Expert Forecasts for the 2024 North Atlantic Hurricane Season

[Hurricane2022]

CSU April 4, 2024 23 11 5
TSR April 8, 2024 23 11 5
UA April 8, 2024 21 11 5

[Teban54]

University of Arizona also has a high numbers forecast but lower ACE than other agencies and experts,

https://i.imgur.com/PlmTgc5.jpeg

https://has.arizona.edu/news/2024-hurri ... kyle-davis

156 ACE for a 21/11/5 season seems very low, and is basically akin to the end of October 2020 before Eta, Theta and Iota, when the season was at 27/12/5 with a similar ACE. Are they expecting a similar west-based season where the hurricanes and majors only reach such intensities close to land (or are otherwise short-lived in general)? I find it hard to believe when 2024 has an even more pronounced +AMO signature than 2020, and stuff like typhoon-induced TUTTs (which really hurt 2020's CV season) are impossible to forecast this early.

[aspen]

University of Arizona also has a high numbers forecast but lower ACE than other agencies and experts,

https://i.imgur.com/PlmTgc5.jpeg

https://has.arizona.edu/news/2024-hurri ... kyle-davis

156 ACE for a 21/11/5 season seems very low, and is basically akin to the end of October 2020 before Eta, Theta and Iota, when the season was at 27/12/5 with a similar ACE. Are they expecting a similar west-based season where the hurricanes and majors only reach such intensities close to land (or are otherwise short-lived in general)? I find it hard to believe when 2024 has an even more pronounced +AMO signature than 2020, and stuff like typhoon-induced TUTTs (which really hurt 2020's CV season) are impossible to forecast this early.

I wouldn’t be too surprised if we have another quantity-over-quality season (lower-than-expected but still high ACE). Maybe similar to 2020, the basin is so active that it ends up harming its overall quality in some way we won’t really know until the season is in full swing, like the WAM being on overdrive and pumping out so many broad waves. 2020, 2021, and 2023 all had lower-than-expected ACE compared to their NS totals, so perhaps 2024 follows suit.

[al78]

al78, I know that it’s mentioned that it’s impractical to forecast the direction of the storms and the threat to CONUS. But is it in bad taste to suggest that with even a mild La Niña by peak season, higher than average SSTs, and forecast of relaxed tradewinds/shear in the Caribbean; the Gulf and East Coast should be prepared for a greater than normal risk this season than previous seasons? Obviously, factors like Saharan Dust and placement of the Bermuda High will matter as well and that’s harder to forecast this far out from the start of the season. But even compared to an average season, the risk to CONUS is greater with the 3 factors previously mentioned, correct?

No I think that is reasonable. The wording I used in the published forecast document (under "Analogue Years" at the top of page 3) is that whilst activity is forecast to be very high, this does not automatically mean a very destructive season is imminent. I used the examples of 1998 and 2010 to illustrate that very active years with a similar total ACE index can have very different impacts (1998 was devastating both in monetary and humanitarian terms whereas 2010 was much more benign with no U.S. landfalls, unprecedented for a season with >10 hurricanes); however, higher activity in total may make a high impact season more likely. If we can think of the appearance of favourable steering winds through the season as quasi-random, it is reasonable to think the more storms that form at sea, the greater the chance of a storm coinciding with those favourable steering winds and being steered towards land, and if it is going to come ashore, it is matter of luck whether it makes landfall as a weak tropical storm with low impacts or a devastating cat 4/5 hurricane.

It probably should be noted that whilst ACE index focuses entirely on storm duration and intensity, devastating impacts are not restricted to wind, in fact water is frequently the most destructive element in a hurricane (e.g. Mitch 1998).

