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New D.C. area norms (1981-2010) discussion


Ian

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The numbers of 90+ days actually decreased a bit from the 71-2000 avg as per my count.

http://www.ianliving...torical-period/

Cup half empty or full on DCA snow avg? 14.5" -- at least it will be a little easier to reach?

DCA: 14.5"

IAD: 22.0"

BWI: 20.2"

I-95 outside of DCA/BWI corridor:

RIC: 10.3"

PHL: 22.4"

NYC: 25.1"

BOS: 43.8"

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DCA: 14.5"

IAD: 22.0"

BWI: 20.2"

I think that was an increase in snowfall at BWI? Surprised by no 90F avg high days.

was

DCA: 15.2"

IAD: 18.2"

BWI: 21.2"

would be interesting to see change up and down the coast

DCA only has one day with a raw probability over 50% at 90+.. most other high ones are mid-40s or less.

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was

DCA: 15.2"

IAD: 18.2"

BWI: 21.2"

would be interesting to see change up and down the coast

DCA only has one day with a raw probability over 50% at 90+.. most other high ones are mid-40s or less.

Thanks. Thought BWI was <20".

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Are all of the years included in the averages, or are the outliers thrown out?

I guess I should edit this post. I am referring to precip, not temps, and mainly snowfall.

These codes tell you

C = complete (all 30 years used)

S = standard (no more than 5 years missing and no more than 3 consecutive

years missing among the sufficiently complete years)

R = representative (observed record utilized incomplete, but value was scaled

or based on filled values to be representative of the full period of record)

P = provisional (at least 10 years used, but not sufficiently complete to be

labeled as standard or representative). Also used for parameter values on

February 29 as well as for interpolated daily precipitation, snowfall, and

snow depth percentiles.

Q = quasi-normal (at least 2 years per month, but not sufficiently complete to

be labeled as provisional or any other higher flag code. The associated

value was computed using a pseudonormals approach or derived from monthly

Looks like rain monthly normals are all complete (which is good since I ran with that earlier this yr, tho May comes into question IMO: http://www.washingto...RU7mF_blog.html).. snow all the key months are all 30 yrs except Feb which has an S -- perhaps to remove 2010s skewing? Mar is S as well, maybe overall variability of that mo. Daily rain is all complete record, snow is pretty mixed it seems. January seems to have the most C on the whole... maybe they need a C month to base the rest off of? I dunno, not a statistician. ;)

Daunting -- so much to examine just at one location.

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was

DCA: 15.2"

IAD: 18.2"

BWI: 21.2"

would be interesting to see change up and down the coast

DCA only has one day with a raw probability over 50% at 90+.. most other high ones are mid-40s or less.

I think you made a typo between BWI and IAD. Because BWI's old average was 18.2 and you have that under IAD.

http://www.erh.noaa.gov/lwx/climate/bwi/bwisnow.txt

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Awhile back I did a spreadsheet using all the BWI snowfall data from 1883-2011 (I'm a stat geek and was just curious). The results were:

Average: 21.86 inches

Median: 19.6 inches

Mode 17.3 inches

So I think the new snow total is a better representation of this area historically. The old average of 18.2 was too low IMHO.

Though at some point in that data set they used Baltimore before BWI I think (even though the page is called BWI snow) so it might be biased.

:snowman:

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Plus, it looks like RIC was 16.4" for 1961-90. That's quite a decline.

2009-10 really saved it from becoming a single digit site.

I thought for sure RIC was outside double digit territory - no kidding 2010 saved them. It says something that so many surrounding stations managed a modest increase and Richmond fell so much. Like Ian said, should make it a lot easier to be above average the next decade or so.

I think the 100 year average is still somewhere close to 14". But then how many years are average for east coast cities anyway?

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the snow "norms" mean nothing to me...I will never pay any attention to them....I guess it is good to have a number for the public and media that lies between the average and median.....I will never use it....

the temps norms may make a little more sense....though a smoothed monthly figure based on daily norms is also silly to use but we really have no choice in terms of departures....the old temp norms in the winter were way too cold....January is the biggest change at 1.1 degrees warmer than 1971-2000......these new norms will change winter outlooks a bit and folks will need to familiarize themselves with them.....

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the snow "norms" mean nothing to me...I will never pay any attention to them....I guess it is good to have a number for the public and media that lies between the average and median.....I will never use it....

the temps norms may make a little more sense....though a smoothed monthly figure based on daily norms is also silly to use but we really have no choice in terms of departures....the old temp norms in the winter were way too cold....January is the biggest change at 1.1 degrees warmer than 1971-2000......these new norms will change winter outlooks a bit and folks will need to familiarize themselves with them.....

only at DCA can we remove a decade where we averaged 15.0" and add a decade where we averaged 16.8" and LOSE 0.7" off our norm.....yay!!

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only at DCA can we remove a decade where we averaged 15.0" and add a decade where we averaged 16.8" and LOSE 0.7" off our norm.....yay!!

I didn't bother to check, but were the '71-'00 normals smoothed for annual snowfall?

I just checked BOS, and theirs is "wrong" too but only by a negligible amount. The new normal is 43.8" but the actual is 44.0".It seems weird that DCA would be an entire inch off.

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I didn't bother to check, but were the '71-'00 normals smoothed for annual snowfall?

I just checked BOS, and theirs is "wrong" too but only by a negligible amount. The new normal is 43.8" but the actual is 44.0".It seems weird that DCA would be an entire inch off.

yes...it was smoothed up from 14.8" to 15.2"

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I thought for sure RIC was outside double digit territory - no kidding 2010 saved them. It says something that so many surrounding stations managed a modest increase and Richmond fell so much. Like Ian said, should make it a lot easier to be above average the next decade or so.

I think the 100 year average is still somewhere close to 14". But then how many years are average for east coast cities anyway?

RIC never deserved to be a single digit site despite the 81-10 average. There was one 30 year period, I think 1921-50, where the average was 10.6". I still consider 13" to be the rule of thumb for an average season. You can only hope the 2010s continue to deliver, however.

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here's the change in daily temp norms at dc with rounded figures since that's all that's on lwx:

post-1615-0-11502300-1310078155.gif

Interesting that low temps have increased far more than high temps. Obviously looking at averages is a dangerous game, but I can't help but wonder to what extent such an increase can be attributed to increased development and increased UHI effect as a result. More likely it is multiple causes, and with such a limited data set it could even be random chance - but it's still fun to speculate!

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Thanks Ian and Jason for these great links, I have been studying the data most of today,and passing it on to a few of my observer friends whose new normals they now know. They greatly appreciate it!

Kevin

DCA:

http://www1.ncdc.noa...743.normals.txt

IAD:

http://www1.ncdc.noa...738.normals.txt

BWI:

http://www1.ncdc.noa...721.normals.txt

List of stations (the USWXXXXXX code at the end)

http://www1.ncdc.noa...allstations.txt

Thx to Jason Samenow for the links..

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