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.

Erin begins to exit stage right but not before prompting a few more concerns in Atlantic Canada

In brief: Erin is chugging out to sea now, but not before possibly delivering an enhancement to already extreme wildfire risk in Nova Scotia, New Brunswick, and Prince Edward Island. Rough surf and rip currents will linger on the East Coast and in Atlantic Canada through Sunday. Invest 90L remains worth monitoring for Bermuda. Invest 99L is worth monitoring for the Windward Islands. And flooding chances mix with beneficial rainfall heading into next week in the southern Rockies and Plains.

Hurricane Erin

(NOAA/NHC)

Erin is booking it this morning. The strong, sprawling category one hurricane is moving northeast at over 20 mph. The good news this morning is that all watches and warnings for land have been discontinued. Rough surf and rip currents will continue to impact the East Coast, Bermuda, and Atlantic Canada, but the worst of Erin’s impacts to land seem to be over now.

Erin looks like a hurricane that is beginning to undergo extratropical transition, except it’s gigantic. (Weathernerds.org)

What’s next for Erin? Well it remains a large storm, with a wind field of tropical storm-force over 350 miles now. It should pass well south of land, but gale-force winds are likely in southeast Massachusetts, Nova Scotia, and the Avalon Peninsula in Newfoundland as this passes. Rough surf with waves of 3 to 6 meters may break on the coast of Nova Scotia today and in the Avalon & Burin Peninsulas of Newfoundland later and tomorrow. Even as Erin weakens and turns extratropical in the cooler North Atlantic waters, the size of the gale-force wind field may grow further, keeping Erin a powerful feature on the weather map through the weekend.

Yesterday I noted the wildfire potential with gusty Erin winds blanketing a very dry Atlantic Canada. Well, the fire risk today at least seems pretty noteworthy in Nova Scotia, PEI, and parts of New Brunswick, with “extreme risk” drawn in those areas.

Extreme fire risk for much of Atlantic Canada outside of Newfoundland today. (Natural Resources Canada)

That risk should remain and expand into Newfoundland tomorrow. For some areas, the risk may diminish as Erin passes, particularly for Newfoundland. In Nova Scotia, New Brunswick, and PEI, however, the risk may stay at extreme levels through the entire weekend. A rare situation for this part of the world.

Erin’s remnants will park themselves south of Iceland for a time before probably moving into Europe as a (much weaker) storm next week.

Invest 90L

Let’s work our way back south now to Invest 90L. This one continues to lack much organization today, but models continue to insist it will eventually get its act together.

Invest 90L has very broadly disorganized thunderstorms, but that’s it at this point. (Weathernerds.org)

Over the next few days, this broader area may try to consolidate some, and we should see gradual development into a tropical depression or tropical storm. Invest 90L will track around the western edge of high pressure just west of the Azores, meaning it will continue on a north-northwest or northward trajectory. Model guidance at this point seems to suggest it will stay east of Bermuda on its way north, but we’ll continue to watch this, particularly once we (presumably) get some development out of this area.

Tropical model guidance has a relatively tight spread keeping 90L east of Bermuda, but it’s close. (Tropical Tidbits)

Interests in Bermuda should continue to monitor 90L over the next couple days. We do not expect this one to explode and rapidly intensify to a high-end storm like Erin did. But we could see it quickly come together as a tropical storm.

Invest 99L

Backing off to the south and east now, we look at Invest 99L. This one has had the opposite problem of 90L. Models have insisted it would eventually succumb to shear and dry air, and it’s been as resilient a wave as we’ve seen all season. Well, Invest 99L’s luck may be running out.

Invest 99L is looking much less organized and much uglier than it has all week. (Tropical Tidbits)

Over the next 3 to 4 days, Invest 99L will continue to have a puncher’s chance at perhaps sneaking into tropical depression status before likely getting ripped up again in the Caribbean. Interests in the islands should at least keep an eye on this, particularly for the Windward Islands. But this seems like mostly just a scattered heavy rainmaker right now. Beyond the islands, it seems likely that this will remain buried in the Caribbean or end up moving ashore in Central America eventually as a remnant disturbance. But we’ll continue to watch in case something should change.

