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If Tammy becomes a hurricane and leaves in 7 days... then the base probability of another 2 hurricanes is about ~21%.

Right now only half of the models for Late guidance 18Z show it becoming a hurricane, so conditioning on the 21% above by 50% leaves ~10% which is near the market probability. OFCL doesn't show a hurricane in 5 days (and at best I can assign 47% probability that the forecast is off by -5kt or more at 5 days which is still less than 50% above); but if OFCL does update to show a hurricane I will sell some of NO shares.

NHC now forecasting Tammy to be a hurricane. Late guidance shows most of the models of it becoming a hurricane, so I assign a probability of Hurricane Tammy being #7 as 67%, pushing up the question to ~14%

Now NHC is forecasting Tammy to become a hurricane in 48h (Manifold has it at 85%, I put it at least 75%)), so I am betting with some small YES bets with the probability as 17%.

NO, The likelihood of having more than 8 hurricanes in the Atlantic is low, given the advanced stage of the hurricane season and data from the previous year. The National Oceanic and Atmospheric Administration (NOAA) predicts a maximum of 11 hurricanes for the current season. NOAA's outlook for the 2023 season anticipates 14-21 named storms, 6-11 of which could become hurricanes, with 2-5 potentially reaching major hurricane status. NOAA expresses 70% confidence in these predictions. The historical data from last year also supports the current assessment, making the probability of more than 8 hurricanes in the Atlantic less likely (NOAA, 2023, August 10; 2022, Atlantic Hurricane Season).

(2023, August 10). National Oceanic and Atmospheric Administration.

Also take a look here for last year results (2022, Atlantic Hurricane Season. (n.d.). )

Still at 6 hurricanes. Based on my own workbook, the cumulative probability is ~ 34.4% for at least 2 more hurricanes (this only counts storms originating in NA basin, and doesn't consider whether the storm crosses basins or which basin it strengthens in). Edit: This actually counts if there was a hurricane present during the time frame (so it's possible the strengthening to hurricane happened prior, in which case it might be over-estimating the probabilities):

@parhizj blah blah

@will58c3 blah blah? 😦 The market should be much lower... 34% for 8 hurricanes, but for the question it asks for 9 hurricanes... ("more than 8") so it should be closer to 11% for base rates...

@parhizj sry. North Atlantic basin as opposed to Pacific, right? Or opposed to Gulf or Caribbean?

@will58c3 Question title includes "Atlantic".

It doesn't seem to specify North or South but South are very rare.

@ChristopherRandles Atlantic hurricanes include Carribean and Gulf. I was wondering if Atlantic basin means something different (I don't think it does).

@will58c3 No that’s the intended meaning—Atlantic season broadly construed.

@will58c3 Without putting more words in the mouth of the question creator, in best tracks they mark Gulf of Mexico as a sub basin of the Atlantic so I’m assuming that includes the Gulf of Mexico

@parhizj I was just referring to your comment not the title of the market,

@will58c3 Oh, in that case specifically applies to that dataset where Gulf of Mexico is a sub basin, so it is included.

@parhizj yeah i basically share your reaosning and statistics (w/ bit different methodology) 👍 obv there's the africa disturbance now.

At 6 hurricanes just past the peak of the season, and need three more… there is one disturbance that looked like it would become a hurricane but latest GFS from 00Z doesn’t show that anymore (latest NHC outlook from 8AM EDT still has it at 70% though) through the start of October, leaving October and November for 3 more hurricanes. ECMWF extended ACE forecast shows higher than normal energy the first week of October (2nd-9th), and lower than normal energy approaching the middle of October (9th -16th). With El Niño (through JJA at 1.1 and forecast to likely (65%) be above 1.5 for SON) we may see a less active hurricane season going through November.

https://x.com/philklotzbach/status/1703735688364204109?s=20

Of these three years that have the same number of hurricanes so far, one had 8 or less, and two had more than 8 putting the probability using these analogs at 66%. Note that only 2012 of those three years had hurricanes develop in October, so perhaps it should be a bit less?

The CSU forecast from Aug. 3 also had 9 hurricanes forecast.

Given all this I think the market probability of less than 66% is justified at the moment so I won’t bet for now.

Unless I'm missing something those two markets should match since there were 8 hurricanes last year. Potential for arbitrage.
https://manifold.markets/octothorpe/will-there-be-more-hurricanes-in-th?r=Tmljb0RlbG9u

Will there be more hurricanes in the 2023 Atlantic Hurricane season than in the 2022 Atlantic Hurricane season?

82% chance. This question covers the Atlantic hurricane season beginning on June 1, 2023, and ends on November 30, 2023, and resolves YES if there are more than eight hurricanes (the number in 2022).

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Edit: nevermind, misread.