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October 2012 Forecast Contest, Temperatures


Mallow

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  • 2 weeks later...

After 27 days ...

DCA .. +2.5

NYC .. +1.3

BOS .. +2.1

Probably more downward pressure on DCA than BOS from now to end of month, as DCA will be into cold advection much earlier and also more of it ... in fact BOS could gain slightly from current value with 2-3 days more in the +5 zone so that my estimates for end of month are DCA +1.8, NYC +1.4 and BOS +2.3. I also anticipate that we may be dealing with a few days of estimated values and waiting for final numbers especially NYC.

The closest set of forecasts that I can see from a quick look through them would be the first one from goobagooba and (s)he would be even closer if I have underestimated cooling at DCA. ChicagoWx and C-C-GA have similar tied for second place type efforts (I think) with DCA and NYC nailed but BOS too low so they could close in on goobagooba if BOS falls off rather than rising a bit. Lots of rather similar scores likely (again, my opinion) in the 150-200 range with a cluster of guesses that are generally too high or too low by about a degree each station..

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Goobagooba, I guessed right then (s)he on weather forums is almost always a he. I am also a he but that would probably be a bit less obscured by my username.

Uncle W, can you elaborate on your point about the smoothed data?

I'm guessing Uncle is differentiating between the finalized normals and what you would get by just using the raw actuals.

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I'm guessing Uncle is differentiating between the finalized normals and what you would get by just using the raw actuals.

yes that's what I mean...You're using actuals and comparing it to finalized normals which in NYC's case is about 0.4 below the actual for each month...

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For DCA, the 1981-2010 normals average only 0.1 degree below the 1981-2010 average temperatures for each month.

-0.1 I can live with but it still isn't the actual average...I should have said -0.4 for most months...An annual temperature +0.4 is a significant number above average...I'm a numbers guy and this drives me nuts...

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This is only a problem if Mallow uses the same provisional data, and if the provisional data really don't factor in the rounding errors.

I have no idea whether either of these issues affect the contest or not. I understand what you're saying about rounded means but are you sure the climate data are allowing this error to accumulate, or are they posting a running anomaly based on the final methodology? I have never checked it out, have you actually seen these numbers reposted at different values later? If so, how long after the end of the month are the final numbers available?

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Actually, the problem seems to be solved by the NWS. They seem to be keeping track of adjusted daily means by dividing the total of max and min by 2 x n (n = number of days). This eliminates the rounding error. I checked NYC which is still showing +1.1 as the anomaly. The sum of daily anomalies was listed as 44 which would have implied a monthly anomaly of +1.4 but with 17 days having a rounded up daily mean, that reduces the actual sum to 35.5 (44-8.5) which divided by 31 gives 1.1 as reported.

So when you look at the tables during the month and see days that you think are pushing the average up by rounding, the running anomaly is adjusting this out of play, I think. For example, for the same station after 3 days in November, the total of three days is -15 (daily anomalies) but the month is given as -5.3 and there have been two out of three days rounded already, that would imply the total is actually -16 rather than -15 (hence -5.3).

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Actually, the problem seems to be solved by the NWS. They seem to be keeping track of adjusted daily means by dividing the total of max and min by 2 x n (n = number of days). This eliminates the rounding error. I checked NYC which is still showing +1.1 as the anomaly. The sum of daily anomalies was listed as 44 which would have implied a monthly anomaly of +1.4 but with 17 days having a rounded up daily mean, that reduces the actual sum to 35.5 (44-8.5) which divided by 31 gives 1.1 as reported.

So when you look at the tables during the month and see days that you think are pushing the average up by rounding, the running anomaly is adjusting this out of play, I think. For example, for the same station after 3 days in November, the total of three days is -15 (daily anomalies) but the month is given as -5.3 and there have been two out of three days rounded already, that would imply the total is actually -16 rather than -15 (hence -5.3).

October 2012 ended up averaging 58.0 in NYC...This is an average of the 31 days max/min temperatures...From 1981-2010 the 30 Octobers that were compiled the same averaged 57.3...The new monthly normal 1981-2010 is 56.9 smoothed...It's almost like comparing apples and oranges...As far as the contest goes it means little...

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  • 4 weeks later...

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