Hilary heads north, aiming to drench the California deserts, while low-end Gulf development odds inch up a little

One-sentence summary

The forecast for Hilary is basically unchanged with a severe to historic rainstorm coming for the California deserts and parts of Nevada, while the odds of lower-end Gulf of Mexico development have nudged up a little and some welcome rain heads for South Texas.

Hurricane Hilary: Major flooding potential still likely in the California deserts

We’ll start with Hilary today. Hilary is beginning to feel the influence of cooler water and begin the transition from major hurricane to moderate hurricane and major rainstorm.

Hilary will graze central Baja as a hurricane tonight, then meander north as a tropical storm and major rainstorm in northern Baja, southern California, and Nevada. (NOAA National Hurricane Center)

Hilary’s forecast track remains basically in line with the forecast since yesterday, coming north into SoCal as a tropical storm, a status which it may maintain all the way into Nevada. There are currently tropical storm warnings across most of Southern California, a first for them in modern history. Rain will actually start today as Hilary interacts with an abnormally strong trough off the California coast. This is an event we call a PRE, or predecessor rain event. I don’t want to oversaturate you with science, but you can read about what they are here. Suffice to say, this is not a common feature in California, Arizona, and Nevada.

Hilary is sitting off the southern tip of Baja this morning, racing north, while rain breaks out ahead of the storm. (Weathernerds.org)

These types of rains can just help juice things up for the main event (tomorrow) from Hilary itself. Let’s talk things out by region to give you a sense of the impacts.

LA, Orange County, and San Diego

From what I’ve seen on social media, some people in Los Angeles think a hurricane is coming for them. While there will be impacts from Hilary in LA, the OC, and San Diego, the impacts will be worse inland in the deserts. Still, preparations for the summer equivalent of a big winter storm should probably be made, particularly along the immediate coast.

Forecast peak wind gusts for the California desert, Orange County, and San Diego areas will be 35 to 45 mph or a bit stronger on the coast from LA south to San Diego. (NWS San Diego)

Wind gusts won’t be incredible, but they will probably push on tropical storm intensity along the coast and in the Channel Islands. Terrain in these areas means that wind will vary. With the storm going east of the mountains, winds will basically mimic a Santa Ana wind event, at least in terms of direction. So basically, areas that see the strongest winds in Santa Ana events in LA and San Diego will probably see the strongest winds with Hilary.

Rain totals in LA and San Diego will be 1 to 3 inches, enough to certainly cause some flooding, but the most serious impacts would be very limited in these areas I think to the immediate coastline and any burn scar areas, where heavy rain could lead to debris flows or mudslides. For the vast majority of metro SoCal, this will be a curiosity and inconvenient event, not a catastrophic one.

This also includes places like Riverside and San Bernardino, metro Inland Empire cities that are generally west of the north-south mountains.

Mojave Desert, Palm Springs, Imperial Valley, Death Valley

This is the area that those of us that are meteorologists are most concerned with in terms of extreme to catastrophic flooding impacts.

Rain totals of 4 to 7 inches are likely in the desert regions of Southern California, with extremely dangerous and damaging flooding possible in places like Death Valley, Joshua Tree, and the Imperial Valley. (NWS San Diego)

This is basically San Diego County east of the mountains, Imperial County, eastern Riverside and San Bernardino Counties, and Inyo County in California. Rain totals will equal 1 to 2 years of rainfall over 1 to 2 days for some of these areas. For those of you scoffing at 5 inches of rain leading to catastrophic flooding, remember that the deserts and areas with terrain are nowhere near as equipped as many places in the East to handle this type of rain and these type of rain rates. Land composition is much different in the West than the Central and East, and that means thresholds for severe outcomes are different.

Anyway, this is the region we are most concerned with. Travel between the coastal metros and places like Death Valley, Vegas, Kingman, Phoenix, and Yuma will almost certainly be disrupted for a time due to flooding and/or infrastructure damage. Damage in some parts of Joshua Tree National Park and Death Valley could be severe and extensive. As someone who has spent time in both parks, this saddens me a bit. Hopefully it’s not as bad as it could be, but these forecast totals are definitely troublesome. Please heed the warnings of your local National Weather Service offices (most likely San Diego, Phoenix, or Las Vegas) as this event unfolds.

Las Vegas and southern Nevada and Utah

Depending on exactly how the storm unfolds, impacts across Nevada may range from modest to severe. A high risk for flooding on Sunday is posted into Death Valley, but it does not include Las Vegas or southern Nevada at this time.

