Matt Lanza

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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Eye on the Tropics: Ramping up toward the peak of hurricane season

Today’s update will talk briefly about that Gulf disturbance coming to Texas this weekend, but more about what is behind that system as it appears the tropics are waking up, and they may not shut back down for a while.

Tropical outlook in a sentence

We expect a low-end system to form in the Gulf this week, another system will make an attempt to develop in the Atlantic, east of the Lesser Antilles, and with more waves emerging off Africa, more development will be possible heading into early August.

Gulf system

Eric has done a good job each morning discussing what we know and expect from the potential late week system in the Gulf. As of this afternoon, the system is a disorganized “blob” of thunderstorms over and around Cuba.

Disorganized storms near Cuba will have a window to develop as they move toward Texas Friday and Saturday. (Weathernerds.org)

However, as that moves into the Gulf, it will find decreasing wind shear and fairly warm water to work with. It seems there are two things that will hinder this system’s development into anything worse than a depression or moderate tropical storm: 1.) It will enter the Gulf disorganized. And 2.) It will move at a steady clip, so it’s going to run out of time over water fairly quickly to develop. So the ceiling is constrained by time. Still, a strengthening tropical storm in the Gulf on approach to land is nothing to sneeze at or write off completely, so we’ll monitor this closely. Of note, the morning model data so far is not any further bullish on this system’s development prospects, and the National Hurricane Center maintains a 40 percent chance of development over the coming days. Regardless, we will see some locally heavy rainfall associated with this, be it as a disturbance or organized depression or storm. Thankfully, it is expected to keep moving at a steady pace. We will continue to monitor it for you, and Eric will have the latest in the morning.

Invest 99L

The NHC has given the disturbance classified as Invest 99L about a 90 percent chance of development out in the open Atlantic Ocean, just east of the Lesser Antilles.

Invest 99L is fairly far south and still a good bit east of the Lesser Antilles, and it appears to be gradually organizing into a depression as of Tuesday afternoon. (Weathernerds.org)

This system is very, very close to being a tropical depression already (as of this writing at 1 PM Tuesday). Invest 99L is going to be interesting. It’s rather far south and small, which will help shield it from a rather significant plume of Saharan dust off to its northeast. It is moving into an area of warm water temperatures and pretty low wind shear. Theoretically, this is a good candidate for development over the next 3 to 4 days as it approaches the islands. The various intensity models are very split on what happens here. I wouldn’t take the ultra high-end ones literally, but you can clearly see two camps: One that keeps the system middling over the next few days and another that says this thing will strengthen as it approaches the islands.

Intensity forecasts of Invest 99L in the open Atlantic vary from some holding it weak to others going off to the races with intensification. Much is still unknown here. (Tropical Tidbits)

Which camp is right? Great question, and one we don’t have an answer to at this time. There are good meteorological cases to be made for both a lower-end system, as well as one that perhaps organizes faster than anticipated.

Either way, interests in the eastern Caribbean should be monitoring the progress of Invest 99L closely. For us in Texas? It would be unlikely that this would survive the trip here. In fact, no storm within 150 nautical miles of where Invest 99L was centered this morning has ever made it to Texas, with the exception of Hurricane Allen in the Rio Grande Valley in 1980. So, if you’re playing odds, you’ll take those odds. We’ll continue to watch it however.

Of note, the next two names, which both could be utilized this week are Gonzalo and Hanna. The earliest “G” storm on record was Gert on July 24, 2005. The earliest “H” storm was 2005’s iteration of Harvey on August 3rd. Both records could fall.

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