Griteater's Winter Outlook (2012-2013)

[griteater]

Griteater’s Winter Outlook (2012-2013)

I'm going to submit this in 2 posts. The first on Climatology, and the 2nd on this year's winter outlook...

Climatology
I’m going to start off by running through some select winter climatology data for Charlotte (CLT) in order to establish some trends in winter temperatures and snowfall, at least in this area. Here’s the average winter temperature (Dec/Jan/Feb/Mar) for Charlotte going back to the late 1800’s. I’ve used a 10 year running average to smooth out the data and to show any noteworthy trends. As you can see, while there have been some cold periods (60’s) and warm periods (90’s), there’s no discernible trend with the average winter temperatures if you consider the full spectrum of the data.



However, if we dig a little deeper and look at the number of winter days with high temperatures of 42 degrees or less, we can see a noteworthy warming trend.

Aside: I chose 42 degrees as an arbitrary threshold value to represent those below normal days (below normal around here anyway) that contain the kind of temperatures that can produce measureable wintry precipitation. No doubt, you’d like to see highs that are much colder, but you have to consider cases where the high occurred at midnight prior to precip arrival…or cases where there was measureable precip in the AM, followed by warming afternoon temps. For CLT, 77% of calendar days with measureable snow contained high temps of 42 or less, and 94% of calendar days with 4 inches of snow or more contained high temps of 42 or less (based on daily high/low temperatures for CLT going back to 1893).

Looking at the graph for CLT, we see that the 10 year average for the number of winter days with high temps of 42 or less was around 24 days at the beginning of the 1900’s, and that number has decreased to around 14 days at the beginning of the 2000’s, a 42% decrease over that 100 year period.



Here’s another way to look at the warming trend, particularly in the last 20 years…from 1894 to 1990, 91% of winters in Charlotte experienced double digit (10 or more) number of days with high temps of 42 degrees or less. Post 1990, only 64% of winters experienced double digit number of days with high temps of 42 degrees or less.

Comparatively, let’s look at the number of winter days with high temperatures of 32 degrees or less. Here, the warming is even more noticeable. The 10 year average for the number of winter days with high temps of 32 or less was around 5 days at the beginning of the 1900’s, and that number has decreased to a 10 year average of only 1 day at the beginning of the 2000’s, an 80% decrease over that 100 year period.



Now let’s look at snowfall. Here’s the average annual snowfall for Charlotte (using a 30-year running average). We see a sharp rising trend during the ‘snowy’ years from the late 50’s through the late 80’s, and a sharp fall since 1990. The current 30 year annual average of 4.0 inches is an all-time low since official records have been kept (back to 1879). Note: the long term annual snowfall average for the period 1879 to 2012 is 5.7 inches.



A couple of additional stats:

• The 30-year average for the number of annual measureable snow events (0.1 in of snow or more) at CLT was around 3.1 events per year in the early 1900’s, and is down to around 2.0 events per year in the early 2000’s, with the current 30 year average of 1.6 at an all-time low.
• The 30-year average for the number of annual snow events of 4 inches or more at CLT has held steady through the recorded history at around 0.5 events per year. So, per the long term averages, Charlotte receives a snowfall of 4 inches or more once every 2 years.

Note on Last Winter (2011-2012)
I have deduced that last winter was indeed the ‘worst’ winter of all-time in Charlotte (‘best’ if you like winter golf). The average Dec-Mar temperature was 50.2, the 5^th all-time highest for winter. However, there were only 2 days with high temperatures of 42 or less, which was the fewest of all-time. Also, there was no measureable snow.

[griteater]

Griteater’s Winter Outlook (2012-2013)

Here's Part 2...