[Teban54]

University of Arizona also has a high numbers forecast but lower ACE than other agencies and experts,

https://i.imgur.com/PlmTgc5.jpeg

https://has.arizona.edu/news/2024-hurri ... kyle-davis

156 ACE for a 21/11/5 season seems very low, and is basically akin to the end of October 2020 before Eta, Theta and Iota, when the season was at 27/12/5 with a similar ACE. Are they expecting a similar west-based season where the hurricanes and majors only reach such intensities close to land (or are otherwise short-lived in general)? I find it hard to believe when 2024 has an even more pronounced +AMO signature than 2020, and stuff like typhoon-induced TUTTs (which really hurt 2020's CV season) are impossible to forecast this early.

I wouldn’t be too surprised if we have another quantity-over-quality season (lower-than-expected but still high ACE). Maybe similar to 2020, the basin is so active that it ends up harming its overall quality in some way we won’t really know until the season is in full swing, like the WAM being on overdrive and pumping out so many broad waves. 2020, 2021, and 2023 all had lower-than-expected ACE compared to their NS totals, so perhaps 2024 follows suit.

I understand the temptation that "a lot of recent years were quantity-over-quality, so maybe it's the start of a new trend", which also showed up in the S2K seasonal poll multiple times. However, not sure if I agree. 2017, a landmark quality-heavy season, wasn't even that long ago and was almost immediately preceding what folks are calling the "quantity-over-quality period". (2017 was not devoid of the recently scrutinized "shorties" or short-lived tropical storms either: in fact, it set a record for the lowest ACE from the first 5 named storms, so those TSes were record-breakingly short.)

To my amateur eyes, there seems to be an inverse relationship between quantity and quality. Like you said, a huge number of storms can hurt overall quality - but the reverse had also happened in years like 2004 and 2017, neither of which seems very "active" in terms of TS counts. If anything, I think 2024 may be one of those years with better chances of it happening again, given the expected SSTA patterns focusing activity in the deep tropics. It makes sense from a theoretical standpoint, too: strong hurricanes typically cast storm-induced shear on nearby disturbances and waves, preventing them from developing into named storms.

This also reminds me of the last time people thought of something as the start of a new trend: In 2013-16, when many people thought the multi-decade +AMO period had ended (with 2011/12 sometimes brought into the mix), and even CSU was seriously considering if not endorsing the idea, and with these suspicions lasting well into 2018. I'll also note that the last undisputably active season before then was 2010, and the peak of such opinions was around 2017-18; the gap between 2010-2017 is similar to 2017-2024 where we are now.

[LarryWx]

University of Arizona also has a high numbers forecast but lower ACE than other agencies and experts,

https://i.imgur.com/PlmTgc5.jpeg

https://has.arizona.edu/news/2024-hurri ... kyle-davis

156 ACE for a 21/11/5 season seems very low, and is basically akin to the end of October 2020 before Eta, Theta and Iota, when the season was at 27/12/5 with a similar ACE. Are they expecting a similar west-based season where the hurricanes and majors only reach such intensities close to land (or are otherwise short-lived in general)? I find it hard to believe when 2024 has an even more pronounced +AMO signature than 2020, and stuff like typhoon-induced TUTTs (which really hurt 2020's CV season) are impossible to forecast this early.

2010, an analog for several forecasters and a strong Niña that immediately followed a strong El Nino had a whopping 19/12/5 along with an ACE of “only” 165. With that in mind, I don’t see a 21/11/5 being too out of line with ACE of 156. And the aforementioned 2020’s 180 ACE for a 30/14/7 season doesn’t make 21/11/5 156 seem out of line. 1916’s 15/10/5 and ACE of 144 is another that tells me a 21/11/5 156 isn’t far-fetched.

[ScottNAtlanta]

University of Arizona also has a high numbers forecast but lower ACE than other agencies and experts,

https://i.imgur.com/PlmTgc5.jpeg

https://has.arizona.edu/news/2024-hurri ... kyle-davis

156 ACE for a 21/11/5 season seems very low, and is basically akin to the end of October 2020 before Eta, Theta and Iota, when the season was at 27/12/5 with a similar ACE. Are they expecting a similar west-based season where the hurricanes and majors only reach such intensities close to land (or are otherwise short-lived in general)? I find it hard to believe when 2024 has an even more pronounced +AMO signature than 2020, and stuff like typhoon-induced TUTTs (which really hurt 2020's CV season) are impossible to forecast this early.

