10:00am CT Update: The National Hurricane Center upgraded this system to Tropical Depression 14 on Thursday morning. Our forecast below remains accurate. Matt will be providing a big-picture update this afternoon.
Original post: This update will consist of both a short weather outlook about the rest of this week, and a longer section on the threat posed by the tropics. In short, the latest model guidance suggests an increased likelihood that Invest 97L may impact Texas, although much uncertainty remains. We’ll also have to keep an eye on Invest 98L, although this seems a bit more of a distant threat.
Thursday
Today’s weather will be a lot like Wednesday’s, which is to say hot and sunny, with high temperatures in the mid- to upper-90s. With slightly drier air in the region, conditions won’t feel quite so humid this morning or this evening, but as an easterly, and southeasterly wind develops this afternoon we’ll feel the beginnings of an onshore flow. A few stray showers may develop near the coast today. Low temperatures will fall into the mid- to upper-70s.
Yep, it will be hot again on Thursday in Texas. (Pivotal Weather)
Friday, Saturday, and Sunday
Honestly, we don’t anticipate a whole lot changes with our weather and this August-like pattern, except that the onshore flow will return more humidity at the surface. We’re going to see hot days in the mid-to-upper 90s with oodles of sunshine and only very slight rain chances with coastal counties the most likely areas to see precipitation.
Next week
Our weather next week will depend to a large extent on Invest 97L, but the bottom line is that we may see increasing rain chances by Monday or Monday night. This is probably a good time now to talk tropics.
Good afternoon. We’re continuing to follow activity in the tropics, and are focusing on Invest 97L. This is because it is the closer system and more immediate “threat.” That said, I’m afraid there’s not much useful intelligence we can share. In terms of track and intensity all options remain on the table. Here’s what we know:
As of this afternoon, Invest 97L is located almost due south of Hispaniola, and is a rather disorganized area of storms. Although it faces some difficulty with wind shear and dry air, forecasters with the National Hurricane Center predict there is an 80 percent chance this system will at least become a tropical depression, if not more organized over the coming five days.
Satellite appearance of 97L at 2:20 pm CT Wednesday. (NOAA)
Another factor is a disturbance over South America, which may interact with 97L as it nears Central America (you can see clouds related to this in the satellite image above). All of these variables mean that we have relatively little confidence in how strong the system may get between now and the weekend. I don’t think it will get much beyond a low-end tropical storm in the Caribbean, but the tropics do love to surprise us.
In terms of track we have lots of questions, too. The existing trough over the southern United States would normally pull a system like this northward, into the Central Gulf of Mexico, and toward Louisiana or the Florida Panhandle. However, that trough is forecast to weaken. As that happens the Bermuda High pressure system over the Atlantic is expected to expand westward. So there is a fairly narrow window for 97L to get pulled north. Still, this is the solution favored by models such as the HWRF, shown below, which brings a strong tropical storm or weak hurricane to the Florida Panhandle late on Sunday.
HWRF model forecast for Invest 97L at 10 pm CT Sunday. (Weather Bell)
What seems a little bit more likely to me is that the system pushes into the Yucatan Peninsula and then emerges into the Bay of Campeche on Sunday. From there it could plow due west into Mexico, or take a more northwesterly track toward Texas. Most of the modeling, at this point, shows little intensification of 97L along such a track due to variety of factors. But with that said, you never want to see a low pressure system in the warm Gulf of Mexico in August. Like, ever.
Some early 18z model track model guidance. We are showing this only to illustrate the broad range of possibilities. (Weather Bell)
So what happens? The model guidance is of little help and, unfortunately, neither are we until 97L forms a better center, and we get a better sense of some of the factors mentioned above. If something were to eventually track toward Texas the earliest we probably would see effects is Monday or Tuesday. Our advice, as always, is be prepared, not worried.
Houston’s weather for the next several days will be influenced by high pressure to our west, and a slightly drier atmosphere thanks to a more northerly flow. By this weekend our eyes will turn toward the Gulf of Mexico, and the potential for a tropical system to disrupt our weather. We still have a lot of questions about Invest 97L in terms of intensity and track, but it seems clear that this tropical wave will move into the Gulf of Mexico. More below.
