Matt Lanza

August 18, 2023 Outlook: Atlantic potpourri, Texas rain chances, Hilary to soak the desert

One-sentence summary

The tropics are busy, with Hurricane Hilary likely to become a severe rain and flooding threat in the low deserts of California, while the Gulf will watch a tropical wave progress toward South Texas early next week.

Happening now: All the things

I’ve always found that it’s helpful to orient myself with a map, so let’s get oriented on what’s happening by looking at a satellite image of the East Pacific and Atlantic Oceans.

It’s a busy time in the tropics with multiple areas to watch. (College of DuPage)

What we’ll do today is work mostly left to right from that map above and discuss Hilary, the Gulf disturbance, Invest 98L, Invest 99L, and the “wild card” area below.

Hurricane Hilary: An exceptionally rare flooding threat for the SoCal deserts

I’m going to keep this section brief this morning. We discussed Hilary’s forecast in depth in our special post yesterday evening. We will have another one for you later this afternoon. Hilary has absolutely exploded into a category 4 hurricane with 145 mph maximum sustained winds.

Hilary has gone beast mode since inception, from a tropical storm to a category 4 storm in short order. (Weathernerds.org)

The general idea on Hilary is unchanged today, likely to come north into or just off the coast of central and northern Baja and eventually into California as a remnant tropical storm or depression. This leads to all sorts of potential issues in SoCal, but the primary one? Flooding.

NOAA’s Weather Prediction Center has issued a “high risk” of excessive rain on Sunday for Palm Springs, the Coachella Valley, and low desert regions of southern California for the first time on record. (Pivotal Weather)

The Weather Prediction Center already has a high risk of excessive rainfall posted for Sunday for Palm Springs and the Coachella Valley. This is the first time on record that they’ve issued a high risk in the low deserts east of the mountains in California. High risks from the WPC are very well correlated to bad outcomes. Over 80 percent of all flooding-related damage has occurred during high risk days and near 40 percent of all flood-related deaths have occurred on high risk days. In other words: High risks mean business.

Much of Southern California is expecting 2 to 4 inches of rain. The deserts will see 2 to 6 inches, with amounts of 6 to 10 inches in the mountains. (NOAA)

Rain totals will be exceptional for some of these areas on the east side of the SoCal mountains. This will cause significant flooding and potential damage, in addition to mudslides in some mountain areas. We’ll talk more about this later today, but as I said last night: Eric and I are quite familiar with flooding here in Houston. We encourage anyone in Hilary’s path, particularly in the deserts of California and Nevada to take this thing very, very seriously.

Gulf Wave: South Texas rains & potential development

The forecast for the upcoming Gulf system has not changed a whole heck of a lot unless you take the operational European model as gospel. Again, this thing will be hauling west. Look for it to emerge off Florida’s west coast on Sunday and make land in Texas on Tuesday. This limits how much time it will spend over the Gulf, and it’s likely why the NHC is still only giving it about a 30 percent chance of developing.

The big story since yesterday is that the operational European model has shifted to get more in line with the GFS and the Euro ensemble mean, which aims the bulk of the precipitation toward South Texas.

Rainfall from the Gulf wave is expected to occur primarily over the open water of the Gulf of Mexico, (sarcasm warning) an area not currently experiencing drought. There is a chance for higher amounts of rain between the Victoria Crossroads and RGV. (Pivotal Weather)

The good news? South Texas needs rain. The bad news? So does East Texas and Houston. So it appears this will help ease things a bit for Corpus and perhaps the Valley, with isolated 2 to 4 inch totals, depending on how well organized it is, exact track, etc. Eric has more over at our Houston-focused site, Space City Weather.

In terms of tropical development, this continues to look as if the speed will hinder it a bit. That being said, some modeling has shifted a bit toward this thing trying to make a last minute effort to organize. And it may be that this is what occurs. It blobs its way across the Gulf, and then in the 18 hours prior to arriving in Texas it makes a go at depression or tropical storm status. Interests along the Texas coast should continue to monitor the progress of this, just to be safe. We’ll keep you posted throughout the weekend on any forecast developments.

