of Sunday afternoon on 8/27/2017:

48 hours 2.png

And here is the map of current highway closures around town…this does not include surface street!

48 hours 3

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And Now We Wait…

Posted by on Aug 26, 2017 in blog, Storm Warnings, storm water | 0 comments

From Space City Weather

Harvey has arrived in Houston.

Numerous flash flood warnings are posted right now across the Greater Houston area, as an eastern flank feeder band of the storm flows ashore.

Harvey slowly meandering between Victoria and Goliad, shipping intense rains into Houston. (College of DuPage)

These heavy rains are likely to continue throughout the day today. There may be lulls at times, but the dominant weather we see in Houston today is heavy rainfall, leading to street and possibly bayou flooding.

Rain totals have begun to add up. Generally 1-3″ north and east and 3-6″+ south and west since yesterday.

Rain totals through 6:45 AM Saturday are beginning to add up. (Harris County Flood Control)

As the day progresses, rain totals will balloon further. Some models show really impressive rain totals in the Houston area today. I would expect an average of 4-8″ today across the region, with higher amounts possible, especially on the south and west sides and perhaps a few spots east of the city with lesser amounts.

Bottom line in all this, you need to be prepared for significant travel inconvenience and disruption today. And if you can stay put, please do so.

Other concerns

Tornadoes have occurred overnight in some of the cells rotating in. Continue to have a way to get warnings throughout the day today, as isolated tornadoes will continue to be possible. My hope is that the pace of the tornado warnings slows a bit as the day goes on. But continue to have your phone or a weather radio to alert you.

Winds will continue to be gusty at times. Harvey is weakening between Victoria and Goliad, close to tropical storm strength.

It should continue to weaken from a wind standpoint as the day goes on. Still, some occasional 30-40 mph gusts are expected around Houston. Galveston will gust 40-50 mph at times. This could lead to sporadic power outages.

Eric will have more on the longer-range forecast later, but not much has changed since yesterday.

Rainfall over the next five days continues to look extreme. (NOAA)

As we said last night: This is a marathon, not a sprint, and you should be prepared to deal with inconveniences, headaches, and travel problems for the next several days.

More a little later.

Posted at 7:20 AM Saturday by Matt

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Harvey is a Cat3

Posted by on Aug 25, 2017 in blog, Storm Warnings, storm water | 0 comments

As we watch the storm inch towards the Gulf Coast just east of Corpus Christi this evening, the winds will back down from the 115mph+ (some models even claim up to a 125mph Cat4 by end of the night!) beast he is right now. Rain bands have already been battering the coast from Brownsville to Beaumont. And some of them are already dropping some quantity of rain. While the Houston area won’t experience the high winds, the rain will continue to fall. And fall. And fall. As Harvey stalls out of South Texas and then heads East, whatever that may look like, the Houston area will still be getting rain. So there is definitely going to be wind damage in and around Corpus Christi, and there is going to be flooding from the I35 corridor all the way into Louisiana. Some of it will be extensive and devastating. More updates to come!

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Harvey- Winds At Landfall Then Rain for Everyone Else

Posted by on Aug 25, 2017 in blog, Storm Warnings, storm water | 0 comments

From Space City Weather 

Good morning, everyone. After an overnight lull in strengthening, perhaps caused by some dry air working its way into the circulation of Hurricane Harvey, the storm has begun intensifying again. As of 6am CT it had sustained winds of 110 mph, but with the central pressure continuing to fall, the storm’s winds will almost certainly increase. For Texas, there will be two epochs of Harvey: the catastrophic effects from wind and surge during the next day or so for the central Texas coast, and the unfolding, widespread, major flood event from Saturday through the middle of next week for a large swath of the state, including Houston. We will discuss both this morning.

Wind and Surge

We remain confident in the forecast track for Harvey during the next 24 hours, as it moves northwest across the Gulf of Mexico, and comes ashore somewhere near Port Aransas. If you live in, or have property from Rockport to Matagorda, preparations for devastating winds—probably about 120 mph sustained, but maybe higher—should be completed by early this afternoon.

