Good morning. This post will address our increasing rain chances toward the end of this week, and then discuss the tropical storm likely to form in the Gulf of Mexico this weekend. The short summary is: The system will bring a lot of moisture with it, and while it may directly impact Texas, it may also make landfall east of the state. Please bear with us, we should have better confidence in a day or two.

Wednesday

The high pressure system that has been responsible for several hot and sunny days will start to retreat slowly to the northeast, and this will allow for more clouds to form today. This will lead to a few scattered showers this afternoon and evening, with perhaps a 30 percent chance of rain at your location. High temperatures should still get into the mid- to upper-90s so this will be something of a transition day to a wetter pattern.

Thursday and Friday

These days will see a mix of sunshine and clouds as upper-level disturbances rotate around the southern edge of the high pressure system. About two-in-three areas will rain each day, and for the most part two-day accumulations should be on the order of 0.5 to 1.0 inch of rain. This should help to moderate temperatures some, and we should look for highs in the low 90s both days.

Saturday and Sunday

If you’ve got outdoor plans for the weekend you’re going to be rolling the dice. Saturday looks like it should have slightly less rain coverage than Sunday, but both days are probably above 50 percent in terms of your odds of seeing at least a passing shower. Sunday’s weather will be determined, in part, by the evolution of a tropical system now in the Caribbean Sea that should move into the Gulf of Mexico this weekend. And because there is so much uncertainty about that, it’s really hard to have much confidence in the weather forecast for Sunday and beyond.

Tropics

The National Hurricane Center now gives the Caribbean system, known as Invest 99L because it has been designated an “area of investigation,” an 80 percent chance of developing into at least a tropical depression or storm within five days. We think it’s highly likely that a tropical storm will form in the southern Gulf of Mexico by Sunday. So what happens after that?

Yesterday the bulk of the model guidance suggested 99L would move toward the Mexico mainland or Texas, but we cautioned there was a high amount of uncertainty. Accordingly, overnight, the models have shifted dramatically. Now the models bring 99L toward Texas and Louisiana. Why the big shift? The upper-air pattern is complicated, and the models are struggling to identify where there will be a weakness in a ridge of high pressure over the southeastern United States, which would allow 99L to turn north. Another challenge is that, right now, the tropical system has no defined center of circulation. The models (shown below) should therefore be treated with skepticism.

So what does this all mean? We probably will see additional shifts in projections of 99L’s track for the next couple of days, and you absolutely should not focus on any single model run. When our confidence increases, believe me, we’ll let you know.

As for impacts, the primary threat from this system is probably heavy rainfall, particularly along the storm’s track and to its east. However the Gulf of Mexico is plenty warm, and if the storm were to track toward Texas or Louisiana (instead of Mexico) it would have time to strengthen into a hurricane. These impacts are possible from later on Sunday through Tuesday.

If we get any clarity on the tropics forecast, we’ll update later today. If not we’ll see you on Thursday morning.

Good morning. Houston will have two more hot and sunny days before our weather transitions to a wetter—and perhaps a much wetter pattern—toward the end of this week and into next week. We’re going to need to watch the tropics closely, as we expect the Gulf of Mexico to see one and perhaps two storms between now and September 10.

Tuesday

High pressure remains firmly in place for now, and this means Houston will see a hot and sunny day with high temperatures generally in the upper 90s. Skies will be mostly sunny, with light southerly winds. This will be a classic, late August day with a warm night.

Wednesday

Beginning Wednesday the aforementioned high pressure system should begin to slowly recede northward, and this may open the region to some slight rain chances. Areas south of Interstate 10 may see about a one-in-three chance of rain, with lesser chances inland. Skies should be mostly sunny, with highs in the mid- to upper 90s.

Thursday and Friday

With the high pulling away, we should start to see some atmospheric disturbances rotating around its southern periphery. This should bring increased cloud cover and approximately 50-50 rain chances for the end of the work week. This will help to moderate high temperatures, likely holding them in the low 90s.

Saturday, Sunday, and beyond

Saturday should see about 50 percent rain chances, and Sunday higher still as tropical moisture levels push into the area. Rain chances will be higher the closer one lives to the coast, with residents in Brazoria, Galveston, and Chambers counties probably having about a 70 percent chance of rain by Sunday. Skies this weekend will be partly sunny, with highs in the low 90s.

The wet pattern will likely continue into the first half of next week. How wet we get will depend on the ultimate track of a tropical system we anticipate will move in the Southern Gulf of Mexico at that time. If this tropical system moves into Texas, some part of the state could see 10 inches or more of rainfall during the Monday through Wednesday time frame of next week, but it is way too early to have any specificity of whether this will be Brownsville, Corpus Christi, the Houston area, or elsewhere.