Invests 99L and 98L: Most likely for the fish

Both Invest 99L and Invest 98L are expected to probably remain out at sea over the next 4 or 5 days, with slow development possible from either or both area. The NHC has given 99L a 40 percent chance to develop and 98L a 70 percent chance. Invest 98L has the better chance to get a name, but Invest 99L is probably the more important of the two to watch, as it has a chance to at least graze the northeast Caribbean islands as it comes west. So should it organize, impacts would be possible in, say, the Virgin Islands or Puerto Rico. That is not the likely case however.

Although several models track Invest 99L toward the northeast Caribbean islands, virtually all of these models barely organize 99L into a depression. (Tropical Tidbits)

So interests in Puerto Rico and Virgin Islands should monitor 99L, but this doesn’t seem as if it will be a serious threat.

The medium range (days 6 to 10): The wild card wave

During the 6 to 10 day period, we’ll take Hilary and the Gulf wave off the board. Invest 98L and 99L, whatever they become should both be heading out to sea. That leaves us with the “wild card” area. Why am I calling it that? Because it has low odds of developing, but it is growing some model support. What is expected to happen is a piece of the monsoon trough, which Invest 99L is attempting to break from now may break off and sneak into the southern Caribbean. For the Windward Islands, this probably will just bring an increased chance of showers this weekend or early next week.

There are a couple options here. If it starts to organize, it will begin to feel the tug of a deep trough over the western Atlantic and get yanked north across the Greater Antilles and into the open waters, maybe grazing Bermuda on the way out. If it struggles, it may just sort of percolate in the southern Caribbean and/or dissipate.

Any tropical system in the Caribbean *should* get yanked north by a rather deep trough for August off the East Coast of the U.S. (Tropical Tidbits)

Either way, I wouldn’t expect serious impacts from this system, should it develop. For now. However, given the time of year, warm water, etc., you should continue to monitor the progress of this through next week.

Fantasyland (beyond day 10): The western Caribbean may gyrate

We’ll keep this brief a.) because this post is long enough and b.) we really can’t say with any confidence what will happen here. But, it continues to look as if a Central American gyre may develop and that will be worth watching. There is some chance for Gulf or Caribbean development in that pattern, but any details or specifics are impossible to pinpoint right now. But the final days of August will probably not be exceptionally quiet ones.

We’ll be with you all weekend, so if anything changes, you’ll know.

Hurricane Hilary poised to bring potentially extreme rainfall to the Southwest U.S.

Although we are branded as an Atlantic hurricane site, we here at The Eyewall feel Hurricane Hilary deserves special attention, given that it could produce some very significant impacts to parts of the Southwest U.S., where many of our readers have friends or family. Thus, we will be covering Hilary extensively into next week. Feel free to spread the word.

One-sentence summary

Major Hurricane Hilary is rapidly intensifying off the coast of Mexico, and although it will weaken as it comes north, it is setting up to bring a potentially extreme rain and flooding event to parts of the deserts and/or mountains in California and Nevada.

Happening now

Hurricane Hilary has exploded since yesterday, now classified as a major, category 3 storm, with maximum sustained winds of 120 mph.

The sun sets on a rapidly intensifying Hurricane Hilary, south of Baja. (Tropical Tidbits)

Additional strengthening is likely, and Hilary is expected to become a category 4 storm by tomorrow. Hilary has been able to tap into an exceptionally favorable environment for rapid intensification, and that will allow the storm to peak at a high end. Warm water and low shear will do that.

Hilary’s trek toward Baja

Tropical storm watches and warnings are posted for Baja, including Cabo with tropical storm conditions beginning at Cabo tomorrow night. If you know anyone visiting Cabo (or any southern Baja locations), my guess is that they are well prepared to handle a tropical storm type impact. Models are in high confidence that Hilary will pass safely offshore to keep impacts moderate there. The main threat may be heavy rain that causes flash flooding, as well as very rough surf at the coast.