2010, an analog for several forecasters and a strong Niña that immediately followed a strong El Nino had a whopping 19/12/5 along with an ACE of “only” 165. With that in mind, I don’t see a 21/11/5 being too out of line with ACE of 156. And the aforementioned 2020’s 180 ACE for a 30/14/7 season doesn’t make 21/11/5 156 seem out of line. 1916’s 15/10/5 and ACE of 144 is another that tells me a 21/11/5 156 isn’t far-fetched.

Another thing about 2010 was that is was a very end weighted season. Alex didn't form until 25 June and the next hurricane wasn't until August 21st. Danielle, Earl, Igor and Julia were long lasting hurricanes that built up some ACE points, but there were also a lot of "trash" storms that year.

[Teban54]

All professional forecasters are calling for an above-average season. (Note this is the number of hurricanes, and not affected by short-lived tropical storms that people are becoming skeptical of recently.)
 https://x.com/philklotzbach/status/1778197929632915538

[CyclonicFury]

NC State University forecast is out

15-20 named storms

10-12 hurricanes

3-4 major hurricanes


https://news.ncsu.edu/2024/04/nc-state- ... ne-season/

The ratio of hurricanes to major hurricanes is a bit odd, also the named storm forecast is a bit lower than some other agencies.

[aspen]

NC State University forecast is out

15-20 named storms

10-12 hurricanes

3-4 major hurricanes


https://news.ncsu.edu/2024/04/nc-state- ... ne-season/

The ratio of hurricanes to major hurricanes is a bit odd, also the named storm forecast is a bit lower than some other agencies.

They’re forecasting an awfully high H:NS ratio too, which I don’t see happening. For a 15-20 NS range, I’d say 6-12 H is a more probable range, which makes more sense with their MH range too.

[cycloneye]

The Weather Channel is up with a very active season with 24/11/6.

https://weather.com/storms/hurricane/ne ... hOS_QV6WL4

[Category5Kaiju]

So...I think it's safe to assume at this point in time that there's a much greater chance than normal that we might have to use the aux list?

[cycloneye]

Here is the list of all so far.

[CyclonicFury]

Michael Mann at the University of Pennsylvania has released his forecast, and it's the highest-ever from a credible forecasting agency. He is predicting a whopping 33 (27-39) named storms!

https://penntoday.upenn.edu/news/2024-t ... prediction

[Category5Kaiju]

Michael Mann at the University of Pennsylvania has released his forecast, and it's the highest-ever from a credible forecasting agency. He is predicting a whopping 33 (27-39) named storms!

https://penntoday.upenn.edu/news/2024-t ... prediction

If that happens, I think the WMO and NHC are going to agree to make the Atlantic naming lists like the WPAC where they roll independent of year

[jasons2k]

It wouldn’t surprise. This season looks insane. I hope everyone stays safe.

[CyclonicFury]

Here's the full forecast from UPENN. Apparently it's based off a statistical model, which explains why it is so insanely high.
https://web.sas.upenn.edu/mannresearchg ... hurricane/

University of Pennsylvania EES scientists Dr. Michael E. Mann and Shannon Christiansen, and Penn State ESSC alumnus Dr. Michael Kozar have released their seasonal prediction for the 2024 North Atlantic hurricane season, which officially starts on 1 June and runs through 30 November.

The prediction is for 33.1 +/- 5.8 total named tropical cyclones, which corresponds to a range between 27 and 39 storms, with a best estimate of 33 named storms. This prediction was made using the statistical model of Kozar et al. (2012, see PDF here). This statistical model builds upon the past work of Sabbatelli and Mann (2007, see PDF here) by considering a larger number of climate predictors and including corrections for the historical undercount of events (see footnotes).

