Matt Lanza

July to end with a cold front? Really?

In summertime, few things are coveted more in Houston than a cold front, and as we flip the calendar from July to August, we’re going to get just that. Now, don’t get too excited. It is not really going to translate into opening the windows and letting the gloriousness flow.

It’s not going to feel quite this nice this weekend, unfortunately.

Rather, this will probably bring us some rain chances, perhaps some strong storms today, and maybe a tinge less humidity than we’ve had late this week. But beyond that? Not much. We never really, truly cool off. Let’s go through the details

Today & tonight

For the most part, today looks fine. Expect a mix of sun and clouds, along with very hot weather. Look for mid-90s and high humidity. Rain chances in Houston and points south should be confined to primarily just a passing downpour. During the afternoon, we expect showers and storms to fire up between Dallas and Huntsville. Those storms will drop into the northern third of the metro area by late afternoon, with places like Conroe or The Woodlands or northwest Harris County standing the best chance at storms before 5 to 7 PM or so.

The Storm Prediction Center has areas north of Houston in a “marginal” (1/5) risk for severe weather today. Any severe storms should be fairly isolated. (NOAA)

Storms today do have the potential to be strong to severe, but we don’t expect widespread severe weather or anything like that.Strong, gusty winds and hail would be the main risks from the strongest storms.

The front will slip into metro Houston tonight. The strongest storms should begin to ease up a bit after sunset, but we wouldn’t be shocked to see some noisy storms with locally heavy rain moving through the I-10 corridor and just south through late evening and toward midnight. We should see storms generally dissipate after midnight, but if they were to continue going, it would areas south of Houston most likely to see them.

Saturday

With showers and storms generally expected to diminish overnight, we think Saturday will start mostly quiet. However, if there are some morning showers or rumbles of thunder, they would likely be close to the coast or well south of Houston toward Matagorda Bay.

I have to be honest here: Given recent model performance of late, there is still see some uncertainty in exactly how things may transpire tomorrow. But in general, look for some additional showers and storms to fire up along what is left of the cold front south of Houston (Brazoria, Matagorda, Wharton, and Jackson Counties most likely) before it dissipates. Additionally, there could be some storms that fire to the west of Houston Saturday afternoon, perhaps near the Katy area north toward Waller and Grimes Counties.For the city of Houston and points north, much of tomorrow could be a quiet and fairly pleasant summer day. But I would not place rain chances at zero. Highs will be in the low-90s with morning lows in the 70s.

Sunday

Sunday’s forecast is a bit tricky as well. The front should have basically lost any definition and fallen apart by Saturday night and Sunday morning. But there will likely still be enough of a “trigger” for thunderstorms around. However, with atmospheric moisture generally on the wane, we suspect Sunday’s storm coverage and rainfall intensity will be less than we see on Saturday. All that said, I would probably take a more pessimistic stance on Sunday than what models are explicitly showing right now (which isn’t very much in the way of rain). So let’s expect scattered storms and hope for better on Sunday.

Sunday’s high will top off in the low-90s with storms, mid-90s with only a handful of them, and we’ll see morning lows in the 70s.

Rainfall this weekend will be erratic, with some folks seeing little to no rain, others perhaps seeing a couple inches, and many seeing something in between. This map gives you an idea of where the heaviest is currently expected to fall, though that could change. (NWS via Weather Bell)

Total rainfall this weekend? Some may see locally heavy rain that could add up to an inch or two or even more. Others may not see much of any rain at all. And still more of us will see something in between, closer to a tenth or quarter-inch. The map above should just give you a rough idea of where the heaviest rain could fall.

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Eye on the Tropics: Watching the next wave closely, though it has hurdles ahead

With Hurricane Hanna behind us, the obvious question is, “What’s next?” We have one system at present to watch, and then the situation gets a little trickier to figure out.

Tropical outlook in a sentence

The disturbance just dubbed “Potential Tropical Cyclone 9” by the National Hurricane Center is the one we are watching for development this week. Although we do not expect an especially strong system, it is still far too early in the game to dismiss any scenario or track.

PTC #9

The road forward on where Potential Tropical Cyclone 9 goes and what it does is a long one, and we are still at the beginning. Possibilities range from no impact at all on the United States to an impact on the Gulf, US East Coast, or something in between. Basically, everything. That’s a less than helpful forecast, but it’s the only realistic one that can be offered right now. The National Hurricane Center’s designation of this disturbance as a “potential tropical cyclone” means it has confidence a depression or storm will develop and impact land soon. They will initiate advisories on this system this morning, which will allow for watches and warnings to be issued for Caribbean islands. Their first forecast is below.

