Storms possible again this afternoon, and a troubling heat statistic

My family and I were driving through Houston on Tuesday evening, after a long day in the car returning from a family reunion, when the heavens opened up. I certainly did not expect to hit that kind of storm, with winds in excess of 40 mph at some locations, and relatively brief heavy rainfall. But it goes to show you what summertime Houston can do in absence of dominant high pressure and with a sea breeze during the afternoon and evening hours. Today could see similar activity, although I don’t think it will be as widespread.

The other two big stories are the heat and the potential for a tropical depression in the Gulf of Mexico. I’ll discuss the latter below. But in regard to the heat, Matt shared this sobering statistic with me. Before the storms fired up on Tuesday, Bush Intercontinental Airport hit 98 degrees for the fourth straight day. Since 1888 that has happened only three other times this early in summer: in 1902, 1998, and 2011. All three of those years ended up in the top-15 warmest summers, and 2011 was the warmest summer on record.

Houston finds itself on the edge of a high pressure system over the southwestern United States. (Weather Bell)

Wednesday

Houston remains on the periphery of an intense ridge of high pressure situated over the Western United States. Effectively, this means that we’ll see hot weather, as well as a chance of showers and thunderstorms this afternoon and evening driven by the sea breeze. Coverage should be less than on Tuesday afternoon. Otherwise, look for highs again in the upper 90s, with sunny skies. Lows tonight will remain around 80 degrees, or just below.

Thursday

Another day like Wednesday, albeit with temperatures perhaps a degree or two cooler, and rain chances a little bit lower as well. For most of us, this will simply be a hot and sunny day.

Friday, Saturday, and Sunday

Beginning Friday our weather will be largely dependent on the development of the tropical system in the southern Gulf of Mexico, and its eventual track northward. I’ll discuss the system in the section below, but for now our forecast—which is very much subject to change—is as follows.

Friday will likely see mostly sunny conditions, with highs in the mid-90s, and increasing rain chances along the coast. These showers may spread inland overnight. However, as Matt has discussed, this likely will be a lopsided tropical system, likely with the vast majority of its effects on its eastern side. So if the “center” makes landfall even slightly east of Houston, we’ll fall on the dry side of the storm. I think this will happen. So while there is definitely a chance of heavy rainfall in the Houston region on Saturday, it now seems more probable that we’ll see little to no precipitation.

NOAA rainfall accumulation map for now through Sunday. (Weather Bell)

Regardless of what happens on Saturday, by Sunday the system should be moving away from the region, leaving us with mostly sunny skies, a lingering chance of showers and thunderstorms, and highs in the mid-90s.

Gulf of Mexico disturbance

The disorganized system of showers and thunderstorms is still expected to coalesce into a tropical depression or storm this week, and the National Hurricane Center gives it 90 percent chance of doing so. As this system presently lacks a center, there is the usual uncertainty in track and intensity forecasts. With that said, the overall pattern now favors a more northward track, and this likely would bring the low pressure system toward southern Louisiana, rather than Texas. This is why I’m leaning against heavy rainfall in Houston this weekend, but not ready to make a definitive call. I definitely have more concerns about Louisiana, however, especially the New Orleans area which may see 10 to 15 inches of rainfall.

European model ensemble forecast for “probability” of a tropical depression this week. (Weather Bell)

In terms of intensity, the combination of wind shear and ingestion of dry air will likely limit this system’s potential to that of a low-end tropical storm. But again, it’s difficult to say anything definitive at this time.

August-like heat continues in Houston with minimal relief ahead

Let’s be honest. It has felt like August lately. I mean, really. For Hobby Airport, the last 3 afternoons have tied for the 5th hottest 3-day stretch of high temperatures this early in the season (trailing several 3-day periods from 1998 and 2011, both notoriously hot Houston summers). For Houston officially it’s the 12th hottest 3-day stretch so early in the season. It’s hot, it’s early, and it’s not going to get much better this week.

Today

Look for temperatures surging into the 90s again today. We hit 98° at Bush and 99° at Hobby on Monday. Maybe we’ll do a degree or so cooler than that today.

August-like heat will continue today, with hopefully a couple more cooling showers in the area than we saw yesterday or Sunday. (Weather Bell)

Upper air temperatures are a little cooler today, and there should be better coverage of showers in the area. While we don’t expect everyone to see rain today, at least some places will, and there could be a few heavy downpours as well. Regardless, it’s going to be hot, so please take care outdoors. And it’s yet another ozone action day for those with respiratory ailments to take note of.

