Matt Lanza

Could the 2025 Atlantic hurricane season have some tricks up its sleeve? Breaking down the CSU Outlook

Late last week, the team at Colorado State University issued their always hotly anticipated seasonal hurricane outlook for the Atlantic Basin. To clear this up at the beginning, their forecast calls for:

  • 17 named storms (normal 14)
  • 9 hurricanes (normal 7)
  • 4 major hurricanes (normal 3)
  • Accumulated cyclone energy: 155 (normal 123)

Nothing about this forecast on the surface is especially notable or alarming or fascinating. It’s simply a slightly above average forecast.

But what is somewhat notable about their forecast is some of the under the hood items they address. First, we are likely to be coming out of a La Niña event, something we discussed last back in February. But as the CSU team notes, we don’t know for sure if we’re headed for El Niño or ENSO neutral (La Nada) conditions. ENSO neutral summers combined with warm water temperatures “typically provides a more conducive dynamic and thermodynamic environment for hurricane formation and intensification.” In other words, hurricanes like those background conditions.

We do not yet have a “plume” from the C3S suite for April, but the March plume skewed slightly toward El Niño development.

Multi-system ensemble of various forecast models predicting a trend toward positive sea-surface temperature anomalies this summer, possibly giving a slight edge to a developing El Niño event. (Copernicus)

If we get to El Niño conditions by late summer or fall, that does not guarantee that conditions will shift to become more hostile to hurricane development. But that may take the edge off a bit. However, if we “hang” near the neutral line or even in weak La Niña territory, any hostile conditions may be apt to stay away, ensuring a busier season than usual.

In addition to the forecast for named storms and such, the CSU team also does try to convert that seasonal outlook to a prediction of U.S. landfall risk. Indeed, with a more active season expected, the odds of a U.S. landfall are also higher. They have a 51 percent chance of a major hurricane landfall on the U.S. coast, compared to a historical average of 43 percent. The odds on the East Coast are 26 percent, compared to 21 percent typically. And in the Gulf of Mexico, the landfall odds between the Florida Panhandle and Brownsville are 33 percent versus a 27 percent average.

According to the CSU team, all model guidance is pointing to an above-normal season. Water temperatures remain well above long-term averages across the Atlantic. As we noted earlier this year, however, this is not last year’s Atlantic sea-surface temperature profile. But it’s still quite warm.

March 2025 minus March 2024 sea-surface temperatures, showing year over year warming in the Caribbean, Gulf, and mid-latitudes, but not in the tropical Atlantic. (NOAA PSL)

From the map above, you’ll notice that the eastern Atlantic has cooled markedly since last year, however the Gulf, Caribbean, and northern Atlantic Ocean are all warmer. The fire that was burning all last summer in the eastern Atlantic is still smoldering, but it has been somewhat extinguished. The Gulf and Caribbean are another matter. The Gulf is warmer than 2024 by a good bit but still lags 2023. While the Caribbean was warmer than 2024 in March, it has since cooled some in April, taking it back under 2024 levels. Water temperature conditions can change quickly, but the bottom line is that the Atlantic, with the exception of the eastern basin are in the upper echelon of warm years at this point. The warmer overall waters in March in the eastern North Atlantic (north of the tropics), along with the warm Caribbean do correlate to active hurricane seasons.

The bottom line is that the underlying data support the idea of an active hurricane season — but not to the levels feared last year. But there aren’t very many red flags at this time arguing against that outcome. At least last year, we had the expectation of a developing La Niña to help grease the wheels a bit, and a slow development could have slowed the hurricane season a bit. This year? There’s no real glaring red flag that says the season will bust. But hurricane seasons always have surprises. Hopefully this year’s involves calm.

Colorado State’s seasonal hurricane forecast is just that, a seasonal forecast. Should you plan your life based on this? No. But they generally have good skill. And their skill in the last 10 years or so has been great. You still have a few weeks, but it’s time to start thinking about, refreshing, and planning for the season ahead. There’s a lot of uncertainty this year in terms of FEMA and federal response to storms, so it probably behooves you to plan that kit even a bit more than usual. We have tips on our preparedness page, which we will go through and adjust any broken links when we have some time in the coming weeks.

A quieter week after an incredible rainfall forecast, as huge footprint of major flooding continues

Headlines

  • Weather forecasts verified exceptionally well with the ongoing Mid-South flooding.
  • Numerous rivers are experiencing or soon will experience major flooding as all this feeds into the larger Ohio/Mississippi Basin.
  • A much quieter week is expected this week.
  • Next week may be a good bit stormier, however.

Exceptional flooding, exceptional forecasting

Now that it’s over, we can say that last week and weekend’s rainstorm sadly lived up to the expectations set days before. Take a look at the map comparison below. Use the slider to toggle between the rainfall forecast issued on Monday and the observed rainfall based on MRMS analysis.