Rain totals will vary across Baja, but in general, the heaviest rain is expected in the north, as well as near Cabo, with flash flooding possible. (Weathernerds.org)

Hilary will begin to weaken as it encounters cooler waters off Baja, and it is expected to make landfall in the north or just scrape the northern coast of Baja before coming ashore in California. Hurricane force winds are possible in northern Baja but they may come up just short.

Hilary will come close to making landfall along the northern coast of Baja, though it may just scrape the coast and come ashore in California. Either way, the impacts will be (mostly) similar. (NOAA NHC)

That being said, interests along the Baja Peninsula should continue to monitor Hilary’s progress as it comes north.

The main event: Rain and flooding in the desert

For those of you living in the Desert Southwest, particularly interior California, you hear “hurricane” and you may think wind. Yes, winds may be part of the issue, particularly along eastern facing slopes of the mountains in SoCal. But take it from someone who lives in Houston and helped get people through Hurricane Harvey: Heed the warnings about rainfall.

The current rainfall forecast for the Southwest shows anywhere from 2 to 6″ over a broad area, with locally higher amounts, perhaps up to 10″ or even more in parts of California and Nevada.

The desert is in for an absolute soaking. While there will be heavy rain and flooding concerns in the coastal cities between San Diego and Ventura pending the exact final track of Hilary, the primary risk of severe flooding is in the mountains and deserts inland from the coast. (NOAA)

How much rain is this? Death Valley averages a bit over 2″ of rain a year, and they’re currently forecast to receive anywhere from 2 to 5 inches with Hilary. You can do the math. Rain like this comes down harder than usual and can quickly lead to flash flooding, arroyo flooding, and potentially longer-term issues in some spots from too much rain.

Put simply: This has the potential, if not the likelihood of being one of the most significant rain events in recent years in the deserts of southeast California and southern Nevada. For folks in Phoenix, this probably is not your storm. But for folks in Vegas and over the passes from LA and San Diego, this has potential to cause significant and severe disruption Sunday and Monday into early next week.

In addition to the rain, there will be significant marine issues along the coast from swells and rough seas. Tropical storm force winds are possible down to lower elevations in spots and along the coast, and stronger winds are likely in the mountains. We’ll get a better read on specifics of that once Hilary’s final track comes into view.

Anyone with interests in SoCal, Nevada, along the Colorado River in western Arizona and even north into parts of Idaho and Montana will want to be ready for Hilary’s arrival and plan to deal with some disruptions, if not significant ones Sunday and Monday. Folks just west of these locations, into the Central Valley and Central Coast of California and the Sierra will want to monitor forecast progress as well. A shift west could change impacts from Tahoe down through Santa Barbara.

All in all, this is looking like a high impact storm. We’ll keep you posted.

August 17, 2023 Outlook: Gulf and California love

One-sentence summary

Atlantic action stays out at sea, a Gulf system remains a possibility next week, and <checks notes> California will be impacted by Hurricane Hilary.

Happening now: Still waiting

We’re not ones to tempt fate here at The Eyewall. We legitimately want everyone to have a peaceful hurricane season with minimal stress and anxiety. So, while we are still waiting for something to come of the “noise” in the tropics this week, we’re not complaining either.

Two waves in the Atlantic have a 60 percent chance each to develop in the coming days. They have been dubbed Invest 98L (east) and Invest 99L (west). Both are expected to remain out at sea, thankfully, but you can see them on satellite this morning.

The two Atlantic tropical waves on satellite this morning don’t look especially close to organizing yet, but they’re getting there. Both are expected to remain out at sea. (Weathernerds.org)

Earlier this week, I said the trailing wave might have a better shot to do something. As of today, I think it’s really a toss-up. Either invest could be “the one,” but neither looks exactly superb as of yet. We still anticipate that the upper level pattern will safely steer both disturbances out to sea.

Both invests are expected to remain out at sea per most model guidance (the Euro ensemble members shown here), but even if it weren’t to turn out to sea entirely, any development is expected to be slow and lower end. (Weathernerds.org)

Interests in the Lesser Antilles should make sure this doesn’t change, so keep an eye on things the next couple days just to be safe. Meanwhile, let’s look closer at the northern Caribbean and southwest Atlantic this morning, where the ingredients for our more meaningful Gulf disturbance will slowly come together over the next few days.

Unsettled weather off the coast of Florida and north of Hispaniola should come together in the eastern Gulf this weekend to provide a slight chance for tropical development. (Tropical Tidbits)

The primary impetus for this disturbance is currently just north of Hispaniola. This will race off to the west-northwest and merge with some additional activity in the eastern Gulf and we’ll have our disturbance. The NHC gives it a 30 percent chance of developing next week. The general spirit of things: “A disturbance with a low ceiling potential for development will race west across the Gulf next week toward Texas” seems to remain the story here. A good idea to keep tabs on this one, but there’s a very good chance this will not cause any significant problems.

What of the rain? The hope was (and still is) that this disturbance can drag enough Gulf moisture into drought-plagued Texas and/or Louisiana to help deliver some rainfall and provide some relief from drought. If you look at the forecast rain totals next week from the deterministic and operational GFS (left) and Euro (right), you can see some substantial differences. The GFS suppresses diffuse rain to the south, while the Euro is like “Heck yeah, brother!”

Click to enlarge forecast maps of the GFS & European model rainfall through next Thursday. (Pivotal Weather)

Well, let’s look specifically at the Euro. If you unpack the Euro ensemble, which is an average of 50 different European model runs with different tweaks at initialization, the picture that’s painted is a bit different than that of the operational model shown above. The map below shows the European ensemble probability of 1″ or more of rain. Not high!

Probabilities of 1″ or more of rain next week are highest offshore and south of I-10 in Texas, meaning any serious drought relief inland seems unlikely from this disturbance. (Weather Bell)

Ensembles help us a lot in these situations because they can validate or invalidate critical deterministic guidance. In this case, it puts an awful lot of doubt on that European operational model that brings 1 to 4 inches of rain to Texas and southwest Louisiana. It has the placement farther south and west and probably with lower odds.

Bottom line: While some rain is likely in drought-stricken Texas, this may not be the droid you’re looking for.

Interlude: Californication

Our site is intended to primarily cover Atlantic tropics, but every so often, something interesting and worth discussing happens on the Pacific side too. Today we focus on California.

Rare as it is, California can get impacted by tropical storms, although it takes a heck of a lot of things to come together to get that to happen. The last time this officially happened was in 1939 when a tropical storm made landfall near San Pedro (between the Port of Long Beach and Rancho Palos Verdes). As recently as last year, Hurricane Kay brought remnant impacts to California that were rather significant. Suffice to say though, it’s unusual. Hurricane Hilary just formed in the Pacific, and the official forecast track will raise an eyebrow or two.

Hilary has exploded into a category 1 hurricane and should become a major hurricane before weakening as it approaches Baja or Southern California late this weekend and Monday. (NOAA NHC)

This has support from modeling. As Hilary comes north, it will be steered by a trough to its north and the insanely sprawling, near-record ridge over the Midwest and Plains. Hilary should come north, roughly parallel to Baja but offshore initially. It will then likely get drawn inland somewhere between Point Conception (west of Santa Barbara) and the central coast of Baja in Mexico. The most likely outcome right now is a Baja landfall north of Cabo and San Carlos. Anyone in Cabo, tropical storm conditions are possible, but hurricane conditions are currently expected to stay offshore.