ENSO (El Nino – Southern Oscillation)

It’s well advertised that the ENSO state for this fall/winter will either be positive neutral or a low-end weak El Nino. On the IRI/CPC site (http://iri.columbia..../SST_table.html), there are 25 models listed for ENSO forecasting. In looking at the verification plumes for these models, the one that appears to be performing as well as any over the past 2 years is the ESSIC Intermediate Coupled Model. In recent months, it had been forecasting a low-end weak El Nino, but in the October release, it is now forecasting a positive neutral ENSO. Here’s the verification plume and forecast for the ESSIC (the black line is the actual ENSO value over the past 2 years, and the red dots are the ESSIC forecasts):

Looking at the 850mb Trade Wind Index Anomalies for the West Pacific (2^nd set of data here - http://www.cpc.ncep....indices/wpac850), the index value has been negative for the months of July-October for every developing El Nino since 1979, without exception. That’s not the case this year, as the index was moderately positive in both July and August. Negative values of this index indicate a weakening or reversal of easterly low-level equatorial winds in the western Pacific, a hallmark of a developing El Nino.

Lastly, the OLR (Outgoing Longwave Radiation) pattern over the past 1-3 months is more indicative of neutral ENSO conditions as opposed to a developing El Nino, with neutral OLR anomalies along and east of the dateline in the equatorial Pacific. One would expect to see negative OLR values in this region in a developing El Nino (even a weak one), indicating persistent tropical convection.

While I believe that this fall/winter will end up being classified as positive Neutral, whether it ends up as positive Neutral or as a low-end weak El Nino is moot, as its impacts are likely to be same either way. More on that later.

One additional note on ENSO – since 1878, there have been 12 neutral ENSO winters following a La Nina winter (note: I used the MEI.ext for classifying ENSO prior to 1950). Those years are: 1881 (i.e. 1880-1881 winter), 1888, 1891, 1896, 1908, 1935, 1944, 1986, 1990, 1997, 2002, and 2009). In those 12 winters, Charlotte received greater than average snowfall in only 1 winter (1881). Only 3 of the winters had near average snowfall (1908, 2002, 2009), and the rest (8) had below average snowfall.

PDO (Pacific Decadal Oscillation)

The PDO has been decidedly negative going all the way back to the spring of 2010. The August and September values of the PDO were some of the most negative Aug/Sept PDO values on record. In looking at sea surface temperature anomalies in the north Pacific, it does appear that the strongly negative PDO has weakened (Oct NOAA PDO value confirms this). In spite of this, it’s my belief that the PDO will average moderately negative for this fall/winter, and here’s why:

1. We are currently believed to be in the midst of a negative decadal PDO cycle where negative PDO years/winters are more common than positive PDO years/winters. Here’s a graphical depiction of the current negative PDO regime (note the positive PDO regime from the late 1970’s through the late 1990’s, and negative regime thereafter):
   

1. It’s more common for weather patterns associated with a robust, developing El Nino, or multi-year El Nino, to move a multi-year negative PDO toward neutral or positive values than it is for a single positive neutral or weak El Nino year to do so.
   
2. The ECMWF Seasonal (EURO) and JAMSTEC models are forecasting a –PDO SST configuration for the winter.
   
3. The CFSv2 Ensemble PDO plumes have risen some with the October forecast, but nevertheless, they continue to forecast a negative PDO for the winter:
   

ENSO / PDO Analogs

In looking at prior years that match the ENSO/PDO signal for this winter, the main things to focus on are the pattern in the North Pacific and the Subtropical Jet Stream. The pattern in the North Pacific tends to be strongly tied to the PDO. When the PDO is positive, the tendency is for large-scale troughing to occur south of Alaska’s Aleutian Islands. When the PDO is negative, the tendency is for large-scale ridging south of the Aleutians. Below is a 500mb composite of my ENSO/PDO analogs for this winter. They include ENSO neutral and low-end El Nino years that also had a –PDO (note: I use the 1971-2000 climatology set for ENSO, and I define –PDO as the Oct-Feb PDO averaging -0.40 or lower – from the Univ. of Wash data). In the composite, you can see the large-scale ridging south of the Aleutians. It’s important to note that composite maps can very well mask varying patterns in the individual years. However, when viewed individually, each year in the composite set exhibited some level of ridging south of the Aleutians. The downstream effect of this is troughing in western North America, with neutral heights or weak ridging in the southeast. The AO and NAO play a huge role in the resulting mean heights in the southeast. More on that later as well.

