Matt Lanza

To solve Louisiana’s Mississippi River salt water crisis a significant weather pattern change is needed. Is any in sight?

At The Eyewall, we’ve focused on hurricanes and tropical storms since our launch in June. Some of you have asked what we’ll do during the offseason, and the answer is we will probably pull back our posts to every few days unless there’s a major weather event, and we will focus on extreme weather impacts in North America. We don’t want to offer clickbait or drama, but a forecast, an explanation, and context. I’ve decided to roll out something of that nature today with a focus on the Mississippi River salt water intrusion crisis in Louisiana.

One-sentence summary

The situation with salt water creeping up the Mississippi River in Louisiana is a complex one but one that has a basic solution (more rainfall) that does not look likely to be in the cards over the next 2 to 3 weeks in any meaningful capacity.

What is happening?

If you’ve been following the news lately, you may have heard about salt water creeping upriver in the Mississippi River in Louisiana. In the most simple terms, as dry weather has led to low river flows in much of the Mississippi Valley, denser salt water has been able to creep north at the bottom of the river. This isn’t unprecedented, but it isn’t common either. This happened to a much lesser extent last year and more notably back in 1988, when the salt water barrier shifted over 100 miles up the river west of New Orleans. This led to a couple days of salt water intrusion into New Orleans’ water supply which ended quickly.

WWNO, the NPR affiliate in New Orleans has a great rundown of what’s happening.

Tulane’s School of Public Health & Tropical Medicine also published a “5 things to know” that is helpful.

Virtually the entire Mississippi Valley is in drought right now, with a good chunk of the Missouri and Ohio River Valleys that feed the Lower Mississippi also in drought or abnormal dryness. The hot, dry summer in Louisiana in particular has exacerbated the dryness and drought there, with the entire southern two-thirds of the state in either exceptional or extreme drought.

Louisiana is in pretty terrible drought right now, but the situation upstream on the Mississippi is only marginally better, with widespread dry or drought conditions into Minnesota and along the Missouri and Ohio Rivers as well. (US Drought Monitor)

The last 60 days have seen 5 to 50 percent of normal rainfall along the Mississippi south of Memphis. The Ohio Valley and Missouri Valley have both seen 50 to 75 percent of normal rain. All this combined with the extreme drought in Louisiana has led to a confluence of problems and an expanding salt water wedge.

Over the last two months, rainfall has been 25 percent of normal or less in much of southwest Mississippi and Louisiana, and only marginally better than that in most areas along the Mississippi, Ohio, and Missouri Rivers. (NOAA)

What is the rainfall outlook?

To solve this problem, the main thing you need is just simply rain. It needs to rain in the Ohio, Missouri, and Mississippi Valleys sooner than later. Is there anything in sight over the next two weeks? Not really. The Lower Mississippi Valley should see minimal relief. The Ohio Valley looks quite dry. The Missouri Valley and Upper Mississippi are more mixed, but we’re just not seeing signs of any appreciable rainfall over the next two weeks.

Both the European model (shown here) and the GFS model are advertising below average precipitation over the next two weeks over virtually the entire Mississippi River drainage basin. (Weather Bell)

This is why you are seeing so much news about preparations for this in New Orleans and other Louisiana communities. Without meaningful rain over the next two weeks, you will continue to see the salt water migrate north. Current weather forecasts push us out to about mid-October and current projections for the wedge have it getting to New Orleans in later October. Even if 10 inches of rain fell over Memphis on October 15th, it would take some time for that water to flow downstream and get to New Orleans and southeast Louisiana. And isolated rain is not the answer. This problem requires a lot of upstream rain over a broad area. So it seems pretty clear that this problem is going to worsen.

So when can we expect a change? Well, when we look at the Climate Prediction Center’s outlook for weeks 3 and 4 (and granted, this is from last Friday), we can see signs of life in Texas or the Southern Plains, but probably nothing that would help “solve” the problems in Louisiana.

The situation within the Mississippi Basin does not look to improve a whole heck of a lot in mid October either. (NOAA)

The CPC outlook for October is positive with a lean toward above normal rainfall in the mid-Mississippi Valley. I’m not sure if changes over the last week since this map’s release have necessarily lowered chances of this outcome, but I don’t believe they’ve helped much.

The bottom line: The situation with salt water in the Mississippi River is going to worsen in the coming weeks, and there is not necessarily any strong signal for changes in the rain patterns over the key areas required to alleviate the problem. We need to see a change in the rainfall chances in either or all of the Ohio, Mississippi, and Missouri River Valleys before we can be confident that some help will be on the way. And at least into mid-October and possibly late October, that’s not likely to occur.

September 28, 2023 Outlook: Complex interactions between Philippe and 91L complicate the Atlantic forecast some

One-sentence summary

A complex interaction between Philippe and Invest 91L enhances a bit of uncertainty in the Atlantic next week as it relates to the islands, though most outcomes still favor minimal impacts in Puerto Rico, the Virgin Islands, and Lesser Antilles.

Happening Now: Philippe and 91L (future Rina?) and where will they go?

Looking at satellite this morning, the Atlantic is just jammed up with Tropical Storm Philippe and Invest 91L back to back. Personal space anyone?

Tropical Storm Philippe and Invest 91L are basically adjacent to each other, and at some point something will need to give in terms of which of these becomes the “big dog” of the Atlantic pack. (Weathernerds.org)

Anyway, this is actually important context to start today’s discussion with because the future and the future of any impacts will be somewhat contingent on which of these two becomes the dominant system in the Atlantic. On one side you have the GFS model, which has tended to overdo Philippe’s actual intensity, meaning that it has tended to slow it, park it as 91L interacts with it, and then take it north into the open ocean as a hurricane. The Euro essentially kills off Philippe and then sheds its remnants in the islands with some rain, while 91L tracks west as a weak system before turning north and strengthening.

Confidence in Philippe’s track is high until it gets just north of Anguilla, and then all bets are off. (Tomer Burg)

Interestingly, the setup here is one that seems to keep in play a Fujiwhara interaction between the two systems. What is that? Basically, the two systems would track close enough to one another to impact each other’s track. In this case Philippe would likely slow, stall, or get pushed to the south since it’s ahead of 91L, and 91L would basically slingshot over the top of Philippe either west or northwest and out to sea. The GFS operational model shows this quite well.

Philippe (at right) may slow or stall while 91L “slingshots” off to the west or northwest. Once that interaction untangles, Philippe would be free to turn north. (Tropical Tidbits)

In most possible outcomes, impacts to the islands are not exactly serious, so let’s make that abundantly clear. The arithmetic here is that if 91L (or as the GFS says, Philippe) ever explodes in intensity, it will “feel” upper level steering and turn north out to sea. Is there a chance that the system stays weak, tracks into the islands, and then blows up? I suppose that’s possible, but if it gets to that point, the theory would be that dry air or land interaction limit a lot of upside. So for folks in Puerto Rico or the islands, it would be unlikely that this is a major noisemaker as it comes in. We’ll continue to watch this, but for now the thinking is that it will just be an annoyance out there more than anything. Presumably if one of them does develop into a hurricane and turns out to sea it would happen east of Bermuda. We’ll keep watch and let you know if anything changes.

The medium-range (days 6 to 10): Noise off the East Coast?

We’re starting to get some sort of idea as to what might come next. Models have been consistently showing some sort of upper low or storminess between the southeast Gulf and off the North Carolina coast next week, but they have been wildly different run to run on details. The forecast idea today seems to be honing in on an upper low developing off the Carolina coast before a piece of it drifts southward toward or off the coast of Florida. Another lower-end system could theoretically develop from this, though the odds are fairly low.

The upper level map from the European model for next Monday shows the upper low exiting off the East Coast, with just enough “spin” (or vorticity) left behind to linger off the coast, unlikely to develop but worth watching. (Tropical Tidbits)

This probably means minimal impacts right now beyond rough surf and rip currents. But this is probably at least worth keeping a side eye on.

Fantasyland (beyond day 10): Still no substance to any threats

We’ve been saying that it may be wise to keep an eye on the northwest Caribbean or eastern Gulf in the late period all week. We continue to be faced with a weather map that does not really show any specific threats; just some noise. So I have no reason to believe that something *will* happen beyond day 10, but I also know that the big picture in the atmosphere doesn’t completely shut the door on that potential. We’ll keep watch.

September 26, 2023 Outlook: Beyond Philippe and Invest 91L riding its coattails, it’s tough to make much of anything else

One-sentence summary

Tropical Storm Philippe and Invest 91L in the Atlantic remain no serious concern at this time, and while things look to stay a bit active next week, it’s tough to say exactly what that means with any specificity.

Happening Now: Annoying Atlantic

We have Philippe, and we have Invest 91L that continue to churn in the Atlantic. Philippe has gotten virtually no stronger since yesterday. Invest 91L continues to have high odds of development, probably by tomorrow or Thursday.

Invest 91L is expected to essentially tail Philippe west, and while Philippe dissipates near the islands, 91L should be gathering some strength as it readies to curve northward. (Tomer Burg)

You can see from the map above how the track of Philippe is essentially trailed by the area of potential development from 91L, which is the red highlighted area. The intensity of each system will determine just how close it gets to the islands. The current thinking is that Philippe will dissipate north of the islands in the coming days. Invest 91L should take over as the better organized system, but even in the most extreme case, it would most likely pass north and east of the islands. Even if it did track farther south and west and closer to the islands, that would be due to a weaker system. So, it’s probably wise to keep watch on how this all plays out if you live in the northern Leeward Islands or Puerto Rico, but the vast majority of decent data seem to support a miss.

The medium range (days 6 to 10): Noisy near Florida

Early next week should be dominated mostly by what we see in the Atlantic. But as we get to the middle and end of next week, we have noise continuing to percolate in the modeling on either side of Florida. We’ve had some bizarre solutions printed out by modeling since the weekend, including systems backpedaling southwest from off the Carolinas to something in the eastern Gulf moving northeast across Florida and out to sea to some model solutions showing absolutely nothing whatsoever.

