How strong will Helene get?

[MarioProtVI]

140mph/938mb was both the peak and landfalling intensity operationally. Post-season review has potential evidence for a bump up in windspeed as a drone that NOAA released just prior to landfall measured 158mph 10-second wind (not sure what that reduces to in 1-minute sustained winds).

Must be why NHC said that 120 kt might’ve been conservative.

[Category5Kaiju]

I didn't know where to put this but Helene continues the trend of an major increase in landfalling CAT4+ hurricanes since 2017. Certainly for the US but basin-wide too. Even during the historic 2003-2005 period it was just Charley. Then before that it was Andrew!

It almost seems like the Atlantic sacrificed major hits on the East Coast for major hits on the Gulf Coast.

At this point, it almost feels like we're going to see a Cat 3+ hit along the Gulf Coast in 2025 and 2026 and beyond. I'm basically expecting that it will happen.

[ljmac75]

140mph/938mb was both the peak and landfalling intensity operationally. Post-season review has potential evidence for a bump up in windspeed as a drone that NOAA released just prior to landfall measured 158mph 10-second wind (not sure what that reduces to in 1-minute sustained winds).

Is the full data on that available? I've only seen a screenshot of it.

[Travorum]

140mph/938mb was both the peak and landfalling intensity operationally. Post-season review has potential evidence for a bump up in windspeed as a drone that NOAA released just prior to landfall measured 158mph 10-second wind (not sure what that reduces to in 1-minute sustained winds).

Is the full data on that available? I've only seen a screenshot of it.

Unfortunately I haven't been able to find the full data, just the screenshot, although the data visualization appears to come from Andy Cox (@infovizard on socials) if anybody knows more about that:
 https://x.com/MichaelRLowry/status/1839513795661574492




The only other info I have is that this data likely came from the eastern eyewall, the TCPOD mentioned that they were dropping two unmanned drones to operate from 5000ft down to the surface, one in the SE eyewall and one in the E eyewall. The longitude in the screenshot seems to line up with the E eyewall, and that is where the strongest winds were found in the first pass of the last recon flight.

[InfernoFlameCat]

I didn't know where to put this but Helene continues the trend of an major increase in landfalling CAT4+ hurricanes since 2017. Certainly for the US but basin-wide too. Even during the historic 2003-2005 period it was just Charley. Then before that it was Andrew!

And Dennis as well.

[Teban54]

I didn't know where to put this but Helene continues the trend of an major increase in landfalling CAT4+ hurricanes since 2017. Certainly for the US but basin-wide too. Even during the historic 2003-2005 period it was just Charley. Then before that it was Andrew!

Here are the number of Cat 3 and Cat 4 CONUS landfalls compared in the 1995-2009 period vs. 2010-2024 period (so far). The two periods nicely divide up the current +AMO era evenly.

1995-2009:

• Cat 3+: 10 hurricanes (Opal, Fran, Bret 1999, Charley, Ivan, Jeanne, Dennis, Katrina, Rita, Wilma)
• Cat 4+: 1 hurricane (Charley)

2010-2024:

• Cat 3+: 9 hurricanes (Harvey, Irma, Michael, Laura, Zeta, Ida, Ian, Idalia, Helene)
• Cat 4+: 7 hurricanes (Harvey, Irma, Michael, Laura, Ida, Ian, Helene)
• Cat 5: 1 hurricane (Michael)

While the number of Cat 3 CONUS landfalls was similar in the two periods, there was indeed a major uptick in Cat 4 landfalls. In fact, during 2010-24, more hurricanes hit CONUS as Cat 4 than Cat 3!

Another trend is a significant increase in storms that strengthened all the way until landfall. In 1995-2009, 7 out of 10 MH landfalls were weakening at CONUS landfall, either slightly or significantly. But in 2010-2024, 7 out of 9 MH landfalls intensified, typically rapidly, until they were stopped by land.

Keep in mind, this is despite the latter period containing the very inactive years of 2013-15, and the textbook example 2010 with hyperactivity but sparing CONUS entirely. If 2010 had more west-based tracks typical of La Ninas, 2013 played out as forecast, and even the earlier parts of 2022 and 2024 were more active, the number may have been even higher.

