Griteater's Winter Outlook (15-16)

[griteater]

There are no guarantees with seasonal outlooks, EVER, but here are my thoughts on the upcoming winter…

 

 

 

 

 

 

 

 

 

 

Discussion Points

1.       We have a very strong El Nino in progress where the ocean and atmosphere are well coupled.

 

2.       The combination of El Nino and the ongoing +PDO regime strongly favors the presence of a low in the North Pacific this winter.  In addition, I would expect the low to be fairly persistent through the winter since the MJO has less of an impact in modulating the pattern when ENSO is strong.

 

             

 

 

3.       Jan-Feb during the very strong El Nino of 97-98 featured a strong low in the NE Pacific with the heavy negative height anomalies extending into Western North America…and the downstream ridge placed in SE Canada and over the Great Lakes / Northeast.  That combination is a death sentence for cold air in the eastern U.S.

 

             

             

 

 

 

4.       Here’s why I believe we won’t be as warm as 97-98 in the east in the upcoming winter:

 

a.       From a SST anomaly perspective, this is a basin wide event, and I would expect that to continue over the next few months.  In contrast, the 97-98 nino was a strongly east based event.

 

                

 

 

b.      I compared other ENSO forcing parameters from this year with the east based ninos of 82-83 and 97-98.  The parameters were: 1) upper level VP anomalies, 500mb Omega anomalies, and OLR anomalies.  I compared the time periods of Jul to late Aug with late Aug to mid Oct, to track the lower frequency movement.  In doing this, the one thing that stood out was that each of these forcing parameters was shifting slightly east during the 82-83 and 97-98 ninos, but shifting slightly west during this year’s nino.

 

c.       Lastly, the Aleutian Low / Western Canada ridging couplet this October has been impressive.  I believe it’s just another hint that the north Pacific low won’t plow well east into western North America despite the strength of this nino.

 

             

 

 

5.       AO/NAO: –AO and –NAO are generally favored during El Ninos, though not as much during the very strong ninos.  The NAO has been positive in 14 of the last 18 winter months (Dec-Mar) and 7 of the last 8…and I don’t see any changes afoot to buck this trend.  In contrast…piggybacking off the July to winter AO correlation that WSI reported back in August, I looked at some multi-month summer to fall correlations for the AO/NAO.  The strongest correlation I found was this…in the 22 El Ninos since 1950, the sign of the July to Sep averaged AO matched the sign of the subsequent winter’s Dec-Mar averaged AO <and> NAO in 18 of the 22 cases.  The July-Sep averaged AO this year was -0.65.  In addition, the Oct Eurasia snow cover advance and North Pacific pattern have been favorable for negative tendencies.  Conventional wisdom this winter seems to be that we start off with a +AO/+NAO in early winter, transitioning to a –AO/–NAO in the 2^nd half. 

 

My call for the Dec-Mar averaged AO is neutral to slightly negative…and for the NAO, neutral to slightly positive.

 

 

6.       Temperatures – the 2 big takeaways are: 1) With my projected expansive ridging centered across south central Canada, I would expect that we won’t see the number or ferocity of arctic blasts as experienced the past 2 winters, and 2) I’m projecting strong warm anomalies over the northern plains, centered on Bismark, ND.

 

 

7.       Precipitation – I favor a southern stream that is more active than normal, but not a high end southern stream winter in the mold of 82-83 and 86-87.

 

             

 

 

At first glance, it may seem odd that I have a below normal precip forecast in Mississippi and Alabama during an El Nino, but the climo precipitation in this area is quite high…and my take is that El Ninos favor more cool sector precipitation with lesser amounts, whereas neutral and La Nina winters favor more showery and convective precipitation with heavier amounts.  Here is the climo precipitation map for the month of February:

 

             

 

 

 

Continued on next post...

[griteater]

Southeastern U.S. – the remainder of this outlook is focused on winter precipitation prospects for the southeastern U.S. (AL, GA, Carolinas, E TN, SE VA).

 

Here are Dec-Mar snowfall averages per ENSO phase for select SE sites.  I’ve listed them in the order of their general affinity for higher totals during stronger El Ninos:

 

 

 

Getting right down to the basics, the 2 key components needed in the southeast for good winter storms are: 1) A cold air mass that isn’t retreating, and 2) A storm that doesn’t climb the ladder, and stays south.  Of the ENSO phases, El Ninos yield the best chance at achieving point #2.  Per climo, the stronger the El Nino, the stronger and farther south the subtropical jet stream as seen here with 200mb zonal wind anomalies (the warm colors extending from Baja into the Gulf of Mexico denote the stronger than normal subtropical jet stream).

