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.
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.
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.
The Gulf of Mexico this week is the hottest it's been at any point in any year on record by a wide margin. Weekly averaged Gulf sea surface temperatures have never broken 87°F but this week topped 88°F, an astonishing 1.4°C (2.6°F) above the 1991-2020 average. pic.twitter.com/bw2p8RRsBE
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.
We have a lengthier post than usual today to catch you up on the doings of the Atlantic, which may be opening its doors to business this week. We’ll call it a soft opening for now. Just a reminder that you can subscribe and get these posts in your inbox, by signing up for email updates to the right (on desktop) or at the bottom (on mobile).
And a reminder that we’re here to cover the entire Atlantic basin, not just the Texas coast.
One-sentence summary
Hurricane season should pick up some later this week, with one or possibly two systems potentially trying to develop in the eastern Atlantic.
Happening now: Peak season begins this week. Maybe.
The tropics look to remain quiet the next couple days at least, but as waves begin to emerge off Africa this week, we’ll watch the late week period for the potential of some development. If we look at the satellite imagery over Africa this morning, we can see the beginnings of this burst of activity.
Bright colors indicate thunderstorm activity, and there’s a lot of that over the western portions of Africa this morning. (Weathernerds.org)
From this morass, we expect about two primary disturbances to show themselves. Both the GFS & European models are now in decent agreement on that for day 5.
You can click to enlarge this image showing where two disturbances should emerge by the end of this week off Africa. (Tropical Tidbits)
The eastern Atlantic seems to be the most likely area for development to occur at the tail end of the near-term period, and it would likely be one or two waves that could do it. That being said, there is going to be a lot of “noise” out there with this stuff. You really need these disturbances to break out of this noise to have a good shot at developing; destructive interference can be a thing. The National Hurricane Center currently has odds of 30 and 20 percent for these disturbances to develop in the next 5 to 7 days.
The NHC has 30% odds of development for the main disturbance expected to emerge off Africa later this week, a fair starting point at this time. (NOAA NHC)
I would say the odds of one system developing is probably above 50 percent right now. The odds of two systems developing is probably 20 percent or less. Either way, we at least know where to watch this week. We’ll talk about the future of these waves below.
Elsewhere, the European model is slightly bullish on a third piece of activity that makes it close to the Lesser Antilles later this week. I would say the odds of that area becoming something are extremely low right now, so we’ll leave it at that. There is another tropical wave that should make it across the Caribbean or end up near the Bahamas later this week as well, but that will not develop this week. More on that one below.
The medium range (days 6 to 10): An in-depth look at what will drive the bus in the Atlantic
So, with so much noise heading into the period and two dominant features in the eastern Atlantic to focus on, let’s check up on three things to see how this might go: Steering currents, dust/dry air, and wind shear.
Steering currents
Where will these systems go? Beginning later this week, high pressure over the central Atlantic will begin to weaken. By Sunday (day 7), we have a map up at 20,000 feet in the atmosphere that looks like this:
On Sunday, day 7, with high pressure near the African coast and another high over the U.S., it seems plausible that any disturbances in the Atlantic would be likely to gain latitude and turn out to sea rather quickly heading into next week. (Tropical Tidbits)
High pressure has reformed itself by then, somewhere south of the Azores or near the coast of Africa. What does this mean? Well, at first, given the weaker high pressure, we’ll probably see any system(s) in the eastern Atlantic turn to the northwest fairly quickly, particularly if they form quickly. As that happens and the high re-strengthens, that system or those systems will probably get pushed back to the west some. The good news is that it does not appear (for now at least) that the high pressure area will build west as the potential system(s) comes west. This should keep the exit door open to the northwest and north in the Atlantic. The vast majority of ensemble data suggests this to be the case as well. Ensembles give us 30 to 50 runs of the same model with tweaks, so we get a realistic “spread” of options, and in this case, almost all take it out of the way.
The European ensemble, which has been the most aggressive (read: too aggressive) developing things this hurricane season is probably overaggressive here too, but it gives you a sense of a.) what we’re watching and b.) why we feel good about any system turning out to sea. (Weathernerds.org)
The ensemble here is saying to us “Hey, you’ve got a tropical wave here that has a shot at developing, but it will probably turn northwest before it really gets to impact any land.” We expect that it will turn north right now, but we are not sure exactly when. Obviously we will watch this closely, but for now at least, we think this will turn northwest.
Dry air and dust
There is an awful lot of dry air and dust in the Atlantic — right now.
Widespread dry air and dust (which tropical storms do not like) dominates the central Atlantic, but conditions are less hostile immediately off the African coast right now. (Univ of Wisconsin SSEC)
But notice how it relents some near Africa. Initially, dry air probably won’t be a huge obstacle to overcome. But, if you trust modeling, the dry air is going to be a feature, not a bug.
Dry air is not going away completely, which means that any developing systems will have to deal with this in some capacity as they move west or northwest. This probably “caps” intensity of any system(s) a bit. (Tropical Tidbits)
Above, you see a map of mid-level atmospheric moisture on day 8, next Monday. If we box in the area where disturbances *might* be, and then we delineate dry air from moist air, you can see that there’s definitely dry air back in the vicinity of where this system or these systems may be. Tropical storms do not like dry air. It inhibits their growth and development. Assuming dry air is nearby, then you may have a situation where there is a “cap” on how strong these systems can get.
Shear
Another reason to potentially keep a lid on the ceiling for whatever forms is wind shear.
Wind shear looks moderate north of about 20° latitude, so it seems likely that any system is going to either a.) have to fend off some shear early on or b.) eventually encounter it if it comes west, which will also act to keep development odds in check a bit. (Tropical Tidbits)
The wind shear anomalies shown above for the medium range period are less than optimal for tropical storms to develop and strengthen. Wind shear is when winds move in varying directions with height, something that’s not great for hurricanes. The less wind shear, the more hospitable the environment is for tropical systems to grow. For now, this is an okay looking map if you’re rooting against storms.
As always, there are exceptions to the rules, but I think when you look at the sum of the parts right now, between shear, dry air, and the steering pattern, we are not in terrible shape in the Atlantic basin, despite the noise from modeling over the next 10 days.
Elsewhere
Aside from all this, we will have to wait and see if there is any consistency from models on the potential that the lead wave today can manage just enough to survive into the Gulf and then develop, something operational models show to some (modest) extent.
There should be a tropical wave in the Gulf next week (this map from the European model on Monday shows it just south of Louisiana), but odds of development are low to very low at this time. (Tropical Tidbits)
The upper pattern may support the Gulf being open for the Mexico or Texas coast next week, with high pressure centered over Missouri, farther north than it has been most of summer. The question as always is can we do anything with it? We’ll discuss that more through the week.
Fantasyland (beyond day 10): Active pattern may continue
As of right now, there are no specific concerns in the Atlantic heading out into the longer range. I do believe the pattern will remain fairly active, but the question will be whether or not the hurdles of shear and dry air will be low enough for storms to overcome. We’ll have to wait and see.