Wednesday’s highs in Texas — it could be worse in August. (Pivotal Weather)
Wednesday
Conditions will be quite warm today as a northerly flow continues to bring slightly drier air into the region. Dry air warms faster, so we can probably expect highs to reach into the upper 90s for most of the metro area. Rain chances remain near zero with the abundance of dry air. Our evening and overnight weather should again feel slightly drier, although the effect will be more pronounced for inland areas. For August, we can’t complain.
Thursday and Friday
The pattern remains more or less the same for the rest of the work week, although we anticipate winds turning from the north to the east on Thursday, and this will slowly modify our air mass to become a bit more moist. Look for highs in the mid- to upper-90s, which should not be too extreme. Lows should fall into the mid-70s, which is tolerably pleasant for the depths of August. A few stray showers may develop near the coast on these days, but we don’t anticipate any organized rainfall.
As we’ve been telling you for essentially weeks now, the tropics are becoming very active. Some of this is just basic math—as we approach late August and September, the tropics usually come alive. But there is more at play this year, with things happening in the background that should allow for basically an “outbreak” of sorts of tropical systems across the Atlantic basin in the days ahead.
Tropical outlook in a sentence
There will be at least two legitimate opportunities for tropical systems to develop and potentially impact some part of the Gulf of Mexico over the next 10 days, and an additional system or two may develop farther out in the Atlantic as well.
Invest 97L: First in line
The system the models are most bullish on is Invest 98L, which we’ll discuss below. But the one we are most concerned with more immediately is Invest 97L, because this is closer to us, and it is the type of system that can sneak up on us and cause some problems.
The National Hurricane Center says Invest 97L has a 70% chance of development in 5 days, while Invest 98L behind it has a 90% chance of development (NOAA)
Invest 97L is currently over the eastern Caribbean Sea. It’s not terribly well organized, and you can see a satellite loop from Tuesday afternoon showing mostly just a “blob” of storms at this point.
Invest 97L is on the right-hand side of this loop and is the “blob” of storms in the Caribbean Sea. (Weathernerds.org)
Over the next few days, 97L will plod along in the Caribbean, interacting at times with a disturbance over South America. So development is only expected to be slow or gradual. Eventually, it will end up in the western Caribbean, somewhere near the coast of Honduras or the Yucatan. I can hear 75% of our audience now saying, “Wait, that’s how Harvey happened, right?” And the answer is, “Sort of, yes.” It’s the elephant in the room here, obviously, so let’s discuss and compare real quick.
By the time the disturbance gets into the Western Caribbean this weekend, the upper air pattern will be favorable for it to gradually lift north. Here’s a map from the GFS ensemble valid on Saturday afternoon. We’re looking at the 500 mb level, or about 20,000 feet up, basically the large-scale steering pattern for this time.
Saturday afternoon’s forecast upper level pattern off the GFS Ensemble mean shows a couple key players in Invest 97L’s ultimate outcome.(Tropical Tidbits)
On Saturday afternoon, 97L should be off the Yucatan or Belize or just north of Honduras. It will be steered to the west by high pressure near Bermuda, while at the same time, a trough of low pressure in the upper atmosphere over the Lower Mississippi Valley is going to try and “pull” Invest 97L to the north. So at this point, the system should be moving to the northwest.
So in that respect, a middling system that gets pulled north and west across the Yucatan and into the Gulf of Mexico, Invest 97L is similar to Harvey. But I’m going to intentionally stop with the similarities there because the potential of what this does is much different from Harvey.
There is a chance that the trough remains strong enough to continue in its effort to “capture” Invest 97L, allowing it to come north into the Gulf and toward Louisiana or perhaps the Upper Texas Coast. That scenario can’t be ruled out. There is also a chance that Invest 97L gets “missed” by the trough and ends up stationary without much to steer it over the Gulf of Mexico. While that’s not a huge rainmaker on land, that becomes problematic because there would be a chance Invest 97L could strengthen while sitting offshore. Another possibility is that the Bermuda high continues to expand so much so that it just pushes 97L into Mexico as a weak rainmaker. Harvey was a once in a lifetime storm in terms of rainfall, so we don’t want folks to worry about a “Harvey” type storm right now. There are indeed some similarities in the initial overall big picture, yes. But that’s where it ends right now. What we should be doing (and what Eric and myself will be doing) is making sure we are prepared to take action late this weekend or early next week just in case it becomes clear that 97L will become a problem for us. We will keep you posted.