The National Hurricane Center’s opening forecast for Potential Tropical Cyclone 9. There is *very* high uncertainty on details later in the forecast. (NOAA)

From their technical discussion, it’s worth noting that there is a very high degree of uncertainty. As they note:

It cannot be stressed enough that since the system is still in the formative stage, greater than average uncertainty exists regarding both the short-term and longer-term track and intensity forecasts.

PTC 9 has some hurdles ahead. A look at the satellite image from this morning shows a lot of “stuff,” but not a lot of healthy organization right now.

Potential Tropical Cyclone 9 has a lot of thunderstorms associated with it as of this morning, but it remains mostly disorganized. (Weathernerds.org)

That shouldn’t minimize it as something to watch, but given how things have gone in recent years, it’s nice to see a disturbance struggling to organize. One of PTC 9’s problems is that it has a large size. It’s a lot easier to spin up a smaller system that grows, but this one covers a large chunk of real estate already, so to get it started requires some effort. The other problem is that there are multiple clusters of thunderstorms within the broader circulation, any of which could become dominant. That obviously has implications on the long-term track.

The disturbance is also surrounded by a lot of dust and dry air.

PTC 9 has dust or dry air to content with on its west, north, and east flanks. (University of Wisconsin CIMSS)

The problem here from a forecast standpoint is that since we don’t know where in this broad circulation the thunderstorms will consolidate to help develop a defined tropical depression or storm. we cannot quite give you a definitive starting point. Without a solid starting point, forecast accuracy 3, 5, or 7 days from now will obviously suffer.

What we can tell you is that PTC 9 has hurdles in front of it. Between the dry air, a likely encounter with a weak trough in the Bahamas Friday, and another, stronger trough over the Southern U.S. next week, as well as any land interaction on its way west, it will need to overcome some challenges and insulate itself from these threats or else it will struggle to develop.

That said, anything from where the system consolidates to how strong these troughs and other features actually are (compared to what they’re currently forecast to be) could impact where PTC 9 goes and how strong it is. For now, the best advice with this system is to not worry about it (we’re certainly not), but check back in on it every day or two to see what has changed.

And for those of you wondering, if we do get a storm out of this one, it will be named Isaias, and pronounced:

Beyond Isaias

Things get complicated beyond PTC 9/Isaias. Intriguingly, there are no other systems showing up on the models with any frequency or confidence right now. This is implying that we may enter a quiet stretch for a time again. There’s some background support for this as a feature that typically helps suppress storm development should move through the Atlantic Basin this week. On the flip side, the 2020 M.O. has been for random stuff to flare up seemingly out of nowhere. So in that sense, it’s tough to argue a quiet period.

Whatever the case, I do think we will have a slightly quieter stretch post-Isaias, with the risk of a more significant ramp up in activity by the middle or late portion of August.

Major flooding in the Rio Grande Valley as Hanna moves into Mexico

Good morning. We’re here to offer up a brief update on Hanna as the storm works its way into Mexico this morning.

Houston area

Things are quiet this morning in Houston. There are some showers south and west of us and another batch moving across the coast of western Louisiana. As some of this works into Texas, we should see showers and storms become scattered across the area.

Showers and storms in Louisiana will likely work toward our area today, bringing at least scattered rains, some heavy, to the Houston area. (College of DuPage)

Some folks won’t see much, but others may see a couple inches of rain in an hour or two this afternoon. An isolated severe storm is also possible. More typical scattered showers and storms will continue to be possible tomorrow and Tuesday, as onshore flow continues.

Rio Grande Valley

Hanna has moved into Mexico this morning, but the storm’s rains continue in the Valley. Mission has probably been the hardest hit of any of the cities in that area, and a flash flood emergency is posted for that area through late morning, as upwards of 10″ of rain has fallen, with more coming.

The heaviest rain as this is being written is falling east of Mission and just west of Harlingen. Several more inches of rain is likely to fall today and tonight as Hanna dissipates inland in Mexico.

Totals are impressive, especially just north of the Valley.

Areas in purple on this map of estimated rainfall are likely to have seen 9 to 10 inches or more of rain so far. (NOAA NSSL)

You can just make Mission out as the western-most purple area on the map, with upwards of 9 to 10 inches of rain. Other hard hit areas include Weslaco and Harlingen. The area just northeast of there with maximum totals is estimated to have received close to 20 inches of rain.This is right on the Arroyo Colorado near Arroyo City on the Cameron/Willacy County line.

Conditions should improve in that area tomorrow with more scattered showers and storms, but flooding could worsen in spots still today before subsiding. We will have the latest on the rest of this upcoming week tomorrow morning.

