In brief: Houston will continue to see scattered showers and cooler temperatures for a couple of days. Then, rain showers should become more widespread during the second half of the week, and we are starting to see the possibility of heavy rainfall by next Monday or so.
Potential flooding
Over the last day or so, the model trends have been pushing toward a wetter pattern than expected for the next week to 10 days. Since the region has been so dry, and rain chances will be hit or miss over the next several days, I’m not anticipating any serious flooding during this week. However, in part due to a front stalling north of the region early next week, we could see the potential for more widespread and sustained showers.
The bottom line is that we’re watching things, and something like a Stage 1 flood alert may be necessary for early next week, potentially the Monday and Tuesday time frame, for coastal areas. Again, even in a worst case scenario, we’re probably talking about something that floods lower-lying streets. I just wanted you to be aware of our thinking.
NOAA rain accumulation forecast for now through Monday night. (Weather Bell)
Tuesday
Today will be something of a repeat of Monday, with showers developing offshore and moving inland during the morning and early afternoon hours. However, coverage does look likely to be slightly less than on Monday. Skies, otherwise, will be partly sunny, with highs in the low 90s. Rain chances will slacken during the evening hours. Lows on Tuesday night will drop into the upper 70s.
Wednesday
Like on Tuesday, rain Wednesday will be of a fairly scattered nature, with perhaps only about half of the area seeing a passing shower. Accumulations should not be too significant, with the hardest hit areas perhaps picking up a half inch or so, and most of the region less. Highs, again, should be in the vicinity of the low 90s with partly sunny skies.
Thursday, Friday, Saturday, and Sunday
Rain chances will increase as we get into the second half of the week, and weekend. I can’t find much to differentiate the weather on any of these four days, which is why I’ve lumped them together. Each day is more likely than not to see rainfall, and there will be chances for showers overnight as well. High temperatures each day will range from the upper 80s to lower 90s, so quite a bit cooler than is typical for late August. I don’t really have any flooding concerns for this period, but showers could definitely put a damper on outdoor activities. It certainly won’t be raining all the time, but showers may pop up any time.
Early next week
As a front stalls north of the area, this should provide some additional lift and juice our rain chances. Since we’re talking about a period a week from now, the details are going to be hazy. But with the potential for widespread showers, and some heavy rainfall, we necessarily cannot rule out the possibility of some flooding. We’ll see. Daily highs will remain in the vicinity of 90 degrees. Most of our modeling shows rain chances slackening as we get toward the second half of next week, for what it’s worth. Which probably is not a whole lot.
Atlantic tropics
After a quiescent period, there is a new system to watch. There is a chance that an area of low pressure in the Atlantic could develop over the next week or so, as it moves toward the Caribbean Sea. Yesterday afternoon some of our best global models were hot to trot, and ready to develop this system into a tropical storm, but this morning they’ve backed off some. There’s not much else we can do but watch at this point—the next month is the period during which we should be most concerned about the potential for powerful hurricanes to strike Texas. For more detailed coverage, be sure to check out The Eyewall.
In brief: After a long, hot August the Houston region’s pattern will change significantly this week. In the absence of high pressure we’ll see significant daily rain chances and lower temperatures. Rain accumulations will be greatest near the coast, but even inland locations may pick up an inch or more of rainfall.
Up until this past weekend, Houston has largely been beneath a potent high pressure ridge this month. It has not been directly centered over the region, which is why daily high temperatures have not been as blistering hot as the summer of 2023. But our daily high this month has nonetheless averaged 98 degrees, with a total of eight days reaching 100 degrees or higher. Additionally, we have recorded almost no rainfall. Much of the region has received 0.5 inch, or less, for the entire month of August. It’s not for nothing that I believe August is by far the worst month of the year for Houston.
