Griteater's Winter Outlook ('14-'15)

[griteater]

Griteater’s Winter Outlook ’14-‘15

 

I’m going to throw another winter outlook into the pile.  Before I begin though, let me first acknowledge that the verification against my winter outlook from a year ago was NOT good, at all.  In spite of that, I approach this year’s version like a burnt cornerback who must have a short memory and move on to the next play.  Here goes…

 

This outlook will consist of a series of posts covering the following sections:

1.       Current Climate/Seasonal Forecast Indices

2.       Cold Winter Patterns in the Southeast U.S.

3.       Wintry Precipitation Patterns in the Southeast U.S.

4.       North Pacific Pattern

5.       AO/NAO

6.       Southern Stream

7.       Winter Forecast Calls

 

 

Current Climate / Seasonal Forecast Indices

 

ENSO

As of its October release, the average of all 25 ENSO models on the IRI site indicate a prediction of an official, weak El Nino this fall/winter with respect to ONI.  Meanwhile, the MEI rankings have been oscillating between positive neutral conditions up to moderate El Nino conditions since the spring.  Finally, there are well-respected meteorologists that I/we follow on this board and off that have indicated that the atmosphere is already in an El Nino state, and is here to stay.  Regardless of the specifics around exactly how the ONI, MEI, and other ENSO indicators turn out, my take is that the best way to characterize ENSO for the upcoming fall/winter is ‘Weak El Nino’.

 

PDO

The monthly value of the PDO was below zero in 42 of the 43 months during the period from the middle of 2010 to the end of 2013.  Since then, we’ve seen a flip to positive PDO numbers.  The recently released NOAA PDO number for October was strongly positive compared to climo.  Given the current positive mode of ENSO and the 500mb pattern evolution this year in the North Pacific, my belief is that the PDO will run moderately to strongly positive through the winter.

 

QBO

We will be firmly entrenched in a –QBO regime this winter.  When analyzed at the 45mb level in the lower stratosphere, my call is that the Jan-Feb averaged QBO will be negative and falling (i.e. not reaching max –QBO at 45mb until spring or summer).  You can view the progression of the QBO with comparisons to prior years here.  The current QBO is most closely following the progression of 62-63 and 81-82.

 

Solar

Even though we are in the vicinity of the solar max for the current solar cycle, this solar cycle has been a relatively weak one.  One way to define solar maximum and minimum conditions during the winter is by using 10.7 cm solar radio flux.  Solar maximum conditions are achieved when the 10.7 cm radio flux exceeds 150 (x 10 ^-22 W m^-2 Hz^-1).  Solar minimum conditions are achieved when the 10.7 cm radio flux falls below 105 (x 10 ^-22 W m^-2 Hz^-1).  As seen on this chart, the 90 day solar flux average crested in the spring and has fallen back into the neutral range, though still elevated.  Solar activity can be fickle, and we recently had a spike in solar flux, but my projection is that the 90 day solar flux average for Dec-Feb this winter will fall into the neutral range.

 

Two winters from now (’16-’17), we will likely have descended into sustained solar minimum conditions which will almost certainly continue into the 2020’s.

 

[griteater]

Cold Winter Patterns In The Southeast U.S.

 

I analyzed the 16 coldest winters (which I always define as Dec-Mar) in Charlotte since 1949 (coldest 25% of winters).  Here are stats that I compiled:

 

When looking at the various seasonal forecasting indices and teleconnections (AO, NAO, NPI, PDO, ENSO, EPO, PNA), the strongest correlation for cold winters in Charlotte was the AO and NAO, followed by the NPI.

 

15/16 coldest winters had a –AO.  Of those 16 winters, only 6/64 months had a +AO.

14/16 coldest winters had a –NAO.  Of those 16 winters, only 9/64 months had a +NAO.

10/16 coldest winters had a –NPI (i.e. –NPI indicates the presence of an Aleutian Low; +NPI, an Aleutian High).

 

Of the top 16 coldest winters, 7 had the combination of a –AO, –NAO, and –NPI.  Here is a 500mb height composite of those “Holy Grail” cold winters:

 

 

The composite depicts the Aleutian Low negative anomalies (-NPI) in a classic position located directly between Hawaii and Alaska’s Aleutian Islands; a trough (negative anomalies) in the eastern U.S.; neutral anomalies in between the two in the western U.S. (neutral anomalies in western North America actually imply some level of ridging since slight ridging is the climo pattern in that region during winter); -EPO ridging through and to the north of Alaska; and the above normal height signature over the Arctic regions characteristic of the –AO/–NAO.

