The Eyewall

In brief: The Mid-Atlantic coast is likely to see multiple rounds of minor to moderate tidal flooding with a slow moving coastal low this week. The West is likely to see another round of heavy rain, something that is still very needed in that region.

Before we begin today, a quick personal-ish note. For those unaware, I (Matt) moved to Connecticut over the summer to be closer to family, experience autumn again, and for of course for work. But while I was still in Houston in 2025 I was asked to help out with a documentary being developed, centered around friend and colleague, Chris Gloninger. Chris’s story became newsworthy for leaving broadcast meteorology after receiving actual death threats for discussing climate change in Iowa.

Whatever your thoughts on climate change, I think most of us can agree that discussion and differences around how to approach climate change solutions are reasonable, but taking it to the “death threat” level is overboard and reprehensible. Chris has since devoted his career toward advancing the public’s understanding of climate science and impacts. The documentary will not just focus on Chris but also on how communities respond when extreme weather strikes, with a deeper look at the horrific Texas Hill Country flood of 2025 and the 2025 budget and staffing cuts to the National Weather Service.

To get the movie to the finish line, the film needs some crowdsourcing to finish things up. It’s a 501(c)(3) for those curious. Some of you may be all-in on helping, some of you may not want to touch anything climate related, and some of you may not know what’s up here. For that latter group, there will be a Zoom event this Wednesday with Sarah Gibson, who was delightful to talk to and work with, Chris Gloninger himself, and Jeff Masters, who was the original hurricane weather blogger and who The Eyewall draws a good deal of inspiration from. (You should also read Jeff’s current work over at Yale’s Climate Connections blog, along with another inspiration for The Eyewall, Bob Henson).

Even if you aren’t interested or able to financially contribute, it may be an event you’re curious to attend. Dr. Masters will also be giving an update on the upcoming El Niño winter. Here is the link for the Zoom meeting on Wednesday, October 21, at 7:30 p.m. EDT / 6:30 p.m. CDT. To receive an invite, please RSVP at [email protected].

East Coast storm

As we noted last week, our biggest issue heading into this week will be yet another slow moving nor’easter-type storm off the East Coast. This one remains sort of floating between a nor’easter or a tropical system. I’m going to just refer to it as a “coastal low,” because the difference in impacts, be it a nor’easter or a tropical storm will be minimal. These things matter from a scientific perspective but not from a public preparedness perspective.

That said, there is a 30% chance this will take up a name this week, per the NHC. Google’s Deep Mind shows about a 60% chance of development this week. To be honest, I don’t know enough about how Google’s model will discern between tropical and non-tropical in its algorithm, so this could be high, low, or something in between. Either way, it stands to reason that a nominally strong coastal low is going to take up residency this week off the North Carolina coast.

Here’s what the European model showed this morning in terms of surface pressure and precipitation.

So, good news/bad news here compared to what we discussed the other day. First, the good news is that the residency time near the coast and frankly the proximity to the coast looks a little more manageable today compared to Thursday. The bad news is that this will still produce multiple days of rough surf and tidal flooding that will likely contribute to another round of coastal erosion.

At this point, it looks like the most significant tidal impacts through midweek will be on Delmarva and in the Virginia Tidewater.

We may squeeze out another tide cycle or two of flooding beyond the end of this forecast, but it looks like late Tuesday through Wednesday will be worst right now for that issue. There is at least some risk that a tide cycle could verify with major coastal flooding at a location or two between Delmarva and the Outer Banks. This is implied on the coastal flooding risk map for the Tidewater through Thursday.

Bottom line: If you live on the coast from Delaware through the Outer Banks, you’ll probably be impacted by either erosion, coastal flooding, or rough surf over multiple days this week.

While the storm system will sit offshore, it will still be breezy at times this week as well. Wind gusts into tomorrow could be around 35 to 45 mph on the Mid-Atlantic coast. Some gusts in the Outer Banks could approach 50 mph. Here’s a map for tomorrow afternoon.

Slightly less intense wind gusts will persist into Tuesday and Wednesday. The system should pull far enough east to lower impacts by later Thursday and Friday.

Peek at the Pacific

Hurricane Trudy off the coast of Mexico is the latest in an endless string of hurricanes in the Eastern Pacific. Over the next few days it will begin to weaken. However, a surge of tropical moisture from that area is once again going to lift northward into the Desert Southwest, an area that has been absolutely soaked over the last month or so. After a relatively weak monsoon season, this was needed. And some places are seeing rainfall departures of 3 to 6 inches above normal, and even more in spots.

Lake Powell’s water level has jumped about 2 feet over the last week or so, which is a literal drop in the bucket of what’s needed out there, but it’s a start.