Also, apparently ERCOT needs our help again this week, so for the good of, like, everyone, please try to cut energy usage where you can.

Wednesday & Thursday

Both days should see sun, clouds, and very slight storm chances. Call it maybe 20 percent coverage. Maybe. The forecast is reminiscent of a 1990s Sears commercial. Another scorcher indeed. Look for solid mid to upper-90s on both days. There will be very little relief. Please make sure you’re taking it easy and checking in on anyone vulnerable in this kind of heat. We went from springtime to August-type weather in what felt like a matter of hours, so it’s tough for your body to adjust to this quickly.

Friday into the weekend

Besides the heat, which is the most pressing weather story today, we do continue to keep a close eye on the tropics. The National Hurricane Center has slowly but steadily been bumping up the odds that Invest 92L in the Bay of Campeche would develop into a tropical depression or storm this week. We sit at 70-percent odds as of 6 A.M. This morning, 92L remains a disorderly mess, so we continue to agree with the idea of very, very slow development.

Invest 92L this morning looks about the same as it has the last few mornings: disorganized and “blobby.” (Tropical Tidbits)

The good news is that a couple things remain true forecast-wise with 92L today: It is not expected to significantly develop. It is expected to track near us or to our east. It is expected to be fairly lopsided, with most rain staying well east of Houston. On the unfortunate side, it likely means our somewhat excessive early-season heat will continue.

More specifically, expect 92L to gradually lift northward beginning Friday. Given the wind shear over the Gulf, dry air over Texas, and general disorganization of the system initially, development will be slow. Expect a possible center of circulation with something like 80 to 90 percent of the rainfall displaced to its east. Lopsided will be the appropriate word choice, I think. The system should head close to the Gulf Coast somewhere between about Galveston Bay through central Louisiana on Saturday. I would expect a depression or low-end tropical storm at this time and unlikely anything worse. The system is then expected to slide east across Louisiana and toward the Southeast and be out of our hair by the end of the weekend.

So how much rain are we expecting?

Rainfall as forecast through early next week clearly looks highest well east of our area. A number of folks in the Houston area may see no rain through Monday and no rain from Invest 92L. (Pivotal Weather)

For the Houston area and points west, it’s likely to be sparse. Most folks should see maybe just a couple passing showers between now and Sunday. A few places will see slightly heavier showers, especially near the coast. But also, some places will see no rain at all. East of Houston and along the coast, the situation is a little trickier. Between here and Lake Charles, including Beaumont and Port Arthur, most places will probably see 1 to 2 inches of rain or less from passing showers and the rain shield from Invest 92L. Depending on the exact track and organization of 92L, this could change a bit in either direction. But in general, if there are going to be issues with flooding, they would likely be east of roughly Lafayette, LA.

Still, as always, we encourage you to check in once a day to see how this is progressing. And this is a good opportunity to build or refresh your hurricane kits and plans, which will help you all season long.

For those curious, elsewhere in the tropics, Tropical Storm Bill formed off the Carolina coast yesterday and is heading out to sea. The next name on the list is Claudette, which will make some folks around here cringe.

We will continue to watch, but at this point we believe heat to be the bigger story in Houston even into the weekend. Eric is back in the hot seat tomorrow and will have the latest then.

It isn’t normal to hit 100 degrees this early in summer in Houston

Houston summers are notably hot and humid. Many of us hate it, but it’s almost a badge of honor of sorts for us, right? Anyway, Hobby hit 100° yesterday and Bush hit 99° as well. For Hobby, that’s the third earliest date since 1930 that we’ve hit the century mark for the first time in a year, just being beat out by May 31, 1998 (100) and June 5, 2011 (102). At Bush Airport and officially for Houston, we tied for our eighth earliest first 99° reading. May 29, 1996 and June 2, 2011 top that list. The average for our first 99° at Bush is July 16th, and the average for our first 100° at Hobby is July 17th. This is very early for this kind of heat. Granted, we’re going to be dealing with a borderline historic ridge of high pressure in the West the next several days, so I guess it should not be much of a surprise, but after a very wet May, color me a bit surprised we went this far this fast. Hopefully not a harbinger of things to come this summer.

So the obvious question is: Will the heat last? Let’s try to answer that.

Today

While we expect today will be another scorcher of a day, we may end up a degree or so cooler than yesterday, and we may also see a couple more showers than we did yesterday too. Maybe. Most folks will still probably stay dry today though.

