Eric Berger

A tropical depression has formed in the Gulf, and Texas needs to pay attention

Good evening. The National Hurricane Center says a tropical depression has formed in the Gulf of Mexico, and this system may become Tropical Storm Wilfred in the next day or so. Before we get too deep into the forecast I just wanted to highlight a couple of changes from this morning’s post:

  • The depression is expected to begin moving northward a little sooner than expected, so impacts for Texas could occur sooner
  • The forecast models are now in a little better agreement that the tropical system will come near, or possibly even ashore the Texas coast, increasing the rainfall threat

Alright, now let’s jump into the forecast. The 6pm CT “track” prediction from the hurricane center highlights some of our uncertainty when it comes to the depression. After the storm moves slowly north on Friday and Saturday it should run into high pressure building over Texas after the passage of a front. This is what will likely push the system westward, toward Texas.

6pm CT Thursday track forecast for TD 22. (National Hurricane Center)

After Sunday we’re deep into the realm of speculation, as we’re not sure what will happen by Monday or so. The system could plow west or southwest into Southern Texas or Mexico (track “A”) in the map below. It could follow a track up the Texas coast (“B”). It may also essentially stop, and get pulled to the northeast, toward Louisiana, as the high retreats (“C”). We really do not know and anyone who says they do know right now is not being honest with you. Each of these tracks would have drastically different outcomes for Houston, which is why our overall confidence in next week’s weather is very low.

The National Hurricane Center anticipates the storm will gradually strengthen and come near hurricane strength by Sunday. While the Southern Gulf of Mexico is fairly warm—plenty so for strengthening—the storm will likely take on dry air from the north which will not help its organization. Moreover, a slow-moving system will churn up cooler water from deeper in the Gulf. Bottom line: While we’re always concerned about September storms intensifying in the Gulf, in this case we’re more concerned about the moisture from this system than winds.

Any number of possibilities are open with the depression’s track next week. (National Hurricane Center)

As we’ve been saying, the depression has the potential to become a prodigious rainmaker over the next week for Texas and northern Mexico. We think the cold front and storm’s position will probably keep its heavy rainfall offshore through this weekend, but by Monday or so that may change. It is going to depend how close the storm’s center comes to Texas as most of the heavy rainfall should be near the center, and on the eastern half of its circulation.

Because of the track uncertainty, the entire Texas and Louisiana coasts need to be paying close attention to the potential for heavy rainfall next week. We don’t have to tell you about the potential for mischief from slow-moving tropical systems. But with that said, we are still very much in the wait-and-see mode with this system—the greatest likelihood is that the Houston area sees a few inches of rain next week, not a dozen or more.

GFS ensemble model forecast for precipitation through Thursday, September 24.

Given that this system is likely to exist for at least the next several days we also have concerns about high tides. Coastal tides are already running about 2 feet above normal, and by this weekend may reach 4 to 5 feet above normal, which will pose problems in low-lying areas along the Gulf of Mexico and Galveston Bay. This is our largest concern after the potential for heavy rainfall.

Matt will have our next update on Friday morning by 7:30am CT.

Tracking a cool front, and a developing tropical system in the Gulf

Good morning. We’re continuing to anticipate the arrival of a cool front late on Friday or Saturday morning, which should make for a rather pleasant early fall weekend across the region. It won’t exactly be cold, but it sure will be less humid. Meanwhile, we’re also anticipating the formation of a tropical storm or depression in the Southern Gulf of Mexico fairly soon—this will have to be watched closely but the forecast for now mostly keeps inclement weather out of the Houston region. More on this below.

Thursday

The really hot weather is almost over, we promise. And it has been hot. Both Hobby Airport and Galveston again tied heat records on Wednesday with highs of 96 degrees. Temperatures should be about 5 degrees cooler today with partly cloudy skies, and rain chances of 30 percent or so. These rain chances will be driven by an upper-level low pressure system and enhanced by daytime heating. Low temperatures tonight will be in the mid-70s for most.

Friday and Friday night

Friday should be similar to Thursday in terms of sensible weather, but things should begin to change late Friday night or Saturday morning. As Matt wrote yesterday, this will not be a knock-you-off-your-feet front blowing in from the northwest, but rather over the weekend we’ll gradually see drier air moving in. This should become noticeable on Saturday morning.

Temperature change forecast for Saturday morning, at 3am CT, shows cooler air moving in. (Weather Bell)

Saturday and Sunday

This will leave us with a pleasant weekend. Right now I’d peg highs in the upper 80s, with mostly sunny skies, for most of us. With lower dewpoints, these temperatures will feel much more comfortable. Low temperatures should get into the mid- to upper-60s on Saturday and Sunday mornings, except for the coast, which will stay a bit warmer. So clearly not cold, but after months and months of summer, the difference in humidity will be notable. Enjoy this taste of fall for a few days Houston, you’ve earned it.

See full post

Summer hangs on for a few more days before a front moves into Houston

Good morning. This post will discuss our rain chances toward the end of the week, a modest cool front this weekend, and also dig into Hurricane Sally, which is nearing the northern Gulf of Mexico coast and will bring devastating flood impacts there.

