Accumulated Cyclone Energy

[Cookie]

can anyone explain to me how it works and how the numbers that are shown in the ACE thread are arrived at?

thanks

[RL3AO]

Its a pretty simple formula. You take the wind speed in knots and square it then divide by 10,000.

There are a couple rules though. You don't count tropical depressions (so you start when its 35kts or greater). You don't count time as a subtropical storm. You also don't count special advisories.

So if the storm is 40kts.

40 * 40 = 1600
1600/10000 = 0.1600

So the ace for that advisory is 0.1600

If the next advisory is 45kts
45 *45 = 2025
2025/10000 = 0.2025

The storm total would be 0.1600 + 0.2025 = 0.3625

If it weakened to a 30kt tropical depression, the ace would be 0 since its not a storm or hurricane.

[Cookie]

ahh thanks for taking the time to explain look very complicated in the other thread but makes me more sense now!

[senorpepr]

Now here are a couple extra caveats...

Initially, ACE is calculated based on it's cardinal advisories. As mentioned before, 35 kt or greater qualifies it for ACE, as long as it's purely tropical (subtropical doesn't count). 03, 09Z, 15Z, and 21Z advisory packages are used... special advisories are ignored in the count.

However, after the storm is said and done (usually after a post analysis), the 00Z, 06Z, 12Z, and 18Z positions from the best track are used to calculate ACE... using the same constraints as above.

Another measure that is calculate is Hurricane Destructive Potential or HDP. It's calculated the same was as ACE, expect only when wind speeds are at or exceed 65 kt (hurricane-force).

[Cookie]

ok thanks mate!