Activity is measured in accumulated cyclone energy (ACE). If a storm is active across two distinct months, I’ll do my best to estimate the breakdown of ACE into the two months. I may ask Claude Opus 4.7 for assistance in resolving the question if needed.
Source for resolution: https://tropical.atmos.colostate.edu/Realtime/index.php?loc=northatlantic
In the unlikely case of a tie, I will use the number of storms in a month. In case of an even unlikelier subsequent tie, I will use the number of active days in a month. I am confident no further ties are likely.
Update 2026-10-10 (PST) (AI summary of creator comment): Monthly cut-offs for ACE calculations will use UTC time across the board.
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@MachiNi You have given the resolution source. There are 2 possible methods from this page:
EFGH all stated to be in Sept per 'TC active dates' 0.8+3.8+1.3+1.3 = 7.2
Isaias in Oct 7.2
The alternative is to use graph values
31 Aug 3.7
30 Sep 10.8
Oct so far 18.0
So this gives 7.1 and 7.2 rather than both 7.2
This could be rounding differences?
Perhaps more likely is that it is regarding a time zone date discrepancy regarding Edouard first counting advisory:
INIT 01/0300Z 28.6N 91.8W 35 KT 40 MPH
This is in September UTC but in August local time. The graph method appears to use UTC time and this gives different values. However your description seems to hints at estimating split of a storm ACE between months which causes need to know the time zone for monthly cut-offs.
If there is another Tropical storm in October it won't matter. In case there isn't, then will you use UTC time or some local time for the monthly cut-offs?
@MachiNi Sorry I think I stated part of that the wrong way around. The TC Active dates column appears to use UTC time while the graph method uses a local time.
Anyway it appears you are saying that September and October are both on 7.2 and so with no more activity it goes to number of storms rather than calculating the ACE for the two months to more decimal places to see if that gives a decision before resorting to number of storms to decide the issue.