Eric Berger

This post will attempt to set expectations for the timing of Nicholas’ rains and winds later today, tonight, and on Tuesday for the greater Houston metro area. Given that there remain some questions about the storm’s precise track and movement speed, these remain estimates, rather than set-in-stone predictions. But we recognize that this information is important for planning purposes, and so we’re giving it our best shot. Thank you for understanding that this is an, uhhh, fluid situation.

The center of Nicholas has been wobbling somewhat this morning, but the National Hurricane Center says the storm is still moving generally northward, and should approach the Texas coast this evening near Matagorda Bay. The storm retains 60 mph winds, and is being hampered by a bit of dry air and wind shear. However, this shear may relax enough to allow Nicholas to strengthen into a Category 1 hurricane before landfall. It will be close. The storm then should move almost directly overhead the Houston area on Tuesday. This post discusses what to expect from this track.

Monday day time

So far, as expected, showers and thunderstorms have been manageable today due to their fairly rapid motion. We should continue to see fast-moving showers traveling from the southeast to northwest throughout the daytime hours. Some of these could be briefly severe, but we don’t anticipate any significant flooding. Winds may also pick up this afternoon, but are unlikely to gust above 30 mph from the east-southeast.

Monday night and Tuesday morning

Based upon our latest data, the period of greatest impact now seems likely to occur between sunset on Monday and about noon on Tuesday. If you want to be perfectly safe, the best plan is to remain off the roads in the Houston area from around 6 pm CT Monday through the middle of Tuesday. However, we realize that this may not be possible for everyone.

In terms of winds, we expect things to start getting breezy by around 10 pm to midnight, particularly along Galveston Island, where gusts may briefly reach hurricane strength. In Harris County, sustained winds may reach 30 to 40 mph, with gusts in the 50s to 60s, especially by midnight or shortly after. This may well lead to some power outages, especially south and west of Houston. I inquired to CenterPoint about their expectations for power losses tonight, but have not heard back. Past experience with such winds suggests there will be isolated to scattered outages due to debris and tree branches that get blown into lines. A storm surge of 2 to 4 feet is likely along the upper Texas coast.

With regard to rainfall, the heaviest storms associated with the core of Nicholas are likely to approach the southern part of the region, including areas such as Lake Jackson, by around 9 pm. The storms should then move near the central part of the metro area, including the I-10 and I-45 south corridors, around midnight or shortly thereafter. As the core of Nicholas moves near the area, the rains should be just ahead of it, possibly exiting Houston by Tuesday morning, or around Noon.

How much rain is going to fall?

This, as ever, is the difficult question. Our highest resolution models continue to indicate the possibility of very intense rainfall rates of 3 to 5 inches per hour, which will quickly back up streets and bayous. It is not advisable to be out and about when these kinds of storms hit—especially because it will be dark, and driving in these conditions is dangerous.

The good news is that it still appears as though Nicholas will keep moving as it tracks through Houston on Tuesday, and away from the region on Tuesday night. This should help to limit overall rainfall totals for most to 5 to 15 inches of rainfall, with a few isolated areas seeing 15 inches or more. Rains totals will be greatest for coastal counties and the next inland tier, which includes Harris and Fort Bend counties.

What about air travel? Schools? The Harry Styles concert?

We’d love to be able to give you concrete answers on these questions, but we don’t have them. I think airline flights from after about 6 pm today through Noon on Tuesday are a big question mark, and I’d probably at least expect some delays.

Area schools should be closed on Tuesday, period.

As for Harry Styles, man, I don’t know. My daughter has been waiting months for this concert and right now there’s a chance the really heavy rains will hold off until after the show is over. But there’s also a reasonable chance its cats and dogs as the show is letting out of the Toyota Center. If they don’t cancel the concert, I’ll hope to be able to provide some better guidance later this afternoon. The safe thing is not to go, of course.

Our next post will come by 2 pm CT.

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Good morning. Tropical Storm Nicholas has a better defined center of circulation this morning, and it has reformed north of where forecasters believed it to be earlier. This, combined with an expectation that Nicholas will now move a little bit more quickly once inland, have led to some changes in timing and rainfall amounts in the forecast. As a reminder, we’re continuing to predict Stage 3 flood conditions for some parts of the greater Houston area through Wednesday. Some, but not all, of our region will see prolonged heavy rainfall beginning later tonight.

Storm status

Tropical Storm Nicholas has strengthened to have maximum sustained winds of 60 mph this morning, as of 4am CT, and is moving to the north-northwest. The storm will likely make landfall this evening between Corpus Christi and Matagorda Bay.

This will bring tropical storm force winds to the Matagorda Bay region on Monday afternoon, and these could spread up the coast to Galveston Island on Monday evening. Tropical storm force wind gusts will spread inland into portions of Harris, Fort Bend, and Colorado Counties late Monday or early Tuesday before beginning to weaken during the afternoon hours. These winds should not be great enough to produce widespread power outages in the Houston metro area, but some local problems are definitely possible.

Storm surge values of 3 to 5 feet are possible from Port O’Connor to Sargent, and 2 to 4 feet from Sargent to Galveston to High Island. Some significant inundation is possible around Matagorda Bay.

For nearly all of us in the greater Houston metro area the biggest concern, by far, will be rainfall.

How wet will it get, and when?

The Houston region should see scattered to numerous showers on Monday, but the heavier rainfall that is most concerning to us should fall between a 36-hour period from Monday evening into Tuesday night, or Wednesday morning. So this is the time when you should plan for the most significant impacts.

