Eric Berger

Beta’s bands continue to impact Houston roadways and bayous

5:45am CT Tuesday: Good morning. We are continuing to closely monitor heavy rainfall in and around the Houston metro area due tropical moisture. Some areas south of Interstate 10 have received 5 to 10 inches of rainfall during the last 24 hours and more is in store today.

Tropical Storm Beta may or may not be a tropical storm any longer—the official forecast pegs it at 40 mph sustained winds, with fairly low confidence—but this matters little to the ongoing forecast. Its center has continued moving slowly inland this morning, and is probably located some few dozen miles northeast of Victoria Texas, along the Highway 59 corridor. The storm has drifted a little bit further inland than forecasters anticipated, and it should wobble around there for about 24 hours. After this time it should start to lift to the northeast, and pull away from the Houston metro area by later on Wednesday.

4am CT Tuesday track forecast for Tropical Storm Beta. (National Hurricane Center)

The biggest threat from this slow-moving tropical system remains rainfall. After widespread rainfall on Monday, the grounds and bayous south of, and along Interstate 10 are now saturated. Minor flooding is now occurring at some locations along Clear Creek and a high tide (at 5:43 am Tuesday) in concert with Beta’s lingering surge is not helping matters. Several other waterways, including Buffalo Bayou and lower South Mayde Creek are also experiencing some issues in West Houston.

Because areas of south and central Houston have received an additional 2 to 5 inches from Beta since midnight, the National Weather Service has issued a Flash Flood Warning until 8:30 am CT. If possible, please stay off roadways this morning in this warned area.

Flash Flood warning in effect until Tuesday at 8:30 am CT. (National Weather Service)

The overall pattern today should be similar to Monday, with bands of rainfall moving in to the Houston area. It is not clear where the strongest of these bands will set up, but radar trends this morning indicate they could be slightly more narrow than those seen on Monday. The likely effect of this is intermittently moderate to heavy rainfall. The good news, if we can find some, is that the heaviest of these storms are generally only dropping 1 to 1.5 inches of rain per hour. This is heavy rain, but not the sort of 2+ inches per hour rates that can quickly back up bayous and roadways. However the constancy of the rainfall adds up.

Right now I do not think Tuesday night will be quite as bad as Monday night, but our overall confidence in rainfall totals at this point is low. Worst case scenario, some areas could see an additional 5 to 10 inches of rainfall today and tonight. Most areas will probably see less.

Our next update will come by or before 9 am CT.

Storms over Houston metro area ease off a bit, but they’ll likely be back

11:55 pm Monday: Congratulations, everyone. We survived Monday—although for the southern half of Houston it was a rainy mess. Rainfall estimates show that some areas near the border between Harris County and Fort Bend and Brazoria counties received 6 to 8 inches of rain during the preceding 24 hours, and it has brought some waterways to bankfull. It did not help that the heavy rains on Monday night came just as a high tide was pushing into Galveston Bay, making it more difficult for area bayous to drain. Otherwise, as expected, areas north of Interstate 10 generally received 2 inches of rain or less.

Radar estimates of rainfall for Monday. Note the swath near Southern Harris County. (NOAA)

So far, even in the hardest hit areas, this has been a mostly street flooding event. But what happens next? We think the next 24 hours will produce plenty of precipitation as well. This is because although Tropical Storm Beta made landfall at 10 pm CT Monday on the southern end of Matagorda Bay, it’s center should now remain nearly stationary for the next 24 hours or so. This means the Houston region will lay within the storm’s northeast quadrant.

We’re most concerned about the areas that have already received 5 or more inches of rain during the preceding day (pink and reddish hues on the map above). As hoped, showers now moving into this area near midnight are lighter and a bit more scattered than earlier on Monday. The storm’s heaviest rains are now more tightly clustered near its center, further to the southwest of the Houston metro area.

Overview of Houston area radar at 11:40pm CT Monday. (RadarScope)

Some of our mesoscale models suggest this clumping of heavier rains could gradually build northeast toward Sugar Land (in a few hours) and Houston and the Interstate 45 corridor by around sunrise on Tuesday. I don’t have great confidence in these models, but it seems as plausible scenario as any. We may also see more feeder bands develop offshore and move inland into metro region during the overnight hours. Additional rainfall amounts of 3 to 6 inches for parts of Houston cannot be ruled out through Tuesday morning.

Our next update will come no later than 7 am CT on Tuesday.