 

One other note…if we look at the data back to 1879, the ENSO breakdown of the top 25% coldest winters (34 total) in Charlotte is as follows (using the MEI Rankings to categorize ENSO). 

 

15/34 coldest winters were El Nino (9 Weak, 4 Moderate, 2 Strong)

12/34 coldest winters were ENSO Neutral

7/16 coldest winters were La Nina (2 Weak, 2 Moderate, 3 Strong)

 

Note that the most common ENSO state was a weak Nino.

[griteater]

Wintry Precipitation Patterns in the Southeast

Utilizing hourly precip data from Weather Underground, I compiled the total Dec-Mar wintry precipitation (liquid equivalent of total snow and ice in inches) in Charlotte for each year since 1973 (earliest date for hourly records).

 

Here are the top 15 winters with total amount of wintry precipitation noted in parenthesis (again, liquid equivalent of total snow and ice in inches):

1978-1979 (4.69)

1995-1996 (2.63)

1979-1980 (2.20)

1973-1974 (2.01)

1982-1983 (1.98)

1986-1987 (1.93)

2013-2014 (1.85)

1999-2000 (1.72)

2002-2003 (1.63)

1981-1982 (1.56)

1983-1984 (1.51)

1987-1988 (1.49)

2009-2010 (1.48)

1974-1975 (1.46)

2003-2004 (1.45)

 

In looking at the various stats and teleconnections associated with these winters, it was a real mix with few strong correlations.  For ENSO, moderate El Ninos led the way as seen below.

 

Using the MEI Rankings for classifying the fall/winter ENSO…

6/15 were El Nino (1 Weak, 4 Moderate, 1 Strong)

6/15 were ENSO Neutral

3/15 were La Nina (1 Weak, 1 Moderate, 1 Strong)

 

 

Now a quick look at a city with higher wintry precip climo…Asheville.  If we look at the top 15 snowfall winters for Asheville since 1950, the ENSO stats were similar but with a bit more of a lean toward El Nino (8/15 were El Nino).  Also, -AO and -NAO winters were more prevalent in the high snow years in Asheville (10/15 with –AO, and 11/15 with –NAO). 

[griteater]

North Pacific Pattern

Of all the elements that go into making a winter outlook, the one to me that is the toughest to formulate a forecast call for is the pattern in the North Pacific.  In spite of this, well known tendencies show their hand when ENSO and the PDO are in sync (either both positive as expected for this winter, or both negative).

 

I will attempt to forecast the North Pacific pattern using the following factors:

1.       ENSO/PDO Combo

2.       Persistence Pattern

3.       Aleutian Low Positioning

 

 

ENSO/PDO Combo

I created the composites below in order to analyze typical positive ENSO / +PDO 500mb patterns, segmented by Nino strength.  You will notice that some years are in multiple composites.  I did this for cases where ENSO was borderline between two ENSO classifications when looking at both the ONI and MEI.  For example, the 77-78 winter was a weak Nino per ONI, but a moderate Nino per the MEI rankings.  For this reason, I included 77-78 in both the weak Nino and moderate Nino composites.  For the PDO, I included winters with a positive PDO, and winters that were neutral but leaning and/or trending positive.

 

 

Here are my thoughts on these composites:

1.       The Aleutian Low is weaker and positioned more to the west in the Weak Nino / Positive Neutral composite.  The weaker Aleutian Low is indicative of a more variable pattern in the North Pacific compared to the stronger Nino years.  The strong Nino composite has the Aleutian Low farthest east and more expansive.

 

2.       Weak Nino / Positive Neutral has the best signal for –EPO ridging up through Alaska and into the Arctic (i.e. best signal for cold, cross-polar flow out of Siberia), and has the weakest signal of the three for storm waves tracking through the desert southwest / northern Mexico into the southern Plains.

 

3.       Moderate Nino has the best signal for a +PNA / -AO / -NAO combo.  AO/NAO stats back to 1900 confirm this.  Also, the composite indicates an active southern stream.

 

4.       Strong Nino shows a pattern with ridging across the northern Plains and south/central Canada downstream of the big Aleutian Low.  This tends to choke off cold air transport from the north and favors warmer Pacific flow.  Strong Nino has the strongest signal for an active southern stream.

 

 

Persistence Pattern

Let’s take a look at the pattern in the north Pacific and western North America over the past 2 years.