National Hurricane Center forecast track at 4am CT, with probability of hurricane force winds (red high, green low). Also storm surge warnings are shown in red markings along the coast.
Storm surge will be a major problem for low-lying coastal areas. According to the latest National Hurricane Center storm surge forecast, the following numbers represent the realistic “worst case” inundation. This means the depth of water above the ground. You can visit the site itself to zoom in to any location along the Texas coast.

  • Mustang Island to Sargent, including Matagorda Bay: 6-12 feet
  • Sargent to Jamaica Beach: 5-8 ft
  • Jamaica Beach to High Island: 2-4 ft
  • Galveston Bay (Seabrook, Shoreacres, Nassau Bay, Kemah, San Leon) 2-4 ft

For Houston, aside from the above surge numbers, the effects from the immediate landfall of Hurricane Harvey will be relatively modest. As we’ve discussed, winds Friday night and Saturday morning should be manageable, although some areas may briefly see some tropical storm-force winds. The power grid is designed to withstand these conditions—so hopefully most of us will keep the lights on.

Inland flooding

After landfall, Harvey is forecast to move inland perhaps 50 or 100 miles, and then it loses all steering currents for awhile. The most likely scenario is that after wobbling around this weekend, Harvey slowly begins to move to the northeast toward the greater Houston area. It’s center may move back over water, or remain over land, but eventually it should get pulled into a trough over the northeastern United States. (Last night I mentioned the slim possibility of the storm stalling out in the Rio Grande Valley, and while I’m not entirely ruling that out, it seems less likely with this morning’s model guidance).

All of this wobbling and slow movement and proximity to a warm source of moisture (the Gulf, and its bathwater-like temperatures in the upper 80s) will lead to very heavy rainfall and devastating flooding for much of the Texas coast and inland counties. We can’t say exactly where the heaviest rainfall will come (there may be some isolated areas that receive a Tropical Storm Allison-like 35 inches), but we can say with growing confidence that a large region will see 10 to 25 inches of rain between Friday and Wednesday.
The following map represents the best effort by expert forecasters at NOAA to predict where the heaviest rains will fall during that time frame, and indeed it includes much of the greater Houston area. I do not believe it is an exaggeration, nor does it over-hype the threat. Harvey presents a grave threat to the Texas coast from Corpus Christi to Beaumont.

Rain accumulation forecast for now through Friday morning, Sept. 1. (NOAA)

Key takeaways

  • If you live along the central Texas coast heed evacuation warnings, make final preparations this morning, and prepare to endure what is likely to be the strongest hurricane to strike the region since Hurricane Celia, in 1970, or perhaps even Carla, in 1961.
  • For Houston, effects from Harvey’s landfall today and Saturday morning do not appear likely to be dangerous in terms of wind and surge. If you have to work, or make last minute preparations for flooding, there is still time.
  • The outer rain bands will bring precipitation to Houston today and Saturday, but as of now the forecast models show nothing too extreme through at least Saturday afternoon. This is likely the calm before the heavier rains move in later on Saturday night, and then in earnest on Sunday and Monday.
  • The timing and amounts of heavy rain in Houston are not precise. But be prepared for flooding, and tropical deluges from Sunday through Wednesday. Many roads will become impassable. Homes will be flooded. It will be pretty miserable for a lot of people.

We will update again before noon, today. Also, if you’re interested, I’ll be conducting a Facebook live event in conjunction with the Houston Chronicle at 11:30am. I also spoke with NPR’s David Greene early Friday on Morning Edition.

Posted at 6:10am CT on Friday by Eric

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Harvey Update as of 8pm on Thursday August 24, 2017

Posted by on Aug 24, 2017 in blog, Storm Warnings, storm water | 0 comments

From Space City Weather

As of 8:00pm CT tonight, a well-organized Hurricane Harvey is moving northwest, toward the Texas coast. It packed 85-mph winds, but forecasters at the National Hurricane Center still expect it to come ashore late Friday night, or Saturday morning as a major hurricane. The most likely landfall location is between Corpus Christi and Port O’Connor. The storm’s strong winds and storm surge, likely at least 10 to 12 feet above normal tide levels, will pack a punch along the central Texas coast. For people in low-lying areas from Corpus to Freeport, these are potentially life-threatening conditions, and I urge you to heed the warnings of the Corpus Christi National Weather Service office and local officials.