Regarding the subtropical jet stream, the map below shows the zonal wind anomalies at 250mb for my ENSO/PDO analogs for this winter. The yellow/orange coloring shows westerly winds that are stronger than normal, with the blue/purple coloring showing westerly winds that are weaker than normal. In the ENSO/PDO composite set for this winter, we see fairly weak westerly anomalies extending from off Baja California into the central U.S. By comparison, typically the higher-end El Ninos (moderate & strong) exhibit a pattern that favors a stronger and more southerly displaced Subtropical Jet Stream whereby the zonal wind anomalies contain stronger westerlies that extend off Baja into the Gulf of Mexico, favoring a pattern in the southeast that is active with storms that are infused with deep tropical moisture. Given 1) the projected ENSO state for this winter, 2) the fact that we are coming off back-to-back La Ninas, and 3) the aforementioned lack of El Nino-like tropical convection east of the dateline, I would expect the contributions of the Subtropical Jet Stream toward an active and stormy pattern for the southeast to be a little weaker than average for this winter.

Artic Oscillation (AO) / North Atlantic Oscillation (NAO)

The winter state of the AO and NAO are huge in determining the amount of cold air available and the resulting 500mb pattern across the southeast. It’s well documented that a –AO and –NAO are the preferred states for a colder than normal central and eastern U.S. during the winter. Here are the factors I will use to examine the AO/NAO state for this winter:

1. ENSO and AO Tendencies
   
2. QBO/Solar Combo
   
3. October Snow Cover and Siberian High in Eurasia
   
4. October AO
   

None of these factors when viewed individually offer strong enough correlation for forecasting the winter AO/NAO. However, we can attempt to forecast the AO/NAO when viewing them as a whole. My focus in the subsequent sections will be on attempting to forecast the AO. The NAO is essentially the North Atlantic portion of the AO, and it typically (but not always) aligns itself with the AO. I think it makes more sense to look at the all encompassing AO when making a forecast, instead of attempting to focus on a specific region of the AO.

ENSO and AO Tendencies

I looked at the percent monthly AO breakdown for winter (Dec-Mar) based solely on the fall/winter ENSO designation (using 1971-2000 climatology for ENSO). Here are the results:

ENSO / -AO / AO / +AO

El Nino / 50% / 24% / 26%

Neutral / 42% / 25% / 33%

La Nina / 37% / 31% / 32%

So, to further explain, in looking at line 1, during El Nino winters, the AO was negative 50% of winter months (Dec-Mar), the AO was neutral 24% of winter months, and the AO was positive 26% of winter months. I define –AO as a monthly value of -0.5 or lower, neutral AO as between -0.5 and 0.5, and positive AO as +0.5 or higher.

Note that if we consider the percent monthly AO breakdown for all winters (Dec-Mar) since 1950, we get the following:

-AO / AO / +AO

43% / 27% / 31%

Thus, if we compare the AO values per ENSO year vs. the AO values for all winters, we see that El Nino winters have contained more –AO winter months than the average (50% vs. 43%), Neutral ENSO winters have contained a near average number of –AO winter months (42% vs. 43%), and La Nina winters have contained less –AO winter months than the average (37% vs. 43%).

Secondly, I looked at the monthly AO breakdown for winter (Dec-Mar) of strongly negative and strongly positive AO months, again based solely on ENSO. I define strongly –AO as a monthly value of -2.0 or lower, and strongly +AO as a monthly value of +2.0 or higher. Here are the results:

ENSO / Strongly –AO / Strongly +AO

El Nino / 20% / 3%

Neutral / 10% / 5%

La Nina / 11% / 5%

Once again, El Nino was the preferred state. 20% of El Nino months experienced a strongly –AO, with around 10% of Neutral and La Nina months experiencing a strongly –AO.

QBO / Solar Flux Combo

QBO

Many papers have been written on the effects of the QBO (Quasi-Biennial Oscillation) and solar cycle on the stratospheric polar vortex; with a warm, disturbed vortex, favoring a negative AO, and a cold, undisturbed vortex favoring a positive AO. The QBO is a fairly predictable oscillation in the stratosphere above the equator, where the zonal winds change between east (-QBO) and west (+QBO) with time. We are currently in the middle of a –QBO in the lower stratosphere. The current –QBO phase has flat-lined and is lasting anomalously long. 2000-2001 is a good comparison with respect to the length of this current –QBO phase. The negative anomalies that year lasted 18 months at 30mb, and 17 months at 50mb. Based on this comparison, the –QBO at 30mb should be moving to neutral by April 2013, and the –QBO at 50mb should be moving to neutral by June 2013. Bottom line, I expect the QBO to average solidly negative in the lower stratosphere through the winter.

