Ask the expert: A meteorologist answers burning questions about the fall forecast

By Sarah Duffy

The Weather Channel recently released its fall forecast, detailing the intricacies and drivers of the weather patterns we can expect in the coming months.

We decided to go deep with Senior Digital Meteorologist Jonathan Erdman, to learn how the forecast will likely influence severe weather and health this fall and what these climatic patterns reveal about the future of a (potentially) shifting fall season for years to come.

As marketers continue to be tasked with crafting strategies that are agile enough to keep up with both the changing environmental and media climate, a basic knowledge of how seasons are evolving can help you stay ahead by understanding, adapting and navigating consumer needs.

Q: What do you expect for fall 2023?

Generally, we expect a warm-to-hot fall over much of the US, especially in the central states. Parts of the northeast and west coast may not be as hot, at least for September.

Across much of the US, September is becoming a summer month. Our latest outlook shows that will particularly be the case in parts of the south and along the Gulf Coast.

But October might be a curveball. In an El Niño year, cooler air gets dumped into the central and eastern US more often. That could cause a colder-than-average October in parts of the northern Great Lakes and New England.

The south may still lag warm, especially the desert west area. But overall, there could be a pretty big shift from warmer to colder weather as we move from September to October.

Q: Is a warm September followed by a dramatic cooling in October typical for an El Niño year?

Yes. Looking at the last eight strong El Niño events, September is generally warm in most areas with an abrupt shift in October that makes the weather cooler.

But when it gets to November, temperatures trend to warmer than average across the entire northern and southeast US but cooler than average in the southwest.

Overall, we anticipate a whiplash of a fall, with September being warmer than average, October being cooler, and November being warmer. Keep in mind that those observations of prior years don’t include the effects of climate change, and El Niño is not the sole influence on the atmosphere.

Q: With September effectively becoming a summer month, are we looking at a new reality in which fall starts later?

I’d say that’s correct. It’s skewing warmer deeper into the fall and in some parts of the country, that trend is fairly pronounced. The weather likely won’t feel like fall until sometime in October for most of the country.

Fall is obviously a transition between the warm time of the year and the cold time of the year. Those transitions can be abrupt; weather patterns shift dramatically and suddenly you’re turning on your furnace, wondering what happened to fall.

These shifts in seasonal patterns are becoming more dramatic and happening more frequently.

Q: Where do we see the fingerprints of climate change in this outlook and how do meteorologists typically account for it?

Scientists are telling us that – because climate change is warming the higher latitudes faster than the lower latitudes – the jet stream is slowing down. Typical jet streams move west to east every four to five days.

But if the jet stream is weakened, it causes more wavy and loopy air patterns that get more erratic. That means the weather conditions sort of become stuck, leading to both more persistent cold and wet areas and hot and dry areas.

What is a jet stream?

Jet streams influence the weather patterns across the globe. Shaped like winding rivers, jet streams are strong, relatively narrow air currents located about 5 to 7 miles above the ground that form when cold and hot air meet. These streams typically run west to east, pushing air masses that cause changes in day-to-day weather.

One example is the stuck pattern we saw over Canada which produced its hottest May on record and ignited a record number of wildfires. This fall, the jet stream will probably get into these blocky, loopy patterns that may get stuck for a while. These changes can occur abruptly but then last for days or weeks.

Q: How will warmer temperatures in the oceans combined with an El Niño season impact the severe weather outlook this fall?

This hurricane season is excruciatingly difficult to forecast. A stronger El Niño tends to reduce the number of hurricanes, particularly in the Caribbean Sea and the Gulf of Mexico.

But it’s not just El Niño. We have some of the warmest water on record in the Atlantic that – if we were solely considering that factor – we might expect to cause one of the most active hurricane seasons ever.

So, we have two competing aspects: El Niño typically causing fewer storms, and record warm water typically causing more storms. And we don’t really know how those seemingly opposing factors are going to mesh.

The best guess we have is there will be a lot of storms that come off Africa, curl out to sea in the North Atlantic and not be a problem for the US. If the right atmospheric setup is there, some of those could flirt with the East Coast. If there is a bigger threat this year, it is for the East Coast versus the Gulf Coast.

For generally severe weather, it has been quite a summer for thunderstorms. With an overall warmer-than-average fall forecast, we could expect more severe thunderstorms. September will likely be pretty active, especially in parts of the upper midwest, possibly areas of the northeast and, of course, the southwest as the humid air lingers.

Q: How do we anticipate warmer temperatures to impact the seasonality of allergies in the coming months?

In the fall, ragweed is the key driver of allergies. That tends to pick up in August and cut off with the first freeze.

A warm September could be a challenging month for allergies, especially if there is persistent sunshine with dry weather and wind. If areas of the south don’t get the cold fronts in October, there could be a longer and more active allergy season that extends into November.

Q: Our forecasts only go through November but is there anything we can expect for winter in an El Niño year?

Winter in an El Niño year is generally wetter and colder in the south and snowier in the mid-Atlantic. We are starting to see the first vestiges of that in this November forecast.

Looking ahead to December in a typical El Niño year, that’s the wildest map of them all. If you draw a line straight down the plains, everything east of that line is likely to be much warmer than average and everything to the west will probably be much cooler than average.

A strong El Niño winter tends to bring more severe weather to Florida around February or March. But given all the warm water around Florida right now, it could be quite an active late winter for severe storms in the southeast and parts of the Gulf Coast.

Finally, we could also see a drier-than-average winter for the northeast, which has endured many heavy snowstorms over the last few La Niña winters.

But again, all those predictions are based on El Niño being the only driver of the atmosphere, which won’t be the case.

In short, this will be fun to watch.

How can you brand stay ahead of the competition this fall? Get strategies here.