 

 

 

I would expect that we will see a few good southern stream waves this winter, with an accompanied gulf or Deep South low.  The stronger the El Nino, the higher quality these southern stream waves tend to be.  Will they be timed with any cold air?

 

Great, Deep South tracking, strong El Nino winter storms of the past include: 2 late Jan storms in 1966, Feb 1973, and Mar 1983. 

 

For additional reading on the topic of the subtropical jet stream, see this webpage: http://www.ldeo.columbia.edu/res/div/ocp/drought/storm_track.shtml

 

In addition, in compositing the winters that had a weak southern stream pattern vs. the ones that had an excellent southern stream pattern, the key features supporting the excellent pattern are the North Pacific Low and high latitude blocking (-AO/-NAO).  The high latitude blocking is a key element in pushing the mean storm track farther south.

 

 

 

For most of the southeast, I project the prospects for snow and ice to be ‘slightly better than normal’ for this winter, with a projection of ‘better than normal’ for the higher mountain peaks in western NC and east TN.  The areas of near normal include the northern half of AL, E TN, and SE VA.

 

 

 

In terms of timing, I project that the best winter pattern compared to climo will occur between mid Feb and mid Mar.  There have been some good Dec winter storms in moderate and strong El Ninos of the past, and I wouldn’t discount the prospects in Dec this year.

 

For temperatures, the general consensus favors a warmer start to winter, followed by a cooler 2^nd half…having said that, in my analysis, I didn’t see a strong warm or cool signal for any particular month.

 

 

Enjoy your winter, and regardless of my forecast, what I would REALLY like to see this winter, is something like this (Sumter, SC – Feb 1973):

 

               

[Met1985]

Grit great info and layout as usual man. Thanks for taking the time to post this and I like your predictions!

[Cold Rain]

Nice read, Grit!  Hope it works out a bit colder and snowier than your forecast!  Also, nice usage of the word "afoot".

[packbacker]

Great writeup as always!  Not sure we will have the patience to wait until mid-Feb for a snowy pattern to setup :-)  Plus that gives us like 2 weeks of winter until our (central NC) snow chances shut off.

 

Also interesting that ATL averages as much snow as GSO in strong+ nino's....suppressed track FTW.

[mackerel_sky]

Great info! Thanks for taking the time to do the write up! It's will be tought to wait til Feb, if we have to, but if we could get the tracks a little more south, then mby would be in business !

[FallsLake]

Very good write up. I'm hopeful for something to occur in December. That would make a weak middle part of winter easier to take. Last year was horrible having to wait until February.    

[packbacker]

Very good write up. I'm hopeful for something to occur in December. That would make a weak middle part of winter easier to take. Last year was horrible having to wait until February.    

 

I am not sure about Dec but there are some strong nino's with good Jan's (66, 73, 88) but there are some ones that make you wait and of course there are some complete duds.   The fact that we have a similar north pacific to last year and that didn't get going until Feb it's a good bet we are going to be waiting.  Lots of cliff jumping the next few months as we roast...

[FallsLake]

I am not sure about Dec but there are some strong nino's with good Jan's (66, 73, 88) but there are some ones that make you wait and of course there are some complete duds.   The fact that we have a similar north pacific to last year and that didn't get going until Feb it's a good bet we are going to be waiting.  Lots of cliff jumping the next few months as we roast...

That will be entertaining itself... 

[SnowNiner]

Thanks Grit, good examination for sure.  Very interesting that Charlotte has done so well with snow in strong Nino years.  With all the "flood of pacific air" talk you get with strong Ninos I thought it would be much less. 

[calculus1]

Grit, your work is much appreciated, as always.  Great presentation and science.

[Snowless in Carrollton]

One problem I have with griteaters forecast is that it shows below normal precip for much of the south. Aren't el ninos typically wet in the deep south ? It even shows drier than normal close to Atlanta.

[jburns]

One problem I have with griteaters forecast is that it shows below normal precip for much of the south. Aren't el ninos typically wet in the deep south ? It even shows drier than normal close to Atlanta.

 

That's why it is a forecast and not a straight regurgitation of analogs.

[tonysc]

"Great, Deep South tracking, strong El Nino winter storms of the past include: 2 late Jan storms in 1966, Feb 1973, and Mar 1983."

 

One could only hope......especially for one like Feb 1973.

[strongwxnc]

Thanks for the detailed writeup sir.

Sent from my iPad