A comparison of the rainfall forecast issued Monday and the observed rainfall late last week and weekend. Additional rain was expected south and east. (Pivotal Weather)

Is this a perfect rainfall forecast? No, but my goodness it’s pretty darn close. The Weather Prediction Center, which is an arm of NOAA issues these larger scale precipitation forecasts daily. I reference these forecasts regular in my day job and for our readers both in Houston and elsewhere. They’re valuable. But they have exceptional utility ahead of major events such as this flood in the Mid-South. The folks at the WPC, much like those at other national centers under NOAA’s umbrella are the absolute best of the best in our field when it comes to marrying forecasts with historical analysis and numerical prediction models. As a public service, I’ll remind you that the budget cuts currently being proposed to NOAA will cost more in both lives and property in the long run than they’ll save in the short run.

All that said, this forecast was exceptional, but so were the impacts. Here is a look at the wide swath of double-digit rainfall totals seen through this event.

A non-comprehensive look at rainfall totals in excess of 10 inches across the lower Ohio Valley and Mid-South. (NOAA)

Many rivers in western Kentucky, southwest Indiana, or southern Illinois will be at their highest levels since 2018; in some cases on the White River in Indiana, it will likely be their highest levels since 2005 or 2008 floods. A few spots on the Kentucky River will actually set new records from this event.

The Kentucky River is setting new records in places. (NOAA)

In Frankfort, the state capital, a record from 1978 is threatened from the Kentucky.

Those recurrence intervals are pretty amazing from southwest Tennessee through central Kentucky. For Memphis, this was the 2nd wettest four-day stretch on record, just falling about an inch shy of a June 1877 flood event there. Six flash flood emergencies were issued for the event across Arkansas, Texas, Mississippi, Tennessee, Kentucky, and Missouri.

Rivers that are forecast to be in moderate (red) or major (purple) flooding encompass a huge swath of the Mid-South and Ohio Valley. (NOAA National Water Prediction Service)

Dozens of river gauge locations are expected to experience major flooding. All this water is going to flow into the Mississippi River eventually, and depending on where you are on the river, the forecast crests right now are the highest since somewhere between 2011 and 2020.

All this water is flowing into the Mississippi, which is expected to reach major flood as far south as Baton Rouge by next week. (NOAA)

This one will go down in the record books with some of the bigger Mid-South floods.

Quiet week for the most part

Fortunately, the forecast this week there looks fairly calm with some rain later in the week, likely at manageable levels. Elsewhere across the country, we get to still discuss winter. Cooler temps will allow for some locally heavy snowfall from Ontario, across southern Quebec and into interior northern Maine, where as much as 4 to 8 inches could fall tomorrow.

Winter is not quite over just yet. (NWS Caribou)

Otherwise, the late week storm system mentioned above may allow for a return to some fire weather conditions in the southern Plains. Unlike in March, however, quite a few areas have seen some decent precipitation recently. So hopefully that puts a bit of a lid on severe fire weather concerns for the Plains.

Back at it next week?

I think the next significant weather item to watch will be a chance for multiple days of severe weather next week in the southern Plains. Exactly what that looks like or how it unfolds is TBD, but there are definitely signs in the models that after a quiet-ish week this week, we pick up the pace again next week.

I’m going to aim for a couple more posts this week. One will discuss the hurricane outlook issued by Colorado State. I may try to get another one later in the week on water issues and low snowpack in the interior West. We’ll see how this week goes!

Going, going, gone?

I want to leave you with a couple fun links today. As baseball season ramps, up, there are two new ballparks in play this year with the A’s in Sacramento and the Rays playing at Steinbrenner Field in Tampa. Over at Fangraphs, Michael Rosen did a two-part look at the weather effects in the new ballparks. Both have interesting quirks. Sacramento’s field will have some of the lowest humidity of any ballpark in the league. Tampa will have some fascinating winds which may make Rays games pretty fun to watch. Anecdotally, I did watch parts of some Rays games during Opening Week, and there were some interesting dynamics in play on fly balls. I encourage you to check those links out!

Looking at the next 24 to 36 hours of severe weather and flooding in the Mid-South

Thunderstorms are cranking up as anticipated this afternoon all across the Mid-South all the way north to northern Indiana with a bunch of severe thunderstorm warnings about 7 tornado warnings at the time I am writing this.

A static radar image as of 5:30 PM CT over the Mid-South and Midwest. (NOAA)

A “high risk” for severe weather was issued from eastern Arkansas to just south of Evansville, Indiana today. The reasons included the potential for strong tornadoes, very large hail, and very strong wind gusts. Basically, it’s about as optimal a broad-scale severe weather setup as you could reasonably look for. It could also end up being a tornado outbreak day as well. We’ll see what happens over the next few hours, but as these storms march east, it’s likely that all severe threats will increase this evening.

A high risk (5/5) is in place for severe weather threats between eastern Arkansas and western Kentucky. (NOAA)

We’ve been discussing the rain risk the last few days and the potential for catastrophic flooding to emerge in these areas. Round one tonight will start that process. We can get a sense of the potential for rain over the next several hours looking at the HRRR model, which is a high-resolution model we use for thunderstorm forecasting. It shows a bullseye of 3 to 6 inches showing up between now and 7 AM CT on Thursday in western Tennessee, just east of Memphis.

