Matt Lanza

Fernand’s finale, Erin’s warm Europe, an AI modeling W, and a major Phoenix haboob

In brief: Fernand will soon become post-tropical as it heads out to sea. Warm weather in Europe thanks in part to Erin’s remnants will soon end. Today, we also discuss how AI modeling fared during Hurricane Erin, as well as a massive haboob that descended on Phoenix, Arizona yesterday.

Tropics: Fernand, and Erin’s remnants in Europe

We are starting off Tuesday with essentially a clean slate. There are no current areas of interest with respect to the tropics. The only item out there is Tropical Storm Fernand. The storm should become post-tropical by later today or tomorrow as it scoots out to sea.

Fernand is gone to the fishes. (NOAA NHC)

In fact, Fernand is kind of cool to look at on satellite imagery this morning. It’s become almost a “naked swirl,” as virtually all deep thunderstorm activity around the storm has vanished or been left behind due to wind shear.

Fernand is approaching “naked swirl” status. (Tropical Tidbits)

Fernand will be funneled off toward Europe where it should be absorbed into the larger storm system that also contains the remnants of Hurricane Erin. Temperatures are running about 6 to 10 degrees above normal in western Europe with that storm system sitting just south of Iceland. The circulation around it pumps very mild air into Europe, particularly western Europe, and London has ended up with low 80s instead of low 70s for highs.

Tuesday afternoon temperature anomalies in Europe shows most of western Europe warmer than usual. (Tropical Tidbits)

Somewhat cooler weather and some breezy unsettled weather is on the way to Europe as this storm system dislodges. Anyway, the point of a longer note than usual this morning is to show how even “fish” storms can provide interesting things to discuss.

There are no other tropical concerns today.

A feather in the cap for AI weather modeling

Speaking of Hurricane Erin, let’s talk briefly about verification. When it comes to writing our daily updates here, we are vehemently anti-AI. You’re always going to hear from a human when you read The Eyewall. However, when it comes to weather modeling, AI (or really, machine learning) is adding new, extremely valuable tools to the arsenal we have to forecast with.

Some of the initial results are in from Hurricane Erin’s forecast, and Google’s Deep Mind AI model scored a pretty significant win for these new tools. Between hours 12 and 72 of the forecast, the GDMI on the plot below (shared by former NHC Branch Chief James Franklin) outperformed the best tropical models and even the NHC. Notably the NHC also outperformed the models in that timeframe as well, a win for them.

Model track error during Hurricane Erin for various weather models. (James Franklin on BlueSky)

After hour 72, the picture becomes a little blurrier for AI with the HAFS-B (HFBI) taking control. TVCN represents a consensus aid, and the GDMI from Google beat it all hours. I was more impressed to see how it handled intensity, truthfully, as AI modeling has tended to struggle a bit in that department.

Google’s Deep Mind model (GDMI) outperformed most guidance through hour 96 of the forecast for intensity. (James Franklin on BlueSky)

Again, Google’s Deep Mind outperformed virtually all traditional model guidance through 72 hours. Even later in the forecast horizon, it ended up in the top third of guidance.

So what can we really say here?

First off, let’s just call it what it is: Certain AI modeling, which require far less computational resources and take extraordinarily less time to run is able to perform essentially as good or better than traditional modeling when averaged over the life cycle of a major hurricane. That last part is important. It’s just one storm, yes, but this is something we have anecdotally noted since last year. AI modeling tends to be much more stable with respect to storm track, particularly in the first 3 days of the forecast, which is certainly important.

However, averages are just averages, and while the AI modeling performed outstandingly over the lifespan of Erin, there’s a difference between storm-life statistical average and operational effectiveness in real-time. Also, Erin’s forecast track frankly didn’t have a ton of major uncertainty in the 5-day time horizon. There were questions of exact turn timing and location, but short of that, it became more a matter of semantics than anything. The intensity forecast was really well done by AI modeling all things considered.

So it’s important to contextualize this. Google’s Deep Mind represents one AI model. Hurricane Erin was one storm. But AI modeling has proven time and again that it can hang with the best modeling, particularly with respect to track but also now in some cases intensity too. It’s also important to note that the National Hurricane Center outperformed most model guidance on track and intensity. The assumption here is that given the technical expertise that resides in the NHC, as these AI models become more proficient and get validated, those will be further incorporated into the NHC forecast process. And the NHC should continue to shine overall.

Haboob in Phoenix

Shifting gears now, the Phoenix metro was overtaken by a massive haboob yesterday. What’s that? It’s a massive dust storm usually kicked up by the winds of strong thunderstorms moving over the desert or dried soil. And indeed, yesterday’s haboob in Phoenix was something else.

(Jim Tang on Twitter/X)

You can read more about the history and etymology of the term haboob here, but while these are somewhat common in the Southwest, one of this magnitude overtaking a major metropolitan area is pretty incredible to watch. The good news is that it wasn’t just all dust. Much of the Valley of the Sun and beyond saw some good rains as well yesterday.

A sampling of 24-hour rain totals ending this morning across the Phoenix region. (NOAA)

A continued chance of isolated to scattered monsoon thunderstorms will be with parts of Arizona at least from today through Thursday.

Fernand exiting, 99L dissipating, and the Atlantic quieting down

In brief: The Atlantic tropics are going to trend quieter, with Fernand heading out to sea and Invest 99L finally reaching the end of the road. Behind those? Not much. A significant typhoon hit Vietnam today. Flooding risks will continue in Oklahoma and Arkansas this week.

Tropics

We don’t have a heck of a lot to discuss today in the Atlantic! Tropical Storm Fernand continues to slowly work out to sea and away from Bermuda.

Fernand heads out to sea and should be absorbed into the broader weather pattern by later tomorrow or Wednesday. (NOAA NHC)

Fernand has strengthened a little since our post yesterday, as expected. However, it’s not exactly healthy. The center seems somewhat displaced to the north side of the thunderstorms, and it’s pretty evident that wind shear is beginning to really hamper Fernand.

Fernand is fighting wind shear and will soon have to fight cooler water too. (Tropical Tidbits)

Meanwhile, to the south, Invest 99L has finally met its fate it would seem. Where did all the thunderstorms go?

(Weathernerds.org)

Thankfully, it just took some time but it got here. Look for the remnants of 99L to spread west across the Caribbean, bringing some scattered heavy rain and storms before eventually being buried in Central America or even South America as a small-scale feature. No development is expected, and this should probably close the book on this version of Invest 99L.

Beyond these areas, we see nothing of note in the Atlantic tropics for the next week, probably longer. A very rare and welcome late August and early September break seems to be in the offing this year. We will absolutely take that.

Typhoon Kajiki around the time it made landfall in Vietnam. (Tropical Tidbits)

In the Pacific, Typhoon Kajiki made landfall in north-central Vietnam this morning (U.S. time) as the equivalent of about a category 2 hurricane. Around 600,000 people were ordered to evacuate ahead of this storm.

Arkansas and Oklahoma flooding risks

Rain across the Plains will go on as expected, with heavy rain in parts of Oklahoma in particular.

Heavy rainfall across eastern Oklahoma and NW Arkansas today and tonight. (NWS Tulsa)

A second round of heavy rain is likely heading into later week as well. This round will be either Wednesday night, Thursday, and Thursday night.

More rain later this week. (NWS Tulsa)

More details in our post yesterday. We’ll keep it there for now. More on Tuesday!

No schadenfreude from Tropical Storm Fernand, as we check out flooding risk and wildfire issues today

In brief: Tropical Storm Fernand is heading out to sea, not a threat. Invest 99L is heading into the Caribbean, unlikely to develop. Heavy rains are likely this week in the Southern Plains and parts of the Southern Rockies, with flash flooding risks. Wildfires are an issue out West, and while cool weather will dominate the country this week, additional heat and fire risk will bubble up in Oregon, Washington, and British Columbia.

Today’s post will take a look at the tropics, the main storylines for the upcoming week, and some wildfire updates.

Tropical Update

Tropical Storm Fernand

(NOAA/NHC)

Starting off Sunday southeast of Bermuda, where Tropical Storm Fernand is churning. While Fernand has, at times, looked pretty decent this morning and afternoon, it generally seems to be struggling overall. It’s a modest tropical storm at best, and the good news is that it’s heading out to sea. This will be its closest pass to Bermuda, so no real impacts are anticipated.

Fernand looks like a true tropical storm, nothing more, nothing less. (Tropical Tidbits)

As Fernand exits off to the north and northeast, it could see a quick burst of some organization, trying to drive it up to stronger tropical storm intensity. But for the most part, Fernand will be a footnote in the 2025 Atlantic hurricane season.

Invest 99L

To the south of Fernand, Invest 99L continues to confound and defy model projections of dissipation.

Invest 99L is approaching the southern Leeward and northern Windward Islands on Sunday afternoon. (Weathernerds.org)

It still looks robust, but despite the persistent thunderstorm activity, 99L has never been able to get itself together. This is a disturbance that in another timeline would be a major hurricane bearing down on the islands. Thankfully, it is not, and over the next couple days, Invest 99L will face its harshest environment yet. Wind shear and some dry air will push at this system, likely keeping no worse than it is at present. It will deliver above normal moisture and thunderstorm chances across the central Caribbean, perhaps up through Jamaica and eventually into Central America.

Invest 99L’s moisture plume will bring some locally heavy rain chances this week across the Caribbean, including to Jamaica before it gets absorbed into the broader pattern over Central America. (Pivotal Weather)

Development seems unlikely, but this is probably worth checking back in on in a couple days to make sure.

Next 7 days in the Atlantic

Beyond these two specific systems, it’s hard to really tell what might be next to watch. With a cool front draped from the Gulf, across Florida, and into the southwest Atlantic, that seems like the most typical type of setup we’d expect to see a chance for something to sneak under the radar. I wouldn’t be shocked to see an area of interest drawn in that region, probably in the 10 to 30 percent range in a day or two. But aside from that, we have no other specific threats or concerns we’re seeing out there for the next 7 to 10 days. We talked a bit about that yesterday if you want to read more.

Southern Plains & Rockies flooding risk this week

Bringing things back to terra firma, it’s going to be a busy week in the Central U.S. in terms of flooding risk. The outlook over the next 5 days, including the rest of today calls for meandering slight risks (2/4) of flash flooding across the Southern Rockies in Colorado and New Mexico and the Plains.

The slight risk of flooding (2/4 in yellow) maneuvers around the region between Sunday and Thursday. (NOAA WPC)

The rain chances look most significant tonight from western Kansas into northwestern Oklahoma. Tomorrow, the rain chances really pick up in eastern Oklahoma, particularly closer to the Tulsa area and northwest Arkansas. Isolated areas will likely see 3 to 4 inches or even a bit more from tomorrow’s storms. The heaviest rain chances will likely shift back west into the Rockies on Tuesday into Wednesday morning. Another round of potentially significant rain and thunderstorms will be possible in Oklahoma into northwest Arkansas on Thursday.

Significant rainfall is likely over the next week from the Front Range into the Ozarks, with the highest rain totals focused on Tulsa and Northwest Arkansas. (Pivotal Weather)

The current rainfall forecast calls for 2 to 4 inches this week over a wide areas between the Rockies and Ozarks, with the peak totals occurring near Tulsa or Fayetteville up to 6 to 8 inches. Flash flooding will almost certainly become an issue at times in these areas this week. Locally heavy rains in the Southwest will probably cause some flash flooding in southern Colorado or northern New Mexico. Burn scars will be susceptible to that, particularly in New Mexico, thankfully mostly north of the Ruidoso area, though still in portions of the state. Localized severe thunderstorms are possible as well.

Wildfires

Meanwhile, in Oregon, the Flat Fire has grown to over 20,000 acres, with 1,000 homes under evacuation orders and another 3,000 in potential evacuation zones. Additional wildfires were causing issues in the West, including the Pickett Fire in Napa Valley. Meanwhile, the fire risk we’ve been discussing in Atlantic Canada is materializing in Nova Scotia, where strong winds are hampering efforts to contain the Long Lake fire in Annapolis County. This one seems to be thorniest of the several ongoing fires that preceded Hurricane Erin’s passing this weekend. Thankfully, some rain is forecast, but with drought as severe as exists in this area, much more will be needed.

Chilly? weather

The other big story this week will be the autumn preview, also known in virtually every state’s seasons meme as “False fall.” Yes, much of the country will experience cool temperatures this week, with a number of record lows even possible in parts of the Midwest and Mid-South around midweek!

Potential record lows on Wednesday morning in the Midwest and Mid-South. (NOAA WPC)

This cooler pattern is beginning to look like it wants to sit around for a bit. Although it will moderate some, any real hot weather will be confined to the extremes of the country this week, primarily in the Pacific Northwest and up into British Columbia. Wildfire risk is likely to increase in those areas through the week, as persistent hot and dry weather continues, along with the potential for dry lightning.

Tropics starting to quiet down a bit just in time for the historical peak in activity

In brief: Hurricane Erin has transitioned to post-tropical, but it will still churn up waves, tidal flooding, and rip currents from the Mid-Atlantic into Atlantic Canada. An enhanced wildfire risk exists today and tomorrow from Maine into Atlantic Canada as well. Invest 99L is nothing to worry about. Invest 90L may broadbrush Bermuda tomorrow or early Monday as a tropical storm. But the tropics may be going into a calm period for a week or two after these systems.

Current state of the tropics

Let’s walk through our systems in the Atlantic to start today.

Hurricane Erin (post-tropical)

Erin has been deemed non-tropical now and would be considered an extratropical storm or post-tropical. The Canadian Hurricane Centre is still issuing forecast maps for Erin.

Erin’s post-tropical forecast track into tomorrow has it passing well south of Newfoundland. (Canadian Hurricane Centre)

Erin is accelerating out to sea now, passing well south of Newfoundland. Erin still has maximum sustained winds around 80 to 90 mph, however as it plows east-northeast. Again, post-tropical does not mean non-hazardous! Large waves will continue to generate outward from Erin, pounding the coast of Atlantic Canada, particularly along the south-facing coast of Newfoundland. High tides and tidal flooding are expected to continue from the Mid-Atlantic into New England as well, though those conditions will ease up some relative to where they were a day or so ago.

Wildfire risk remains high in Atlantic Canada today and tomorrow, with “extreme” risk for Nova Scotia, New Brunswick, and PEI today and tomorrow. While this is not directly related to Erin, the slightly breezier conditions from the storm and drier air in spots will not help matters should a fire start occur.

Extreme wildfire risk is in place today and tomorrow for portions of Atlantic Canada, with tomorrow’s outlook shown above. (Natural Resources Canada)

For Maine, the risk of wildfire is not considered high by the Storm Prediction Center, so this highlights a bit of a discontinuity between how the U.S. and Canada assess fire risks. That being said, the State of Maine has highlighted Downeast and some other parts of the state for a “very high” wildfire risk today.

High to very high wildfire risk for Maine today. (Mainefireweather.org)

Either way, conditions will gradually improve after tomorrow with some rain chances possibly returning to Maine on Monday and Atlantic Canada on Monday and Tuesday.

Invest 99L east of the Islands

Well, Invest 99L has not changed a whole lot since yesterday, meaning it’s still got thunderstorms but it has little to no organization.

