How many Category 5 Atlantic hurricanes will make US landfall during 2023 Atlantic Hurricane season?
resolved Dec 1
3 or more

We're a little over a month away from June 1, and predictions have been published by the Colorado State University Tropical Meteorology Project team.

Their forecast predicts a slightly-below-average season, with 13 named storms, six which will achieve hurricane strength, and two reaching Category 3 or higher (major hurricanes).

There have been four storms to reach Category 5 (Michael - 2018, Dorian - 2019, Lorenzo - 2019, Ian - 2022) within the past five years, and only three of those reached the US mainland.

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GFS 00z shows a possible candidate in starting to develop in a ~week. ECMWF 00z forecast does not show development.

becoming a major hurricane

and hitting 16 days from now.

This is very speculative though this far out

If it reaches category 5 but then weakens and landfalls as a category 1, does that count? What if landfalls as tropical storm or depression?

@ChristopherRandles Good point. @LBeesley do you want to clarify this and also to say what sources you will use to resolve. There are some immediate sources (NHC advisories/discussions) and longer-term sources (preliminary best-tracks, best tracks) that might provide different data.

@ChristopherRandles I’ve been pondering this, and considering the rarity that a storm reaches Category 5 and makes landfall as a Cat 5, I’ll accept any landfall for a storm that reaches that level of strength even if it doesn’t maintain at the time of landfall. That opens the betting up to the Irmas, Katrinas, and Idas of hurricane seasons past.

I rely solely on the NHC website for my hurricane tracking data and updates. HTTPS://

@LBeesley This also means we could potentially have our first tomorrow if Idalia does what so many September storms in the gulf have done before

bought Ṁ5 of 1

@LBeesley Ian was reclassified as a 5 last spring, but it's still pretty rare.

bought Ṁ50 of 0

@LBeesley Idalia forecast to strengthen from 65kt to 105kt. 140kt would be more than double the forecast. None of these models in the intensity forecast suggest that.

@ChristopherRandles Yeah, none of the models show a cat 5 and it is moving fast, but it could become a cat 4. New advisory has 110kt, but keep in mind this is before landfall and it could increase between then and the forecast points since they are 6 hours apart and the intermediate advisories are 3h apart.

bought Ṁ5 of 1

@parhizj "even if it doesn’t maintain at the time of landfall."

so hurricane / tropical storm / tropical depression all count?

Post tropical? Subtropical?

sold Ṁ56 of 0

@ChristopherRandles Wait Lee could still count??

@LBeesley I previously took your meaning to be a cat 5 immediately before landfall as you said "even if it doesn’t maintain at the time of landfall" made me think that way ( in otherwords (the last NHC advisory prior to landfall would be a cat 5 but the advisory when it is inland would be a cat 4 or weaker)) ... but it would help if you could clarify whether a cat 5 hurricane days before landfall that weakened well ahead of landfall like with Lee would count so long as it makes landfall in the US (even as a tropical storm)

Most of the time Lee has been landfalling Canada or not at all. Now it looks more like a cat 5 hurricane landfalling Maine! (as weak hurricane or TS). I assumed at least a hurricane counted from your comments but perhaps I was wrong and could well be outnumbered by others making different interpretation.

@parhizj Lee making landfall on mainland US would count. I know it hasn’t been Cat 5 since last week, but considering its history of attaining that strength, it would be the first of this season if the storm makes landfall in the Northeastern US.

@LBeesley Is there any lower bound in strength needed? eg even as tropical depression or remnant low would count?

@ChristopherRandles Imo the storm should still hold shape and be recognized as the named storm system at the time of landfall. I’m setting lower bound at tropical depression, because from my experience, “post-tropical-storm” or “remnants of” is recognizing that the system is an array of thunderstorms that don’t pose the threat that the fully formed cyclone would even at depression strength.

@NicoDelon seems that way. A normal reading of this market's criteria is not at all how it is ultimately being interpreted now. I guess if Maine gets hit, bye bye Mana.

bought Ṁ20 of 1

@AlQuinn I still think the question is still some what fair even though the criteria didn't meet my assumptions since the uncertainty in the hurricane track&intensity error is far greater than the uncertainty I had yesterday in the market resolution criteria.

@AlQuinn thankfully the other cat 5 markets make strength at landfall a condition.

@NicoDelon True. In this case, by analogy, it feels as if a "will Minneapolis, MN get hit by a M7+ earthquake" is resolved YES because seismic waves from an earthquake with epicenter in Alaska were detected in Minnesota.

@AlQuinn You spent 30 mana and can bail out at a profit. But yes, I get what you are saying, it does feel very different to most readings of the title.

@ChristopherRandles yeah I don't care about 3k fake money, let alone 30 (I'm just here because getting better at prediction takes practice) but one of the problems (and virtues) on MM is the ease of market creation, which leads to low-effort markets that are misleading. It's one thing to miss a bunch of edge-cases when setting up a question, but abusing language so that Maine being hit by a cat 1 hurricane is "a category 5 making landfall on the US" is something else... No offense to Spongepad who is a decent chap and who I judge is also not doing anything in bad faith; I'm just a little irritable today, perhaps.

@LBeesley Another question: what definition of landfall do you operate with? Lee will be very large. Technically, for now it seems likely to be making landfall in Canada, not the US, but tropical storm force winds may be experienced in the US and parts of the storm may go over the US. I take it that's not sufficient to resolve YES.