Heavy rains have fallen this evening south and southwest of Houston

Good evening. Training bands of moderate-to-heavy rainfall from Tropical Storm Beta are continuing to move across the greater Houston area this evening. The heaviest rains from 6 to 9 pm fell generally to the south-southwest of Houston, from Friendswood and Pearland through Sugar Land. A few locations received 4 to 5 inches during this three-hour period and it is starting to back up bayous. Other parts of Houston have largely been spared.

Three hour rainfall estimates for 6 to 9pm CT Monday. (NOAA)

These southern areas appear to have won the Beta lottery this evening with a nearly stationary banding feature that is continuing to feed off moisture from the Gulf of Mexico. The National Weather Service has issued a flood advisory for this general region, suggesting an additional 1 to 2 inches of rainfall may occur over the next several hours. So far, the vast majority of area bayous and creeks remain within their banks. According to Harris County Jeff Lindner, here are the waterways of most concern at the moment:

  • Lower Keegans Bayou: overbanks at Roark…flooding is ongoing
  • Willow Waterhole: near bankfull at Westbury
  • Brays Bayou: water levels are within 2-5 feet of bankfull from Gressner Dr to Rice Blvd
  • Clear Creek: Near bankfull along the entire channel and overbanks near I-45
  • Turkey Creek: Within 3 ft of bankfull at FM 1959

Waterways aside, these heavy rains have created a dangerous situation on some area roadways. Tonight is not a great night to be out and about.

My read on the radar is that this prolonged banding feature that has been running up the Gulf Freeway for much of today and this evening, and ultimately bending into Sugar Land and now west Houston, is running out of steam. Offshore, the next band appears to be developing slightly to the north and east, and if this happens it should give some of the region’s aforementioned, hardest hit areas a reprieve in an hour or two.

Our next post will come by or before midnight to see whether I have read the radar correctly.

Storms lighting up I-45 corridor as Beta’s rains spread into Houston

7:55 pm CT Monday: Tropical Storm Beta is limping toward the Texas coast this evening, at a speed of about 5 mph, and will come ashore near Matagorda Bay tonight. It has maintained sustained winds of 45 mph today, but its overall organizational structure is poor. Now that the storm is nearing land, we should start to see some very gradual improvement in coastal flooding over the next two days. The bigger issue is rainfall, particularly a persistent band of showers up the I-45 corridor this evening.

Track

First of all, the most likely track for Beta now is that the storm comes barely inland near Matagorda Bay, and noodles around for pretty much all of Tuesday before beginning to lift to the northeast. Please note it is entirely possible that the center of the storm will slide far enough east that it reemerges over the Gulf of Mexico later on Tuesday or early Wednesday and then scoots up the Texas coast toward Louisiana. If this over-water track happens it will not have much sensible change on our weather in terms of winds and seas. At this point, the near-term track of Beta is almost immaterial—we’ve felt the lash of its winds, and its waves. Now all that’s left is how much rain it puts down over the next two days before exiting stage right.

4pm CT Monday track update for Beta. (National Hurricane Center)

Rainfall

For the most part Beta’s rainfall has been moderate today, and the good news is that most of the storms that have moved through have produced rainfall rates of 0.5 to 1.0 inch per hour. This is within the capacity of our streets and bayous the handle. The one problem area is roughly the Interstate-45 corridor between Galveston and Pearland. Some communities along and adjacent to the freeway have seen in excess of 5 inches today as storms have basically trained over the area since around noon. Even at relatively moderate rainfall rates, these totals add up over time. As a result the National Weather Service has issued a flash flood warning for this area through 8:30pm.

Area of flash flood warning in effect until 8:30pm CT. (National Weather Service)

So what happens this evening and overnight? This I-45 band has slowly been lifting north, so the areas “under the gun” will hopefully get a reprieve later this evening, and we’d expect the heaviest rains to probably fall a little to the east of where they occurred today. However, if the band does not move it could lead to rises on Clear Creek, Chigger Creek, Cowart Creek, and Mary’s Creek—all of which remain comfortably within their banks for now.

At 7:45 pm another area of heavy rainfall just north of Pearland was pushing into Sugar Land and West Houston. Most of these areas, except for Sugar Land, have generally only see 1 to 2 inches of precipitation so far today, so they can handle the additional rainfall. But these will be strong storms as they push through and need to be monitored for additional development.

Pocket of heavy rainfall headed to the northwest at 7:45pm CT. (RadarScope)

The high resolution models do not have a great handle on trends during the overnight hours, and I want to see what happens with these banding features before hazarding a prediction beyond the next hour or two. Therefore I will update again by about 10 pm CT tonight.

Baby Lanza update