Rain forecast from the HRRR model between this evening and Thursday morning showing 3 to 6 inches in western Tennessee. (Pivotal Weather)

That area between Jackson and Dyersburg, TN may be at highest risk for flooding from this first round of rain. Once the severe weather exits tonight, the front will basically stall out over or just north of the Tennessee Valley. As that happens, the severe weather threat for tomorrow will shift back south and west some into northeast Texas, Arkansas, and western Tennessee.

Thursday’s severe weather risk shifts farther south and a bit west. (NOAA)

What about the rain? Tomorrow’s heaviest rains are going to focus near or just north of where tonight’s heaviest rains will occur. According the Storm Prediction Center’s high resolution ensemble forecast, the average rainfall tomorrow will peak around 2 to 4 inches in northwest Tennessee, between Dyersburg, Martin, and Clarksville. There is some degree of uncertainty in how much exactly falls and where it falls. So all of western Tennessee should be on guard.

Average rainfall forecast for tomorrow across the Midwest and Mid-South shows a bullseye in northwest Tennessee and parts of Arkansas. (NOAA SPC)

Arkansas should also watch this, particularly between Pine Bluff and Memphis, TN. Some of the “under the hood” guidance indicates that as much as 5 to 8 inches of rain could fall in these areas. As such, a high risk (level 4 of 4) exists for these general areas tomorrow for flooding rainfall.

A high risk (4/4) for flooding focuses on northeast Arkansas, western Tennessee, and portions of Kentucky. (NOAA WPC)

High risks for flooding are important to denote because they are extraordinarily well correlated to damaging, deadly flooding. The vast majority of the worst flooding we see in this country occurs on these high-risk days. So tomorrow could be the first volley in a very bad series of them.

Beyond tomorrow, the general trend will be to lift the rain north on Friday into the Ohio Valley or even farther north before it slowly, painfully slowly sags back south and east on Saturday, finally exiting Sunday morning. This period will probably see additional bad flooding spread to the north and then back south again. Again, this appears to be an extremely rare, catastrophic flood event that will unfold over multiple days beginning tomorrow across Arkansas, Tennessee, Kentucky, and portions of Illinois, Indiana, Ohio, and Missouri. Additional “high risks” are likely to come.

Potential for catastrophic flooding by the weekend in the Mid-South and near the Ohio Valley

The National Weather Service in Paducah, KY did not mince words this afternoon in their briefing on the upcoming rainstorm across the Ohio Valley: “Significant and potentially historic rainfall will begin Wednesday afternoon, with numerous rounds of heavy rain continuing into the first half of the weekend, leading to potentially catastrophic flash flooding.”

I have a whole post eventually coming to my Substack page on words and how we use them. But suffice to say, whenever the NWS uses a word like “catastrophic,” it is an extremely deliberate decision that more than one person agrees to. In other words, they understand the weight of the word “catastrophic,” and after discussing it as a team, they agree to use that phrasing. Because they’re convicted of an outcome that they believe will indeed be possibly catastrophic.

National Blend of Models (NBM) forecast rainfall through the weekend with pockets of 10″ or more between northeast Arkansas and southern Indiana. (Pivotal Weather)

And the model data today continues to provide ample additional support for a wide ranging, widespread, potentially historic and/or catastrophic outcome. Within their area forecast discussion, the technical briefing the forecasters at the NWS provide that essentially explains or justifies their decision-making, the Paducah office maintained that type of language. “We cannot overstate the extremity of the flooding danger with this event incoming and these historic forecast rainfall amounts.”

To the north, in Indianapolis, their forecast discussion stated it had the potential to be one of the most significant rain events in the last 15 years. “This has the potential to be near the top of the list for highest impact heavy rain/flooding events for central Indiana in the last 15 years.”

Same story in Memphis, where their office also warned of catastrophic flooding. “Catastrophic flooding remains possible in portions of the Mid-South Wednesday through Saturday as the previously discussed front stalls right along the I-40 corridor.”

I wanted to just post that so folks, especially new visitors, didn’t think that we’re just randomly going ballistic over something. No, this is objectively a very serious threat between Arkansas and Ohio that is going to make the national news. All we can do at this point is hope for the best.

A very serious severe weather threat

There will also be severe thunderstorms at times, especially tomorrow (Wednesday) and Saturday I think.

A moderate risk (4/5) is in effect for Wednesday between central Arkansas and southwest Indiana due to possible tornadoes, damaging winds, and large hail. (Pivotal Weather)

Being from Houston and having dealt with a 5-day rain event in 2017 by the name of Harvey, these types of events are long-duration tests of will. I’ve found that rather than trying to focus on every single element of the threat, it’s better to break it into manageable chunks. Today, that’s the overall rainfall threat (as laid out above), in addition to Wednesday’s severe threat. The moderate risk (4/5) was issued to cover all forms of severe weather (strong tornadoes, large hail, and damaging wind gusts), and all of them look potentially potent tomorrow. I will refer you to your local NWS office or some of the other fine weather blogs out there for more on the severe threat. There will be additional rounds of strong to severe storms across the Mid-South through Saturday, with perhaps Saturday itself being the second peak day of the event, in addition to peak concerns about flooding.

Stay safe everyone.