A moderate risk (level 3/4) of excessive rain is posted in Nevada on Sunday. (NOAA)

A moderate risk (level 3 of 4) is posted for most of Nevada tomorrow for excessive rainfall. We expect some degree of flooding here, particular in isolated spots and in favored mountain locations. Total rainfall in Las Vegas is expected to be on the order of 1 to 3 inches, an amount that will surely cause some flooding issues, but hopefully not the severe issues we’ll see in the California deserts.

Rainfall of 1 to 3 inches is expected in the Las Vegas metro, with higher amounts in the mountains. A widespread 1 to 4 inches is expected across the southern half of Nevada. Impacts will be less significant in northern Nevada. (Pivotal Weather)

Even up into southwest Utah, rain totals of an inch or two are possible for places like St. George and even not far from Zion National Park. Flood watches are posted for all of Nevada except Reno/Tahoe and north. Much of Utah is also under a flood watch.

Flood watches extend north of Nevada into southwest Idaho and southeast Oregon as well, where remnant rain will produce localized flooding.

Arizona

Heavy rain and pockets of flash flooding are likely in western Arizona as well from Hilary.

Rain totals of 1 to 3 inches are likely along the Colorado River downstream from Lake Mead in Arizona. Flood watches are posted west of Phoenix and Flagstaff. (Pivotal Weather)

Flood watches are posted for all of western Arizona, including Prescott, Yuma, and Kingman. Rain totals of 1 to 3 inches are likely here with lesser amounts in eastern Arizona. Flooding is not currently expected to be an issue in Phoenix.

The bottom line: Hilary will bring varying impacts across the southwest, but the most concerning ones will occur in the deserts of California where we are very concerned about flooding. Please be ready for a rough Sunday and/or Monday in those areas.

Gulf of Mexico development chances inching up

The National Hurricane Center has upgraded the potential for the Gulf system to attain tropical depression or tropical storm status early next week to 50 percent.

There is a 50 percent chance that the tropical wave entering the Gulf of Mexico can become a depression or tropical storm before coming ashore in South Texas next week. (NOAA NHC)

Looking on satellite this morning, the disturbance aiming to come into the Gulf is showing some spicy thunderstorm activity, but it lacks any real organization still at this point.

There are definitely thunderstorms erupting around a disturbance moving into the Florida Straits today, but there remains little to no organization from this system. (Weathernerds.org)

This currently is just a few blobs of heavier thunderstorms moving into the Gulf. As this comes west, it will probably encounter a little bit of a less hostile environment and may begin to slowly organize. But it’s going to be hauling west and will have less than 48 hours over the Gulf meaning even if does organize, it will likely come ashore in South Texas as depression or low-end tropical storm, at worst.

The main impact from this, besides some modest marine impacts, will be rainfall, much needed rainfall at that. However not all of Texas gets to play.

Rain over the next 5 days is expected to be highest from Corpus Christi to Brownsville and inland into Mexico. (Pivotal Weather)

In fact, much of the Houston area may see little to no rain from this system. Perhaps a bit south of I-10 or near the coast. Corpus Christi? Brownsville? Laredo? Perhaps 1 to 3 inches of extremely beneficial rain. That will extend into Mexico, which also could use some rainfall. But drought conditions that have taken hold in much of East Texas are going to remain or worsen. As we head into early September, the persistent ridge that has been bringing day after day after day of high heat to Texas may begin to weaken some, but it does not want to let go just yet. Sadly, there is no well-defined “next best” chance of rain for drought-plagued parts of Texas after this.

Elsewhere: Multiple Atlantic waves

A quick look at the NHC fruit basket shows three Atlantic disturbances, from left to right Invests 90L, 99L, and 98L.

Invest 98L has the best odds of developing over the next few days out over the open Atlantic, while newly minted Invest 90L has about a 40 percent chance of doing so in the Caribbean. (NOAA NHC)

Of the three, Invest 98L still has the best chance of forming into something, though it will remain out over the open Atlantic. Invest 99L is a nothingburger. Invest 90L may draw in most people’s eyeballs. We’ll keep an eye on this one, but at this point development looks sluggish and lower-end. Just wanted to make sure you knew we weren’t ignoring the rest of the Atlantic!

Hilary continues to look like an extremely serious flood threat for California, Nevada, and parts of Arizona

One-sentence summary

Morning forecast models continue to underscore the seriousness of the flooding threat facing the Southwest via Hurricane Hilary’s abundant rainfall.

