Winter Outlook 2019-2020

[Ralph Wiggum]

Want to begin by stating most of the comments in this outlook and stats are being based off of KDYL and not necessarily KPHL proper unless otherwise noted.

Coming off of winter 2018-19 where most areas in and around Philly metro nickel and dimed their way to BN seasonal snowfall totals, winter weather enthusiasts can only hope the coming winter of 2019-2020 will be more of a bounceback season in terms of both seasonal snowfall amounts and quantity of snow per storm. Last season featured a fair amount of chances, but the majority of those turned out to be minor/nuiscance coating to 2" type events with just a couple of 3-6" systems tossed in thanks in part to a transient pattern overall and more fropas than actual storm systems affecting the area.

With the ENSO currently in a neutral phase and forecast to remain as such (chance for fluctuations towards weak El Nino) thru spring 2020,  major hemispheric impacts should be mainly muted. However, there are tendencies for the East and Northeast US to be colder than normal during these phases.

Taking a look upstairs into stratosphere, the SPV appears to be relatively stable with elongation over Asia/Siberia and also into the N Central US with a bubble ridge over the North Atlantic and also over the Bering Sea which are putting a  'squeeze'  on the SPV. In response, the TPV is taking some damage and looks to undergo some splitting over the next several weeks with (in general) a piece moving into position near Hudson Bay and another near Siberia. Determining IF the TPV continues to show tendencies to remain split as we delve into the winter month is TBD, but seeing the TPV starting to hint at this in November is never a bad signal.

In response to the PV activity, the AO/NAO, which have been hanging around the negative overall since summer will have major implications on apparent weather in our region. With the PV having pressure on it to force splitting and the general temp anomalies during a neutral ENSO/weak nino, chances for severe cold outbreaks, ie lobe of the PV paying a visit, is increased during winter 19/20. 

Soil moisture is expected to increase over the Mississippi River Valley and into the Southeast over the next several weeks which will help carve out a few different storm tracks, one of which is a suppressed look at times (remember that PV plunge pressing South?), one off of Hatteras NNE/ENE, and the other up the Tennessee Valley and just West or over the I95 corridor. The Clipper will pay a couple of visits this winter as well.  Of course there will still be other tracks but the primary ones have been laid out.

Solar activity is low and appears to have bottomed out. As 2020 approaches, solar/sunspot activity is expected to slowly increase. Historically, there has been 'some' correlation between the period of least solar activity into the subsequent increase and -NAO/-AO sustainability. The exact reasons 'why' are not quite clear to me as I have not studied this particular facet of forecasting as much as I would like, but it is something that I have noted during my limited research on the subject.

The WAR which was a significant factor last winter is still appearing to be a player at times. However, there is something invariably different in this feature and model progs over the past several months. Many LR forecast trends had been showing this feature linking up with a SE Ridge every time it has surfaced. Though as lead times lessened, the WAR has, for the most part, remained separate from any subtropical ridging and has either verified as flattening at times OR actually feeding the -NAO. THIS IS CRITICAL and one of the keys to the winter forecast. If the WAR continues to be the catalyst to aid in development/strengthening of the NAO ridge over Greenland, the chances for a larger than usual winter storm(s) in the Northeast and Northern part of the Mid Atlantic region increase. With that said, there is a higher than normal chance for at least one 10"+ type snowstorm for the area. 

Without delving too much into detail on the PAC, the development and resurgence of the Aleutian Low has been a welcome feature as has been the split flow off the SW US Coast and a linkage at time from the tropical Pacific across old Mexico and into the Southeast US as it undercuts ridging that is apparent in the PNA region. This is likely in part to the ENSO phase specifically the warning recently in the subtropical Eastern PAC regions (weak Nino tease?). The EPO ridge has also been showing itself, and although displaced at times, may become more of a player aiding in CPF emerging and funneling  into the Plains then spilling East.

So, while some may read this and assume wow, he's all-in on an epic winter, that is hardly the case at all right now. There are many features that look very promising, BUT there are also features that counter those positives such as location, location, location. If the PV split or continues to be pinched/squeezed who is to say exactly where it will go as the pattern becomes convoluted? It could easily dive into the Western Plains as much as it may become displaced over the OV. PV could also fight back and remain one organized entity anchored over the North Pole which would put a wrench in my thoughts. Also, the storm track tendencies mentioned do not assume cut and dry frozen precip every time. And what's to say a PAC firehose won't develop at times like we struggled with last winter? 

I could go on and on about what ifs, but suffice it to say every forecast, especially seasonal forecasts, have nuances that can significantly affect the outcome. This is no different.

With all of this said, my thoughts are for near normal to just above normal snowfall for my forecast area which for Doylestown is right around 30". I dont do the monthly breakdowns as that is just something I've never gotten into. I really cant say with any confidence whether this will be a front loaded or back loaded type of winter (or normal balance). Though if going by sheer pattern evolution, I would be more prone to say December will produce this year. Provided things dont collapse there should be a fair amount of tracking opportunities early. 