Tropics

The National Hurricane Center has highlighted three areas of interest on its forecast map this morning, but for our purposes the only one that matters is the orange “X” in the Caribbean Sea. The National Hurricane Center gives this system a 60 percent chance of developing into a tropical depression or storm during the next five days, and nearly all of our reliable model guidance suggests it will become a tropical storm in the southern Gulf of Mexico on Sunday or Monday. Whether it becomes a hurricane depends upon several factors, including its interaction with the Yucatan peninsula. This is impossible to predict for now.

I am going to show you two forecast maps for the eventual track of this tropical system. They are ensembles from the GFS model and the European model, and the purpose of this is to demonstrate the considerable uncertainty in track. It is also clear that some kind of storm will very likely be coming to the Mexico mainland or Texas coast early next week, and that areas along and to the north of its track will be on the receiving end of significant tropical moisture. This is why we say that Texas is at risk for heavy rainfall early next week, but we cannot say precisely where.

The GFS model, shown above, is more south than the European model. This would likely keep the heaviest rains south of the Houston region next week. Matt and I, for now, are leaning slightly in favor of this solution as the more realistic solution. But again, our overall confidence is quite low.

The European model brings a storm along a more northerly track about six days from now. This would bring heavier rains to Texas, including potentially the Houston area, next week.

The bottom line is that we need to watch the Gulf of Mexico closely. There are signs that yet another tropical storm may move from the Caribbean Sea into the Gulf of Mexico about a week after this one. We are approaching the peak of hurricane season and the tropics are acting accordingly. We’ll be on top of it for you.

Good morning. We are into the final week of August, and this brings both good and bad news. The good news is that we’re much closer to the end of summer than the beginning. Based upon our climate normals, the warmest stretch of summer in Houston lasts from July 31 through August 8, when the average temperature is 85.8 degrees. (That’s simply an average of the daily high and low temperature). We are, reasonably, about one month from when we can expect fall’s first significant cool front.

The bad news is that we still have about a full month of summer left, and it coincides with the absolute peak of hurricane season for Texas. Although we see no immediate threats to the greater Houston region (read more below), the next few weeks do look active for the Gulf of Mexico. So we’re asking you to hang on for one more month, after which we’ll escape the heat of summer and the main threat of tropical activity.

Monday

Monday will see a continuation of conditions the region experienced over the weekend, which is to say hot and sunny. High temperatures for inland areas could well flirt with 100 degrees, and even coastal areas should be solidly in the low- to mid-90s. Skies will be mostly sunny, with only light southerly winds. This will be a day for care during the hottest, afternoon hours. Overnight lows should be in the upper 70s.

Tuesday

Another hot and sunny day, with high temperatures in the upper 90s. Winds will again be calm.

Wednesday and Thursday

Our overall pattern should begin to change by the middle of the week, as high pressure lifts away from the area. This should bring a few clouds to our skies, and introduce rain chances of perhaps 30 to 40 percent each day during the afternoon hours. This may also help to moderate temperatures slightly, from the upper 90s to mid-90s.

Friday, Saturday, and Sunday

The weekend forecast is far from settled, but for now it appears as though the combination of low pressure and increasing levels of tropical moisture should combine for healthy rain chances, especially by Sunday. For now I’d guess we’ll see highs in the low 90s, with partly sunny skies, and at least a 50 percent chance of rain showers each day. Under some scenarios, heavy rain is possible by Sunday, but that will depend to some extent on tropical development, discussed below.

Tropics

After Tropical Storm Henri moved into the northeastern United States this weekend, there are no active systems over water. However that could change later this week as a tropical wave moves into the Caribbean Sea. The National Hurricane Center gives this wave a 30 percent chance of developing into a tropical depression or storm within the next five days.

The global models are generally pretty bullish on this system eventually developing in the Southern Gulf of Mexico this weekend, and it’s something we’ll be watching closely as it will influence our rain chances this weekend. For now the bulk of these models suggest the storm will come ashore somewhere along the Mexican mainland, south of the Texas border. Although it is far too early to have much confidence in this, such a scenairo would also be unfortunate, give the recent landfall of Hurricane Grace near the resort town of Tecolutla.

After this system, there are hints of more potential activity in the Gulf of Mexico about two weeks from now, which would be consistent with early September. As we said above, the next month is the peak of hurricane season for Texas, so have a plan and be prepared.