 

2013 featured a strong and very persistent ridge just off the west coast and into the Gulf of Alaska.  Moving into 2014, we’ve seen the ridge weaken a bit and move east into the western U.S.  At the same time, we’ve seen an increased presence of an Aleutian Low (negative anomalies south of Alaska), including Aleutian Low anomalies during the key month of October.

 

The pattern progression in the North Pacific over the past 2 years and the climo presence of an Aleutian Low during weak Nino / +PDO winters both support a forecast call of an Aleutian Low in the mean charts for the upcoming winter.

 

 

 

 

 

Aleutian Low Positioning

Now let’s take a look at the positioning of the Aleutian Low.  As covered in the previously displayed composites, the climo position for the Aleutian Low during weak Nino / +PDO winters is to the west with the negative anomalies located to the south of the western end of the Aleutian Islands.  Looking at past composites, the October Aleutian Low placement typically provides clues to how the climo winter positioning of the Aleutian Low should be adjusted.  As seen below, the 2014 October Aleutian Low was centered more to the east, in the Gulf of Alaska.  This favors an eastward adjustment of the climo position of the Aleutian low during weak Nino / +PDO winters.

 

 

 

North Pacific Pattern Call: It’s my belief that the mean 500mb pattern in the North Pacific will support a weak to moderate strength Aleutian Low that is positioned east of the weak Nino / +PDO climo positioning, and somewhat similar to the climo position for moderate Nino / +PDO winters, with the negative anomalies centered  between Hawaii and Alaska’s Aleutian Islands.  I don’t believe we will see an easterly placed Aleutian Low in the Gulf of Alaska in the full winter averaged charts, although we could see it positioned there at times.  Persistent east based Aleutian Lows are typically reserved for higher end Ninos.

[griteater]

AO / NAO

 

 

October Indicators

The October precursors for a wintertime averaged –AO and –NAO were excellent:

 

1.       Eurasian snow cover extent (SCE) and snow advance (SAI) were both 2nd highest in history (since late 60’s / early 70’s).  The October Pattern Index (OPI) was the 2^nd most negative in history (since 1976).  Each of these strongly favors a –AO winter.

 

2.       Poster WxMidwest’s North Pacific Indicator favors a –NAO winter.

 

3.       Other October indicators that favor high latitude blocking this winter include an extreme –AO blocking episode in early October, favorable stratospheric wave activity during October, and forecasted warm anomalies appearing in the stratosphere in Siberia over the next couple of weeks.

 

 

Non-October Indicators

1.       ENSO - historically, –NAO/–AO winters have been more common in El Nino winters (42%/50%) compared to Neutral (28%/39%) and La Nina (28%/28%) winters.

 

2.       QBO/Solar – there isn’t a single good QBO/Solar analog for this winter.  There are 5 winters that match the projected “Negative and Falling” QBO phase in the lower stratosphere at 45mb; however, none of those 5 winters occurred during neutral solar flux conditions (3 occurred during solar flux max winters, and 2 occurred during solar flux minimum winters). 

 

The highest QBO/Solar correlation in the data that I’ve compiled occurs when we are in the front end of the –QBO cycle at 45mb (Neutral and Falling or Negative and Falling), combined with solar minimum.  That combination has occurred 5 times (62-63, 76-77, 86-87, 95-96, 09-10).  The Dec-Mar NAO was negative in all 5 winters and strongly negative in 4 of the 5 winters.  For the AO, the Dec-Mar AO was strongly negative in all 5 cases.  We should be able to revisit this combination a time or two as we end this decade and go into the 2020’s.

 

3.       Decadal Trends – the current 10 year running mean for the NAO is close to zero indicating that there is no strong decadal trend.  For the AO, the 10 year running mean is slightly negative.  Neither of these lends predictive support for the AO or NAO this winter.

 

Bottom Line: The sum of the October and Non-October indicators favor a –AO/–NAO winter.  One ‘fly in the ointment’ that could challenge the –AO/–NAO call would be if we experience solar max conditions this winter.  We are likely to see occasional solar max flare ups, but in my opinion, we are unlikely to see sustained conditions that would classify the winter as a solar max winter.

 

 

High Latitude Blocking – Positional Analysis

I put together the composites below showing a comparison of winters when the high latitude blocking was focused in the Eastern Hemisphere (“on the other side of the pole”) vs. in the Western Hemisphere (I didn’t include winters in which the high latitude blocking was distributed equally in both hemispheres).  The noted response along the east coast is above normal heights in the East Hemi composite vs. below normal heights in the West Hemi composite.