For tonight’s post I wanted to discuss the most likely scenario for immediate effects in Houston, and then reconsider the uncertainty about what comes next. The National Hurricane Center anticipates that sustained winds on Friday night and Saturday morning in Houston and Galveston have about an 80 percent chance of reaching 39 mph, or greater. I think that’s possible, and certainly chances are higher southwest of Houston, in places like Sugar Land. However, at this point the available model data indicates that winds will be manageable in the Houston region during Harvey’s landfall. This is important for a number of reasons, not the least of which is that minimal tropical storm force-winds are something the region’s power grid should be able withstand. Mostly.

Harvey’s satellite appearance at 8pm CT Thursday. (NOAA)

In terms of rainfall, the picture is more grim. It still appears as though the Houston region will see manageable rainfall totals through most of Saturday. That is not to say it won’t rain hard at times, and streets may briefly flood. But for the most part I don’t expect mobility to be greatly impaired. If this forecast changes, we will of course be all over it.

Now, looking ahead to the period of Sunday through Wednesday, uncertainty in the track forecast reigns. We’ve hammered this point for a couple of days, but the point remains that we can’t be sure where the storm is going to go after it reaches the coast. It’s like putting a bowling ball down in the middle of an alley—where will it roll? Harvey is going to be something like that. And unfortunately, for us to really get a good, solid handle on rainfall, we ultimately need to know where the center is going to go. Perhaps the best way to handle this is to spitball some probabilities. So let’s discuss three different scenarios.

The Euro special

Odds: 40 percent. Earlier today we discussed the European model solution for Harvey, which brings the storm into the Texas coast, stalls it, then pulls it back over the Gulf of Mexico and eventually into southwestern Louisiana. Under such a scenario, depending upon the track, much of the Houston area would likely get 5 to 25 inches of rainfall, with the greater totals closer to the coast.

The wandering 59 special

Odds: 35 percent. This solution is favored by many members of the GFS model ensemble, in which Harvey comes inland, and wanders around Corpus Christi, and the rest of the Valley until Sunday or Monday. Then it moves up the Highway 59 corridor, into Houston, over Beaumont, and off into Louisiana. Such a scenario would likely bring 10 to 25 inches of rain to much of the Houston metro area, but totals might not necessarily be greatest along the coast.

Drowning in the Rio special

Odds: 25 percent. Not all of the GFS ensembles pull Harvey back to the north. Some stay in south Texas and peter out. NOAA’s new hurricane model, the HMON, has depicted such a scenario over the last few runs, too. The HMON forecasts that Harvey’s remnants burn themselves out in northern Mexico and southern Texas. Under this scenario Houston might get 5 to 10 inches of rain from Harvey—a lot of rain, but certainly manageable. If this happens, more than a few people will be mad at meteorologists for having stood in line at grocery stores today, and now what they heck are they going to do with all these Pop Tarts?

Key takeaways

  • A major hurricane is coming to the Central Texas coast. It will have bad consequences for that region. However the best available data as of Thursday night suggests the immediate impacts on Houston won’t be extreme.
  • The unanswered question is what happens to Harvey once it reaches the coast. Where will it go, and will it go fast enough? Houston’s rainfall totals over the next five days depend on this, and we just don’t know.
  • Big-time floods are coming to Texas. Certainly the Corpus Christi area and points immediately north and west of there will get too much rain. Flooding will spread to other parts of Texas too, quite possibly Houston. But right now we can’t say that for certain. As I’ve said, it’s either going to be pretty bad, or really really bad here.

We’ll have a comprehensive update early Friday morning.

Posted by Eric at 8:15pm CT on Thursday by Eric

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