Solar Flux

With respect to the solar cycle, we are coming up on a solar max for this winter. However, the solar max is fairly weak, and the solar flux values are expected to fall in the range of what is considered to be neutral. Generally, F10.7 cm solar flux values of 105 or less denote solar minimum values, while values of 150 or higher denote solar maximum values. You can see the 45-day forecasted solar flux values here - http://www.swpc.noaa...latest/45DF.txt (second set of data).

AO Based on QBO / Solar Flux Combo

Since 1950, the following winters experienced a –QBO pattern in the lower stratosphere (for clarity, when I state “1957”, for example, I’m referring to the 1956-1957 winter): 1957, 1959, 1961, 1963, 1966, 1969, 1971, 1975, 1980, 1982, 1990, 2004, 2006, and 2008. Of those years, the very best QBO comparisons with this winter are 1959, 1966, and 1975.

Once again, I looked at the percent monthly AO breakdown for winter (Dec-Mar) based solely on the –QBO analog years. Here are the results:

-AO / AO / +AO

48% / 21% / 30%

So, in the –QBO winter analog years (same as this winter), 48% of the winter months experienced a –AO.

By comparison, looking solely at +QBO winter analog years yields the following:

-AO / AO / +AO

40% / 24% / 36%

Thus, when looking solely at the QBO, the occurrence of –AO months are a little more frequent than the average in –QBO winters, and a little less frequent than the average in +QBO winters.

Factoring in solar flux forces me to remove the –QBO analog winters where the solar max was anomalously high (1957, 1959, 1980, 1982, 1990) and where the solar min was anomalously low (1975, 2008). That yields the following with respect to the percent monthly AO (winter Dec-Mar):

-AO / AO / +AO

61% / 32% / 7%

So, the percentage of –AO winter months increased when factoring in the removal of anomalously high and anomalously low solar flux winters (in an attempt to better match the conditions of the upcoming winter)…but in both cases, there was more of a signal for a –AO as opposed to a +AO when looking at the individual winter months.

October Snow Cover and Siberian High in Eurasia

Several papers have been written on the correlation between Eurasian snow cover in October and the resulting AO for the subsequent winter. When the expanse of October snow cover in Eurasia is high and the rate of the snow cover advance south of 60N in Eurasia is high, the atmospheric response to the snow cover favors a –AO for the winter. When the expanse and advance of the snow cover is low, the atmospheric response favors a +AO for the winter. Here are two papers that expound on this subject:

http://www.nws.noaa....ohen_062211.pdf

http://web.mit.edu/j...Jones_GRL11.pdf

By all accounts, the expanse and rate of snow cover advance in Eurasia this October has been above, to much above normal. In the Cohen paper from June 2011 (1^st link above), it talks about the atmospheric response to the snow cover. When the October Eurasian snow cover is anomalously high, the tendency is for the Siberian High to be stronger and more expansive than normal across northern Eurasia. The paper states that the high pressure located initially across northern Eurasia then spreads across the Arctic Ocean, leading to a –AO during the winter.

The opposite rings true in low snow cover Octobers in Eurasia. In these years, the Siberian High tends to be weaker than normal across northern Eurasia, eventually leading to a +AO during the winter.

Below is a composite of Sea Level Pressure (SLP) in Octobers prior to the Top 10 most negative AO winters on record since 1950 (I used the Hurrell data for the Dec-Mar AO: https://climatedatag...nam_pc_djfm.txt). I’ve circled in red the area in northern Siberia where the SLP’s are anomalously high.

Now here’s a composite of SLP in Octobers prior to the Top 10 most positive AO winters on record since 1950. I’ve circled in red the area in northern Siberia where the SLP’s are anomalously low.