Flooding risks

Yesterday saw a flash flood emergency, our first in quite some time, this one in Roanoke, Virginia. Read Kevin Myatt’s always excellent coverage in the Cardinal News for more on that event. But 3.38 inches of rain in an hour is more like Gulf Coast style than Appalachia. Very impressive stuff.

Flash flooding risk today will be mainly in Georgia and South Carolina back across the Gulf Coast, as a stationary front is draped across the region. But as we go into next week, we continue to see a pretty strong signal for heavy rain in the Plains. A slight risk (2/4) for excessive rainfall and flooding remains painted on the maps for Monday between the Front Range and Kansas & Oklahoma.

Slight risks for heavy rain (2/4) are in place on Monday from the Rockies to the Plains. (NOAA WPC)

Colorado Springs, Wichita, Tulsa, and Oklahoma City are all included here. For Tuesday, that risk shifts mostly back into Colorado and New Mexico. Rain totals over the next week continue to look quite healthy in these areas, with perhaps 1 to 4 inches in Colorado and parts of New Mexico and 3 to 6 inches in Kansas and Oklahoma.

Rain totals over the next week are stout between the Rockies and Plains. (Pivotal Weather)

Considering the Rio Grande has dried up to a trickle or worse, any amount of rain that could find its way into the system would be beneficial.

Hurricane Erin lashing coastal North Carolina with tropical storm conditions

In brief: Hurricane Erin is passing by the Outer Banks today, and it will begin to accelerate out to sea. Coastal flooding will remain an issue into tomorrow for the East Coast, particularly from North Carolina into New Jersey. Mostly wave impacts for Atlantic Canada, but also perhaps some wildfire concerns there too. The rest of the tropics are noisy, but only one wave bears much watching (Bermuda). Also, the latest on upcoming heavy rains in the Plains.

Hurricane Erin

(NOAA/NHC)

Erin is making its closest approach to the U.S. this morning. The very large storm sits about 210 miles east of Cape Hatteras, and it has begun to turn to the north northeast. The tropical storm-force wind field of Erin extends out over 300 miles from the center. Despite the fact that the storm has weakened to about 105 mph this morning, the hurricane-force winds extend out 105 miles from the center. This is a massive storm.

Erin is large and in charge. (Tropical Tidbits)

A 2 to 4 foot surge on the ocean side of the Outer Banks will be ongoing, coupled with powerful waves. It is expected that this evening’s high tide cycle will be the highest though, with Duck, NC seeing a water level up to about 7 feet, less than a foot below the 2003 Isabel record there and the highest since a nor’easter in 2022.

Tidal forecast at Duck, NC. (NOAA NWS)

Flooding will be minor to moderate on the Pamlico Sound side of the Outer Banks, with downeast Carteret County seeing the worst this evening around 8:30 PM. High water levels are expected to continue into Friday, and it’s likely that some travel will become impossible through today and tonight in the Outer Banks, Ocracoke, and Carteret County.

Even farther up the coast, the tidal flooding will be significant. Cape May, NJ is expecting a peak water level of 8.2 feet this evening, which will be the highest since the “Snowzilla” nor’easter of January 2016. Same goes for Lewes, Delaware.

Tidal forecast at Cape May Harbor (NOAA NWS)

Erin will continue to exit tomorrow, and conditions up and down the East Coast will slowly improve. For Atlantic Canada, the main impact will be rough surf, particularly in Newfoundland and perhaps Nova Scotia, where breaking wave heights could be 3 to 5 meters high. Erin should transition to an extratropical storm by Saturday.

Wildfire concerns?

A minor note, but perhaps a notable one, there will be somewhat enhanced wildfire risk in Atlantic Canada as Erin passes. Note the fire weather danger outlook for today is pretty high to extreme in parts of Newfoundland and even Nova Scotia and New Brunswick.