So not the winter to end all winters but certainly not a dud either. Chances for HL blocking are increased which should increase the likelihood of at least one major event (KU??). PV will drop down and give a period(s) of severe cold but there should be some balance with the pattern relaxing and moderating between episodes.

[Newman]

Good stuff Ralph. Don't take this as a post trying to steal your spotlight. Just trying to share some thoughts. Anyway, I would think a PV split is most likely to occur later on in the winter, as the QBO would have descended enough into the easterly phases which support such a thing occurring. It could still occur even without a favorable QBO, however. But the progression of the QBO is admittedly not occurring as fast as I had hoped. Save for a miraculous uptick (which is very much possible), the QBO might not be too much of a factor this year. That's fine though. Last year it's something that helped kill us. The ENSO is in an overall favorable look - Cooler ENSO regions 1.2 and 3. Regions 3.4 and 4 much warmer. It's very much a Modoki look. A warm Atlantic/AMO is still evident in the data sets and SST maps. The PDO is actually cooling off a bit with the NP warm blob starting to regress to the west a bit south of the Aleutians. What I fear the most this winter is actually what we've got potentially in store for us next week. The ridge out west is just a bit too far west, aided by the warmer SST's a bit further west. We've actually been stuck in a +TNH pattern for a while now which supports my analog set as well. Cold dumps into the central states and Great Lakes, the SE ridge tries to pop, and you get cold before and after each storm, but as the storm comes in the trough axis is just a bit too far west. 

 

Now, I've been delving into this upcoming winter since July/August and have stuck with this SST composite and 500mb composite since September. I don't see any reason to change now.

As I mentioned above, the cold will be there I believe with the mean trough centered across the central states and Great Lakes. The question is how does it modulate when storms come through? With no HL blocking, you can bet App runners and coastal screamers will be a real threat. Kinda like this upcoming Tuesday/Wednesday storm. It's a battle between the Ridge/Trough orientations, WAR, and incoming cold press. If HL blocking does commence this winter, I truly believe it's off to the races. The Pacific is favorable enough for there to be some hope.

[Ralph Wiggum]

@Newman

Great post!

You touched on several of the indices/oscillation teleconnections which I purposely avoided lol. The QBO I dont believe we can count on to determine HL blocking timing and/or placement. Many learned this the hard way last year, myself included. The PAC has more times than not failed us recently BUT we have still managed to get the cold thanks almost solely to the EPO ridge. As you said, a Western displaced PNA/EPO ridge will give many of us fits this winter....but based on progression over recent weeks, things appear headed in the proper direction. The appearance of the Aleutian low after a period of HL blocking over that region is a refreshing and welcoming signal.

I've actually been more focused on the Atlantic side in recent years...more specifically the WAR and it's influence or lack thereof on the NAO. Given the state of low solar activity among other factors, the AO should spend a fair amount of time in the neg or neutral territory as we have seen in recent months. This feature is probably the key player on winter weather for you and I as well is the placement/timing of any NAO ridging. Again, it is how the WAR is impacting the NAO which is going to be a key driver once again this season. I'm convinced we get the cold spells (no winter long torch) thanks to the EPO and we will have the neg AO a portion of the time. We will get a blend of snow, thump to rain, and cold rain this winter. Question is, can we can get the holy trinity (-AO/-NAO/-EPO) to work in unison at any point for the KU? Confidence is higher than normal that this is realized at least once.

[FPizz]

Good stuff guys and good luck Ralph.  Plus, you both are in my top 10 list of favorite tv characters. 

[The Iceman]

Great write up Ralph, I always enjoy reading your thoughts. Overall thinking the same right now, average winter across the board. Some nickle and dime front enders, and maybe 1-2 SECS. Our average down here is only like 24 inches so it doesn't take many hits to get to that. Last year was awful and we made it to 17 inches.  I think the key player is the AO this winter. If we get that to be negative the majority of the time we will do ok. We may not hit the big one but we should get several 3-6 inch events at least. 

[Ralph Wiggum]

52 minutes ago, The Iceman said:

Great write up Ralph, I always enjoy reading your thoughts. Overall thinking the same right now, average winter across the board. Some nickle and dime front enders, and maybe 1-2 SECS. Our average down here is only like 24 inches so it doesn't take many hits to get to that. Last year was awful and we made it to 17 inches.  I think the key player is the AO this winter. If we get that to be negative the majority of the time we will do ok. We may not hit the big one but we should get several 3-6 inch events at least. 

The chart below seems to fit in well with my thoughts as we progress into late Nov. Caveat moving forward is whether this will be a recurring theme this DJF or a flash in the pan with a pattern rollover in Dec. We will know in a few weeks: