Matt Lanza

In brief: A morning update on Hurricane Isaias, now the season’s first major hurricane. The exact intensity remains a little challenging for landfall, but at this point, the western Florida Panhandle should be preparing for a major hurricane to make landfall tonight.

I just want to get a quick morning update out on Hurricane Isaias.

Over the last 12 hours or so, Isaias has steadily strengthening, with its core incubated from the disruptive wind shear that surrounds it. What this has led to is an environment over exceptionally warm water where the storm can thrive. Certainly, it’s not without flaws, but this is a bonafide major hurricane over the Gulf.

The track forecast is basically unchanged, with a western Florida Panhandle focus for a probable landfall tonight.

In terms of what it comes in as? Well, we’ve been warning you all along that this storm is likely to weaken toward landfall, but the margin of error was a little too close for comfort. That remains the case this morning. Isaias is probably going to get another 6 to 8 hours of time to strengthen before it can’t keep back the shear any further. By that time, we expect Isaias to be 100 to 150 miles south of the Florida Panhandle, meaning it will have only that long under a hostile shear environment to weaken.

Whether it actually happens or not, folks from Gulf Shores through about Panama City should be preparing for a major hurricane to make landfall by midnight.

The only other notable changes have been that the surge forecast has been bumped up some, and the tornado risk tomorrow expanded a bit into South Carolina.

The surge is now a bit higher near and east of the landfall point, and it is correspondingly a bit lower in Mobile Bay and on the Alabama coast.

In terms of the tornado risk tomorrow, a yellow slight risk (2/5) extends from the Panhandle into southeast Georgia and South Carolina.

The SPC did consider adding in a more substantial tornado intensity risk contour but held off for now. So at this point, while this is the risk, there is a slight chance we could see this get nudged up some before tomorrow. Either way, scattered instances of tornado warnings seem likely tomorrow in the yellow or dark green shaded areas above.

That’s all for now. We’ll be back with another update this afternoon.

In brief: Hurricane Isaias is a category 2 storm this evening, with the forecast basically on track as expected. Landfall will occur tomorrow night, likely between Mobile and Fort Walton Beach, FL as a formidable hurricane. We discuss the latest. We also take a look at the West, where the Desert will be impacted by two (2) remnant tropical storms over the next week.

I don’t want to bury the Isaias coverage here, so scroll through for some thoughts on Tropical Storm Rachel’s Southwest U.S. impact.

Isaias

Hurricane Isaias has been fascinating to watch today. It started off looking ok. Then, we saw some “under the hood” elements that suggested it was gearing up to intensify. Its satellite presentation actually degraded a bit this afternoon, and after about 3 PM ET, we have seen what appears to be steady intensification ongoing.

Deep thunderstorms started to pop on the western eyewall and then began to wrap around and expand into the evening, and as of this writing, Isaias looks like a reasonably healthy hurricane, despite enduring about 25 knots of wind shear near the center. Be thankful for this wind shear because without it, Isaias would be on the way to elite hurricane status I think. It’s sitting over water temperatures that are over 2 degrees Celsius warmer than normal, which is surely helping, and it’s also passing near the healthiest ocean heat content in the Gulf of Mexico.

Isaias may be able to fight the intense shear around it off for another 18 hours or so. The center appears to be somewhat incubated from the worst of the shear. By tomorrow afternoon or evening, it may become too much to hold off, and Isaias will begin to shed some intensity in the few hours before landfall. Notably, over 95 percent of Google’s 1,000 member ensemble brings Isaias over 115 mph tonight or tomorrow. This model has been absolutely steadfast and resolute in suggesting that Isaias would make a run at major hurricane intensity over the open Gulf before weakening on approach.

So what does this mean for the folks in the path of the storm? It means you need to prepare for a significant hurricane impact. Even if Isaias does weaken some before landfall, it may not appreciably change the surge and wind outcomes on the immediate coast. It may also allow for the wind field to expand farther north and east, so the inland areas under tropical storm watches and warnings will also need to assume there will be power outages and the like as the storm presses inland. Charge your phones tomorrow and tomorrow night.