The flood threat is very real, but it is slightly mitigated by the fact that Nicholas is now expected to continue moving to the northeast after it reaches Houston, and seems less likely to slow down. This should, hopefully, bring down rain totals somewhat. To that end, the map below represents an average expectation of the rainfall your location will get from Nicholas. For much of our region, these should be mostly manageable totals.

However, it is important to note that we are most concerned about locally higher amounts, which are likely during a tropical system that produces training thunderstorms with extremely high rainfall rates. Therefore, some locations may see as much as 10 to 20 inches of rainfall from Monday evening through Wednesday morning. While these bullseyes are more likely near the coast, they are definitely possible as far inland as Harris, Montgomery, or Waller counties.

Please note that we have issued a Stage 3 flood alert, on the Space City Weather scale, in expectation of these bullseyes.

Conclusions

Nicholas will soon be here. While conditions across the region should be OK for much of today, they may deteriorate fairly quickly this evening or after midnight. In our next post we will try to provide a firmer time for the onset of heavier rain in the metro area—whether that’s 8 pm, midnight, or later. Our next post will come no later than 10:30 am CT.

Good afternoon. The purpose of this post is to emphasize that while we have a pretty good handle on the forecast for Tropical Storm Nicholas over the next 24 to 36 hours, after that many questions remain. And for this reason, we want readers to understand that while Houston may see heavy rain over the next three days, other parts of the state are very much at risk as well.

As of 1pm CT, Nicholas still has 40 mph winds, and it is moving north-northwest across the southern Gulf of Mexico. Winds from the storm may reach South Texas by Monday morning, and the upper Texas coast by around Monday night. It’s possible that Nicholas becomes a Category 1 hurricane, and there will be some effects from this wind and surge. However the greatest threat remains rainfall, so that’s what we’ll now discuss.

I know you’re tired of reading about “uncertainty,” but you’re going to have to bear with us for another 12 to 18 hours on that score. Why? Because Nicholas only now is beginning to develop a reasonably well defined center of circulation, and we’re starting to get better data from reconnaissance airplanes flying into the storm. This improved information will be fed into models. So the computer model outputs after 6pm today will be better, and then models released after midnight tonight should be pretty good. The bottom line: When you wake up on Monday, we should be able to give you a more precise forecast.

In the meantime, it’s important to stress that the greatest threat for heavy rainfall and flooding is not coming on Sunday night Monday, but rather Tuesday and Wednesday as the center of Nicholas moves into the Texas coast. After that, the rains will be largely dependent on the track of the storm—which again we should have a better handle on by tomorrow morning.

Put more explicitly, it is quite possible that some location in Texas inside a triangle from Austin to Corpus Christi to Beaumont sees 20 or more inches of rainfall on Tuesday or Wednesday. (Most areas, of course, will see considerably less). I still probably would favor the Houston, Galveston, or Beaumont regions for the heaviest rainfall, but we just cannot say for sure. So what should you do in the face of this uncertainty? Well, if it helps, you can blame us. But what I would advise is keeping an eye on the forecast, especially tomorrow, when we should have a better handle on things. And then be prepared for the potential of flooding on Tuesday or Wednesday.

Matt will have another update on the situation this evening, before 9pm.

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Ok, now on to the forecast. With this evening’s post we are going to give a general sense of the timing for what to expect, and when. We have some answers about the near-term forecast through Monday, but the bigger and perhaps more important question concerns what comes in the middle of the week.

Invest 94L

As of Saturday afternoon, the Gulf storm, or Invest 94L, remains poorly organized (see for yourself). It is difficult to assign a center to the low pressure system, and this lack of definition is one reason why forecast models are struggling a bit. However, the overall picture seems fairly clear. As the system moves northwest across the Bay of Campeche, it is likely to become better organized on Sunday, and should become a depression by Sunday night or Monday. By that time it should be approaching the northern Mexico or southern Texas coast. After this things the forecast becomes murky. By Monday night or so, the system may either move inland near the Rio Grande River, or turn northerly and track up the Texas coast. If it remains offshore, Invest 94L has a chance to become a reasonably strong tropical storm on Tuesday.

Sunday

Skies should remain mostly clear overnight, but clouds will begin to build across the upper Texas coastal region on Sunday. However, for much of the day any showers and thunderstorms we see should be scattered in nature.

Monday and Monday night

By Sunday night or Monday morning we should start to see more organized storms moving in from the southeast, off the Gulf of Mexico. It’s important to note these rains will not be directly related to the core of Invest 94L, which will remain far to the south. However, as a slug of moist tropical air moves inland we should see widespread accumulations of 1 to 3 inches for inland areas, and 3 to 5 inches of rain for coastal counties. We can’t rule out some bullseyes of 7+ inches. It seems possible that this initial round of storms may wind down on Monday evening or over night.

Tuesday and Wednesday

The real question is what comes after this point, and that will be determined by what the center of Invest 94L does. If the storm’s core moves up the Texas coast (the “Coast hugger” scenario in this morning’s post), our region would probably see manageable rain totals on Tuesday and Wednesday, with the heavier rains offshore or falling over southwestern Louisiana. However if the low moves into Texas and then wanders upward through state—perhaps along the Highway 59 corridor or further inland as in the “Tour of Texas” scenario—we could see a second round of even heavier showers on Tuesday night and Wednesday. For now, it is impossible to say which of these situations will play out, but ultimately this is probably the most important thing to watch in terms of flooding for the greater Houston region. If we’re going to get rocked, it probably would come then.

Our confidence is reasonably high that the rainfall event, whatever comes our way, will begin to wind down on Wednesday afternoon or evening.

Matt will have a full update in the morning, and we’ll have all-hands-on-deck coverage with myself, Matt, and Maria tomorrow.