Forecast high temperatures for Monday remain uncomfortably hot, with heat index values of 105°+ likely in spots this afternoon. (Weather Bell)

Upper air temperatures look stoutly warm this morning, but by evening they’re running a tick or two under Sunday. So, in general, expect mid to upper-90s today. Heat index values will get up over 105° in spots this afternoon, so please exercise caution if outside. In addition, today will be another ozone action day for the area, so take care if you have respiratory sensitivity.

Tuesday & Wednesday

Tomorrow we see a small bite taken out of the heat, so we’ll probably drop off another degree or two compared to Monday. We’ll call it mid-90s. Better rain chances look to arrive Tuesday, as a slightly larger scale disturbance in the upper atmosphere moves across the region. On Wednesday, we’ll see a good setup for at least scattered showers and storms. Look for mid-90s once more. Morning lows will be in the 70s to as warm as 80° perhaps.

If I were classifying rain chances, yesterday was about 5 to 10 percent coverage. Monday will be 10 to 20 percent, and Tuesday/Wednesday would be 30 percent coverage. So, many folks may not see any rain at all, but at least some of us should. Hopefully.

Thursday

On Thursday we stay flat or lose another degree or so in temperature, as we lie between high pressure dominating the West and a trough on the East Coast. Already low overall rain chances may lower a bit more on Thursday. Look for mid-90s by day and 70s to near 80° by night/morning.

Beyond Thursday (Tropics)

Looking out to Friday and beyond, our attention turns to Invest 92L, which I went in depth on yesterday. Honestly, not much has changed since that post. The system is still messy looking. It will still have high shear to deal with, and there will likely be some dry air over Texas that will attempt to fight it back a little bit. So there likely remains a fairly low ceiling on just how intense this system can become.

Invest 92L remains in the Bay of Campeche, a sheared, disorganized mess this morning. (Tropical Tidbits)

As Invest 92L comes north in a very sheared environment, it will likely continue to have the bulk of its moisture kicked off to our east. Again, if you look at a GFS model forecast of relative humidity in the upper atmosphere, generally a decent indicator of how constructive or destructive the environment will be surrounding a tropical system, there is a clear signal for very, very dry air over Texas. This likely means a.) a sharp cutoff to how far west precipitation can expand on the west side of the storm and b.) the risk that some of this dry air gets “entrained,” or wrapped into the system itself as it comes north, limiting how well-organized it can become.

Very dry air over Texas will likely act to limit how far west the rainfall from 92L can come and how strong 92L can become. Even a track right into Houston would likely still see the heaviest rain off to our east. (Tropical Tidbits)

So what does this mean for the Houston area from Friday into the weekend? While I’m certainly sounding very unexcited about rain from Invest 92L in the Houston area, it will boost our rainfall odds a bit from where they are on Thursday. So look for at least isolated to scattered showers or storms on Friday, Saturday, and Sunday as 92L draws north. Uncertainty increases a bit obviously as we march through this weekend, but in general, we continue to feel the heaviest rain will stay to our east, possibly well to our east. But I would expect at least some chance for scattered rain over the weekend. We’ll fine tune this through the week.

Temperatures, especially if rain stays well off to the east of Houston will likely be warm to quite hot heading into the weekend, maybe cooling a bit as rain chances increase.

With respect to your plans for the week or weekend and Invest 92L? I would not make any changes because of this system right now, but I would check back each day for an update to make sure nothing has significantly changed. More tomorrow.

Scorcher of a weekend continues for Houston as we watch the southern Gulf for very slow tropical development

Good Sunday morning to you. As promised, we are here with an update on the tropics, as we watch the potential for development in the Gulf this week.

Quick Houston weather update

I just want to lead with a quick update on our near-term weather here in Houston. It hit 98° yesterday officially, and we’re running slightly hotter already today. We typically don’t see our first 98° day until July 9th, so we’re running close to a month ahead of schedule there. That doesn’t mean we’re necessarily headed for 100° this afternoon, but it’s going to be another scorcher. Please take it easy outdoors. In addition, it’s an ozone action day, so anyone with respiratory sensitivity will want to limit outdoor activity.

Another scorcher is expected Monday, with most locations away from the coast reaching or exceeding the mid-90s. (Weather Bell)

The big difference between today and prior days is with rain chances. Yesterday was close to zero. Today will be slightly above zero. So we feel at least a few locations, possibly parts of the city, will see a cooling downpour this afternoon. Outside of that, it’s just going to be red hot. Tomorrow and Tuesday will likely see a few more scattered showers and storms in the afternoon. Prior to those developing, look for sun, clouds, and temperatures into at least the mid-90s, with morning lows in the 70s to near 80° in spots.

Tropical update

Alright, the main point of today’s post is to discuss the tropics.

