PD1 - 2/18-19/79

[snow.]

I didn't want to hijack Wes's thread, but this was a pretty wretched PAC pattern...of course we had that massive trough over the maritimes and the monster surface high

 

My theory has been that a robust southern stream can overcome these bad pacs or even sometimes atlantics, and that is why in Nino hangovers like 78-79 and some of the years in the 60s had KU's occur in more hostile patterns, whereas we needed better pacifics in the years with the weak southern streams...

[usedtobe]

I didn't want to hijack Wes's thread, but this was a pretty wretched PAC pattern...of course we had that massive trough over the maritimes and the monster surface high

 

My theory has been that a robust southern stream can overcome these bad pacs or even sometimes atlantics, and that is why in Nino hangovers like 78-79 and some of the years in the 60s had KU's occur in more hostile patterns, whereas we needed better pacifics in the years with the weak southern streams...

1979 had a really good atlantic, a classic neg nao from dec through the snowstorm then poof it was gone. 

[ORH_wxman]

The main vortmax in '79 tracked pretty far north when you compare it to KU's for DC such as 2/11/83, 1/25/87, 2/22/87, 1/7/96, and 2/16/03.

 

The massive 50/50 low and antecedent airmass definitely helped out a lot. And as you mentioned, there was some STJ energy that came through Mexico and the southwest that linked up with the main polar jet energy in a split flow pattern which developed the surface low much further south than would have without that energy.

 

So IMHO, some key factors helped out in offsetting the otherwise further-north-than-typical vort track for a DCA KU.

 

1. Huge vortex in SE Canada...big sfc high and great antecdent airmass as result (this is prob the mos timportant feature)...you need the good ATL

2. Split flow in the PJ (almost equally as important) to slow down the pattern a bit despite GOA low

3. Some STJ energy to help cyclogenesis further south

[snow.]

1979 had a really good atlantic, a classic neg nao from dec through the snowstorm then poof it was gone. 

 

it did...but in other years, we don't get a storm with that pattern...not with the PNA so negative

[mitchnick]

1979 had a really good atlantic, a classic neg nao from dec through the snowstorm then poof it was gone. 

yeah, I remember the day the storm ended there was talk about the next system maybe being snow too and by that evening the talk was it would be rain, maybe with some zr at the start

the rest of the winter......well, there was no more winter after PDI     lol

but it was a decent 3 weeks beginning the last week of Jan-PDI; there was a snow event of 3" imby around Thanksgiving but not much else to talk about until the last week of Jan

[mitchnick]

The main vortmax in '79 tracked pretty far north when you compare it to KU's for DC such as 2/11/83, 1/25/87, 2/22/87, 1/7/96, and 2/16/03.

 

The massive 50/50 low and antecedent airmass definitely helped out a lot. And as you mentioned, there was some STJ energy that came through Mexico and the southwest that linked up with the main polar jet energy in a split flow pattern which developed the surface low much further south than would have without that energy.

 

So IMHO, some key factors helped out in offsetting the otherwise further-north-than-typical vort track for a DCA KU.

 

1. Huge vortex in SE Canada...big sfc high and great antecdent airmass as result (this is prob the mos timportant feature)...you need the good ATL

2. Split flow in the PJ (almost equally as important) to slow down the pattern a bit despite GOA low

3. Some STJ energy to help cyclogenesis further south

and we took full advantage of it because as the last flakes fell that morning imby it was 33 or 34! I still remember thinking, wtf, why is it so warm?

[snow.]

The main vortmax in '79 tracked pretty far north when you compare it to KU's for DC such as 2/11/83, 1/25/87, 2/22/87, 1/7/96, and 2/16/03.

 

The massive 50/50 low and antecedent airmass definitely helped out a lot. And as you mentioned, there was some STJ energy that came through Mexico and the southwest that linked up with the main polar jet energy in a split flow pattern which developed the surface low much further south than would have without that energy.

 

So IMHO, some key factors helped out in offsetting the otherwise further-north-than-typical vort track for a DCA KU.

 

1. Huge vortex in SE Canada...big sfc high and great antecdent airmass as result (this is prob the mos timportant feature)...you need the good ATL

2. Split flow in the PJ (almost equally as important) to slow down the pattern a bit despite GOA low

3. Some STJ energy to help cyclogenesis further south

 

I think that was a poorly forecast storm, though I think Wes got it right at the end (he can comment)...And it might have had to do with the pattern....

