question on ace

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JonathanBelles
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question on ace

#1 Postby JonathanBelles » Thu Jun 15, 2006 10:22 pm

what does the ∑ represent in the ace formula?
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#2 Postby wxmann_91 » Thu Jun 15, 2006 10:26 pm

Greek letter sigma, meaning sum.
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#3 Postby JonathanBelles » Thu Jun 15, 2006 10:30 pm

so for alberto=60*60/10000=3600/10000=.36ACE=that doesnt make sense (thats why i wondered what the ∑ was)

HELP
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#4 Postby skufful » Thu Jun 15, 2006 10:31 pm

Yes, it does mean sum. If I remember my math correctly, there is normally a numner on top and bottom. The answer is the sum of the series of numbers from the number on top to the number on the bottom. What is the equation anyway?
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#5 Postby JonathanBelles » Thu Jun 15, 2006 10:33 pm

it's ∑(max kts)squared over 10^4=ACE i believe
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#6 Postby wxmann_91 » Thu Jun 15, 2006 10:36 pm

I believe this is the formula: (from Wikipedia):

Image



Note (source from Wiki as well):
The ACE is calculated by summing the squares of the estimated maximum sustained velocity of every active tropical storm (wind speed 35 knots or higher), at six-hour intervals. The numbers are usually divided by 10,000 to make them more manageable. The unit of ACE is 104 kt2, and for use as an index the unit is assumed. If any storms of a season happen to cross years, the storm's ACE counts for the previous year.
Last edited by wxmann_91 on Thu Jun 15, 2006 10:37 pm, edited 1 time in total.
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#7 Postby JonathanBelles » Thu Jun 15, 2006 10:37 pm

yup im missed that
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#8 Postby LaPlaceFF » Fri Jun 16, 2006 1:49 am

ACE? I have a full house 10's and 2's....
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#9 Postby senorpepr » Fri Jun 16, 2006 6:23 am

Yes, ∑ is the sum of each six-hourly wind speed, in knots, squared.

For Alberto...

40² = 1600
40² = 1600
40² = 1600
45² = 2025
60² = 3600
60² = 3600
60² = 3600
55² = 3025
45² = 2025
35² = 1225
35² = 1225

The ∑ of each of Alberto's six-hourly wind speed, in knots, squared, is 25125. Since ACE is shown in scientific notation (10^4) for simplicity, the ACE for Alberto is 2.5125.
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#10 Postby KWT » Fri Jun 16, 2006 6:36 am

Also there is the HPD that is quite useful which works in the same way as the ACe system but only for hurricanes.
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