Notably, the surge forecast has pretty much held since yesterday, with a 5 to 7 foot peak surge expected, especially near and east of where the center comes in. I would be most concerned about surge in the western Florida Panhandle right now and watch it cautiously around Mobile Bay. Tides will run up elsewhere along the Gulf Coast, as far west as Louisiana and as far east as the Nature Coast.

Rainfall continues to be mostly an asterisk on this storm. I don’t want to minimize rainfall at all. As someone who spent 14 years in Houston, boy do I know. While there will be instances of flash flooding likely all over the Southeast, these should hopefully not be the worst you’ve seen in recent years and hopefully mostly scattered or isolated in nature. Still, respect the water.

The other element is severe weather. As the wind field expands in a high shear environment, Isaias is likely to spawn tornadoes. This seems most likely in the pocket east of where the center comes in, potentially well east across Florida and southern Georgia.

Based on what I’m seeing on some of the other modeling, this tracks, and I would watch for isolated tornadoes in these areas tomorrow night and/or Saturday morning. There may also be a secondary area that shows up north of here on Saturday evening closer to coastal South Carolina. As Isaias weakens through the day Saturday, aside from those areas, the threats and hazards from the storm will diminish.

So, the bottom line with Isaias is that not much has changed. A hurricane will make landfall, probably somewhere between Mobile and Fort Walton Beach, FL tomorrow night. While it will probably be weakening on approach, it will likely come in as a formidable hurricane with an expanding wind field, meaning storm surge and winds near the coast, as well as inland will be impactful. The threat of severe weather and isolated tornadoes will also potentially be impactful in North Florida and southeast Georgia.

More in the morning.

Pacific Tropical Storms Rachel & Simon

Let’s shift from the Gulf into the Pacific, where Tropical Storm Rachel is this evening.

Modeling has Rachel coming ashore late Saturday somewhere between northern Baja and San Diego. While Rachel will be weakening, it will likely still have some degree of tropical storm force winds with it as it moves ashore, meaning that strong winds interacting with the terrain of northwest Mexico and/or California and Arizona will produce locally powerful wind gusts.

In addition to the wind gusts (and some coastal flooding and rough surf in California), locally heavy rain may occur in parts of the Southwest. Not only that, the remnants of what should become Hurricane Simon in central Mexico will also push into the Southwest next week, likely leading to another round of heavier rain. The heaviest rain from Rachel Sunday and Monday will occur in Arizona and Utah. The heaviest rain from Simon later next week will occur in New Mexico and Colorado (and parts of west Texas).

Areas of flash flooding risk should begin to pop up with Rachel this weekend and Simon next week.

It has been quite busy across the Pacific this year.

In brief: Tropical Storm Isaias is slowly strengthening in the Gulf this evening, as it likely becomes a hurricane by tomorrow. It will turn north and race toward the Gulf Coast between Biloxi and the Florida Big Bend on Friday night, making landfall, likely as a hurricane with wind and storm surge, as heavy rain and severe weather spread across the Southeast this weekend.

Tropical Storm Isaias has spent the day getting organized, and just around sunset this evening, it may look actually the worst it has all day. It’s pretty evident that wind shear is impacting the western flank of the storm right now. Satellite estimates are that it’s battling about 20 kts of shear near the center and substantially more than that on its northwest flank, hence the rather ragged appearance of the storm this evening.

Isaias is moving east northeast around 8 mph, away from the shear axis over the western Gulf, which means it should gradually find a little less shear over the next 12 to 24 hours. That’s when we should see Isaias reach its prime and strengthen into a formidable hurricane. Shear will once again begin to hammer Isaias on Friday morning, and this should be when we see it begin to weaken a bit.

First key point: While Isaias is going to fluctuate in intensity over the next 48 to 72 hours, the Gulf Coast, especially east of Mississippi and west of the Big Bend in Florida should be preparing for a hurricane, possibly a borderline major hurricane landfall.

In terms of how strong it gets, Google’s 1,000 member ensemble is still showing about a 75 percent chance of Isaias strengthening into a major hurricane at peak. Google’s operational ensemble is around 50 to 60 percent odds of peaking as a major hurricane. The tropical models lag Google by a bit, though even most of those still peak Isaias as a category 1 or 2 storm. Either way, this is sort of like debating the difference between calling it aluminum or aluminium. There are scientific and classification considerations here, but for all intents and purposes for the eastern and central Gulf Coast it seems it’s going to peak as a pretty decent hurricane.