As we near the end of the month, this pattern is about to change. High pressure anchored over West Texas this summer has backed off, opening the door to moisture from the Gulf of Mexico. Accordingly, a pattern of showers and thunderstorms should persist through this week, and into the weekend. We can expect daily rain chances to go along with high temperatures generally in the low 90s. Overall I don’t have any real flooding concerns, but with the return of high school football and other sporting activities, you’ll definitely need to watch for the potential of showers and thunderstorms on a daily basis.
NOAA rain accumulation forecast for now through Sunday. (Weather Bell)
Monday
A low pressure system in the Gulf of Mexico will help to drive high rain chances today. These showers are presently lurking just offshore, and they should move inland later this morning and throughout the day. Rain chances today, and for much of the rest of this week, will be higher along and near the coast, closer to the source of moisture. But even areas well inland, such as The Woodlands and Katy, will have a decent chance of rainfall each day. Skies will be partly to mostly cloudy today, with highs of around 90 degrees or just above. Winds will be from the east at about 10 mph, with higher gusts. Low temperatures tonight will drop into the upper 70s.
Tuesday
Expect a similar pattern on Tuesday, with the potential for showers and thunderstorms. Not everyone will see rainfall, but a majority of the Houston area is likely to.
Wednesday, Thursday, and Friday
The general pattern of showers and thunderstorms developing offshore, and then moving into the Houston area during the morning and afternoon hours, should continue. Overall, our evenings should be free of rainfall this week, but I would not make any ironclad guarantees. Highs will continue in the vicinity of 90 degrees into the low 90s, a nice contrast to the heat from the rest of this month.
A mild end to the month of August in terms of daily high temperatures. (Weather Bell)
Saturday and Sunday
More of the same, probably. I think we’ll see highs in the low 90s this weekend, with a mixture of sunny and cloudy skies. Daily rain chances will, again, probably be 50 percent or higher, with better chances near the coast. Nights remain warm, with lows briefly dropping into the upper 70s.
Next week
There is some evidence in the global models of another surge in rainfall on Monday and Tuesday of next week, but that is far enough into the future that I’m not overly confident. In any case, the most likely outcome for weather next week is that this wet and somewhat cooler pattern continues for at least a few more days. There’s some evidence of a push back toward highs in the mid-90s during the second half of next week, but I could just as easily see us staying a bit cooler. We’ll see!
In brief: Thursday is still going to feel very hot across Houston, but by this weekend we’ll return to temperatures in the mid-90s with a slight chance of rain. Next week we’re going to see partly cloudy days, with highs in the low- to mid-90s, and widespread showers. And then, all of a sudden, we’re into September.
Past peak summer?
Golly, I sure hate to write that we’re probably done with the worst of summer, because one never wants to tempt Mother Nature. However, we just experienced a stretch of six 100-degree days (we may add one more today, although I wouldn’t bet on that). High temperatures peaked on Tuesday and Wednesday, reaching 102 degrees at Bush Intercontinental Airport. It’s going to be difficult to top that.
The last week has not been any fun, in terms of hot temperatures. (National Weather Service)
We know for sure that Houston highs are on a clear down slope for the rest of this month. Although we certainly can hit 100 degrees in September, at this point the odds are fairly low that we see another sustained stretch of brutally hot weather. I’m not ready to say we’re done with triple digits, but I really do believe we’re past the worst of the summer of 2024 in terms of heat.
Thursday
Today is still going to be really hot, of course. High temperatures will reach the upper 90s today, and some inland locations may hit 100 degrees. But we should be slightly cooler than on Wednesday. There is, perhaps, a 10 percent chance of showers this afternoon. Winds will be light, increasing to 5 to 10 mph from the southeast this afternoon. Lows tonight will drop to around 80 degrees.
Friday
Skies will again be mostly sunny, but for most of Houston highs will likely peak in the mid- to upper-90s. Some scattered showers will also be possible starting in the morning hours, and persisting into the afternoon with daytime heating. Overall rain chances will be about 20 degrees.
Saturday and Sunday
Overall skies should be mostly sunny this weekend, but there likely will be a few clouds during the afternoon. Most locations should see highs in the vicinity of the mid-90s. Rain chances will be on the order of 20 to 30 percent daily, mostly driven by the sea breeze. Lows will remain warm, but should start dropping into the upper 70s.
We’ll have one more very hot day before temperatures start to feel more comfortable. (Weather Bell)
Next week
As high pressure backs off further, we’ll see our region open up to moisture from the Gulf of Mexico next week. This will lead to healthy, daily rain chances on the order of 50 percent. Generally, next week, we can expect high temperatures in the low- to mid-90s, with partly cloudy skies, and periodic passing showers with embedded downpours. The likelihood of rain will be greater near the coast, but everyone should have a chance of seeing some showers. We will likely remain in this pattern through most of next week, and possibly into the weekend.
Tropics
The Atlantic tropics are quiet. In case you missed it, we published a long post from Matt yesterday on why that is, and how long it will last.
In brief: Has the 2024 Atlantic hurricane season been a bust? In short, no. However, we are enjoying a rare period of quietude in late August, and with temperatures incredibly warm in the Gulf of Mexico at present we’ll take it. To get a better idea of what’s going on, and to understand why September is likely to be active, we are sharing this post which was originally published by The Eyewall this morning.
Forecasts called for an incredibly active season
Coming into this hurricane season, there were breathless forecasts calling for anywhere from 20 to even 30 named storms from some folks. Government forecasts were more conservative but even they were the most active we’ve ever seen from NOAA. Colorado State, too. So, as we sit here on August 21st with next to nothing showing up in modeling for the next 7 to 10 days, it’s reasonable for the general public to ask questions about those forecasts.
One of our potential fail modes was if La Niña developed too slowly. Indeed, the pace of the La Niña development this season, while uneven, has generally lagged the strongest projections. At least officially. Here’s a look at the May 1st European model ensemble outlook for the ENSO 3.4 region, the box of temperatures we look at to basically designate La Niña or El Niño.
The spring forecasts for La Niña have (to this point) turned out a little too aggressive. But directionally, they’ve been fairly correct. (ECMWF)
We should begin closing in on an official La Niña designation in the next month or two, but we aren’t quite there yet. Keep in mind, this is by no means a perfect representation of things, and sometimes the atmosphere can behave more Niña-like even if we aren’t officially there yet. But this has not developed as aggressively as some modeling showed in developing in spring.
So, at a very, very distant level, perhaps that has something to do with it. Michael Lowry, in his excellent daily newsletter pointed out yesterday that wind shear has become almost too extremely reversed this month. Typically, during a La Niña, there is more of an easterly component from the wind that counteracts or reduces the usual west to east winds that can cause shear in the Atlantic, detrimental to hurricane development. In a twist of fate, there’s so much of an easterly component to the upper level winds this year that it’s actually causing easterly shear. Otherwise, we might be a good bit busier at the moment. If you look at the basin as a whole since June 1st, winds have been generally lighter than usual in the Caribbean and much of the Atlantic and a bit stronger than usual in the southwest Atlantic and in the Gulf.
Upper-level winds have been generally below average this summer in some key tropical development areas. As such, we’ve accumulated some bang for our buck this season so far. (NOAA PSL)
Let’s dig a little deeper. One thing that’s legitimately fascinating to me right now is what’s happening in terms of upper level background support in the atmosphere. Using a variable known as velocity potential, we can see that in historically active hurricane seasons, you would expect to see a significant area of rising air in the Indian Ocean, bleeding a bit into Africa (green on the top map below). Opposite to that, there would be a significant area of sinking air in the Eastern Pacific Ocean (brown colors below). Why is this important? In order to generate an active outbreak of storms in the Atlantic, you need disturbances tracking across Africa, which tend to get supported by rising air over and just east of there. You also prefer to see the Pacific undergoing sinking air, as a way to keep it from ‘robbing’ the favorable conditions for storminess. Sinking air suppresses thunderstorm development and tends to dry out the air a bit.