 

Could we get something like that in one of our current winters?..It would seem to me that even if we got a displaced PV and the massive surface high, we'd probably have the storm suppressed..

[ORH_wxman]

and we took full advantage of it because as the last flakes fell that morning imby it was 33 or 34! I still remember thinking, wtf, why is it so warm?

 

 

Yeah it was essentially a furnace behind the storm...that week was a torch. Total contrast to the month leading up to that point.

[Bob Chill]

Very persistent and strong blocking leading up to the storm the it all collapsed in the wake.  PDI was on day 110 in the graphs.

 

AO:

 

 

 

NAO

 

 

 

IIRC, persistent blocking patterns are often broken down by big storms. I could be wrong.

 

Interesting note is the Nov AO. Similar to this year so far. If it breaks down as modeled then it will continue on the similar path as 78. 

 

 

 

[uncle W]

From Feb. 5th -19th, 1979 NYC averaged 16.5 degrees and got 20" of snow...max was 34 and the min was zero during that period...there were two or three events and eight days in single digits before the PD1 storm...that was the last measurble snow that winter...It was like the February 1961 storm when it got milder with a major thaw after a long cold and snowy period...

[NJ_Ken]

 

From Feb. 5th -19th, 1979 NYC averaged 16.5 degrees and got 20" of snow...max was 34 and the min was zero during that period...there were two or three events and eight days in single digits before the PD1 storm...that was the last measurble snow that winter...It was like the February 1961 storm when it got milder with a major thaw after a long cold and snowy period...

 

I was getting ready to make a similar post about Philly's weather in February of 79, but you beat me to it. lol. Still, I hate to let good data go to waste so...

In the two weeks before PD1, the highest temperature at PHL was 29 F, and 8 days in that stretch had highs in the teens (including one stretch of 6 straight days when the temperatures never touched 20 F). Low temperatures dipped below 0 F twice and 9 of the 14 days featured lows in the single digits (or below) with only one day having a low temperature above 20 F (and that was during a snowstorm). If you include February 19, 1978 (the date when most of the snow fell for PD1), a total of 27.6" of snow fell in 15 days, Yes, 14.3" fell during PD1, but an additional 13.3" fell in the two weeks preceeding it. Only five days in the stretch had no observed snow, and, on 7 of the 15 days, measurable snow was recorded.

...and, as everybody has mentioned, winter ended with those final flakes of PD1. Even with all that snowcover, it rained two days later, and temps were in the 40s the day after that, and PHL recorded no more measurable snow until the following October.

[usedtobe]

Matt, it's interesting that in many of the negative PNA years of the 60s that had lots of snow, the 8 inch plus storms all had the PNA pop to positive with or just before the storm.  Even 1979 had the PNA index very near neutral as a transient ridge popped behind the shortwave that produced the storm. I wonder if the MJO played a role in those years, especially the enso neutral ones.  When the MJo gt towards phase 8 and the GWO does likewise, you tend to get a temporary el nino look. That's what HM has been suggesting might happen late Nov into early Dec.   The MJO progression if it continues would support that and the ens forecasts of the ao appear to be going towards negative. 

[Amped]

 The setup was pretty lucky. The flow happened to split in the right place at the right time. The pattern was fairly progressive and it probably didn't show up on models until 2 days out.

[WVclimo]

I got about 4" in Cumberland from that storm, before the snow shut off early in the evening. I was stunned the next morning when I turned on the TV and saw the DC newscasts. One of those telecasts where the anchors had barely made it into work, and it showed.

It was the first snow storm I remember that the Metros got buried and my hometown was largely missed.

[ORH_wxman]

Matt, it's interesting that in many of the negative PNA years of the 60s that had lots of snow, the 8 inch plus storms all had the PNA pop to positive with or just before the storm.  Even 1979 had the PNA index very near neutral as a transient ridge popped behind the shortwave that produced the storm. I wonder if the MJO played a role in those years, especially the enso neutral ones.  When the MJo gt towards phase 8 and the GWO does likewise, you tend to get a temporary el nino look. That's what HM has been suggesting might happen late Nov into early Dec.   The MJO progression if it continues would support that and the ens forecasts of the ao appear to be going towards negative. 

