Eric Berger

In brief: Houston will face the threat of heavy rainfall every day this week, but at the same time we also have some uncertainties. It is worth paying close attention to the weather in the coming days. There is a fair bit of nuance in the forecast, so please read carefully.

Assessing Houston’s flood risk

We have dual flood threats this week. The first one, up today and Tuesday, concerns a weak front that will move into the region and provide an impetus for showers and thunderstorms, with heavy rainfall a distinct threat.

Then, later on Wednesday and possibly lasting into Friday, a slow-moving tropical disturbance will bring a surge of moisture into the region and create conditions where very high rainfall rates and serious flooding are possible. However we simply do not know where the greatest rainfall totals from this tropical disturbance will end up.

We are maintaining our Stage 2 flood alert for now across the greater Houston region, but depending on the tropical disturbance we may need to escalate things for the second half of this week. Rest assured Matt and I are continuing to watch this evolving situation closely, and will update as warranted.

Monday and Tuesday

Around sunrise this morning we are seeing a large cluster of storms near College Station and Navasota, and this is being driven by a front (which unfortunately is not going to bring any drier or cooler air with it, this being June and all). Over the course of today this activity will probably move southward, into the Houston region as the weak front stalls over the metro area.

We expect a fairly stormy pattern to persist over the region through Tuesday. That is not to say it will rain all the time, everywhere, but the atmosphere will be very fertile for showers and thunderstorms. We generally expect accumulations of 2 to 4 inches of rainfall during this time period, but you should be prepared for high rainfall rates and local bullseyes of 6 or more inches. This is the kind of rainfall that leads to flash flooding, and hence our call for a Stage 2 flood alert. You will want to be weather aware. Things may calm down a bit by Tuesday evening.

In terms of temperatures, the clouds and rain-cooled air should limit high temperatures to the low- to mid-80s. Conversely, with a very warm and humid air mass in place, overnight lows will not drop too far below 80 degrees. Although we cannot entirely rule out some severe thunderstorms, the primary threat is heavy rainfall.

Wednesday, Thursday, and Friday

This is the period where we have even greater uncertainty, and potentially greater risk. This is due to a low pressure system that is presently just inland over northeastern Mexico. This system should move to the northeast this week, and reemerge over the Gulf of Mexico. After this point it likely will drift toward the upper Texas and Louisiana coasts. It will be slow moving, and bringing a lot of moisture with it, which as long-time residents will know is a potent recipe for a rainmaker.

We are talking potential bullseyes of 20 inches, or more, of total rainfall through Friday. As of today we simply do not know where this low will go, precisely, or where its heaviest rains will fall. It is quite possible that the heaviest rainfall occurs over Galveston Bay, or to the east of Houston over Liberty County or even Beaumont-Port Arthur. But we also cannot rule out very serious impacts over Galveston Island or even within Houston itself.

So how should you be thinking about this? It is distinctly possible that parts of Houston will see serious flooding during the second half of this week, but also possible that the heaviest rains will go east and we will be left with a largely manageable situation during the second half of this week. Until there is more clarity in the outcome, we simply cannot say. What does seem clear is that some part of the upper Texas coast, or perhaps southwestern Louisiana, is going to get rocked with some very serious rainfall and flooding in the late Wednesday or Thursday time frame.

When we can say more with confidence, we will.

Saturday, Sunday, and beyond

Rain chances do appear likely to back down somewhat this weekend, although probably not go away entirely. We can probably expect high temperatures in the vicinity of 90 degrees with partly sunny skies. Next week will likely get us back into the lower 90s, with partly to mostly sunny skies. We shall see!

In brief: Good morning. We’re posting on Sunday because of the potential for flooding this week due to in influx of tropical moisture. We can’t say precisely where the heaviest rain will fall, or when, but there is the potential for some locations to see flash flooding. A Stage 2 flood alert is now in effect.