Now let’s look at the 2012 October map. Here we can clearly see that the Siberian High this October has been stronger than normal. As a matter of fact, it’s as strong, if not stronger than any of the Octobers prior to –AO winters that I looked at (when viewing the individual years).

Bottom line, the anomalously high snow cover extent and advance in Eurasia this October, and the atmospheric response of a stronger Siberian High in northern Eurasia this October, favors a –AO for the upcoming winter.

October AO

The 2012 October monthly AO reading came in at -1.51 which is the 2^nd lowest October reading since 1950. There have been 9 Octobers since 1950 with an AO value of -1.00 or less. Here’s the percent monthly AO breakdown for the total of those 9 subsequent winters (Dec-Mar):

-AO / AO / +AO

47% / 19% / 33%

So, when compared to the AO for all winters, we see here that –AO winter months were slightly more common than the average (47% vs. 43%) following Octobers that experienced a negative AO of -1.00 or below.

If we restrict the –AO Octobers to just include the top 5 most negative AO Octobers since 1950, we get the following percent monthly AO breakdown for the total of those 5 subsequent winters (Dec-Mar):

-AO / AO / +AO

50% / 25% / 25%

AO Call For This Winter: Putting all of it together, my call for this winter’s AO is two months with a negative AO, with one of those two months being strongly negative (-2.00 or lower), one month with a neutral AO, and one month with a positive AO.

Conclusions (Putting It All Together)

When the AO / NAO are positive this winter, I can envision a mean pattern looking like the map below (Dec 2008 from one of my ENSO/PDO analog years, 2008-2009), favoring normal to above normal temperatures in the southeast.

When the AO / NAO are negative this winter, I can envision a mean pattern looking like this map (Feb 1952 from one of my ENSO/PDO analog years, 1951-1952), favoring normal to below normal temperatures in the southeast.

Summary of My Calls For This Winter:

1. For the southeast, I’m going to give a general rating from 0 to 10, with 0 being very warm / no snow, and 10 being very cold / very snowy (compared to average). For this winter, my call is smack dab in the middle – 5
   
2. Specifically for Charlotte, here are a few more details:
   
   • Total snowfall: 3-7 inches
     
   • Total number of measureable snow events: 1-3
     
   • Total # of days with high temperatures of 42 or less: 11-17
     
   • Total # of days with high temperatures of 32 or less: 1-2
     

[*]ENSO will end up being classified as Neutral Positive

[*]Average PDO for the Oct-Feb period will be -0.70 to -1.30

[*]Number of negative PNA days will outnumber the number of positive PNA days 2 to 1.

[*]Contributions of the Subtropical Jet Stream toward an active and stormy pattern for the southeast will be a little weaker than average for this winter

[*]QBO will average solidly negative in the lower stratosphere (30mb – 50mb) through the winter.

[*]AO will be negative 2 months, with one of the months being strongly negative (-2.00 or lower), neutral 1 month, and positive 1 month.

[*]Best chance for below normal temperatures will be across the central and northern Rockies, and upper Midwest.

[*]Western Ski Resorts – I’ll go with a general near average snow across the west, with the following exceptions – below normal in Southern California and Northern Arizona, and above normal in northern Utah, Wyoming, and Colorado.

[griteater]

Had to clean up a few images in there...done now (I think)

[burgertime]

Great post. Good to see something more Charlotte specific!

[griteater]

Adding the last part in a separate post here (too many images...lol)...

The type of widespread winter weather event to look for in the southeast would be a shortwave toppling a Pacific ridge and moving into the Pacific Northwest before diving southeast into the Southern Plains, then tracking east across the upper south underneath a blocking –AO / -NAO setup. An example of this type of storm from my ENSO/PDO analog years would be Dec 31 – Jan 1 1962. That particular storm brought 1 inch to Atlanta, 6.6 inches to Greensboro, and 6.0 inches to Charlotte. Here’s an animation of that storm:

[Met1985]

Well done.

[deltadog03]

Very good read! TY!

[Psalm 148:8]

Great job! Boy do I feel dumb now. Are you a met?

[buckeyefan1]

Well done griteater

[BIG FROSTY]

Great job!!!