Tuesday

Today is going to be just plain hot. Most (but not all, I know) readers are dearly looking forward to the end of summer. But we’re not going to find it today, with clear skies and high temperatures pushing up into the mid-90s. We’ll see slight northerly winds on the back side of Sally’s circulation, but it’s going to be just plain humid and summer-like. Overnight temperatures will likely push into the upper 70s across the metro area to low 80s right on the coast. There is a slight chance, perhaps 20 percent, of some afternoon and evening showers to provide some relief.

Wednesday

Wednesday should be a lot like Tuesday—hot, mostly sunny, and with only a slight chance of afternoon showers. If you like summer in Houston, you’re in luck!

Thursday and Friday

The overall pattern begins to change by Wednesday night or so, as an atmospheric disturbance nears the area. This should allow for the development of some clouds in the sky, and a healthy chance of rain showers. It appears as though rain chances will be highest on the western side of Houston—some areas may see on the order of half an inch of rain, maybe? Temperatures should moderate slightly, into the low 90s, and overnight lows will drop a few degrees as well.

This European model forecast for dewpoints shows the forecast for Friday morning (left) versus Sunday morning. The latter should be quite pleasant. (Weather Bell)

Saturday and Sunday

We’re now pretty confident that some sort of front will push into Houston on Friday night or Saturday morning, but we still don’t have great confidence in the details. At this point it’s probably best to temper expectations. Yes, we’ll see some noticeably drier air. Yes, this should shave a few points of high and low temperatures. But no, at least right now, we can’t definitely say it will feel like fall in Houston. However, the good news is that we don’t expect to go back to highs in the mid-90s and lows near 80 after this front passes. Summer’s days are numbered as we should see more fronts after this one.

Hurricane Sally

Matt will have all the details on an incredibly action-packed tropics in a post later this morning, and you’ll want to be sure and check that out. Regarding Sally, the good news is that the storm not intensified over night, and remains a Category 1 hurricane with 85 mph winds. As wind shear begins to increase, Sally should not get a whole lot stronger over the next 24 hours before it makes landfall. But that’s where the good news ends.

NOAA five-day rainfall outlook for Hurricane Sally. (Pivotal Weather)

Sally is only moving to the northwest at 2 mph. At present the storm remains a few dozen miles east of the mouth of the Mississippi River. Two days from now, on Thursday morning, it should still be over southern Alabama. As anyone who lives in Houston knows, this is a recipe for extremely heavy rainfall. This will occur primarily over southern Mississippi, Alabama, and the Florida Panhandle over the next several days, with isolated totals of 20 inches or more possible. A large swath of heavy rain will then traverse Alabama and northern Georgia along Sally’s eventual track. This will of course lead to devastating flooding.

Sally will make landfall well east of Houston, modest front maybe this weekend

Good morning. The primary weather issues we’re watching this week are the approach of Tropical Storm Sally toward the Louisiana and Mississippi coasts, local rain chances, and the potential for a modest cool front to arrive this weekend. The latter should bring slightly cooler temperatures and some welcome drier air.

Monday

The area of low pressure off the Texas coast that drove widespread showers and thunderstorms on Sunday has moved south, and thus the chance for rain today will be less. Some coastal areas, and locations far west of Houston, may still see scattered showers but for the most part we should be dry. High temperatures should otherwise get into the low- to mid-90s with partly sunny skies. Yes, it will be another hot, summer-like day. Winds will be out of the north at about 10 mph—but this isn’t due to a front or anything, it’s because we’ll be on the backside of distant Sally. More on this storm below. Lows tonight will probably drop into the upper 70s.

Summer continues for Southeast Texas on Monday. (Pivotal Weather)

Tuesday and Wednesday

As the region remains on the backside of Sally, we should see a persistent, if light northerly wind. This should help to limit cloud cover during the middle of the week. This, in turn, will allow highs to push into the mid-90s on Tuesday and Wednesday with the potential for only some isolated showers. So yeah, hot.

Thursday and Friday

The end of the work week should see a slightly more perturbed atmosphere, and this could push rain chances into the 40 percent range, or so, for both days. We will expect that partly sunny skies will allow highs to reach 90 degrees, or the low 90s.

National Weather Service forecast for the front — just south of Houston — on Saturday morning. (NCEP)

Saturday and Sunday

It will be a fairly close thing, but for now we generally think a front will reach the coast on Saturday. Our weekend forecast will depend upon the timing and strength of the front, as well as on whether it actually makes it. But overall, we’d anticipate highs somewhere in the upper 80s, with lows of around 70 degrees—areas inland may see 60s but it’s hard to say for sure. The drier air should be noticeable, however, making for pleasant mornings and evenings this weekend. Skies should be partly to mostly sunny.

Tropical Storm Sally

Fortunately we have not seen too much intensification with Sally overnight—this is something we feared might happen. It is now a 65-mph tropical storm. Although Sally still has about a day to intensify, this relative lack of organization means it is mostly likely the system comes ashore as a Category 1 hurricane. The current track, just east of New Orleans, would spare the city the worst in terms of storm surge and winds. Our primary concern remains the potential for very heavy rainfall from southeastern Louisiana through the Mississippi and Alabama coastal areas. Later in the week, the slow-moving Sally could produce very heavy rains across much of the state of Alabama.

NOAA five-day rainfall forecast shows the flooding potential of Sally. (Pivotal Weather)

The tropics remain incredibly active at this time—Tropical Storm Teddy has formed far out to sea, where it will curve north away from the United States—and we’ll continue to watch things closer to home in the Gulf of Mexico where the waters are quite warm.