So what’s going on right now? So far this August, we’ve actually *had* what we would expect from a hyperactive season in the Indian Ocean. Click to enlarge the image below.
A comparison of velocity potential in hyperactive seasons (top) vs so far this August (bottom). While we have what we’d expect for a period of high activity, something is out of phase inhibiting things. (Eric Webb/NOAA)
We have a ton of rising air in the Indian Ocean this month (purple & blue on the bottom map above). We have that extending into Africa. This is what you’d expect for a busy season. Where it differs, however is exactly where the sinking air (red/orange in the bottom panel above) is located. In a typical hyperactive season, this is focused over the Eastern Pacific. This year, it’s focused on the eastern side of South America. This is Matt speculating wildly here, but: I suspect that we’re seeing the right ingredients in place, but I think we are seeing them out of phase. The rising air in the Indian Ocean extends deeper into the Pacific, and there is more of a neutral Eastern Pacific signal right now. This is helping boost activity in the Pacific.
Today’s 7 day outlook in the Pacific includes Hurricane Gilma and two other disturbances that are likely to organize. (NOAA NHC)
What is in the west will come east
The problem with the tropics is that support like this generally moves from west to east, and eventually this will change. So the quiet now may change in a very, very quick way come September when this (presumably) shifts. For now, the Atlantic is still seeing rampant dust and a slightly displaced intertropical convergence zone (ITCZ) which is sending disturbances off Africa too far north and into dust. So they die off earlier. This too will change.
Widespread Saharan dust (pink, red, orange) extends across much of the Atlantic, and as disturbances are coming off farther north than usual, they’re hitting the dust head on. (University of Wisconsin CIMSS)
In fact, if you look at the forecast of African Easterly Waves (AEWs) from the latest GFS model, you can see this southward shift approaching heading into the next week or two. The waves lined up over Africa are about 5 to 10 degrees farther south in latitude about 4 days from now, which means they will emerge farther south and in more of a traditional area less exposed to Saharan dust in late August and September.
Tropical waves are going to begin emerging off Africa farther south than they have been recently, which should ultimately lead to a boost in activity heading into September. (Quinton Lawton, University of Miami)
So, yes, things are almost certainly going to pick up soon.
Despite perception, this season’s current accumulated cyclone energy is running nearly 3 times higher than usual! We’ve amassed as much ACE so far this season as we’d typically see by the peak day of hurricane season (September 10th). We’ve done this on the backs of only five storms so far, three of which have been hurricanes, and one of which (Beryl) smashed early season records in the Caribbean and Atlantic.
Accumulated cyclone energy (ACE) this season has been historically high despite the perceived slow start to the season. (Kim Wood/University of Arizona)
So despite the perception that this season has been slow to start, it actually has not been. In fact, 2024 is in rarefied air in terms of ACE to date. This perception might have to do with storm inflation, or the idea that we are naming more storms today than we did, say, 20 or 30 years ago. In 2020, basically the benchmark for recent historically active seasons, today marked the formation date for Hurricane Laura, the 12th named storm of the season. Here we are in 2024 sitting at five, and it’s no wonder the perception is skewed. Despite having more than twice as many storms to this point in 2020, we only had half the ACE (26 vs. 55 this year). 2020 kept churning out mostly sloppy storms until Laura, and then things got nasty. We’ve had three legitimate hurricanes this year and only about one “throwaway” storm (Chris). The takeaway message here is that: We can make up ground in September very, very fast. Very fast.
In summary
So, no, this season’s extremely active hurricane seasons have not been a bust so far, and they probably won’t end up being a bust overall. We’ve had a “bang for our buck” season so far with quality storms over quantity as, say, in 2020. And while we are in a lull now, the setup is probably going to change in 7 to 10 days to allow things to crank up in September. Never call it a bust. If it is one, we can discuss why in November. For now, use this quiet time to review your hurricane preparedness plans and supply kits. And stay tuned here for the latest.