[NCSNOW]

Good Job Griteater: Very well laid out and great suport/data promoting your stance. Thanks for investing the time and sharing with the rest of us.

[nchighcountrywx]

_{Thanks for the well thought out write up. It is appreciated.}

_{As always, everyone in the Charlotte area wanting snow, keep your options open for frequent 1.5 hour drives to the NC High Country. Hopefully this will be a cooperative winter for some good snow for all.}

_{Don't expect anything else until December though...we'll have to get a read on how this pattern that is changing now will work out for the return of cold air in December.}

[Northern Foothills Snowman]

Griteater’s Winter Outlook (2012-2013)

I'm going to submit this in 2 posts. The first on Climatology, and the 2nd on this year's winter outlook...

Climatology

I’m going to start off by running through some select winter climatology data for Charlotte (CLT) in order to establish some trends in winter temperatures and snowfall, at least in this area. Here’s the average winter temperature (Dec/Jan/Feb/Mar) for Charlotte going back to the late 1800’s. I’ve used a 10 year running average to smooth out the data and to show any noteworthy trends. As you can see, while there have been some cold periods (60’s) and warm periods (90’s), there’s no discernible trend with the average winter temperatures if you consider the full spectrum of the data.

However, if we dig a little deeper and look at the number of winter days with high temperatures of 42 degrees or less, we can see a noteworthy warming trend.

Aside: I chose 42 degrees as an arbitrary threshold value to represent those below normal days (below normal around here anyway) that contain the kind of temperatures that can produce measureable wintry precipitation. No doubt, you’d like to see highs that are much colder, but you have to consider cases where the high occurred at midnight prior to precip arrival…or cases where there was measureable precip in the AM, followed by warming afternoon temps. For CLT, 77% of calendar days with measureable snow contained high temps of 42 or less, and 94% of calendar days with 4 inches of snow or more contained high temps of 42 or less (based on daily high/low temperatures for CLT going back to 1893).

Looking at the graph for CLT, we see that the 10 year average for the number of winter days with high temps of 42 or less was around 24 days at the beginning of the 1900’s, and that number has decreased to around 14 days at the beginning of the 2000’s, a 42% decrease over that 100 year period.

Here’s another way to look at the warming trend, particularly in the last 20 years…from 1894 to 1990, 91% of winters in Charlotte experienced double digit (10 or more) number of days with high temps of 42 degrees or less. Post 1990, only 64% of winters experienced double digit number of days with high temps of 42 degrees or less.

Comparatively, let’s look at the number of winter days with high temperatures of 32 degrees or less. Here, the warming is even more noticeable. The 10 year average for the number of winter days with high temps of 32 or less was around 5 days at the beginning of the 1900’s, and that number has decreased to a 10 year average of only 1 day at the beginning of the 2000’s, an 80% decrease over that 100 year period.

Now let’s look at snowfall. Here’s the average annual snowfall for Charlotte (using a 30-year running average). We see a sharp rising trend during the ‘snowy’ years from the late 50’s through the late 80’s, and a sharp fall since 1990. The current 30 year annual average of 4.0 inches is an all-time low since official records have been kept (back to 1879). Note: the long term annual snowfall average for the period 1879 to 2012 is 5.7 inches.

A couple of additional stats:

• The 30-year average for the number of annual measureable snow events (0.1 in of snow or more) at CLT was around 3.1 events per year in the early 1900’s, and is down to around 2.0 events per year in the early 2000’s, with the current 30 year average of 1.6 at an all-time low.
  
• The 30-year average for the number of annual snow events of 4 inches or more at CLT has held steady through the recorded history at around 0.5 events per year. So, per the long term averages, Charlotte receives a snowfall of 4 inches or more once every 2 years.
  

Note on Last Winter (2011-2012)

I have deduced that last winter was indeed the ‘worst’ winter of all-time in Charlotte (‘best’ if you like winter golf). The average Dec-Mar temperature was 50.2, the 5^th all-time highest for winter. However, there were only 2 days with high temperatures of 42 or less, which was the fewest of all-time. Also, there was no measureable snow.

