Capital Weather Gang look towards xmas

[usedtobe]

http://www.washingtonpost.com/blogs/capital-weather-gang/post/what-about-santa-the-elves-and-snow-assessing-the-odds-of-a-white-christmas/2011/12/13/gIQAJ5m3rO_blog.html#pagebreak

[Bob Chill]

Good writeup as always. Hard to argue with much but there are some things brewin in both the GFS and Euro right now that have my wennie glasses out of their case. For the exact reasons you pointed out in the article about the epo and crappy ao/nao I'm barely cautiously optimistic about the latest runs.

With all due respect though, I hope your article is wrong.

[Deck Pic]

Nice read Wes.

[usedtobe]

Nice read Wes.

I wish I had seen this morning's 12Z GEFS run as it now has 3 or 4 members showing storm potential. That's not an insignificant number. I'd still bet against it but wouldn't mind them continuing to have that look over the next several days. ThenI might have to do a update. At least it looks like we might be flipping back to a pna for awhile and that the positive epo look on the earlier progs may have been too aggressive. .

[WxUSAF]

A great, to-the-point, understable writeup as always Wes. I just hope the models continue to slowly trend in our favor so you can write a big mea culpa update in a week's time

[usedtobe]

A great, to-the-point, understable writeup as always Wes. I just hope the models continue to slowly trend in our favor so you can write a big mea culpa update in a week's time

I never saw this morning run so that's certainly possible. the epo looks different on a these progs than what had been forecast.

[nw baltimore wx]

I wish I had seen this morning's 12Z GEFS run as it now has 3 or 4 members showing storm potential. That's not an insignificant number. I'd still bet against it but wouldn't mind them continuing to have that look over the next several days. ThenI might have to do a update. At least it looks like we might be flipping back to a pna for awhile and that the positive epo look on the earlier progs may have been too aggressive. .

I hope it doesn't get old to hear, "Great write-up, Wes!"

Thanks.

[ThePhotoGuy]

Nice Job Wes!

It would be nice to have a snowy Christmas.

[Deck Pic]

I wish I had seen this morning's 12Z GEFS run as it now has 3 or 4 members showing storm potential. That's not an insignificant number. I'd still bet against it but wouldn't mind them continuing to have that look over the next several days. ThenI might have to do a update. At least it looks like we might be flipping back to a pna for awhile and that the positive epo look on the earlier progs may have been too aggressive. .

I think the weekend event is a dud....after that not sure....

[Ji]

Bob Ryan tweeted yesterday 0% chance of

White Christmas

[eurojosh]

There's something massively reassuring to weather lovers when forecasters give an absolute yes/no answer two weeks out. And I say that having grown up with Michael Fish's goof as the defining moment of weather forecasting for my generation...

http://en.wikipedia.org/wiki/Great_Storm_of_1987#Criticism_of_the_Met_Office

[usedtobe]

The article was edited fiercely and was printed in the print version of the post, for me a first.

[H2O]

The article was edited fiercely and was printed in the print version of the post, for me a first.

Congrats, Wes. It was a really nice article.

[mappy]

The article was edited fiercely and was printed in the print version of the post, for me a first.

Congrats, Wes!!! Another great article

[usedtobe]

Congrats, Wes. It was a really nice article.

Andy, thanks. It was neat getting an article in the print version, having it mention santa probably helped. I still don't see any snow during xmas week and think we probably will end the month with below normal snow as the models are forecasting the NAO to remain positive with last night's ens mean forecast of the ao again going very positive in the longer ranges.

[Bob Chill]

Wes, now that you're famous you might not want to be bothered with questions but...........I'm interested in what pushed the ao and nao to anomalously high readings starting in mid Nov. They both clearly exited their predominently negative run shortly after Irene but just bounced around in general neutral/pos territory until mid November. They both went sky high at the same time and have been stubborn as hell. Can't all be caused by strat temps can it? I don't know mechanics well enough to identify the cause but it is something I would like to be more prepared for when it happens again.

[Analog96]

Bob Ryan tweeted yesterday 0% chance of

White Christmas

That's pretty stupid if you ask me.

[usedtobe]

Wes, now that you're famous you might not want to be bothered with questions but...........I'm interested in what pushed the ao and nao to anomalously high readings starting in mid Nov. They both clearly exited their predominently negative run shortly after Irene but just bounced around in general neutral/pos territory until mid November. They both went sky high at the same time and have been stubborn as hell. Can't all be caused by strat temps can it? I don't know mechanics well enough to identify the cause but it is something I would like to be more prepared for when it happens again.

Bob, that's a good question and I don't know the answer to it. I doubt that it all has to do with the stratosphere but really don't know. Whatever it was, not many saw it coming. Once it did appear, it made the Dec forecast easier in the east.

[Ellinwood]

Bob Ryan tweeted yesterday 0% chance of

White Christmas

Learn to read.

With this pattern chances for "White Christmas" here in DC rapidly approaching 0%

Getting close to 0%... not saying it was in fact 0%.

[Bob Chill]

Bob, that's a good question and I don't know the answer to it. I doubt that it all has to do with the stratosphere but really don't know. Whatever it was, not many saw it coming. Once it did appear, it made the Dec forecast easier in the east.

It has me confused but that is easy to do. Seeing such a timed and anomalous switch leads me to believe that there is a fundameltal root cause and not some random chain of events. It's quite interesting to me either way. I'm just not smart enough to know where or what to reasearch to form an opinion.

At least I understand enough about a potential solution so I have something to follow as things work themselves out.

[sauss06]

Good write up Wes and Congrats!

