Eric Berger

Beta’s heavier rains moving inland, as coastal waters remain high

1:45pm CT Monday: Tropical Storm Beta continues to slog toward the Texas coast this afternoon. In its 1pm update, the National Hurricane Center said the storm has weakened this morning, with sustained winds dropping from 50 to 45 mph, and a rise in the storm’s central pressure from 996 to 999 mb. This is another indication of a system losing some of its organization. Beta is still moving toward Texas with a landfall tonight near or south of Matagorda Bay.

Although Beta is weakening—a very welcome trend for a cyclone nearing landfall—it is nonetheless creating some unfortunate impacts on our region’s weather. Let’s talk about coastal surge and rainfall, and then take a look at the forecast for the rest of today.

Coastal surge

There are reports of water covering low-lying areas along the coast, and inland along waterways connected to the Gulf of Mexico, such as Galveston Bay and Clear Lake. Based upon the latest modeling, we believe this morning’s high tide was the worst of the surge our region will see, with this evening’s tide perhaps half a foot lower than conditions observed Monday morning. Conditions should slowly improve on Tuesday and Wednesday.

Tide and surge observations and forecasts. (National Weather Service)

Rainfall

We have begun to see some bands of moderate to heavy rainfall move into the coast today, particularly in southern Brazoria and Galveston counties. Fortunately, most of these storms have been producing rain at rates of 0.5 to 1.5 inches per hour. (Rates above 2 inches per hour will generally flood streets). The heaviest band of these training storms is now lifting into the Houston metro area, and will be the focus of activity this afternoon. Currently, it looks like these storms may produce 2 to 3 inches of rain total as they slowly progress northward, so it could impact the afternoon and evening commute home. We don’t anticipate more than some street flooding at this point, but please do take care. Should the situation warrant, we will update the site.

Houston radar at 1:22 pm CT. (RadarScope)

Another threat today is tornadoes. NOAA’s Storm Prediction Center says a few “brief” tornadoes are possible this afternoon and evening, although it is holding off issuing a tornado watch for now. Overall, the environment is not strongly supportive of tornadoes, but we do often see a few in the northeast quadrant of a landfalling storm. Earlier, the National Weather Service issued a tornado warning for an area near Texas City, but a tornado was not confirmed on the ground.

This evening

We will have to continue to watch the progression of Beta’s rain bands this afternoon and evening as the storm moves closer to the Texas coast. However, we do not expect continual rainfall at this time across the area.

Our next update will be posted no later than 8:30 pm CT.

Beta weakening, storm’s worst effects being felt along the coast

6:55 am CT Monday: Good morning. The overall situation with Tropical Storm Beta remains the same. Coastal regions are seeing very high water levels due to tides, surge, and prolonged easterly winds from Beta. We’re expecting intermittently heavy rain over the next few days in the greater Houston region, but we do not anticipate widespread flooding issues. Before diving deeper into the forecast I wanted to allay any lingering fears about a slow-moving tropical cyclone making landfall south of Houston.

We’ve been saying for days this will not be another “Harvey” for the area due to a variety of factors, including dry air over the state. We realize many of our readers have PTSD after that nightmare storm, and that’s why we created our flood scale messaging. As we have done since Friday, we’re still forecasting a Stage 2 event for the coast, and Stage 1 for inland areas. Rest assured, if another Harvey like-system approaches Texas, we will tell you. We’ll be shouting about a Stage 5 flood from the rooftops. This is not that, however. A radar image of Beta this morning (left) and Hurricane Harvey in 2017 shortly before landfall tells the entire story.

Radar images of Beta and Harvey. (RadarScope)

Beta summary

The storm has weakened over night, and now has sustained winds of 50 mph. It is moving slowly to the west, and will likely make landfall along, or south of Matagorda Bay later today or early Tuesday. The storm is continuing to battle moderate wind shear and the entrainment of dry air into its circulation. These factors are unlikely to change much as the storm nears the coast, and the National Hurricane Center anticipates it will remain at its current intensity until landfall. After this time it should slowly weaken as it tracks inland, or along the coast, before exiting to the northeast on Wednesday or Thursday.

Immediate threat

The most pressing problem at the moment is tidal surges along the upper Texas coast and along nearby waterways. Tides are running 4 feet or more above normal along the coast and locations such as Clear Lake, and affecting nearby roadways. Tides will remain high today and tonight before perhaps receding a bit on Tuesday, and likely considerably more on Wednesday. Take care on low-lying roads.

The peak surge should occur with high tide this morning, with high waters again this evening. (National Weather Service)

Rainfall potential

Due to the aforementioned dry air, we do not expect prolonged periods of heavy rainfall across most of the area, however we cannot rule out some training rainfall in isolated areas. Between now and Wednesday, our best guess remains that areas south of Interstate 10 will generally see 2 to 6 inches of rainfall, with areas north seeing 1 to 4 inches. However we probably will end up seeing some 10-inch bullseyes over the region. There may be some spotty flooding associated with this, but for the most part our area’s bayous can handle these kinds of rains. We’ll remain vigilant for any changes to this forecast.

NOAA forecast for rainfall through Friday. (Pivotal Weather)

Winds

Winds over the area likely reached their maximum extent early this morning—Galveston Fishing Pier reported a gust of 49 mph shortly after midnight—and should gradually wane later today. As we’ve been stating, Beta is a not a significant wind threat.

Weather ahead

Both Monday and Tuesday will see a high chance of rain, as bands of rainfall from Beta move onshore. Some training will be possible, but there also should be breaks between rainfall. Our biggest concerns for heavy rainfall are in Brazoria and Galveston Counties, where roads near the coast may already be submerged. Please do not drive into high water today. Highs likely will range from the upper 70s to low 80s. It’s worth noting that Sunday’s high temperature of 78 degrees was Houston’s coolest day since May 9th.

Wednesday should be somewhat of a transition day as Beta lifts away, to the northeast. We probably will see some trailing showers, but the threat of very heavy rainfall should have ended by then.

Thursday, Friday, and Saturday

The second half of the week should see the return of sunshine and, accordingly, highs in the 80s or low 90s. It will be a good time for the region to dry out

Cold front?

Our best global models indicate that a reasonably strong cool front will push into Houston early next week, perhaps around next Monday or Tuesday. It’s still a long way off, but the signal for this front is reasonably strong—we’re hoping to be able to celebrate Fall Day around before the end of the month, when nighttime temperatures in Houston fall to 65 degrees or cooler. So, fingers crossed!

Our next post will come no later than 2:30pm CT Monday.

Beta impacting the coast already, but we still have questions about rain

8pm CT Saturday: We’re still in wait-and-see mode with Tropical Storm Beta, which remains nearly stationary in the northwest Gulf of Mexico this evening. Here are our key takeaways this evening:

  • Beta is fighting dry air, and moderate westerly shear. It still has the potential to strengthen, but the National Hurricane Center no longer expects Beta to become a hurricane before approaching the Texas coast, likely near Matagorda Bay, on Monday or Tuesday.
  • Water levels along the Texas coast in places like Crystal Beach and the west end of Galveston Island are starting to rise in response to Beta, and the storm may inundate low-lying areas for a few days. Final preparations should be taken along the coast soon.
  • Beta still poses a significant flooding risk to Texas and Louisiana that we need to take seriously. But we have lots of questions about this, and unfortunately no good answers right now. We’ll discuss this more below.

Flood chances

So this is a difficult one, and you’re going to have to bear with us while we suss out an accurate forecast. As a tropical storm, Beta definitely has the potential to bring a lot of rainfall to the Texas coast, and that is our primary concern. However, we do not think that is a slam dunk.

You may have seen the five-day rainfall forecast that the National Hurricane Center released with its 4pm CT package this afternoon (shown below). The totals are rather eye catching. This forecast seems to be a bet that because Houston will lie in the northeastern quadrant of Beta as it makes landfall and moves inland, that our region will see very heavy totals.

Estimated rainfall forecast for now through 7pm CT Thursday. (NOAA/WPC)

Yep, this shows a solid 15 to 20 inches along the coast, and a band of 10 to 15 inches across the Houston metro area. This is what you would expect from a typical tropical storm following Beta’s track.

However, there are several ways in which this forecast could go bust. One is that Beta moves far enough inland into Texas early next week that it gets cut off from a moisture supply. Two, Beta is going to be fighting dry air to its west, and this may starve the convection near the storm’s center, which would lessen rain totals along the Texas coast. Finally, we could see the heaviest remains far removed from the center. This is the scenario depicted in virtually all of the global model guidance, both their operational runs and ensemble outputs. Nearly all of this guidance suggests five-day rain totals of 2 to 8 inches across the greater Houston metro area, including Galveston. These models do not do a good job of picking up small-scale convective processes, but there is a strong signal here that is hard for us to ignore.

So what is our advice? We think the NOAA precipitation forecast offers a reasonable “worst case” scenario for rainfall, but we also think there is a reasonably high chance of a bust. We are not going to have the final answer on this for at least a day or two longer.