So what about landfall intensity? As noted, on Friday, we’ll see Isaias likely get hammered by wind shear that worsens throughout the day as it approaches landfall in the evening. If you notice the chart below, the same intensity chart as above, I have us flagging the intensity dispersion right at or immediately before landfall.

Indeed, at or around landfall, about 25 percent of members maintain Isaias as a major hurricane and roughly half have it as a Cat 1 or tropical storm. But here’s the thing about that. Weird things often happen in October in the Gulf. This is why I would encourage folks to prepare for the worst case scenario, not hope for the best case outcome. We’re good at hurricane forecasting today, but we’re far from perfect. And there’s about a 1 in 4 chance that Isaias will come in near its peak intensity, assuming it can get to Cat 2 or 3. It should also be noted that Isaias will be booking it north at 15 to 18 mph in all likelihood, which may limit how much time there is for Isaias to substantially weaken before hitting land.

Key point 2: In this instance, given the accelerated timeline and fast forward motion of Isaias at landfall, it’s wise to prepare for the higher end outcome risk on the Florida Panhandle and in Alabama.

Where will Isaias make landfall? The tropical models like Biloxi, MS through Destin, FL as the landfall window. Google’s model seems to like Mobile Bay through Panama City, FL. This matters to a point because the worst impacts of Isaias are going to be exaggeratedly on the eastern flank of the storm. But basically, anyone east of Biloxi is on notice, with a special notice for folks between Mobile and Destin, FL right now. This could further change between now and tomorrow. Average track errors at this point in the system’s life cycle are still fairly meaningful.

This also matters for storm surge, as the surge near and east of where the center makes landfall will see surge levels of 5 to 7 feet above ground level, formidable. Keep in mind, we have lost more people to surge and flooding over the years than any other element of a hurricane. Take it seriously.

The good news is that the rainfall threat seems to be a little lower overall with this storm. Some areas east of where the center comes in could still see 8 to 10 inches of rain, but it appears that the flash flooding threat and inland extent of flooding, while a noteworthy element of this storm is not likely to a catastrophic one.

One thing I am becoming a little more concerned about with respect to Isaias is severe weather. As Isaias moves northward into the Tennessee Valley, it will spread rain and thunderstorms over a wide area of the Southeast. There are multiple areas within Isaias’s overall circulation that may be primed for some severe weather. Shear is going to be outrageously high. While wind shear is detrimental to a tropical system’s organization, it is an element that can enhance isolated to scattered severe thunderstorms by creating more potential for rotating thunderstorms.

Instability is going to be a big limiting factor, but sometimes with a tropical cyclone and very high shear, that lack of instability may not matter as much.

Key point 3: Some form of a severe weather outbreak may occur east of where Isaias tracks on Saturday or Sunday after landfall.

So the bottom line in all this:

1. * Folks on the Gulf Coast should prepare for a landfalling hurricane, possibly a borderline major hurricane, somewhere between Biloxi, MS and the Florida Big Bend, with the highest odds of landfall right now between Mobile and Destin.

• * Storm surge of 5 to 7 feet above ground at peak will be possible near and east of where Isaias comes ashore.

• * Landfall is likely to be Friday night in the affected area.

• * Heavy rain is likely across the Southeast resulting in pockets of flash flooding.

• * Severe thunderstorms and tornadoes are likely to some extent on Saturday and Sunday across the Southeast and perhaps into the Carolinas, but details are very fuzzy right now.

We’ll have more for you in the morning.

In brief: Invest 92L is now Tropical Depression 9 and likely to become our next named storm, and it has a decent chance to become the season’s first hurricane. The storm is likely to impact the central or eastern Gulf Coast by the weekend, with a focus between Biloxi and Destin, FL right now. The potential exists for a landfalling hurricane or borderline major hurricane by the weekend on the Gulf Coast.

