psuhoffman

I predicted slightly above normal snowfall this year

The monthly snowfall composites back that up

The weighted analog mean produces the follow snowfall predictions BWI: 18.1" IAD: 18.3" DCA: 14" December and January average below normal temps. February much above normal. My current snowfall forecast is slightly above this but I simply added a small bump for the "we're due" index. We've been pretty unlucky lately, maybe we get one good hit and this is that rare nina that ends up slightly above normal snowfall. They do happen once in a while and we are due for one. But for what it's worth the composite mean beat my "gut" adjustments 3 of the last 4 years. So... My call BWI: 20" IAD: 23" DCA: 15"

I ran the composites using my weighted full analog method. It didn't really change the outcome much. December through mid January still looks pretty good. February looks brutal. Is what it is. Definitely not a non winter look though. Winter Mean Dec Jan Feb

Last year 2009 was my top analog, and I actually think that worked out pretty well. This year it's closer to the bottom of the list and barely made the cut. I thought I would have more time once soccer ended, I coach both my kids teams, but I took on a lot more at work and honestly I'm not sure if I'll have time to do a full in depth seasonal forecast but I did take an hour to identify the analogs using my formula. I think I am going to run a new anomaly mean plot where I weight them.

I am starting to lean towards something like this as the mean winter pattern. December-January coldest, February warmest, March is a wildcard.

Did you cancel winter yet?

That’s more important to snow around here in December than the NAO

2019 following the weak nino

I’m not talking about the longer scale -PDO. Within that are shorter term extreme phases. That’s what’s been killing is. We can snow in a somewhat negative PDO. Look at the 1960s! But past mini extreme -PDO periods (typically 4-7 years where the PDO is below -1 most of the time) are always god awful for snowfall. We have to be coming to the end of this mini super negative PDO phase. None going back 125 years last longer than about 6-7 years.

For the whole mid Atlantic 1996 For Manchester MD Feb 9-10 2010 We started with 20” otg, then this crazy convective band set up along the thermal boundary the evening of the 9th. We got 12” in 4 hours and had about 14” new snow that evening before the lull then the CCB associated snowfall developed right over us and snowed all day on the 10th. True blizzard conditions, wind, freezing cold, another 16” or so fell. We ended up with about 30” which was way over any expectation going in. Had close to 50” otg when it was over.

Yes. But that can’t continue forever. Look at all the past similar extremely negative PDO periods. There longest such recorded periods and closest to this one were in the 1950s and 1970s. But those didn’t extend past 6 or 7 years. The extreme -PDO. So we have to be coming to the end of this current cycle soon. There is absolutely no precedent for this continuing much longer.

Historically I don’t disagree. But we’ve said this quite a few times over the last 10 years and it seems our “hit rate” has become pretty low in a more zonal suppressed “big bowl” pattern also, to the point maybe it’s better to just take our chances on the big hit anymore. But since we don’t control what we get it doesn’t matter. Yea I’d take a high chance if getting some moderate 3-5” type events over a very low chance at a 10”+ but it doesn’t seem to be that way anymore. We seem to waste the “high probability” looks just as often as the big hit ones lately.

We all suffer from a perception bias where we notice when someone gets anomalous weather but not all the times “nothing” is happening.