First off I can see you put a lot of thought into you report but i've got a question for you .First on on the report of Charlotte Dec,Jan,Feb ,Mar temps you say you can see a noteworthy warming trend but when you look back at the30's through the 50's and to 60 doesn't it show to looks warmer than now?

[griteater]

^ Appreciate all the feedback...thanks.

[griteater]

First off I can see you put a lot of thought into you report but i've got a question for you .First on on the report of Charlotte Dec,Jan,Feb ,Mar temps you say you can see a noteworthy warming trend but when you look back at the30's through the 50's and to 60 doesn't it show to looks warmer than now?

I believe you are referring to the 1st graph of avg winter temperatures. So the 10 yr running avg winter temps from 1930-1960 would be around 46, with the current 10 year running avg closer to 45. If that's what you are referring to, then yes, there's a slight cool down with that comparison. Let me know if I'm off base with what you are looking at.

If you are referring to the next 2 graphs, those are showing the number of cold days (i.e. days with highs of 42 or less, or highs of 32 or less)...so the downward trend is actually indicating warming

[rduwx]

Nice job griteater!

[Northern Foothills Snowman]

I believe you are referring to the 1st graph of avg winter temperatures. So the 10 yr running avg winter temps from 1930-1960 would be around 46, with the current 10 year running avg closer to 45. If that's what you are referring to, then yes, there's a slight cool down with that comparison. Let me know if I'm off base with what you are looking at.

If you are referring to the next 2 graphs, those are showing the number of cold days (i.e. days with highs of 42 or less, or highs of 32 or less)...so the downward trend is actually indicating warming

Yes I was referring to the 1st graph. But on your second graph did't we start collecting temps by satelite in 1979 ?Also in 1979 that was nearing the end of a cool cycle.We've been in a warm cycle ever since but are ow entering a cool cycle.Also if you look where the tempurature data site are now near airports,beside asphalt parking lots,i'm sure that doesn't produce any heat,NOT,on black roof tops i'm sure you'll get a warming trend.

[griteater]

Yes I was referring to the 1st graph. But on your second graph did't we start collecting temps by satelite in 1979 ?Also in 1979 that was nearing the end of a cool cycle.We've been in a warm cycle ever since but are ow entering a cool cycle.Also if you look where the tempurature data site are now near airports,beside asphalt parking lots,i'm sure that doesn't produce any heat,NOT,on black roof tops i'm sure you'll get a warming trend.

The climate change forum handles these kinds of topics, but my data is purely from surface data reported over time in the city of Charlotte.

[Quixotic1]

Griteater, this was a good write up. Very linear, thorough and well reasoned. Best of luck on your forecast.

[calculus1]

Griteater’s Winter Outlook (2012-2013)

Note on Last Winter (2011-2012)

I have deduced that last winter was indeed the ‘worst’ winter of all-time in Charlotte (‘best’ if you like winter golf). The average Dec-Mar temperature was 50.2, the 5^th all-time highest for winter. However, there were only 2 days with high temperatures of 42 or less, which was the fewest of all-time. Also, there was no measureable snow.

I couldn't agree with you more. I have lived in the Lenoir/Hickory area for almost 30 years now, and I can't recall a winter being so "horrible" as the last one. Like I said in another post, I only had one day all winter where the high was lower than 40 degrees.

Also, this is quite the impressive write-up that you have put together. Thanks so much for sharing and well done on the research!

[jdrenken]

Very well done!

[griteater]

Thought I would give a bit of a winter post mortem and verification against my winter outlook (embedded within the text below).  The grades for each call are 'PASS', 'OK', 'FAIL', or 'MAJOR FAIL'

 

 

Summary of My Calls For This Winter:

1.       For the southeast, I’m going to give a general rating from 0 to 10, with 0 being very warm / no snow, and 10 being very cold / very snowy (compared to average).  For this winter, my call is smack dab in the middle – 5

 

Winter Outlook Grade - FAIL: For the southeast as a whole, I would give this winter a rating of 2.5 on a scale of 0 to 10, or a solid D (my call was a 5).  I’d say there were some areas like the mid and higher elevations of the NC mountains that were in the 4-6 range (around normal), but the vast majority were lower, with some areas in the 0-2 range (Atlanta, Raleigh, Asheville).