Well, as Trudy’s moisture is pulled north, yet another round of locally heavy rainfall seems likely in the West. California should participate in this as well, as a well timed cold front and low pressure system will approach off the Pacific (somewhat tied to the remnants of western Pacific Typhoon Koguma). This should help spread rain out over the entire region, with the heaviest probably associated with Trudy’s remnants in southwest Colorado.

Obviously the rainfall amounts are subject to change, but this looks like another decent rain event for the Southwest.

In brief: A potential storm off the East Coast may move slowly next week, kicking up surf and tides along the Eastern Seaboard. There is some chance it could become a tropical system. This may be a long winter of coastal flood producing storms on the East Coast too.

Back in early February 1998, your author was a mere budding weather weenie in his teenage years, his future already destined by his weather obsession. I even had this newspaper cutout in my locker.

But I recall distinctly a nor’easter from that winter that wreaked havoc on the Jersey Shore. It happened on February 4th and 5th in the super El Niño winter of 1998.

That storm in particular was responsible for over $145 million in damage (in 1998 dollars; $300 million today), about half of which occurred in Virginia. It remains the tide of record in Ocean City, MD and ranks 6th in Lewes, DE.

The storm itself was exceptionally strong, very early. In fact, the surface low pressure values across much of the coastal Southeast and offshore are still February records, according to NOAA’s David Roth. In other words, the storm intensified far south before strengthening further offshore. By the time it was off the Mid-Atlantic coast it was not setting records, but it was still potent and slow moving. The only other semi-recent storms I see with the kind of duration of winds in Jersey as strong as they were in February 1998 were during Hurricane Isabel in 2003, a November 2009 nor’easter (“Nor’Ida”), Boxing Day 2010, and the storm that occurred last February 7-8.

Regardless of those superlatives, it was the coastal erosion that was the really big problem. In both the 1982-83 and 1997-98 “Super” El Niño events, coastal storms caused significant damage not just to California but to the East Coast as well. It was newsworthy in 1983 too, with one coastal expert somewhat presciently just expounding on a theory of the greenhouse effect, which leads to climate change and subsequent sea level rise as a problem. He was prescient for a number of reasons if you read that linked piece.

The lesson from this is that while El Niño is going to make headlines on the West Coast and in California, events of this magnitude are also likely to produce strong impacts on the East Coast too, which is something residents and emergency managers/decisionmakers should be keen to over the coming months. Which brings us to…

Another coastal storm?

For the last couple days, models have been keying in on the potential for slow moving low pressure off the Mid-Atlantic coast. This has happened already this fall, seems to be a calling card of El Niño, and is likely to continue and possibly intensify as we go deeper into the cold season, as noted above. But this feature has shown up in multiple models, across multiple ensembles, and with little agreement spatially (geographically) or temporally (time) on track or intensity.

In looking at recent model guidance, despite the erratic development spread and potential, it seems as though this system has a couple notable elements to it. First, it looks to be slow moving. It develops offshore early in the week and doesn’t really disengage until late week. Obviously if it tracks inland or shifts farther out at sea, that may make a difference in how long the impacts last, but the takeaway here is that it’s in no hurry. The reason seems to be that the upper air pattern as forecast next week (Tuesday shown here) is supportive of high pressure just east of Bermuda, and a ridge of high pressure over Mexico basically “trapping” or blocking in the low pressure area, be it on the coast, offshore, or wherever.

In other words, you’re placing this system between a rock and a hard place. The pattern may not loosen up until Friday or Saturday.

Another notable element is that with these forecast positions of low pressure, sitting over generally warm water off the East Coast, you’re lobbing the potential for a “warm core” or tropical system to develop. Indeed, from last night’s European operational model, we saw a deep warm core system show up in the guidance. Unlike the nor’easter from a couple weekends ago, this one has a slightly higher potential to go tropical.

That said whether it does or does not is sort of immaterial right now. Something we’ll watch, but not anything we can really go overboard on speculation right now. Just for, well, we’ll call it illustrative purposes, here is today’s 12z European operational model. This is merely one of a myriad of possible outcomes.

From an impacts perspective, this would likely feature multiple consecutive high tide cycles with elevated tides and winds at the coast from Long Island through North Carolina. This scenario probably would lead to higher impacts from Delmarva into North Carolina than elsewhere, but this is still rather speculative.

The takeaway here is that we are probably heading for another episode of prolonged higher tides and gusty winds on the Mid-Atlantic coast. It’s too soon to really say whether this will lead to a multi-day coastal flooding event and/or how severe that would be, but after the nor’easter from a couple weekends ago, some of the coastline remains vulnerable to higher tides and erosion risk. And this will almost certainly only be the next of several times we discuss these kinds of storms on the East Coast heading into winter.