The forecast has slowly come into better view today for Invest 92L, which is now classified as Tropical Depression 9, and it appears, as we have been kind of warning about as a possibility, this one may be a potent one for the Gulf Coast.

The area of thunderstorms associated with TD 9 looks frazzled but robust this evening. We’re coming out of the daytime minimum for tropical system thunderstorm development and should see the depression begin to perhaps more aggressively produce storms overnight.

The center of Tropical Depression 9 is expected to drift eastward over the next day and a half as it gradually organizes. From there, we hit the inflection point where this possibly turns into something bigger. And indeed, support for something bigger is increasing today. Let’s start with what we know. We know that some of the best hurricane modeling overall, Google’s AI forecast has bumped up the potential for a hurricane and a major hurricane to approximately 90 and 45 percent respectively.

We know that whatever this is, assuming it generally follows the Google track, will eventually run into a lot of wind shear near the Gulf Coast by Friday night or Saturday, when it presumably approaches landfall.

That wind shear should be detrimental to the storm’s intensity (allowing for weakening on approach to the coast), but as I’ve noted on a couple occasions this week, we have seen late season cases where southwest to northeast wind shear can actually help the outflow of a storm and keep it fairly strong. So I think you need to watch this storm and assume it may come in close to peak intensity and prepare around that. That said, while 55 percent of Google’s broader (not operational) 1,000 member ensemble has the storm peaking as a major hurricane, only 22 percent make landfall as such. That seems to suggest it will come in past peak intensity. Still, it is wise to be cautious when any ensemble is flagging 22% of its members making landfall as a major hurricane.

We also know that it’s going to be traversing some of the highest oceanic heat content in the Gulf. While the Gulf itself is below average in terms of heat content (but above average in terms of water temperature), where this is likely to track will hit some of the most heat-rich water of the Gulf.

It won’t linger long over that patch of water, so it’s unlikely to be super meaningful, but it could be enough to tip the scales one way or another from tropical storm to hurricane or hurricane to major hurricane depending on the storm’s evolution.

We know a boatload of moisture is headed for the Gulf.

Rain totals aren’t eye popping, but they are over a broad area. Flash flooding is likely to be an issue in spots along the Gulf Coast, as well as inland.

We know that dry air could have a big impact on the storm’s western flank.

As the storm comes north and pulls in much drier, autumn air southward across Texas and Louisiana and into the western Gulf, we could see it begin to eat away at the western semicircle of the storm, and it’s possible we end up with a sloppy hurricane that has much greater impacts on the east side than the west, even more than usual.

We also know that this is probably going to lead to a bit of a potent setup for strong to severe storms in the Southeast after coming ashore. While details are not going to be worked out for a few days yet, the SPC did mention the potential for expanding severe risks Sunday and Monday in their discussion today.

So what does this all equate to?

• Tropical development is likely in the Gulf, with advisories almost certain to begin tonight or tomorrow morning.
• The system we are watching is likely to become a tropical storm, a strong tropical storm, and probably a hurricane at some point.
• There is about a 50/50 shot that this becomes a major hurricane over the open Gulf before the storm likely weakens a bit at landfall. (However, the risk of the storm making landfall at peak intensity is not zero).
• Heavy rain is likely along the Gulf Coast and inland, along with the potential for strong to severe storms Sunday and Monday across the Eastern U.S.
• The main target area for landfall appears to be between New Orleans and Panama City, FL, with a slight edge on areas between Biloxi and Destin.
• The storm may have exaggerated impacts on the east side of the center versus the west, meaning landfall, while not the only thing that matters, will be an important delineation for this storm’s worst impacts.
• The timing appears to be between Friday night and Sunday morning for the worst impacts and landfall.

Folks on the Gulf Coast, particularly from Biloxi through Destin really should be preparing now for the potential of a hurricane by Friday night. While details and specifics will change in the coming days, there’s a lot we can see already that’s concerning enough to make it make sense to begin to make preparations. More to come.

Let’s get this out of the way now: The next storm’s name is Isaias, a name that is recycled from the 2020 list, which did a lot of damage on the East Coast, and in some circles was a surprise that it was not retired. It replaced Hurricane Ike on the lists in 2014. It is pronounced “ees-ah-EE-ahs.”