 

 

Even though it didn't break 8" at DCA (though I think IAD did), this is what happened in the 1/26/11 storm. 2010-2011 was a solidly -PNA winter but late that January, we had a nice +PNA burst.

 

It seems we havent had good (even if brief) PNA bursts in the our -PNA winters recently. I took a quick look at the -PNA winters since the PDO has really tanked (2007) and found this:

 

2007-2008: Strong La Nina. The PNA only spiked above +1 twice all winter. The first was 12/4/07. DC had the over performing clipper the next day on 12/5/07. It ipped back below +1 not to be seen again until 2/16/08 through 2/21/08. 2/21-2/22 brought a wintry system to the northeast. DC started as snow but quickly changed to rain. That was it for the winter.

 

2008-2009: No PNA spikes above +1 until 1/14/09-1/18/09. No snows of any note for DC, but it brought the coldest air of the season. 1/18 had a storm hit eastern New England. That was the only PNA over 1 all winter.

 

2009-2010: El Nino...not a -PNA winter. I think we all know that in this forum.

 

2010-2011: One period with a PNA spike over +1...1/22/11-1/28/11. Of course the 1/26/11 storm happened in the middle of that. The largest storm of the season for DCA/BWI region.

 

2011-2012: 2/2/12-2/13/12 was a big +PNA period. It didn't help us with a poor EPO all winter. DCA did get their only measurable February snowfall though in that time...though it was paltry.

 

2012-2013: Early January 1/2-1/4 had a good +PNA period that produced cold, but no snow. The next good +PNA period was late Feb into early March...it broke down when the 3/5-3/8 storm happened. Although the storm was a bust in DC, it was a golden opportunity. Sometimes they don't all work out.

 

+1 is kind of an arbitrary number, but if you lowered a bit to around +0.7, the results are very similar. 2009-2010 actually spent a lot fo the winter in that range between +0.5-+1.0. Also the PNA doesn't always tell the story. You can have a big western ridge and the PNA won't always been large positive...if there is a big Aleutian ridge, then it will force the number toward negative.

 

But looking back toward some of  those -PNA winters of the 1960s, the PNA seemed to spike more often than we've seen recently. Like '64-'65 for example had multiple stretched of solid +PNA conditions. Same with '65-'66 (which was a -PNA winter despite the El Nino). '61-'62 also had multiple spikes of +PNA of near +1. I'm sure the general ENSO state of the time probably had something to do with it. No potent La Ninas between 1956-1970.

[usedtobe]

Even though it didn't break 8" at DCA (though I think IAD did), this is what happened in the 1/26/11 storm. 2010-2011 was a solidly -PNA winter but late that January, we had a nice +PNA burst.

 

It seems we havent had good (even if brief) PNA bursts in the our -PNA winters recently. I took a quick look at the -PNA winters since the PDO has really tanked (2007) and found this:

 

2007-2008: Strong La Nina. The PNA only spiked above +1 twice all winter. The first was 12/4/07. DC had the over performing clipper the next day on 12/5/07. It ipped back below +1 not to be seen again until 2/16/08 through 2/21/08. 2/21-2/22 brought a wintry system to the northeast. DC started as snow but quickly changed to rain. That was it for the winter.

 

2008-2009: No PNA spikes above +1 until 1/14/09-1/18/09. No snows of any note for DC, but it brought the coldest air of the season. 1/18 had a storm hit eastern New England. That was the only PNA over 1 all winter.

 

2009-2010: El Nino...not a -PNA winter. I think we all know that in this forum.

 

2010-2011: One period with a PNA spike over +1...1/22/11-1/28/11. Of course the 1/26/11 storm happened in the middle of that. The largest storm of the season for DCA/BWI region.

 

2011-2012: 2/2/12-2/13/12 was a big +PNA period. It didn't help us with a poor EPO all winter. DCA did get their only measurable February snowfall though in that time...though it was paltry.

 

2012-2013: Early January 1/2-1/4 had a good +PNA period that produced cold, but no snow. The next good +PNA period was late Feb into early March...it broke down when the 3/5-3/8 storm happened. Although the storm was a bust in DC, it was a golden opportunity. Sometimes they don't all work out.