 

Here is the key point – using MEI ENSO rankings, none of the Eastern Hemisphere Blocking winters occurred during El Ninos (4 Ninas and 5 Neutral).  In the Western Hemisphere Blocking composite, 5 were Nino, 4 were Nina, and 3 were Neutral.

 

 

 

Now let’s look at the NAO.  If we do in fact see a –NAO this winter, the strength of the –NAO plays a key role in determining the placement of the positive and negative height anomalies.  As seen below, during weaker –NAO winters, the positive height anomalies near Greenland are centered farther north and east, while during stronger –NAO winters, the positive height anomalies are centered farther south and west (southwest of Greenland).  The response along the east coast is that the negative anomalies are deeper and farther south in the stronger –NAO composite.

 

 

 

AO / NAO Call: It is my belief that the AO and NAO will average moderately to strongly negative this winter.  The winter averaged –NAO positive height anomaly will be west based, with the positive height anomalies extending to the southwest of Greenland.  The risk of high latitude blocking being focused on the “other side of the pole” in the Eastern Hemisphere is low.

[griteater]

Southern Stream

 

Using NOAA’s U.S. Daily Weather Maps websites (NOAA 1 & NOAA 2), I charted the number of southern stream storms that affected the Southern Plains and eastern third of the U.S. for each winter since 1956-1957 (December-March).  Here are the criteria I used to designate a storm a southern stream storm system:

 

1.       Parent surface low had to track southeast of a line from northern Arkansas to northern Kentucky.

2.       Storm must be associated with a 500mb shortwave that ejected out of the Southern Plains (Oklahoma/Texas).  Full latitude troughs and northern stream dominate systems were thrown out.

3.       Weak storms with minimal precipitation across the southeast were thrown out.

 

 

Here’s is the breakdown of average number of southern stream storms by ENSO strength based on MEI rankings.  As shown, El Ninos lead the way, with a peak during moderate Ninos.

 

 

 

Here is the breakdown of average number of southern stream storms by ENSO & PDO.  As expected, the Nino & +PDO composite leads the way.

 

 

 

Here is the list of the top 10 winters containing the most number of southern stream storms.  The combination of Nino, +PDO, –AO, and –NAO winters dominate the list (Note: "2003" in the list means 2002-2003)

 

 

 

Here is the list of the bottom 10 winters containing the least number of southern stream storms.  The combination of Nina, -PDO, and +NAO winters is favored in the list.

 

 

 

Here are some other stats related to the data I compiled on the number of southern stream storms:

 

1.       The annual average is 8.9.

 

2.       The highest 10 year average (10.7) occurred during the 1957-1966 period.

 

3.       The lowest 10 year average (7.0) is the current period (2005-2014).  Since 1957, there have been 5 cases in which there were less than 5 southern stream storms.  3 of those 5 occurrences happened within the last 6 winters.

 

4.       Most southern stream storms by month:

December: 1969, 2002 (5 storms)

January: 1987 (6 storms)

February: 1983 (6 storms)

March: 1958, 2003 (6 storms)

 

5.       The least amount of southern stream storm systems occurred during second and third year La Ninas.  During those winters (total of 6), the average number was a meager 4.5

 

6.       The winter of 2010-2011 featured only 4 southern stream storms.  However, 2 of the 4 were major winter storms in the southeast.

 

7.       The 2 winters that stood out to me the most for the southeast U.S. were the winters of 1982-1983 and 1986-1987.  Both of those winters featured a steady flow of waves in the southern stream with numerous associated surface lows ejecting out of the central Gulf of Mexico.

 

 

Southern Stream Storms Call: Based on the projected combination of Weak El Nino, Moderate to Strong +PDO, and Moderate to Strong -AO / -NAO, my call for the total number of southern stream storms this winter is 11 (Avg is 8.9).

[griteater]

Winter Forecast Calls

 

 

500mb Pattern

Here is my projected December – March averaged 500mb height anomaly approximation:

 

 

 

Temperature Anomalies

Here are my projected December – March Temperature Anomalies:

 

 

 

Here are my thoughts on wintry precipitation: I believe the southern stream will be a little more active than climo, but I’m not of the belief that we will see a parade of southern stream storms representative of higher level Ninos in the mold of 82-83, 86-87, 02-03, and 09-10.  As for wintry precipitation (snow & ice), I will go with a blanket “slightly to moderately above average” projection for the entire southeastern U.S., with no preference for any specific region to receive more, or less, wintry precipitation.  For the purposes of this outlook, the southeastern U.S. covers: E TN, AL, GA, N FL, SC, NC, SE VA. 