Coastal impacts

Water level rises along the upper Texas coast have begun today, and will worsen Sunday into Monday as Beta eventually moves closer to the state. Beta’s winds will drive large swells over the Northwest Gulf of Mexico by Sunday into Monday, which will bring waves on top of a storm surge of 2 to 4 feet along the Galveston and Bolivar beaches. This will flood low-lying areas, including Highway 87. Coastal flooding will also be possible in El Lago, Nassau Bay, Shoreacres, Seabrook and portions of Baytown.

Probability of Tropical Storm-force winds over the next five days. (National Hurricane Center)

The current estimate is that there is about a 50 percent chance of sustained tropical storm-force winds along Galveston Island and southern Brazoria County. However, there are real questions about whether Beta is going to be able to battle moderate shear and dry air to intensify further than its 60-mph sustained winds as it moves toward Matagorda Bay, further down the coast. Along this track, we do not anticipate widespread power outages due to downed lines in Galveston or Houston.

So that’s what we’ve got tonight. Matt will have our update no later than 9am CT Sunday.

Tropical Storm Beta turns west toward Texas: Be wary, but not overly worried

2pm CT Saturday: Tropical Storm Beta made its expected turn west earlier today and is now crawling toward the Texas coast at 2 mph, according to the National Hurricane Center. Its maximum sustained winds are 60 mph. Our overall forecast for the Houston metro area has not changed at this time: We still anticipate Stage 2 flood conditions south of Interstate 10, and Stage 1 for areas north of Interstate 10. Bottom line: We have not seen anything today that makes us any more concerned.

I want to start with a satellite image of the Gulf of Mexico this afternoon that illustrates water vapor—a good proxy for convection. When you look at this image there are a couple of important things to notice. One, the precipitation associated with Beta is strongest near its core and well to its east. Second, the reddish hues across Texas indicate dry air. Some of this dry air is wrapping into the circulation of Beta, which is helping to hamper its intensification. Finally, it’s clear that until Beta moves further west the bulk of its precipitation is going to fall over the Gulf, or southern Louisiana.

Water vapor satellite image for Beta on Saturday afternoon. (NOAA)

In this afternoon post I want to discuss the timing of what to expect after today, and when. The usual caveats apply, this is a dynamic weather system, so forecasts will change. But this is our best guess as of 1:30pm Saturday afternoon.

Sunday

Beginning fairly early on Sunday we could see some outer rain bands from Beta moving into the Texas coast. Most likely these will be light to moderate, at least during the daytime hours. Coastal areas may see upwards of 1 to 2 inches of rain, but inland areas will likely see less. All in all, this should not be too disruptive. Coastal areas may see tides 3 to 4 feet above high tide levels, particularly on Sunday evening, and Monday morning. Tropical Storm force winds may arrive along the coast, from Matagorda Bay to Galveston by Sunday evening or during the overnight hours.

Monday

Most of the best available model guidance suggests we will see similar conditions on Monday as the storm’s center nears the Texas coastline, probably near Matagorda Bay. I should note that overall confidence in this track remains somewhat low, and that a northward jog in the track would bring more serious winds and surge into Galveston Bay. However, we don’t expect that right now. Beta will likely will be a high-end tropical storm or a low-end Category 1 hurricane at this time. Winds will probably increase across the Houston area, although I’m not sure they will reach Tropical Storm-force.

Coastal flooding outlook for Galveston. (National Weather Service)

Tuesday and Wednesday

These are the days when we can probably expect the heaviest rainfall, although amounts are still to be determined. This is the period when we expect Beta (or the remains of Beta) to begin lifting to the north and then northeast, perhaps bringing its circulation near the Houston metro area. By Thursday we should see improving conditions across Texas.

So really, how much rain?

If you remember the satellite image at the top of this post, almost all of the convection and strong storms lay to the east of the storm’s center. We think that the most likely scenario is that this pattern continues during the coming week, and we end up with a situation where most of the Texas coast north of Corpus Christi sees 4 to 12 inches of rain over the next week, with lesser amounts inland. This is very general, ballpark value. The key thing to remember is that this scenario would not lead to widespread, catastrophic flooding.

12z GFS ensemble forecast (shown) and other recent models indicate most precipitation will be offshore. (Weather Bell)

However, we cannot discount the possibility of Beta really getting its act together over the next day or two, and becoming a prodigious rainmaker over Texas. In this reasonable worst-case scenario, areas from Matagorda Bay to Galveston to Beaumont are at risk for 20 inches or more of rain, with 10-plus inches for parts of Houston. That is the high-end risk. But again we do not favor that scenario right now; and if our view changes we will let you know post-haste with a hasty post.

Our next update will come no later than 8pm CT this evening.