Tropical Storm Hanna to deliver a glancing blow to the Houston area

Good morning everyone. Tropical Storm Hanna formed last night, and it wasted no time gradually getting itself organized. As this has been happening, Hanna’s forecast track has continued to shift south, taking most of the significant impacts expected from the storm out of the Houston area. A lack of significant impacts doesn’t mean we’ll have zero impacts, however, so we’ll break down what to expect here and farther south in Texas as well.

Now

As of 5:30 this morning, Hanna was over the Gulf, about 300 miles east-southeast of Corpus Christi. Hanna was moving slowly but steadily just north of due west, around 10 mph or so. Maximum sustained winds were estimated to be 40 mph, but a reconnaissance aircraft from NOAA is headed into the storm to see if that hasn’t increased somewhat. Based on Hanna’s satellite presentation, we can assume it probably has strengthened a bit.

Tropical Storm Hanna on Friday morning had a lot of storms, though most of them were somewhat displaced to the south and east of the center as it tracks west toward South Texas. (Tropical Tidbits)

You can see a robust area of thunderstorms near the center of the storm. If you want to lodge a meteorological complaint about Hanna, it would be that the vast majority of thunderstorms are displaced to the south and east of the center of the storm. In other words, despite the pretty serious look on satellite, the storm does suffer a bit from a lack of symmetry that could indicate that while it’s strengthening, it may not be taking off like a rocket. It is likely still feeling a bit of wind shear, especially on its eastern fringe that is holding it back a little. Still, this is not an unhealthy storm and forecasts of strengthening up through landfall will likely come to pass.

The current National Hurricane Center forecast tracks Hanna toward the coast, arriving tomorrow midday somewhere between about Corpus Christi and South Padre Island, likely close to Baffin Bay.

The official NHC forecast continues to keep Hanna well south of Houston, with the most significant impacts in South Texas, while our area sees mostly nuisance-type impacts. (NOAA)

This will direct the most significant tropical impacts south of Matagorda Bay. Hanna keeps moving west and then southwest into Mexico, where it should dissipate on Sunday night or Monday.

Quick overview of what to expect for the Houston area

Here’s a quick “user’s guide” for what to expect in the Greater Houston area.

Rain: Isolated storms Friday, scattered storms Saturday, more numerous storms Sunday and maybe Monday. Rain totals of 1 to 2 inches on average, with higher amounts possible anywhere, but especially the farther south you go, possibly in excess of 3 or 4 inches in Matagorda. Lesser amounts possible north.

Flooding: Some street flooding is possible with any downpours, as is always the case in our area. Significant, widespread street or bayou flooding is not expected.

Wind: You should not expect winds to get much past 15 to 20 mph in the Houston area. Tropical storm conditions should be confined to the coast, with gusts up to 30 to 35 mph in Galveston and perhaps a bit stronger toward Freeport and the Matagorda Bay region.

Tidal & marine impacts: We expect tides to run about 1 to 3 feet higher than normal for Galveston and maybe a tinge higher toward Matagorda Bay. Minor overwash or tidal flooding is possible. Rip currents will be strong, so please use extreme caution. Waves are expect to be about 4 to 6 feet, maybe higher farther south.

Severe weather: Brief spin ups are possible in thunderstorms, especially as you get close to the coast, where a waterspout or two could occur.

Details for the Houston area

For today, we would anticipate isolated to perhaps scattered showers and storms. Expect a general trend of storms near the coast this morning, spreading inland this afternoon. Some locally heavy downpours are possible, but today should not be much worse than a typical summer day.

As Hanna approaches the south Texas coast tomorrow, expect the potential for steadier, heavier rain south of Houston. This would include Galveston, but we would especially include far southern Brazoria, Matagorda, and Jackson Counties. Tropical Storm Warnings are hoisted from San Luis Pass southward, so those areas are the ones most likely to also see tropical storm conditions. Showers and storms to the north of there will be mostly scattered on Saturday. In other words, some of us will see some heavy downpours, others may not see much of anything. The chance of heavier rain is obviously higher the farther south you go in the area.

The Houston area’s best chance at more numerous showers and storms and heavier rain will probably come Saturday night and Sunday as a surge of moisture comes in off the Gulf and out of Louisiana. That may continue off and on into Monday as well. By Tuesday and Wednesday, we should slowly return to a more typical summer pattern, with hotter weather.

When all is said and done, we expect probably 1 to 2 inches of rain on average in the Houston area, with a skew toward higher amounts south of the city and lower amounts to the north.

The current forecast of total rainfall is about 1 to 2 inches on average for the Houston area. The big ticket rainfall totals from Hanna will likely be south of Corpus Christi and in the Rio Grande Valley (Weather Bell)

However, depending on exactly how storms set up on Sunday, we could see as much as 2 to 4 inches of rain in spots, with the highest likelihood of this being south of I-10 and on the south and east sides of US-59/I-69.

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