The assumptions behind this forecast are (a) the persistence of current North Atlantic Main Development Region (MDR) sea surface temperature (SST) anomalies (+1.9°C in April 2024 from NOAA’s Coral Reef Watch) throughout the 2024 hurricane season, (b) development of a moderate La Nina (Niño3.4 anomaly of -0.5°C) conditions in the equatorial Pacific in late Boreal summer and fall 2024 (ENSO forecasts here; we used mid-April 2023), and (c) climatological mean conditions for the North Atlantic Oscillation in Fall/Winter 2023-2024.

If neutral ENSO conditions (Niño3.4 anomaly of 0.0°C) take shape later in 2024, then the prediction will be lower: 30.5 +/- 5.5 storms (range of 25 – 36 storms, with a best guess of 31).

Using an alternative model that uses “relative” MDR SST (MDR SST with the average tropical mean SST subtracted) in place of MDR SST yields a lower prediction (19.9 +/- 4.5 total named storms). This alternative model also includes positive ENSO conditions.

[crownweather]

Here's the full forecast from UPENN. Apparently it's based off a statistical model, which explains why it is so insanely high.
https://web.sas.upenn.edu/mannresearchg ... hurricane/

University of Pennsylvania EES scientists Dr. Michael E. Mann and Shannon Christiansen, and Penn State ESSC alumnus Dr. Michael Kozar have released their seasonal prediction for the 2024 North Atlantic hurricane season, which officially starts on 1 June and runs through 30 November.

The prediction is for 33.1 +/- 5.8 total named tropical cyclones, which corresponds to a range between 27 and 39 storms, with a best estimate of 33 named storms. This prediction was made using the statistical model of Kozar et al. (2012, see PDF here). This statistical model builds upon the past work of Sabbatelli and Mann (2007, see PDF here) by considering a larger number of climate predictors and including corrections for the historical undercount of events (see footnotes).

The assumptions behind this forecast are (a) the persistence of current North Atlantic Main Development Region (MDR) sea surface temperature (SST) anomalies (+1.9°C in April 2024 from NOAA’s Coral Reef Watch) throughout the 2024 hurricane season, (b) development of a moderate La Nina (Niño3.4 anomaly of -0.5°C) conditions in the equatorial Pacific in late Boreal summer and fall 2024 (ENSO forecasts here; we used mid-April 2023), and (c) climatological mean conditions for the North Atlantic Oscillation in Fall/Winter 2023-2024.

If neutral ENSO conditions (Niño3.4 anomaly of 0.0°C) take shape later in 2024, then the prediction will be lower: 30.5 +/- 5.5 storms (range of 25 – 36 storms, with a best guess of 31).

Using an alternative model that uses “relative” MDR SST (MDR SST with the average tropical mean SST subtracted) in place of MDR SST yields a lower prediction (19.9 +/- 4.5 total named storms). This alternative model also includes positive ENSO conditions.

Interesting that almost all of the previous best guess forecasts were either pretty close to actual numbers or too low of a forecast. Exceptions were 2009, 2010, 2013 and 2016, but even these the forecast numbers were only 3-4 named storms too high.

[JetFuel_SE]

Here's the full forecast from UPENN. Apparently it's based off a statistical model, which explains why it is so insanely high.
https://web.sas.upenn.edu/mannresearchg ... hurricane/

University of Pennsylvania EES scientists Dr. Michael E. Mann and Shannon Christiansen, and Penn State ESSC alumnus Dr. Michael Kozar have released their seasonal prediction for the 2024 North Atlantic hurricane season, which officially starts on 1 June and runs through 30 November.