Hilary will be drawn north in the alley between the so-called “heat dome” over the Plains and an upper low off the Central Coast of California. Exactly where that sets up will determine where Hilary tracks, but model agreement strongly points to a Baja landfall right now (Tropical Tidbits)

Since yesterday, modeling seems to have coalesced around another storm not making official landfall in California, and as shown by the NHC above, it will probably make land in Baja. However, the general theme of things, bringing Hilary north will bring the remnant moisture northward too.

In general, you should expect a good chance of heavy rain in SoCal, especially in the desert and up into Nevada and for portions of western Arizona and southwest Utah beginning Sunday into Monday, but specifics will be tough to nail down. Additionally, strong winds in passes and at higher elevations will be an issue.

Heavy rain from Hilary will potentially cause significant flooding issues in interior southern California and western Arizona up through Nevada. (Pivotal Weather)

That type of rain (3 to 6 inches) in the desert can cause severe flooding issues, so folks between Phoenix and San Diego northward (as well as on Baja obviously) should be monitoring Hilary’s progress. Check out your local National Weather Service office for more localized details.

The medium range (days 6 to 10): A bit of an interlude period

I think the medium range period right now looks like a quieter one with the potential of lingering open Atlantic activity and then a bridge to extended period development in the Gulf, Caribbean, or southwest Atlantic. There are no specific concerns at this time beyond Hilary in California and babysitting the Gulf wave next week.

Fantasyland (beyond day 10): More to come

The system (meaning the atmosphere) remains cranky and noisy beyond day 10 I think. There are several things that might happen, but there is nothing we necessarily feel convicted about that will happen.

For one, as both Eric and I have alluded to in recent days, we could see a gyre setup over Central America, which could spice things up a bit, especially in the Caribbean or eastern Gulf. Some modeling is suggesting that stuff could creep north toward the Bahamas or off the Southeast U.S. coast. The eastern Atlantic may settle down a bit here.

What will ultimately dictate things in the extended range will be the upper pattern. Do we have another ridge over Texas? Will it have nudged back to the Southwest? Will the Bermuda high remain mostly at bay in the Atlantic, keeping the exit door open north and northeast? A lot of things to answer here. We can only speak in broad, vague terms right now. Our advice: Stay tuned.

August 15, 2023 Outlook: The entire Atlantic will continue to fester with some chances for development over the next 2 weeks

One-sentence summary

While there remains a lot of noise in the Atlantic for the next 7 to 10 days, the main items of interest from a land-impacting potential may be disturbances that try to form closer to home in the Gulf or near Central America.

Happening now: Noisy but not expecting a whole lot to formally develop this week

Tuesday morning in the Atlantic basin shows a conga line of thunderstorms stretching from northeast of South America all the way to Africa. This is the inter-tropical convergence zone (ITCZ).

The main wave to watch is heading off Africa today or tomorrow, while lesser waves lead the way, with one potentially heading toward the Gulf early next week. (Weathernerds.org)

On the map above, I’ve annotated the various things we’re watching. Let’s walk through them and what to expect through early this weekend.

Area 1: Easternmost tropical disturbance with 30% odds of developing per NHC

The area with the highest risk of developing over the next week is still over Africa this morning. This particular feature is expected to emerge later today or tomorrow into the Atlantic. It will take a couple days to organize after that, and any development before this weekend would be on the low-end.

A look at “spin” in the mid-levels of the atmosphere over the next 5 days shows a pretty clear disturbance emerge and organize on the right side just off the coast of Africa. That’s our primary tropical wave to watch. (Tropical Tidbits)

I’m actually going to refer you to yesterday’s medium range section for more discussion on this system. Not much has changed in terms of the influences it will feel and why we believe it will launch out to sea. Yes, it has a chance to develop. No, we don’t believe it will develop significantly. And for now at least, we do not anticipate that it will impact land.

Area 2: Tropical wave embedded in the ITCZ halfway across the Atlantic with 10% development odds

The second area highlighted by the NHC is the tropical wave about halfway across the Atlantic. This is embedded in the ITCZ right now, which means it will probably need to break free to really develop. I’m not entirely sure that’s going to occur, and even if it does, this wave will likely be surrounded by dry air and have to fend off some wind shear as it approaches the Caribbean.