One sentence summary: A tropical system seems likely to form in the Bay of Campeche over the next 5 days, and while we will watch it closely, we are currently expecting a fairly disorganized system with a decent chance that the majority of impacts remain shunted off to our east.

In meteorological speak, when we have a specific disturbance we want to get more information on before it gets close to becoming a tropical depression, it is labeled an “Invest,” or area to investigate. In the Atlantic basin, invests are labeled 90L to 99L, and then the list recycles. In the southern Gulf, we now have Invest 92L.

The satellite view of Invest 92L shows a good deal of thunderstorm activity in the Bay of Campeche this morning, but no organization whatsoever. (Weathernerds.org)

From the satellite image above, you can see a blotchy area of thunderstorms and little organization. This is mostly what we expected to see this weekend. Development from 92L is probably going to be slow. In fact, the National Hurricane Center says the chances of a depression forming seem to be most likely later this week, so we’ve got some time to watch. As of now, they are assigning 50 percent odds of development over the next 5 days.

The National Hurricane Center says Invest 92L won’t move much the next few days but has about a 50% chance to develop into a depression by later this week. (NOAA)

In addition, this system is likely to fester and sit over the southern Gulf the next few days without moving much. So that means any impacts here in Texas from 92L likely would not occur until very late this week or next weekend. You might ask why it’s going to struggle to develop if it’s sitting over the southern Gulf, which is about 2 to 3 degrees warmer than normal. Well, for one, it’s sitting over 25 kts. of wind shear, with an area of 40 kts. of wind shear to the north. That’s prohibitive to development.

Wind shear is ripping in the vicinity of Invest 92L, which will likely inhibit development over the next few days.

This shear is not expected to relax much over the next few days. In fact, this wind shear may linger in place through Wednesday or Thursday or beyond.

Given a lack of serious steering currents right now, the system is expected to stay in place over the Bay of Campeche. But, as the week progresses, a strengthening ridge in the Western US, a strengthening trough along the East Coast of the U.S., and a building ridge in the western Caribbean will act to gradually invite 92L to drift northward. The exact track of this system will depend on the actual strength of these features and exactly where the center of Invest 92L forms. In general, modeling is telling us to probably expect a northward drift later this week, with some acceleration to the Gulf Coast on Friday or Saturday. From there, it seems possible that the forward speed may slow. But details on that aspect of things are difficult to really pin down right now. Models seem to favor a track of the center toward areas just east of Houston, keeping most of the Houston area on the less impactful side of the system, but again, it’s too early to be too confident in any track specifics.

In terms of intensity, I think two things are going to seriously inhibit how strong Invest 92L can ultimately get. The first is shear, as noted above. I don’t see any evidence on models that this is going to relax much. That’s the first hurdle this system will have to overcome. It may also further help us in that wind shear could allow for much of the more significant system impacts from rainfall to pushed even farther to our east. For those of you reading us from places other than Houston, it’s important to realize that these early season systems are rarely ever symmetrically put together and impacts from heavy rain in particular can extend hundreds of miles to the east of the center.

The other thing that might lower 92L’s ceiling for intensity would be dry air coming off Texas.

Dry air is going to be abundant over Texas this coming week, some of which may get entrained into Invest 92L, limiting how strong or well-organized it can become. (Tropical Tidbits)

If you look above, you are seeing the GFS forecast of atmospheric relative humidity several thousand feet above us for next weekend. The brown over Texas indicates dry air. The red “L” is the approximate center of 92L as forecast by the GFS on Sunday morning. Don’t focus too closely on that. The green color indicates more ample atmospheric moisture. What is this telling us? Even if the track of 92L shifts 150 miles in either direction, it’s still going to be dealing with dry air possibly getting wrapped in from Texas. That should limit the ceiling of intensity as the storm comes north. Moisture from the storm may be displaced a good bit east of the center as well.

The bottom line, as is often the case with these early season storms: While we will continue to watch closely, at this point we don’t see this as a serious wind-making risk for the area. We are viewing this as a rainfall risk, as well as for some coastal impacts (minor to moderate tidal flooding, overwash, rough seas, etc.). Sitting here on Sunday, I don’t think we need to be especially worried about this either way, but I do feel we should watch things closely this week, just in case anything changes, particularly with respect to rainfall. It’s probably not a bad idea to check in on the forecast once per day and make sure we’re still status quo on things. But truthfully, I feel mostly at ease with where things stand today. Sure, that could change, but for now, we’ll take it!

Look for the latest in our usual Monday morning update tomorrow. Meanwhile, stay cool!