The forecast for the mid-levels of the atmosphere on the last 10 GFS model runs for next Thursday tell us absolutely nothing useful. (Tropical Tidbits)

I think that’s an important element of this. Usually when you have this kind of inconsistency and only tepid ensemble model support, you have enough justification to be skeptical that anything will occur. So while I think this is certainly a region to watch in the days ahead, the most likely outcome is probably that nothing of note happens. We’ll obviously continue to watch to see what evolves in the days ahead.

Fantasyland (beyond day 10): Noise but no signal

We’ve seen no change in modeling since yesterday with respect to the extended range period. There are signs of potentially something in the western Caribbean or southeast Gulf, but there’s no signal whatsoever to what is there. In other words, I see some ensemble members of the various models showing me signs of development, but I see no consistency and no real consensus yet.

Historical points of origin of tropical systems in the first third of October focus our attention on the Bay of Campeche and northwest Caribbean. (NOAA NHC)

Climatologically, that’s exactly where you would be looking in early October. So it’s not a surprise that that is what we’re doing. But until we see any kind of signal in this soup, there’s little we can say beyond “it’s worth watching.” Especially for the eastern Gulf or northwest Caribbean.

September 25, 2023 Outlook: Philippe and perhaps a friend will traverse the open Atlantic this week

One-sentence summary

Neither Tropical Storm Philippe or Invest 91L are expected to impact land at this time, but there are a couple other areas to keep tabs on beyond this week.

Happening Now: Philippe and 91L are not serious concerns

It’s the last full week of September, and in the Atlantic tropics we continue to pace ourselves with a couple storms per week. This week, we have Philippe, which formed over the weekend. We may add Invest 91L to the mix later this week, as it may have a window of opportunity to become Rina.

First, Philippe. While it has plenty of thunderstorm activity that it is maintaining this morning, it’s very clearly ragged looking, an indication that it is fighting off wind shear.

Tropical Storm Philippe is juiced up pretty good this morning, but it is clearly fighting off a good deal of wind shear. (Tropical Tidbits)

Philippe has 50 mph maximum sustained winds, but with the wind shear it is experiencing, it may struggle to intensify much beyond this over the next couple days. If Philippe can survive this stretch, there is some chance it may take a run at hurricane intensity by later in the week out over the open ocean, no threat to land. If Philippe succumbs to shear the next few days, it may actually stay on a westward course and get close to the islands. However, in that case, it would be unlikely to reintensify and impacts would be minor.

Tropical Storm Philippe is expected to hold its own over the next few days, eventually turning out to sea or falling apart northeast of the Lesser Antilles. (NOAA NHC)

So in terms of impacts in the Lesser Antilles, both a stronger Philippe and a weaker Philippe should make no difference. A stronger Philippe turns away faster and much farther east. A weaker Philippe tracks closer but falls apart.

Meanwhile, Invest 91L got tagged this weekend behind Philippe, and it is essentially following Philippe to the west. I’d expect a slow, gradual intensification this week and maybe an organized depression or storm by Wednesday or Thursday.

Invest 91L is expected to essentially follow Philippe to the west and north, though its ultimate outcome will be dictated by how strong it gets; stronger out to sea faster, weaker more south and westward but never organizing much. (Tomer Burg)

Ultimately, 91L’s future may be dictated (much like Philippe’s) by how strong it gets. A stronger storm would be apt to turn away from the islands quicker, whereas a weaker one would track closer but come with limited impacts. Either outcome produces minimal heartburn for the islands. We’ll keep track.

Finally, the NHC has highlighted an area in the far southeast Gulf with a 10 percent chance of development.

That seems reasonable right now. Wind shear is low for the moment, but it is expected to increase and expand over the Gulf this week, which should essentially shut down anything that tries to develop. So we are not worried about this one.

The medium-range (days 6 to 10): Eastern Gulf or East Coast shenanigans?

Could we do another Ophelia situation on the East Coast or even in the Gulf next week? The answer is maybe. Some modeling has hinted at a disturbance in the mid-levels of the atmosphere coming together somewhere around Florida, perhaps not far from where Ophelia developed last week. I think the ballet here is a little more delicate than it was last week, which would mean that we’d need a few more things to come together perfectly for this to happen. But if it were to do so, we could conceivably be talking about another tropical storm either in the Gulf or off the East Coast next week. Something for us to watch, but nothing I have enough confidence in today to say much more about. This is very much a stay tuned situation.

Fantasyland (beyond day 10): Still a bit noisy

I can’t hone in on anything specific right now, but in looking at all the modeling beyond day 10, I would think that we’re onto something, potentially in the western Caribbean. Again, I’m not certain that this will happen, but it’s the one place I’d be watching into mid-October. We’ll fill in the gaps on this as we get a little closer. It’s frustratingly vague to be sure, but that’s simply the reality of trying to forecast 10 to 15 days out.