 

 

“Preseason Rating”:

For the southeast as a whole, I’ll give a general rating from 0 to 10, based on the following:

 

0 = well above normal temperatures, well below normal amount of wintry precipitation (snow & ice), well below normal # of winter storm threats

10 = well below normal temperatures, well above normal amount of wintry precipitation (snow & ice), well above normal # of winter storm threats

 

My call for this winter for the southeast (E TN, AL, GA, N FL, SC, NC, SE VA):  7.5

 

 

Forecast Calls For Charlotte:

Temperature Departures:

Dec: -1 to -2

Jan: -3 to -4

Feb: -3 to -4

Mar: 0 to -1

 

 

Summary of Other Forecast Calls:

1.       The Dec-Mar averaged AO and NAO will end up moderately to strongly negative.

2.       Total number of southern stream storms (as defined earlier) will be 11 (Avg is 8.9).

3.       The Fall/Winter ENSO will be best classified as Weak El Nino (combination of MEI, ONI, Weekly Averaged SST).

4.       The Dec-Mar averaged PDO will be moderately to strongly positive.

5.       The Jan-Feb averaged QBO will be classified as Negative and Falling at 45mb.

6.       The 90 day, Dec-Feb averaged, observed solar flux will fall in the neutral range: 105-150 (x 10 ^-22 W m^-2 Hz^-1).

 

 

Regardless of my prediction, what I would really like to see this winter is something like this…

 

[FallsLake]

Great forecast! This follows along with many other forecast ideas presented over the past weeks but you have provided us with very good details; and that is very much appreciated. I need to now go back and re-read some of those details.

[packbacker]

Wow, great analysis! Looking forward to re-reading this.

[frazdaddy]

Nice work Grit. I'm all in now!

[calculus1]

Thanks for all the time and effort you put into this, griteater!  It was a well-written, very informational forecast.

[WxKnurd]

Great work as usual. Love reading your outlooks, thanks for posting!

[CherokeeGA]

Thank you for this - very good read!

[GaWx]

Grit,

Very well presented forecast and quite an interesting read with your rather unique way of looking at the various factors. Lots of time and effort obviously went into this forecast. Thanks.

[Brick Tamland]

And yet another very positive forecast for snow this winter.

[Cold Rain]

Grit, I haven't had time to read it yet (at a conference all week in Denver). But I approve of the last little bit there. Thanks for putting this together and sharing with the group. I hope you didn't go cold just to avoid getting ridiculed and driven from the boards, though.

[PisgahNCWeather]

Great write up Grit!

[jburns]

Well done, whether it verifies or not.    

[WXinCanton]

Very nice!  Thank you for sharing!

[buckeyefan1]

Awesome writeup once again Grit!  I hope it verifies    

[griteater]

Thanks buckeye et al on the compliments.  I appreciate it.  I get a little carried away with those write-ups, lol.  Curious to see what happens in the high latitudes this winter...all signs look promising

[Met1985]

Great analysis and write up Griteater! Thank you!

[deltadog03]

Great work Grit!!!

[tnweathernut]

That's more reading than I did even back in high school and college, but nicely presented and aligns with many of my thoughts.  Great job, very detailed, and excellent presentation.  Way to go Grit, thanks for taking the time to post it for us to read

 

If it seems almost everyone is going cold and snowy this year, it's b/c they are.  When just about every index and analog suggest it, it's hard not to have a cold and snowy outlook.

[Supercane]

I think both you and RaleighWx did outstanding jobs with your outlooks. Great stuff.

[Ginx snewx]

Fantastic analysis,well written and thought out. Good luck, love the southern stream stats

[Brick Tamland]

That's more reading than I did even back in high school and college, but nicely presented and aligns with many of my thoughts. Great job, very detailed, and excellent presentation. Way to go Grit, thanks for taking the time to post it for us to read

If it seems almost everyone is going cold and snowy this year, it's b/c they are. When just about every index and analog suggest it, it's hard not to have a cold and snowy outlook.

Everyone except for the TV mets around here. Not sure what they are looking at.

[Isopycnic]

Thanks for the great analysis.

[Jonesing for a chase]

Thanks, great job! The Aleutian Low position was particularly interesting and something to watch this winter

[griteater]

Thanks for the kind words all.  I appreciate it