 

My general thoughts going into this winter were that a neutral ENSO after back to back La Ninas, combined with a –PDO, would favor a warmer and less snowy than normal winter.  However, I thought the Arctic Oscillation (AO) would be moderately negative, and thought it would impose enough influence to make winter end up around normal for the southeast in terms of temperatures and winter precipitation.

 

These thoughts were OK overall.  Temperatures for the Dec-Mar period ended around normal across the southeast, but we didn’t have enough super cold days and the majority of the below normal days came in March.  Also, the lack of a southern stream was a major hindrance for winter storms.

 

2.       Specifically for Charlotte, here are a few more details:

a.       Total snowfall: 3-7 inches

FAIL: Charlotte recorded 2.7 inches (all on Feb 16^th)

b.      Total number of measureable snow events: 1-3

PASS: 1 recorded on Feb 16^th

c.       Total # of days with high temperatures of 42 or less: 11-17

MAJOR FAIL: Only 3 recorded at CLT.  For the last 2 winters combined, there have only been 5 total days with high temperatures of 42 or less in Charlotte.  That’s easily the lowest number ever for back to back winters (since 1894).   

d.      Total # of days with high temperatures of 32 or less: 1-2

PASS: 1 recorded at CLT (High of 27 on Jan 25^th, day of light ice storm)

 

3.       ENSO will end up being classified as Neutral Positive. 

FAIL: ENSO ended up being Neutral Negative for late fall through winter

 

4.       Average PDO for the Oct-Feb period will be -0.70 to -1.30. 

FAIL: PDO from the Univ. of Washington site was -0.49 for the Oct – Feb period.

 

5.       Number of negative PNA days will outnumber the number of positive PNA days 2 to 1. 

FAIL: For Dec-Mar, there were 30 days of +PNA and 29 days of –PNA (I used less than or equal to -0.5 for –PNA and greater than or equal to 0.5 for +PNA)

 

6.       Contributions of the Subtropical Jet Stream toward an active and stormy pattern for the southeast will be a little weaker than average for this winter

OK: My ideas were on track here, though a better call would have been to say “weaker to much weaker than normal”

 

7.       QBO will average solidly negative in the lower stratosphere (30mb – 50mb) through the winter.

PASS

 

30mb zonal wind anomalies were:

Dec: -7.07

Jan: -4.13

Feb: -0.23

 

50mb zonal wind anomalies were:

Dec: -11.70

Jan: -9.65

Feb: -8.66

 

8.       AO will be negative 2 months, with one of the months being strongly negative (-2.00 or lower), neutral 1 month, and positive 1 month.

OK: The AO was negative all 4 months, and strongly negative one month (March).  Here are the numbers:

Dec:  -1.75

Jan:  -0.61

Feb: -1.01

Mar: -3.03

DJFM AO: -1.60

 

Though verbatim I missed the mark, I was probably more pleased with this call than any other given the difficulty in predicting the winter AO.  My thinking was that it would be moderately negative.  The combined DJFM value of -1.60 is more along the lines of ‘strongly negative’, as it is the 9^th most negative AO going back to 1899.

 

 

9.       Best chance for below normal temperatures will be across the central and northern Rockies, and upper Midwest.

 

OK: Not bad, but the coldest anomalies out west ended up being west of the Rockies.

 

 

10.   Western Ski Resorts – I’ll go with a general near average snow across the west, with the following exceptions – below normal in Southern California and Northern Arizona, and above normal in northern Utah, Wyoming, and Colorado.

 

Southern California – snowfall was below normal (PASS)

Northern Arizona – snowfall was near normal (FAIL)

Utah, Wyoming, Colorado – snowfall was below normal (FAIL)

Western U.S. (overall) – snowfall was below normal (FAIL)

 

11.   Other: NAO

 

Here’s the monthly breakdown of the NAO for the winter:

Dec: 0.07

Jan: -0.11

Feb: -0.96

Mar: -0.79

DJFM NAO: -0.45

 

12.   Other: Northern Hemisphere 500mb Height Composite and Surface Temperature Anomalies (for DJFM)