High to extreme fire weather danger in Atlantic Canada today. (Natural Resources Canada)

Portions of Atlantic Canada remain in severe to extreme drought conditions, so the combination of drier air being wrapped in from the north and gusty winds as the large swath of Erin passes by definitely can enhance fire danger. This is an element of storms that’s now on a lot of people’s minds in the wake of the tragedy in Maui a couple years ago, as a passing hurricane likely contributed some to drier, windier conditions there. Something for folks in Atlantic Canada to be mindful of over the next 2 to 3 days.

Rest of the tropics

The Atlantic is a multi-colored menagerie of disturbances this morning. We have Invest 99L in the central Atlantic, the tropical disturbance approaching the Caribbean islands that we’ve been discussing for a few days now, and a little fella in the open Atlantic.

It’s a party in the Atlantic! (NOAA NHC)

Let’s start from best odds of development to least odds.

The wave approaching the islands with a 70 percent chance of development is looking ragged but stormy today. There’s no sign that this is going to develop quickly, but it’s starting from a pretty decent baseline.

A tropical disturbance approaching the Leeward Islands will bring thunderstorms and locally heavy rain to the northeast islands this weekend. (Weathernerds.org)

This one is expected to pass northeast of the islands, much like Erin did, so the only impacts will probably be some scattered thunderstorms this weekend. It’s hot in Puerto Rico and the Virgin Islands right now, and heat advisories are posted with hot, dry weather and Saharan dust causing hazy conditions. That will change as this passes. From there, it will probably turn straight north toward Bermuda. It seems as though it will turn out to sea before arriving in Bermuda, but interests on that island should continue to monitor this system in the coming days. As you can see below, most European ensemble members miss Bermuda to the east, but it is at least notable that some of the stronger outcomes get a little closer to Bermuda itself. Again, something to monitor at least.

The disturbance near the islands should miss Bermuda to the east, but there are a couple of solutions that are possible that bring it closer to the island. (Weathernerds.org)

We’ll keep tabs on this one.

To the east, Invest 99L continues to percolate west of the Cabo Verde Islands. This wave has looked excellent since emerging off Africa, but it has yet to do anything to get it over the hump yet to become a tropical depression.

Invest 99L looks beefy again this morning, as does the wave behind it, but conditions are expected to degrade for development in the Atlantic in a day or two. (Weathernerds.org)

As 99L comes due west, it’s likely to run into a wall of wind shear. That should kill any chances of organization. The remnant disturbance should continue west toward the southern Caribbean. Typically, it’s a good idea to maintain some degree of vigilance with systems like this, as their ghosts can sometimes be resuscitated once in the western Caribbean. The bulk of what remains of this disturbance may actually end up close to South America, which would essentially wipe out odds of development, even in the western Caribbean. Still, it makes sense to keep tabs on this one in about a week or so, just to ensure it doesn’t pull a fast one on us.

The wave behind 99L is not expected to develop and should remain out at sea.

Meanwhile, the NHC tagged a little one this morning. That one near 30N/50W is kind of comedic looking this morning when viewed next to Erin.

I am reminded of “Aladdin” with this. (Weathernerds.org)

That’s about it. As Eric noted yesterday, after these systems, we don’t exactly have anything noteworthy to home in on. Yesterday’s Euro weeklies suggest below average odds of tropical cyclone development in most of the basin for the week of Aug 24-Sept 1.

Below normal odds of development next week in the tropical Atlantic. (ECMWF)

Notably, these odds turn neutral to perhaps even above normal by mid-September. So the first part of September may be calmer than usual, but we’re clearly not done with hurricane season yet. But this is good news in the nearer-term.

Heavy rain coming to the Plains?

After a somewhat calmer period of weather in the Southern Plains, we may see a return to more active, wetter weather heading toward next week. The WPC has already issued a slight risk (2/4) for excessive rainfall for next Monday.

Flash flooding will return to the forecast potentially by early next week. (NOAA NWS WPC)

Rain totals are currently forecast to be on the order of 2 to 4 inches over the next 7 days, and there could be some locally higher amounts in parts of Kansas, Oklahoma, or Colorado.

Rain forecast for the next week in the southern Plains. (Pivotal Weather)

We’ll keep an eye on this as well.