Happening now: Hilary holds as a major category 4 storm

Hurricane Hilary remains a powerful Category 4 storm. It has about 12 to 18 hours left before ocean conditions begin to cool, which should allow for Hilary to weaken somewhat as it comes north.

Hilary is close to a textbook looking storm as it turns northwest off the coast of Mexico. (Tropical Tidbits)

Hilary’s forecast track has not changed too terribly much so far today. In fact, one could argue that aside from a little nuance, Hilary’s future track is now mostly locked in and likely has little deviation expected.

Despite a little nuance, Hilary’s track is mostly locked in for the next 48 hours, with a path just off Baja, comfortably west of Cabo, and hurricane conditions possible in central or norther Baja as Hilary treks close by. Hilary is likely to make landfall near San Diego as a tropical storm on Sunday night or Monday morning. (Tropical Tidbits)

The message for folks in northern Baja, southern California, Nevada, and far western Arizona is pretty clear: While there may be a few details-oriented changes between now and Monday, the overall impacts you should expect will likely change very little. In other words, what you see (now) is what you (should) get.

The rain risk in the Southwest: It is very serious

I don’t want to bury the lede here. While there will be tropical impacts, including and especially to parts of Baja, the main and most severe impacts from Hilary will likely be in the form of flooding and extreme rainfall in the Desert Southwest. We don’t take these situations lightly, and if you’re new to our coverage, you might ask why we’re writing so aggressively about this. In the current media landscape, they’re valid questions, but in this case the answer is that this actually is that serious.

Click to enlarge the rainfall forecast through next week for California, Nevada, and parts of Arizona. (Pivotal Weather)

The current rainfall forecast for Indio, CA is about 4.7 inches. In a typical year, Indio expects just under 3 inches of rain. So, this is a place that already struggles to handle rain and has a chance to see more than its annual average rainfall over 2 days. This is exactly why the Weather Prediction Center issued their first high risk in this region for excessive rain on Sunday. As a Houston-based forecaster who has worked closely with the WPC and their rainfall products, I can assure you that issuing a day 3 high risk is not a decision they take lightly.

The day 3 high risk for excessive rainfall is a rarity to begin with, let alone in the California desert. (Pivotal Weather)

They issue high risks only when they are very confident that what they think will happen will happen. High risk rainfall days are associated with most of the flood damage that occurs in the United States.

Over 80 percent of all flood-related damage in the U.S. occurs on high risk forecast days. (NOAA WPC)

So I just want to be clear with folks that this is a big deal. If you live in the Coachella Valley or Palm Springs in particular, as well as “downstream” from any burn scars in SoCal, you need to be prepared for flooding Sunday or Monday. Travel between Vegas, Phoenix, or northern Arizona and LA may very well be disrupted in spots on I-15, I-40, or I-10 due to desert flooding. Same goes for I-8 between Yuma and San Diego. The area between Mexicali and Palm Springs is at highest risk, but there will be pockets of flooding elsewhere, including in the major metros on the coast (LA and San Diego), as well as in Yuma and Las Vegas. Please heed warnings from your local NWS offices. Now is a good time to get to know their websites and follow them on social media.

But the tropical storm part is cooler!

Some of you may be excited by the fact that a tropical storm is coming and big winds and big surf are on the way. And in fact, for the first time since they’ve been issued by the U.S. government, a tropical storm watch was posted today between the US/Mexico border and the Orange/LA County line, as well as Catalina Island. The hurricane warnings are confined between Punta Abreojos to Punta Eugenia in central Baja.

The watch and warning situation in the Southwest as of Friday afternoon. (Pivotal Weather)

The max wind gusts expected aren’t terrible in the major cities of SoCal, with both Los Angeles and San Diego likely to see gusts as high as about 40 mph or so, perhaps a bit stronger on the coast of Orange County or in the North County portion of San Diego and just offshore. Gusts will likely pick up in the mountains and then be at their worst in portions of the desert over a narrow but long-ish region between Ocotillo and Joshua Tree up toward Baker on I-15.

Maximum wind gusts are expected to be generally around 40 mph in LA and San Diego, higher in the nearby mountains, and very strong in the Low Desert, with 50 to 80 mph over a narrow but long area. (NWS San Diego)

Overall, Hilary remains on track to be a highly impactful, potentially historic event for the deserts of California and possibly Nevada. Please follow your local NWS office and heed any warnings if they’re given in your area. Be prepared to stay put for a day or two Sunday into Monday. We’ll have another update for you in the morning.

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.