Remnants of Isaias

The remnants of Hurricane Isaias are moving inland this morning after spewing wind across the South overnight. Wind gusts hit 49 mph in Birmingham, 45 mph in Atlanta, 68 mph in Macon, and 54 mph at Auburn, Wind damn Eagle.

Wind gusts are still in the 35 to 45 mph range over a wide area moving north. Power outages sit around 900,000.

Rain totals were highest near where the storm came ashore, but you can see how rain totals thus far have triggered some flash flood warnings in metro Atlanta. The worst of the rain should stay north and east of there for the remainder of the day.

So what about the rest of the day? We have two primary concerns remaining with Isaias: Rain and tornadoes. So far, the tornado threat has generally failed to materialize in any real serious way. But much of South Carolina and a chunk of East Georgia are under a slight risk (level 2/5) for severe weather with a risk for tornadoes today.

We’ll see that risk shift north a bit tomorrow into eastern North Carolina and southeast Virginia and perhaps up through Delmarva. In addition to the severe weather, heavy rain will overspread most of the Eastern Seaboard over the next day or two, with widespread 1 to 3 inch totals.

There may be a bit of a drier slot between the Triad and Outer Banks in North Carolina and in parts of southeast Virgina. The mountains will see locally meaningful flash flooding in North Carolina (again, nothing remotely close to Helene). Those higher rain totals continue up the Appalachians into the Blue Ridge and Shenandoah.

So, still a bit to go before we can close the book on Isaias.

Tropical Storm Rachel

Rachel has already helped to unleash some havoc in Southern California. Parts of Orange County, specifically around Newport Beach were hit pretty severely yesterday by coastal flooding. The combination of swells from Rachel, higher tides, El Niño vulnerability, and a much ballyhooed oceanic Kelvin wave seem to be multi-faceted, nuanced contributors. We’re coming into another high tide as I write this. We’ll see if that causes as many issues.

Rachel is still expected to track into Baja tonight, right around midnight local time. The storm will track into Arizona from there, spreading wind and rain across the region. The strongest wind gusts tomorrow will be in the higher terrain east of San Diego and across Arizona. The rain, however, will be a little more widespread, with pockets of heavier rainfall likely in the higher terrain, as well across Utah and parts of Nevada and northern Arizona. Flash flooding is likely in some areas.

We could even see some higher terrain snow in parts of the San Bernardino Mountains, the Sierra, and the Uinta Mountains in Utah (and the Wasatch to a much lesser extent). Snow totals won’t be significant (except perhaps in the Uintas) but it’s a reminder of the season to come.

Wind gusts from Rachel will be on the order of 30 to 50 mph with higher gusts in some of that higher terrain.

We should then hopefully see a quieter stretch of tropical weather.

Isaias is one of those storms that is classic autumn hurricane. While working through the various pieces of this forecast this week, I kept coming back to Hurricane Delta back in 2020. And this is partially why I never really thought to downplay this storm as hype.

Much like Isaias, Delta, six years ago to this day, was a storm that had been a major hurricane, turning north, and beginning to weaken in the face of considerable wind shear.

The shear facing Delta was less intense than that of Isaias, but the end result seems to be similar. A look at the radar images of the two storms just past landfall tells that story fairly well.

Both storms lacked much action south of the center. Both storms saw the wind field expand at landfall and shift to the west side of the storm. And both storms produced impressive wind gusts over a broad area.

Why does this happen? One possible explanation of this is the dry air we talked about in the run up to the storm’s development. We did note that Isaias could wrap in drier air off the western Gulf Coast, causing it to weaken. This can also help enhance wind gusts (through stronger downdrafts) simultaneous to weakening the storm overall.

A similar thing happened during Hurricane Delta in 2020 as well:

We also typically see this type of expanding wind effect on all sides of a storm as it begins to lose tropical characteristics. We are passing the threshold of deep warm core (tropical) and more into moderate warm core now, eventually transitioning to cold core (extratropical) by tomorrow afternoon.

So that is a simplistic explanation of what’s happening here, and it’s similar to what happened six years ago today in Texas and Louisiana. The combination of a robust inner core of a storm that held intensity, wind shear both hurting it and helping it, dry air both hurting it and helping it, and a transition to an extratropical storm has led Isaias to come ashore swinging away unlike some other past storms that have made landfall in a weakening state.

In the meantime, the poweroutage.us page says that over a half-million customers are without power nationally, most of them in Florida and Alabama. As the night wears on, the winds will continue to expand north, and this will lead to another escalation in power outages overnight toward Birmingham, Huntsville, and Atlanta. We also continue to expect a decent side helping of tornado warnings tomorrow, so folks in Georgia and the Carolinas should have ways to receive warnings tomorrow.