The prediction is for 33.1 +/- 5.8 total named tropical cyclones, which corresponds to a range between 27 and 39 storms, with a best estimate of 33 named storms. This prediction was made using the statistical model of Kozar et al. (2012, see PDF here). This statistical model builds upon the past work of Sabbatelli and Mann (2007, see PDF here) by considering a larger number of climate predictors and including corrections for the historical undercount of events (see footnotes).

The assumptions behind this forecast are (a) the persistence of current North Atlantic Main Development Region (MDR) sea surface temperature (SST) anomalies (+1.9°C in April 2024 from NOAA’s Coral Reef Watch) throughout the 2024 hurricane season, (b) development of a moderate La Nina (Niño3.4 anomaly of -0.5°C) conditions in the equatorial Pacific in late Boreal summer and fall 2024 (ENSO forecasts here; we used mid-April 2023), and (c) climatological mean conditions for the North Atlantic Oscillation in Fall/Winter 2023-2024.

If neutral ENSO conditions (Niño3.4 anomaly of 0.0°C) take shape later in 2024, then the prediction will be lower: 30.5 +/- 5.5 storms (range of 25 – 36 storms, with a best guess of 31).

Using an alternative model that uses “relative” MDR SST (MDR SST with the average tropical mean SST subtracted) in place of MDR SST yields a lower prediction (19.9 +/- 4.5 total named storms). This alternative model also includes positive ENSO conditions.

Interesting that almost all of the previous best guess forecasts were either pretty close to actual numbers or too low of a forecast. Exceptions were 2009, 2010, 2013 and 2016, but even these the forecast numbers were only 3-4 named storms too high.

Just to put things into perspective, 39 named storms would tie 1964's WPAC for the world record.

[MEANINGLESS_NUMBERS]

Here's the full forecast from UPENN. Apparently it's based off a statistical model, which explains why it is so insanely high.
https://web.sas.upenn.edu/mannresearchg ... hurricane/

University of Pennsylvania EES scientists Dr. Michael E. Mann and Shannon Christiansen, and Penn State ESSC alumnus Dr. Michael Kozar have released their seasonal prediction for the 2024 North Atlantic hurricane season, which officially starts on 1 June and runs through 30 November.

The prediction is for 33.1 +/- 5.8 total named tropical cyclones, which corresponds to a range between 27 and 39 storms, with a best estimate of 33 named storms. This prediction was made using the statistical model of Kozar et al. (2012, see PDF here). This statistical model builds upon the past work of Sabbatelli and Mann (2007, see PDF here) by considering a larger number of climate predictors and including corrections for the historical undercount of events (see footnotes).

The assumptions behind this forecast are (a) the persistence of current North Atlantic Main Development Region (MDR) sea surface temperature (SST) anomalies (+1.9°C in April 2024 from NOAA’s Coral Reef Watch) throughout the 2024 hurricane season, (b) development of a moderate La Nina (Niño3.4 anomaly of -0.5°C) conditions in the equatorial Pacific in late Boreal summer and fall 2024 (ENSO forecasts here; we used mid-April 2023), and (c) climatological mean conditions for the North Atlantic Oscillation in Fall/Winter 2023-2024.

If neutral ENSO conditions (Niño3.4 anomaly of 0.0°C) take shape later in 2024, then the prediction will be lower: 30.5 +/- 5.5 storms (range of 25 – 36 storms, with a best guess of 31).

Using an alternative model that uses “relative” MDR SST (MDR SST with the average tropical mean SST subtracted) in place of MDR SST yields a lower prediction (19.9 +/- 4.5 total named storms). This alternative model also includes positive ENSO conditions.

Interesting that almost all of the previous best guess forecasts were either pretty close to actual numbers or too low of a forecast. Exceptions were 2009, 2010, 2013 and 2016, but even these the forecast numbers were only 3-4 named storms too high.

Just to put things into perspective, 39 named storms would tie 1964's WPAC for the world record.

Beware of model predictions far outside the training dataset.