Dry air on the northern and eastern flank of the wave approaching the Caribbean islands this weekend will likely help keep development odds quite low.

So, the 10 percent odds seem reasonable right now, which is to say not impossible that it might develop but unlikely.

Area 2a: A “piece” of that tropical wave that may race toward the Gulf next week

So, to be clear, no development is expected from this area over the next 5 days. But, if you look at some upper level maps, you can pick out a “piece” of this mid and upper level disturbance that comes hauling, I mean hauling west over the next 5 days. It makes it from the middle of the Atlantic to beyond Florida by day 5.

By Sunday, a disturbance will establish itself in the eastern Gulf of Mexico, disorganized and moving quickly westward.

By the end of the near-term, this disturbance is mostly unchanged and continuing to race west. Again, no development is expected.

The medium range (days 6 to 10): Watching the Gulf? Kind of.

Continuing from above, by day 6 (Monday), the disturbance we’re watching moves to just south of Louisiana. And by day 7 (Tuesday) it has come ashore in Texas. There are significant model differences in exactly where this disturbance will go, but it will likely lead to some tropical rains in parts of Texas and/or Louisiana. But given the uncertainty, it bears some watching.

The speed of this disturbance is something else. That is both good and bad. The good news is that a quick moving disturbance will limit its residence time over a record warm Gulf of Mexico.

Less time over water means less time to organize. Truthfully, the speed of this disturbance itself will be a detriment to development, as systems that move this fast hardly have time to get their acts together. It would be one thing if it were already organized, but it won’t be. Between all that and some moderate wind shear, it seems that this system is unlikely to organize.

The good news is it will bring a meaningful chance of some rain to a bone dry, drought-plagued western Gulf Coast.

As the tropical wave comes west next week, it has the potential to bring locally heavy rainfall from South Texas into Louisiana, but probably not to that entire region. Details will matter, ironed out in the days ahead. (NOAA)

The bad news is that because it’s moving so fast, any benefits may be very brief. We will have more on this as it gets closer.

Aside from the Gulf, we’ll continue to watch the system off Africa that we expect to turn out to sea. There may be a second wave that emerges later in the period as well that has some development chances.

Overall, I think you can classify the next 10 days as semi-active. Yes, we have development opportunities, but none are slam dunk cases.

Fantasyland (beyond day 10): Looking closer to home

I’m not entirely sure how the extended range is going to play out. Broadly, the Atlantic basin looks favorable for development. Realistically, however, there’s not a lot sticking out right now. But there seems to be a slight signal in the modeling that some type of hot spot may exist in the Gulf or near the Yucatan, possibly courtesy of a Central American Gyre (CAG) type pattern. Maybe. Gyres are tough to predict, and specific tropical systems emerging off CAGs are even more difficult to predict more than 5 to 6 days out. So I won’t rampantly speculate for you. Other sites can do that.

There’s a vague but fairly consistent signal in some modeling that the Gulf may be a place to watch next weekend or the following week. (Tropical Tidbits)

The map above shows the 51 European model members averaged together to produce a “normalized” 500 mb height anomaly next weekend, or basically what the pattern is doing 20,000 feet above our heads. There’s clearly a signal that some type of upper low or disturbance may be in the vicinity of the Gulf closer to days 12 to 15. Whether that’s an non-tropical upper low, a disjointed area of storms, an organized tropical system, or nothing at all I could not tell you. I’ve done this long enough to know not play speculation games with CAGgy-type setups (and even non-CAG setups too!). For now, I’ll just say let’s watch and wait; there’s enough signal in the models that says “let’s monitor the Gulf.” However, I would not expect much clarity on the specifics of the final days of August for another week or so.

Aside from that, we’ll keep watch on the Atlantic, but I’m not enthused by anything in particular at this time.