A caveat is that the above calculations only consider wind speed, which is not the end-all (as we've seen with Helene). Many destructive Cat 1-2 or even TS landfalls were omitted. However, they're also roughly evenly distributed across the two periods (Bertha 1996, Georges, Floyd, Allison, Lili, Isabel, Frances, Gustav, Ike / Irene, Sandy, Matthew, Florence, Imelda, Isaias, Sally, Beryl).

[Teban54]

I didn't know where to put this but Helene continues the trend of an major increase in landfalling CAT4+ hurricanes since 2017. Certainly for the US but basin-wide too. Even during the historic 2003-2005 period it was just Charley. Then before that it was Andrew!

And Dennis as well.

Dennis weakened to a Cat 3 just before landfall.

[Cyclenall]

I didn't know where to put this but Helene continues the trend of an major increase in landfalling CAT4+ hurricanes since 2017. Certainly for the US but basin-wide too. Even during the historic 2003-2005 period it was just Charley. Then before that it was Andrew!

And Dennis as well.

For the US it was a CAT3 LF, its likely to me it was CAT4 for Cuba - I just refreshed on Dennis 2005 to see it was a highly devastating hurricane for Cuba overall, like Helene some spot got nearly 30 inches! From the NHC report " Reached 120 kt before Dennis made landfall near Punta Mangles Altos, Cuba near 1845 UTC that day." and "Cabo Cruz reported 116-kt sustained winds with a gust to 129 kt at 0200 UTC 8 July, with a minimum pressure of 956 mb at 0240 UTC just before the eye passed over the station. The anemometer was destroyed, and it is possible more extreme winds occurred."

Also didn't remember Dennis killed 88. I thought Irma's effects on Cuba were going to be gnarly yet heard little.

I didn't know where to put this but Helene continues the trend of an major increase in landfalling CAT4+ hurricanes since 2017. Certainly for the US but basin-wide too. Even during the historic 2003-2005 period it was just Charley. Then before that it was Andrew!

Here are the number of Cat 3 and Cat 4 CONUS landfalls compared in the 1995-2009 period vs. 2010-2024 period (so far). The two periods nicely divide up the current +AMO era evenly.

1995-2009:

• Cat 3+: 10 hurricanes (Opal, Fran, Bret 1999, Charley, Ivan, Jeanne, Dennis, Katrina, Rita, Wilma)
• Cat 4+: 1 hurricane (Charley)

2010-2024:

• Cat 3+: 9 hurricanes (Harvey, Irma, Michael, Laura, Zeta, Ida, Ian, Idalia, Helene)
• Cat 4+: 7 hurricanes (Harvey, Irma, Michael, Laura, Ida, Ian, Helene)
• Cat 5: 1 hurricane (Michael)

While the number of Cat 3 CONUS landfalls was similar in the two periods, there was indeed a major uptick in Cat 4 landfalls. In fact, during 2010-24, more hurricanes hit CONUS as Cat 4 than Cat 3!

Another trend is a significant increase in storms that strengthened all the way until landfall. In 1995-2009, 7 out of 10 MH landfalls were weakening at CONUS landfall, either slightly or significantly. But in 2010-2024, 7 out of 9 MH landfalls intensified, typically rapidly, until they were stopped by land.

Keep in mind, this is despite the latter period containing the very inactive years of 2013-15, and the textbook example 2010 with hyperactivity but sparing CONUS entirely. If 2010 had more west-based tracks typical of La Nina's, 2013 played out as forecast, and even the earlier parts of 2022 and 2024 were more active, the number may have been even higher.

A caveat is that the above calculations only consider wind speed, which is not the end-all (as we've seen with Helene). Many destructive Cat 1-2 or even TS landfalls were omitted. However, they're also roughly evenly distributed across the two periods (Floyd, Allison, Lili, Isabel, Frances, Ike / Irene, Sandy, Matthew, Florence, Imelda, Isaias, Sally, Beryl).

Thanks for the breakdown, its truly crazy there were more CAT4 LF than CAT3 ones during this period!