 

+1 is kind of an arbitrary number, but if you lowered a bit to around +0.7, the results are very similar. 2009-2010 actually spent a lot fo the winter in that range between +0.5-+1.0. Also the PNA doesn't always tell the story. You can have a big western ridge and the PNA won't always been large positive...if there is a big Aleutian ridge, then it will force the number toward negative.

 

But looking back toward some of  those -PNA winters of the 1960s, the PNA seemed to spike more often than we've seen recently. Like '64-'65 for example had multiple stretched of solid +PNA conditions. Same with '65-'66 (which was a -PNA winter despite the El Nino). '61-'62 also had multiple spikes of +PNA of near +1. I'm sure the general ENSO state of the time probably had something to do with it. No potent La Ninas between 1956-1970.

Will nice post,  very interesting. 

[snow.]

Matt, it's interesting that in many of the negative PNA years of the 60s that had lots of snow, the 8 inch plus storms all had the PNA pop to positive with or just before the storm. Even 1979 had the PNA index very near neutral as a transient ridge popped behind the shortwave that produced the storm. I wonder if the MJO played a role in those years, especially the enso neutral ones. When the MJo gt towards phase 8 and the GWO does likewise, you tend to get a temporary el nino look. That's what HM has been suggesting might happen late Nov into early Dec. The MJO progression if it continues would support that and the ens forecasts of the ao appear to be going towards negative.

Thanks. This makes sense. We have gotten few and not been able to time them.

[snow.]

Even though it didn't break 8" at DCA (though I think IAD did), this is what happened in the 1/26/11 storm. 2010-2011 was a solidly -PNA winter but late that January, we had a nice +PNA burst.

It seems we havent had good (even if brief) PNA bursts in the our -PNA winters recently. I took a quick look at the -PNA winters since the PDO has really tanked (2007) and found this:

2007-2008: Strong La Nina. The PNA only spiked above +1 twice all winter. The first was 12/4/07. DC had the over performing clipper the next day on 12/5/07. It ipped back below +1 not to be seen again until 2/16/08 through 2/21/08. 2/21-2/22 brought a wintry system to the northeast. DC started as snow but quickly changed to rain. That was it for the winter.

2008-2009: No PNA spikes above +1 until 1/14/09-1/18/09. No snows of any note for DC, but it brought the coldest air of the season. 1/18 had a storm hit eastern New England. That was the only PNA over 1 all winter.

2009-2010: El Nino...not a -PNA winter. I think we all know that in this forum.

2010-2011: One period with a PNA spike over +1...1/22/11-1/28/11. Of course the 1/26/11 storm happened in the middle of that. The largest storm of the season for DCA/BWI region.

2011-2012: 2/2/12-2/13/12 was a big +PNA period. It didn't help us with a poor EPO all winter. DCA did get their only measurable February snowfall though in that time...though it was paltry.

2012-2013: Early January 1/2-1/4 had a good +PNA period that produced cold, but no snow. The next good +PNA period was late Feb into early March...it broke down when the 3/5-3/8 storm happened. Although the storm was a bust in DC, it was a golden opportunity. Sometimes they don't all work out.

+1 is kind of an arbitrary number, but if you lowered a bit to around +0.7, the results are very similar. 2009-2010 actually spent a lot fo the winter in that range between +0.5-+1.0. Also the PNA doesn't always tell the story. You can have a big western ridge and the PNA won't always been large positive...if there is a big Aleutian ridge, then it will force the number toward negative.

But looking back toward some of those -PNA winters of the 1960s, the PNA seemed to spike more often than we've seen recently. Like '64-'65 for example had multiple stretched of solid +PNA conditions. Same with '65-'66 (which was a -PNA winter despite the El Nino). '61-'62 also had multiple spikes of +PNA of near +1. I'm sure the general ENSO state of the time probably had something to do with it. No potent La Ninas between 1956-1970.

Great stuff. I'd love to pop into a better ENSO regime which might seem harder in a -PDO state but we managed to do it in from 56-70. 6 ninos. 1 Nina. As you said that May have been related to the more frequent and stronger PNA spikes.

[Huffwx]

Loved talking with Wes about PD1 at past conferences. 

[Sparky]

that storm definitely had a wow factor to it.  Probably the highest sustained snowfall rates I have ever seen in the three hours from 7am-10...it was very interesting to watch the intensity and wind pick up in the very wee hours of the morning around 2am ish.