13 replies to this topic

[wntrstrmwrng]

Hi--

I know it is only July but as we get closer to August I can't help but think about the coming fall and winter...  Plus yesterday I was in my shed to get my lawn mower and couldn't help but notice my new snowblower that I bought last year and was not able to use :-)

In a post about La Nina Stormchase has posted:

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The chances of this La Nina episode being moderate or strong are diminishing by the day. That's good news for winter fans but still only one piece of the puzzle. As Ice mentioned, the NAO is a huge player in our pattern during the cold season. Those polar indices generally run in 3 month cycles, so the best case scenario would be for the +NAO to hold through early Nov, then flip negative for early-mid winter. We are trending downward in terms of the NAO decadal cycle -- predominately negative phase late 40's-late 70's, positive late 70s-late 90's. Now we're head down again.

[img width=596 height=432]http://www.wxrisk.co..._timeseries.gif[/img]

I have a question on this as well as a few others:

1) I see that we are hoping that NAO stays postive through early NOVEMBER and then flips to NEGATIVE but I also see that we are declining when you look at it over a yearly period -

What does that mean for us????

2) We've now had two consecutive winters (at least here in central jersey) where we have not had much snow.  Last year was horrible and the year before gave us one big storm towards the end of the year but that was about it :-( 

When we go through cycles like this how long do they usually last?  Are we even in this type of "no/little snow" cycle or does it just feel that way to me?

I'd appreciate any comments...

Thanks!

[devilsfan0405]

96-97 through 98-99 were bad seasons in terms of snowfall (97-98 because of a ridiculously strong El Nino), so there have been 3-year cycles where we didn't get much.

NYC #'s

96-97  10"

97-98  5.5"

98-99  15"

[jfar57]

ftp://ftp.wcc.nrcs.usda.gov/downloads/cen...e3120060918.pdf

interesting chart in here plotting annual snowfall totals for Central Park between 1910 and 2004. 

There are 4 clusters of  at least 6 consecutive winters of below avg snowfall.  (red is trend not average.  Avg is said to be 26.1).  The largest cluster of consecutive years over the avg is 3 years.

[wntrstrmwrng]

Thanks!

That is an interesting chart.  Let's just hope we don't have one of those 6 winter's below average on the horizom...  Also - before this year NYC had several winters that broke the 40 mark even if the last winter above 40 came mostly in one storm...

[jfar57]

even better.....lets hope for a winter that causes a recalibration of the Y axis.

[weathergeek87]

Stormchaser said the NAO should become more and more negative over the next few years....if that's the case, the snowfall "trend" should gradually increase.

[wntrstrmwrng]

Thanks!  That is what I thought he meant by the long-term NAO.  I just wanted to make sure.

[NYBrit]

Cool so I can look forward to more snow each winter!  Hear that terry?!  ;)

[Stormchaser]

Let's keep in mind that a negative NAO certainly does not guarantee a snowy winter, in fact, sometimes it can ensure quite the opposite. The intensity and orientation of the neg NAO are crucial to the upstream weather pattern over the Northeast.

1) Climatologically speaking, places north of 40N latitude (our region & northward) receive their snowiest winters with NAO values slightly negative, while the mid-atlantic and particularly the Southeast need a moderate/deeply neg NAO for decent snowfall chances. The more amplified the north atlantic ridge, the deeper the trough over the Eastern US. Thus, the baroclinic zone, or area of storminess is pushed well south of us in an intense -NAO episode (sometimes well offshore). Coincidentally, the winter of 1995-96, the snowiest winter on record, was also the most negative NAO winter on record -- not because of intensity, but persistence. The NAO remained negative from November right through March and April that winter, which is a remarkable occurence. It's difficult to get a certain pattern to lock in place for more than 5-6 weeks. That particular yr we had a weak la nina, neg NAO, but also a favorable north pacific pattern (positive PNA/PDO -- which usually doesn't coincide with la ninas, hence why '95-'96 was a needle in a haystack type winter). So yes, virtually all teleconnectors were in "our favor" for a snowy winter.

2) Orientation: neg NAO East block VS. neg NAO West block. The former is what you don't want, that is, a block positioned near Iceland/northwestern Europe, while the latter is a classic "Greenland block". Last winter we had a neg NAO "east" block, which means the storm track runs SW-NE well offshore, with the center of the block located near Iceland. The NAO west block, ala, 1995-96, featured the high pressure center over Greenland, meaning the jet stream ran more SSW-NNE up the east coast and into Eastern Canada -- hence the storminess/thermal gradient is much closer to the region.

Either way, I'd take my chances with a -NAO over a +NAO any day. It's just a commmon misconception that a -NAO always = cold and snow (which is doesn't). Most of the time the Northeast is going to be colder than normal in a neg NAO, but snowfall is the tricky part as every pattern is different.

Here's a relatively simple graphic outlining the positive/negative phases of the NAO and it's effects on the sensible weather pattern.
[img width=577 height=546]http://www.ngdc.noaa.../images/nao.jpg[/img]

[NYBrit]

Thanks Storm!  Good write up as ever!

[terryjohnson16]

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Cool so I can look forward to more snow each winter!  Hear that terry?!  ;)

NO! Bring on the southern temps here.

[terryjohnson16]

I hope we get a positive NAO after looking at that map.

[jfar57]

I hope we get another needle in a haystack.  95-96 sounds good to me

[terryjohnson16]

Its weird that we haven't had a really hot July this year. Maybe August will take the cake.