Big picture overview

A couple of factors will bring elevated rain chances into the Houston region this week, likely through Friday. In particular we have an absence of high pressure, a dying front moving in early this week, and perhaps most importantly a slug of tropical moisture associated with a low pressure system in the southwestern Gulf.

Although we don’t anticipate development of this tropical low into a depression or tropical storm, it nonetheless will bring plenty of rainfall potential with it this week, starting today. Because tropical moisture can produce high rainfall rates, and due to the potential for rain totals to stack up this week, we are issuing a Stage 2 flood alert beginning today, and likely lasting through Friday. Most areas will likely pick up 3 to 6 inches of rainfall, but there will almost certainly be higher isolated totals.

What does this mean? On our flood scale this suggests that some locations are likely to experience significant impacts this week, such as closed freeway lanes and flooded streets. Most of the region should be fine, most of the time, but there will be the potential for flash flooding during this period. It also means Matt and I will be monitoring the situation closely and updating as needed. If you’re visiting from out of town for the World Cup—we met some lovely Fußballfans from Germany on Saturday evening—you might want to check out our primer on what to expect in Houston during flooding events.

Sunday quick look

Houston is already seeing some sporadic showers and thunderstorms this morning along the West Loop, and this is likely to set the tone for today. We don’t expect to see anything too organized, but showers and thunderstorms will be possible, if not likely, through the afternoon or evening hours. If you’re gathering outdoors to watch soccer or otherwise enjoy a mid-June Sunday, have a means to find cover if a storm pops up. Highs today will be in the lower 90s, with partly sunny skies.

Remainder of the week

Looking ahead I think Houston will have its best chances for heavy rainfall from Monday evening through Tuesday. Wednesday and Thursday may see slightly reduced coverage but there is the possibility of increasing chances for heavy rainfall again in the Friday time frame. But I’m going to level with you: We are going to need to take this day by day. The big picture is clear, with ample potential for heavy rainfall across the Houston region this week. Yet we cannot say precisely where or when. Needless to say, we’ll be watching closely and share concrete information when we can.

In brief: In today’s post we discuss the onset of truly summer-like humidity and the expectation of three more warm and mostly sunny days. Rain chances return Sunday, and we expect widespread showers on Monday and Tuesday of next week.

Solidly summer-like humidity

Dewpoints across the Houston region have reached the mid-70s of late, and this is pretty much our typical level during summer in Houston. If you wonder why it feels so muggy outside, it is because of this. We basically reach a point during the year when dewpoints never fall below this level, day or night. We’ve not had the full summertime-in-Houston experience yet, with blistering hot temperatures such as highs reaching the upper 90s. And fortunately that does not appear to be in the cards for at least another week or two. But deep summer humidity is here, and likely will not relent until September.

Thursday, Friday, and Saturday

I’ve lumped the next three days together because there really won’t be much sensible change in our weather from day to day as high pressure reigns. We can expect to see high temperatures ranging from the upper 80s near the coast to the lower 90s for inland areas. Skies should be mostly sunny during the daytime with afternoon winds gusting up to 20 mph. Nights will remain warm and sultry, with lows only briefly dipping below 80 degrees. Each day will have a 10 to 20 percent chance of a brief, passing shower but for most of us our days will remain rain-free.

Sunday

This will be a bit of a transition day. I still expect highs in the low 90s for most of Houston, but as high pressure retreats southward we could see some increasing rain chances during the afternoon or evening hours. I don’t expect any kind of a washout, but this could be a nuisance if you have outdoor plans later on Sunday, including after the opening World Cup game in Houston that afternoon.

Next week

The combination of high atmospheric moisture levels and an approaching front (don’t get your hopes up regarding significantly cooler or drier air) will increase rain chances beginning Sunday evening through next Tuesday or so. In terms of accumulation I expect much of the region to see something like 2 to 4 inches of rain during this period, and the rain-cooled air could bring down afternoon temperatures into the mid- to upper-80s. We’re going to be monitoring things for flooding potential, but as of now I think conditions will be mostly manageable. By Wednesday, and the rest of next week, we likely will be back into a pattern of highs around 90 degrees and perhaps a 30 percent chance of afternoon showers.