Invest 99L continues to flare up thunderstorms but has no organizational skills whatsoever. (Tropical Tidbits)

This disturbance is running through the gauntlet of significant wind shear at the moment, so you can forget any development today or tomorrow. The system will continue to book it westward into the Caribbean by Sunday night or Monday, bringing some locally heavy rain and thunderstorms to the Windward Islands in particular. This disturbance is pretty far south. In fact, of the August and September cases of a tropical depression moving through this area, almost all end up in Central America. Based on the model forecast tracks of this one, I would suspect 99L never develops and tracks straight into Central America between Belize and Nicaragua as a locally heavy rain producer.

Invest 99L should continue basically due west toward Central America over the next week. It probably never will develop. (Tropical Tidbits)

That said, we’ll keep an eye on it just in case, but right now I don’t foresee this one becoming a problem.

Invest 90L south of Bermuda

The system south of Bermuda that’s designated as Invest 90L is a little more interesting than the other items on the map. In fact, the National Hurricane Center gives 90L a 100 percent chance of developing this weekend. Basically, expect our next tropical depression before the end of today.

Invest 90L is on the cusp of becoming our next tropical depression or tropical storm. (Tropical Tidbits)

The disturbance is moving northward, and that motion should continue over the next several days. This should keep the center of the system about 200 to 300 miles east of Bermuda at its closest pass on Sunday night. Impacts would probably be limited to rough seas and some gusty winds. From there, this system will track north before merging onto the same highway Erin is taking to exit off to the east-northeast and out to sea. Look for this one to get on that highway by Monday night or Tuesday. Invest 90L will be a quick one to exit the pipeline. The next name on the list is Fernand.

Looking ahead in the tropics

So, we’ve been talking about the above systems all week, and in some cases longer than that. What comes next? I…honestly don’t know. There may be some marginal support for a wave to come off Africa next weekend, but the models are not particularly bulled up on this one right now. I suppose low pressure could form along a cold front off the Carolina coast next week; that’s a common pathway to development, but there isn’t exactly significant model support for that right now either.

The background state of the Atlantic will feature sinking air over the next 10 to 14 days, which is not supportive of significant tropical development. (StormVista)

There are two important signals right now in model guidance. Above, I have a plot showing rising air (blue/purple) and sinking air (warmer colors) in the background of the atmosphere. This is called a Hovmoller plot. Where there is rising air, in general, that’s supportive of thunderstorms in the tropical latitudes. Where there is sinking air, that is not conducive to thunderstorms in the tropical latitudes. While this doesn’t exactly tell you everything, it indicates that the Atlantic is likely going to be fighting an uphill battle over the next 2 weeks, trying to shrug off a background state that leans it more toward subsidence, or sinking air. This likely suggests below average activity, especially given that this is occurring in two of the most active weeks of hurricane season historically.

The ECMWF weekly modeling continues to suggest below average activity in the entire Atlantic Basin in the first week of September. (ECMWF)

The ECMWF model backs this up, as it shows the entire Atlantic basin with below average activity forecast in the first week of September (Sept 1-8).

What should you take away from this? We have a long way to go in hurricane season, but the next two weeks, some of the most active historically, may see a well-timed relaxation in the Atlantic.

Water temperature anomalies in the Atlantic remain above normal, but you can see Erin’s cold wake showing up rather clearly. (Cyclonicwx.com)

Of course, a quiet period will eliminate most of the benefits of Hurricane Erin’s cold wake from all the water it stirred up. Across the Atlantic water temperatures are warmer than normal but generally well short of records set in 2023 and 2024, with one exception, the Gulf, especially the eastern Gulf. Gulf water temperatures are near the top of the charts historically right now, and if and when activity does get back to normal, we’ll hopefully see the Gulf avoid things. For now, we have a nice stretch of time to not worry, which is always welcome in August and September.