Erin restrengthens as it moves north, and we look at the what’s left in its wake (not much, probably)

In brief: Hurricane Erin is getting stronger again, and it may reach major hurricane status as it passes by the Carolinas and brings impactful storm surge to the Outer Banks. We also take a look at what is coming next in the Atlantic, and we are cautiously optimistic about things heading into September.

Hurricane Erin status

As of 11 am ET this morning, Hurricane Erin has continued to regain some of its former strength. The system now has sustained winds of 110 mph and a central pressure of 941 mb. Additionally, its eye has a better appearance on satellite which is another indication of better organization. The storm has about a day, or a day and a half to intensify further before wind shear should start to work on it. Confidence remains high in the track forecast, with Erin set to split the difference between the US mainland and Bermuda before moving out to sea later this week.

Storm surge along the Carolinas will build over the next day, with inundations of 2 to 4 feet above normally dry ground expected. This surge should be most impactful for the low-lying Outer Banks area, leading to numerous roads becoming impassable. Additional concerns include significant beach erosion, and sand being washed onto roads. Tropical Storm Warnings are in effect for coastal areas of North Carolina and Virginia.

A Tropical Storm Watch is also in effect for the island of Bermuda, where there could be high winds and dangerous surf and rip currents.

All that being said, we’ve largely been fortunate with Erin, being that it was such a powerful storm that got close to many landmasses but never directly threatened a landfall. We’ll be glad to put this system in the books over the next couple of days.

What’s next?

With the forecast for Hurricane Erin well in hand, it’s time to look ahead to what is coming next in the Atlantic season. Now that we’ve had the season’s first hurricane (and major, and Category 5 storm) it seems clear that the Atlantic tropics are open for business. We are now firmly in the most frenetic time of the year for Atlantic activity, the period from mid-August through mid-October.

But for the rest of August, at least, the tropics look pretty tame. I don’t want to manifest anything and I am certainly not tempting Mother Nature, but I like the setup for the rest of the month. Moreover, when we peek ahead at conditions for early September, there just is not too much evidence that things are going to start sizzling any time soon. For example, here’s the latest sub-seasonal forecast from the ECMWF model for the first week of September. As you can see, it is predicting just 40 percent of normal activity in the Atlantic basin. Of course such models are far from perfect, but you would rather see such forecasts than the alternative.

European model forecast for “accumulated cyclone energy” from Sept. 1 to September 7. (ECMWF)

With that said, let’s take a look at what we’ve got going out there.

Central Atlantic disturbance

This tropical wave continues to propagate westward, and is edging closer to the Caribbean Sea. As of this morning, the National Hurricane Center gives the system a 60 percent chance of becoming a tropical storm or depression over the next week.

National Hurricane Center tropical outlook.

There are a variety of solutions for this system, which is natural since there is no clearly (or even poorly) defined center of circulation this morning. This makes it more difficult for models to latch onto a center and project it forward. Generally, however, most of our model solutions bring the storm northwestward, likely missing a majority, if not all of the Caribbean Islands. The image below shows the cluster of outcomes from the European model ensemble, and as you can see this is probably a fish storm.

The other thing to note is that if the storm does come closer to the Caribbean islands, including Puerto Rico, it likely is to be weaker (perhaps not even a depression) than if it recurves northward more quickly. The bottom line is that the upper-end intensity of this storm does not look all that high, and if it does get strong it’s probably going to miss land entirely. So we’ll watch it, but not with too much concern.

Invest 99L

The system behind that one actually got tagged as an “area of investigation,” but I’m not overly enthused about its prospects either. We can probably expect this wave to meander westward across the Atlantic and it may eventually move into the Caribbean Sea. As Matt noted yesterday these waves can be tricky, because they spend days doing nothing and then find a favorable patch of atmosphere and organize quickly. But for now there is virtually nothing, zilch, and nada in our models to indicate this will happen with 99L. So we’ll keep an eye on it, partly because beyond this there’s not much else expected to happen over the next 10 days.

Model data is essentially worthless at this point, but I think these tracks are illustrative of what we can expect with 99L. (NCAR)

Which is a great place to be in late August.