In brief: In today’s post we discuss the looming El Niño, and what it means for Houston if it becomes a “super” El Niño this winter. We also discuss our sunny days heading into the weekend, and the potential for rain on Sunday and next week.

Here comes El Niño

It is not quite here yet, but in the coming weeks (perhaps even days) we are likely to see temperatures in the equatorial Pacific flip over to El Niño conditions, which is defined by average temperatures in a certain area of the Pacific reaching 0.5 degrees C above usual conditions. (Conversely, La Niña occurs when temperatures in this region fall 0.5 degrees below normal). We experience a handful of El Niños a decade, so it’s not a huge deal. But there has been a lot of buzz about this particular El Niño because it is expected to become unusually strong (as defined by 2.0 degrees C or higher above normal). Here’s a look at the latest spread in the model data, released this week:

Now, what to make of this? If the bottom legend is confusing, the letters simply represent three months, so when El Niño is forecast to peak it says “OND,” which means October, November, and December of this year. So about four or five months from now. I believe there will be three major impacts for the greater Houston region from El Niño over the coming year, so let’s discuss them.

First up is a beneficial one. By August and September of this year we are likely to see a rapidly strengthening El Niño. You may remember in our Atlantic hurricane season outlook published last week, we spoke about El Niño’s likely increase of wind shear in the Atlantic, which should help reduce the overall number of named storms this year. So by and large, that’s beneficial.

Secondly, depending on when El Niño occurs, it has widely variable impacts on precipitation around the world. For the southern United States, including Texas, the impacts are most pronounced during the winter and early spring months. During this time frame El Niño increases the likelihood of precipitation.

So again, for Texas, this is probably beneficial. We typically don’t get flooding conditions in the winter months, so additional rainfall (or snow?!?) from El Niño probably won’t be a bad thing. And we’re not talking huge changes here. It might be that Houston receives 4.5 inches of rain next February instead of 3.5, or something like that.

As you can see from the initial chart above, El Niño may start to wane next spring, and if history is any guide it probably will start to peter out heading into next summer. However, we have often seen something of a temperature ‘hangover’ following strong El Niños. I am speculating a little bit here, but my guess is that as a result we see a spike in global temperatures that lingers into next summer, and we could see some record-breaking heat in Texas at that time. But that’s a long way off. I can’t even tell you whether it’s going to rain this coming Sunday for certain. Speaking of which, let’s get to the forecast.

Wednesday

With high pressure more or less in place for the next several days Houston will remain in a mostly sunny, steamy pattern. For us that means temperatures generally in the low 90s, with slightly hotter conditions possible inland, and slightly cooler daytime conditions near the coast. Skies will be mostly sunny this afternoon, with just a very slight (10 or 20 percent) chance of a brief shower or downpour. Low temperatures may briefly fall below 80 degrees in Houston, but the reprieve won’t last long. Winds will generally be from the south at about 10 mph, but may gust up to about 20 mph during the afternoon hours.

Thursday, Friday, and Saturday

The rest of the week is likely to see similar conditions, so basically it will feel pretty much like typical June weather out there. Get your sunshine on, Houston.

Sunday

At some point this weekend the high pressure influencing our weather will shift further to the south, opening up our region to the potential for more widespread showers and possibly some thunderstorms. Now I still expect mostly sunny skies on Sunday, but our chances for precipitation will be on the increase. At this point I expect about a 50 percent chance, give or take, however it is possible this number shifts higher (or lower). I don’t expect anything too crazy in terms of accumulations, but given that Houston hosts a World Cup game on Sunday afternoon, we’ll continue to watch for the likelihood of rain before, during, and after the game given all of the festivities around town.

Next week

For much of next week we likely will see partly to mostly cloudy days, with an increased chance of rain for several days. A weak front will move into Texas, but it probably (although not certainly) will die before making its way into Houston. Regardless, after this week’s sunshine a somewhat rainier pattern returns to help keep everything green.