Eric Berger

In brief: In today’s post we provide the latest information on Invest 97L, which is meandering west toward Texas this morning. The primary threat is heavy rain and the potential for flash flooding, particularly east of Houston heading into midweek. We’ll be providing regular updates today and Tuesday.

Invest 97L

The tropical system has not significantly strengthened overnight, which is a good thing for coastal residents concerned about tropical storm force winds and a storm surge. (As of 7 am this morning, the National Hurricane Center still gives it a 70 percent chance of becoming a tropical depression or storm). This tropical system, Invest 97L, still has about 30 hours before coming ashore in the middle of the day Tuesday, so it remains possible that a tropical depression or storm could form before landfall. Coastal areas from High Island up the Texas coast to Cameron, Louisiana, should prepare for the possibility of a landfalling tropical storm.

The bigger issue for most of us, including Houston, is the potential for heavy rainfall from this system. There is likely to be a band of higher rainfall totals the accompanies this system—perhaps on the order of 3 to 6 inches as it moves inland. Tropical rainfall like this has the potential to produce flash flooding.

Right now our best guess based upon 97L’s track is that this band of heavy rain falls just to the east of the Houston metro area, between here and Beaumont. But this could shift (closer to, or further from Houston), and we will want to pay attention over the next two days to see how this system evolves. The most likely period for heavy rainfall is from early Tuesday through Tuesday evening.

In Houston, right now, our expectation is for 0.5 to 2 inches of rain, with greater amounts along and east of Interstate 45. We do not anticipate impactful winds, but again we’ll need to monitor this for possible changes in track and intensity. We will have a post this afternoon, no later than 2 pm, to provide the latest forecast information.

Monday

Today will be business as usual in terms of the heat we’ve been experiencing of late, which is to say we can expect widespread high temperatures in the mid-90s in Houston, with highs in the upper 90s further inland. Scattered showers associated with Invest 97L will be possible to the east of Houston, but I’m skeptical that we’ll see too much activity within the metro area itself. Overall rain chances today are probably only about 20 or 30 percent, with partly to mostly sunny skies. Winds will be fairly light, from the east.

Tuesday

As noted above, Tuesday is when rain showers associated with the tropical system are most likely. While the details are still a bit uncertain, it appears that rain chances will start to increase during the pre-dawn hours on Tuesday and peak during the middle of the day. Will everyone see rain? After a very dry August we’re all pretty desperate for precipitation. Chances are highest to the east of I-45, but at this point I do think a majority of the city and surrounding counties will see precipitation, although areas such as Katy and further west may well miss out. Highs on Tuesday may peak in the 80s for some locations due to showers and cloud cover.

Wednesday, Thursday, and Friday

The rest of the week should see highs in the low 90s, with a mix of clouds and sunshine. Although the threat of heavy rainfall should be gone, we’ll continue to see decent (30 to 50 percent, probably) shower chances each day along with the sea breeze. This should be fairly typical weather for early September.

Labor Day Weekend and beyond

We are going to see a continuation of this pattern into the holiday weekend, most likely. I think daily highs this weekend will be in the low- to mid-90s with partly to mostly sunny skies. Will it rain this weekend? We certainly cannot rule it out, but if we do see precipitation it likely will come in the form of a passing shower that moves through fairly quickly. We should start to get more confidence in the Labor Day weekend outlook after 97L passes on Tuesday.

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In brief: Invest 97L continues to hold its own in the Gulf, with increasing potential that it may develop into a depression or named storm before coming ashore in Texas or Louisiana on Tuesday. We are sharing this update below, published Sunday evening on The Eyewall, due to heightened interest from our readers.

First off, Invest 97L looks mostly the same this evening as it did earlier today, which is a bit of a small feat in and of itself, as typically these nascent systems strengthen more overnight and weaken during the day. That it has held its own indicates it’s probably in shape to organize a bit further.

What has changed as a result of the storm’s development today, and recent model guidance, is two-fold. First, a bigger risk of locally heavy rain in Texas and Louisiana. Second, a higher chance that 97L will actually develop into a depression or storm. The NHC has raised odds to 70 percent this evening, but I would think the odds are closer to 90 percent for a depression and 60 to 70 percent for a named storm. Either way, they are now higher.

Modeling is in good agreement on both track and timing of the system, giving it about 36 or so more hours over water before making landfall near Port Arthur or High Island, TX sometime during the second half of the day Tuesday. Models have become a bit more scattered in terms of intensity of 97L today, with a few more pulsing up into tropical storm status.

At this point, if you live on the Upper Texas Coast east of Baytown through about Cameron Parish, LA, it makes sense to prepare for a tropical storm. This means the potential for heavy rain, gusty winds, some minor to moderate coastal flooding, and rough seas.

The problem with these smaller systems like 97L is that they don’t give you a whole lot of warning and then all of a sudden they ramp up. Think of Hurricane Humberto in 2007 as a prime example of this. It wound up from a disturbance to a small hurricane in about 24 hours. The initial forecast from the NHC for Humberto had max winds of 45 mph. I’m not saying Invest 97L will do that; our modeling has improved quite a lot in 20 years. But I am saying that model guidance still doesn’t always capture these smaller storms properly, and it’s better to err on the side of caution in these areas, especially to the east side of where the storm may come ashore.

I am growing a little more interested and potentially concerned about the potential for flash flooding in parts of Texas from 97L, especially north of Houston and east of I-35. Rain total forecasts have trended up a good bit since earlier today, and I think the potential exists for rain totals to increase more over the next couple days. I’d watch the triangle between Beaumont, College Station, and Lufkin closest right now, but let’s see how things play out over the next couple days before pinpointing areas highest at risk.

We’ll have a full update in the morning.

In brief: A tropical low has developed in the northern Gulf, and it will move generally west toward Texas over the next couple of days. We assess what this means for the greater Houston region this week, which hopefully means some beneficial rains.

Over the last day or so we have seen a low pressure system in the northern Gulf slowly develop. Thunderstorms associated with the low, designated Invest 97L, have become better organized overnight, but so far surface pressures (another indication of organization) have yet to drop significantly. So we have, essentially, a tropical blob sitting out there 100 miles or so south of the mouth of the Mississippi River.

With high pressure over the southern United States we can expect this tropical low to to generally move to the west or west-northwest over the next couple of days. This is likely to bring the system toward the upper Texas coast by midweek, which is to say somewhere probably between Galveston Bay and the Texas-Louisiana border. Of course, in the absence of a well-formed center, there remains some uncertainty in the track.

So something is coming toward the upper Texas coast, and it will likely reach land on Tuesday or Wednesday. Our baseline expectation is that this remains a tropical low pressure system or a depression, but there is a chance for development into a tropical storm. Surface waters are more than warm enough (sizzling actually) to support intensification, and wind shear is relatively low. So if the current system can develop some spin, it will have a chance to organize.

Should you be concerned? Not at this time. The system would be beneficial should it bring some much needed rainfall into the region on Tuesday or Wednesday, but these rains could just as easily fall to our east, over Beaumont or southwestern Louisiana. As for amounts, maybe 1 to 3 inches? It’s difficult to say with any confidence yet. Regarding winds and storm surge, we will keep an eye on things for you, especially with the tropical low so close to Texas.

More tomorrow.

In brief: We actually have some dynamic weather to talk about in today’s forecast! Due to a boundary moving in, the region will see some shower and thunderstorm chances. The most likely time frame for this is Thursday afternoon north of the city, and the evening hours in Houston and closer to the coast.

Rain, actually

It has been a long, hot, and mostly dry August but some real change is on the way. It’s still going to be sizzling today, with temperatures in the upper 90s. But after today most of the region will fall back into the mid-90s for awhile. And thanks to a stalling boundary, we are going to see a healthy chance of rain showers today in the greater Houston area. Not everyone is going to see showers or thunderstorms, but overall chances are probably on the order of 50 percent, which represents our highest likelihood of rain in weeks.

Thursday

With a check of the radar just before sunrise, we can see shower activity developing north of the Houston region, in areas such as College Station and Livingston. These showers should progress into Montgomery County over the next hour or two before stalling out. I don’t think they will get all the way to Harris County, at least for the most part.

We will see sunny skies during the middle of the day, and very hot conditions like we’ve experienced so far this week. However we should see another round of showers and thunderstorms this afternoon, possibly initiating north of Interstate 10 and then moving down toward the coast through the evening hours. This time frame represents when most of the region should see its best chance of rainfall. Accumulations will vary widely, from no rain to some bullseyes of 1 or more inches. Showers should subside by or before midnight.

Friday

We should see a few more clouds on Friday, limiting highs to the low- to mid-90s. Rain chances will be lower, possibly in the 20 to 30 percent range.

Saturday and Sunday

The weekend should bring mostly sunny and (for late August) temperate conditions. Expect highs in the low- to mid-90s. The likelihood of rain showers is not zero, but it’s close. Overall this should be a pretty nice weekend for outdoor activities involving water.

Next week

At this point we should see a summer-like pattern next week, with high temperatures mostly in the mid-90s and a low-end potential for daily showers along the sea breeze. These are typical conditions for early September here.