[usedtobe]

I decided to do a update on the snow chances based primarily on the CPC D+11 prog from last night. That's probably a dubious method but is fun to look at and sometimes like in 2009-2010 can provide a pretty good feel for what might happen for a given pattern.

Here are the dates and how soon it snowed after the center mean date. Remember that the centered mean is dec 26 for the ensemble mean that matched these dates. Therefore, add the number of days to dec 26 to get a feel for how favorable it is to snow for the remainder of the month.

how many days after the mean before 1" inch was observed at DCA

Jan 2, 1964 +10

Jan 1, 1961 +18

Jan 12, 1999 -3 then no snow until March

Dec 28 1953 +13

Jan 8, 1990 March

Dec 14, 1991 A month later

Dec 31 2007 +18

Jan 9, 1967 +10

Jan 2, 1954 +18

Dec 26, 1997 no inch for season.

I didn't look for the snow for the season after that date. The pattern given by the means suggests no snow before Jan 1st but most suggest there will be snow in January. Of course the ensemble mean could have the pattern wrong.

[Deck Pic]

I decided to do a update on the snow chances based primarily on the CPC D+11 prog from last night. That's probably a dubious method but is fun to look at and sometimes like in 2009-2010 can provide a pretty good feel for what might happen for a given pattern.

Here are the dates and how soon it snowed after the center mean date. Remember that the centered mean is dec 26 for the ensemble mean that matched these dates. Therefore, add the number of days to dec 26 to get a feel for how favorable it is to snow for the remainder of the month.

how many days after the mean before 1" inch was observed at DCA

Jan 2, 1964 +10

Jan 1, 1961 +18

Jan 12, 1999 -3 then no snow until March

Dec 28 1953 +13

Jan 8, 1990 March

Dec 14, 1991 A month later

Dec 31 2007 +18

Jan 9, 1967 +10

Jan 2, 1954 +18

Dec 26, 1997 no inch for season.

I didn't look for the snow for the season after that date. The pattern given by the means suggests no snow before Jan 1st but most suggest there will be snow in January. Of course the ensemble mean could have the pattern wrong.

kind of makes sense based on the recent ongoing discussions and the state of the pattern....so maybe 2nd week of January could be a very loose target for our 1st legit event...that would be nice....

[dallen7908]

Hi "used to be".

Could you explain what you did again. I think it was something like this ...

The 10 years listed are the 10 years in which the actual 500 hPa pattern on December 25 best matches the forecast 500 hPa pattern for Dec 25 of this year. You then looked at how many days past that date it first snowed an inch. Is that (at least partially) correct?

[usedtobe]

Hi "used to be".

Could you explain what you did again. I think it was something like this ...

The 10 years listed are the 10 years in which the actual 500 hPa pattern on December 25 best matches the forecast 500 hPa pattern for Dec 25 of this year. You then looked at how many days past that date it first snowed an inch. Is that (at least partially) correct?

but it was based on Dec 26 and it was the mean pattern for a 5-day period centered on that day. The CPC site then picks the best analogs based strictly on centered 5 -day mean patterns. Then I went fro the day of the centered mean and calculated how many days from the analog centered mean was the first day that 1" of snow was observed. D+10 means it was 10 days after the centered mean date of the analog.

Then I took the +10, +18, etc and applied them to the Dec 26 period to get an idea how long from that date one might expect snow. Essentially, all the dates put you into Jan.

[Bob Chill]

I don't think that is dubious at all Wes. It's a pretty creative way to crunch some #'s. Can you link me to the cpc site where you were able to pull the analogs? I would be interested in kicking around a few ideas.

[usedtobe]

I don't think that is dubious at all Wes. It's a pretty creative way to crunch some #'s. Can you link me to the cpc site where you were able to pull the analogs? I would be interested in kicking around a few ideas.

Bob, here is the site, if only does it for the day of the forecast. Look under D+11 at analog.

http://www.cpc.ncep.noaa.gov/products/predictions/short_range/tools/model_guidance.php?dayin=11

[usedtobe]

kind of makes sense based on the recent ongoing discussions and the state of the pattern....so maybe 2nd week of January could be a very loose target for our 1st legit event...that would be nice....

matt or maybe late in the 1st week, I'd guess that the second or third might be more realistic but that's a big, big WAG.

[Deck Pic]

matt or maybe late in the 1st week, I'd guess that the second or third might be more realistic but that's a big, big WAG.

for grins...looks like the roll forward 2 weeks later pattern is pretty standard NIna in the PAC....so not good....the Atlantic side looks better...there are some positive height anomalies where we'd want them but it is still a pretty bad pattern....vortex southeast of GReenland is in a bad spot...big ridge over Europe. pos heigt anomaly over the maritimes and east coast..but closer to perhaps a -NAO look than before...there is no skill here, but I though it would be intersting to take a look

current pattern as of 12/12

day 11 ensemble analog pattern

rolling the analogs ahead 2 weeks

[usedtobe]

for grins...looks like the roll forward 2 weeks later pattern is pretty standard NIna in the PAC....so not good....the Atlantic side looks better...there are some positive height anomalies where we'd want them but it is still a pretty bad pattern....vortex southeast of GReenland is in a bad spot...big ridge over Europe. pos heigt anomaly over the maritimes and east coast..but closer to perhaps a -NAO look than before...there is no skill here, but I though it would be intersting to take a look

current pattern as of 12/12

day 11 ensemble analog pattern

rolling the analogs ahead 2 weeks

I agree, it is kind of fun rolling them forward. Like you I doubt there is much skill but seems like no matter what we look at the pattern remains less than stellar.