Winter 2014-2015 Medium-Term Discussion

[Chinook]

Why is the NAO index only -0.2 today?  The 500mb height pattern is close to what's needed for a -2 or -3 index

 

 

 

[hosj III]

Why is the NAO index only -0.2 today?  The 500mb height pattern is close to what's needed for a -2 or -3 index

 

2014_11_15_12z_500mb_anomaly1.png

Isn't it measured from southern greenland?

[griteater]

Why is the NAO index only -0.2 today?  The 500mb height pattern is close to what's needed for a -2 or -3 index

 

Positive NAO looks like this (flip it for negative).  To have a more negative NAO, the area from off the mid-Atlantic coast over toward Spain would need to be in negative height anomalies...and for the positive height anomalies around Greenland, those would need to be more expansive and farther south (compared to today's image).

 

[hosj III]

Positive NAO looks like this (flip it for negative).  To have a more negative NAO, the area from off the mid-Atlantic coast over toward Spain would need to be in negative height anomalies...and for the positive height anomalies around Greenland, those would need to be more expansive and farther south (compared to today's image).

 

Isn't it the difference between southern greenland and portugal?

[griteater]

Isn't it the difference between southern greenland and portugal?

 

I've seen it calculated in 2 ways.  One is station-based which is the difference in pressure anomalies between Reykjavik, Iceland and Lisbon, Portugal.  The other is principal component-based which is the difference in pressure anomalies over a larger area in the north atlantic (90W - 40E).  The principal component-based is better IMO because it's not subject to localized anomalies affecting the overall north atlantic regime.  NOAA CPC uses the PC-based method in their calculations.

 

https://climatedataguide.ucar.edu/climate-data/hurrell-north-atlantic-oscillation-nao-index-station-based

https://climatedataguide.ucar.edu/climate-data/hurrell-north-atlantic-oscillation-nao-index-pc-based

 

From NOAA/CPC - http://www.cpc.ncep.noaa.gov/data/teledoc/telepatcalc.shtml

"The RPCA (Rotated Principal Component Analysis) procedure is superior to grid-point-based analyses, typically determined from one-point correlation maps, in that the teleconnection patterns in the RPCA approach are identified based on the entire flow field, and not just from height anomalies at select locations."

[donsutherland1]

As of 2 pm EST, a very cold air mass was heading eastward as had been modeled for some time. Temperatures included:

 

Atlanta: 43°

Chicago: 16°

Cleveland: 30°

Detroit: 29°

Indianapolis: 21°

Nashville: 31°

St. Louis: 26°

 

Numerous cities will likely see near record to record low temperatures overnight. Moreover, November 2014 will mark the second consecutive year that exceptional cold moved into the CONUS during November. The oncoming cold shot will likely approach or exceed the coldest shots of last November.

 

Lowest Temperatures for November 2013:

Atlanta: 22°, November 28

Chicago: 11°, November 24

Cleveland: 20°, November 25 and 28

Detroit: 14°, November 24

Indianapolis: 13°, November 24

Nashville: 16°, November 28

St. Louis: 15°, November 24

 

 

Finally, even as blocking is forecast to ease in coming days, past years with strong October blockiness similar to what happened this October and explosive advances of snow cover in Eurasia suggest that this outcome should be temporary. If so, fresh blocking could redevelop in December, possibly the first half of the month.

[donsutherland1]

As of 4 pm EST, the MOS is performing quite well with respect to the cold shot.

 

 

At 3 pm CST, St. Louis was reporting heavy snow with 0.25 mile visibility.

[Hoosier]

Yeah, Don, this cold is something else for mid-November.  And with it accompanied by breezy conditions and some snow in the air, it feels like the dead of winter. 

[Ottawa Blizzard]

Don, what are your thoughts for Toronto and Ottawa? I'm thinking Toronto, at least, has a chance of making it into the top five coldest Novembers of the past 75 years. The current top five are:

 

1) 1951/1976 (tie)

2) 1996

3) 1972/1995 (tie)

4) 1967

5) 1989

[donsutherland1]

Don, what are your thoughts for Toronto and Ottawa? I'm thinking Toronto, at least, has a chance of making it into the top five coldest Novembers of the past 75 years. The current top five are:

 

1) 1951/1976 (tie)

2) 1996

3) 1972/1995 (tie)

4) 1967

5) 1989

It depends on the latter part of the month, but if the warm-up in the medium-term is muted, Toronto could well make a run at the top 5 coolest monthly averages for November.

[donsutherland1]

Yeah, Don, this cold is something else for mid-November.  And with it accompanied by breezy conditions and some snow in the air, it feels like the dead of winter. 

The cold, by itself, is remarkable. That we've had a run of two consecutive Novembers with exceptional widespread cold outbreaks is even more notable.

[donsutherland1]

The exceptional cold produced some of the coldest readings in at least a decade in many parts of the Midwest and East and the coldest temperatures so early in the season in at least 25 years in many of those locations. A quick summary is below:

 

[Srain]

Don, you can add IAH to the record lows. We reached 30F this morning breaking the previous record of 31F set in 1903 for November 19th.

[DaculaWeather]

I have a list of Record Event Reports since the 10th of the month here, oldest to newest. Right now I have to manually upload the file, it was uploaded this morning and I'll upload again when I get home. My weather computer is dead right now...

 

http://www.daculaweather.com/4_record_event_reports.php

[donsutherland1]

Don, you can add IAH to the record lows. We reached 30F this morning breaking the previous record of 31F set in 1903 for November 19th.

Houston's 30° reading was its coldest November temperature since November 3, 1999 when the temperature also fell to 30°. It was also the earliest such reading since November 3, 1999.

[scottmartin49]

Do you fellows make anything of the recurring low track up through the Great Lakes towards James Bay? Couple this with with an onshore, almost 'Bermuda' looking high, and the latest CPC December outlook, and a lot of other forecasts begin to look decidedly iffy.

 

http://www.cpc.ncep.noaa.gov/products/predictions/30day/ 

[Absolute Humidity]

Do you fellows make anything of the recurring low track up through the Great Lakes towards James Bay? Couple this with with an onshore, almost 'Bermuda' looking high, and the latest CPC December outlook, and a lot of other forecasts begin to look decidedly iffy.

 

http://www.cpc.ncep.noaa.gov/products/predictions/30day/ 

Winters with high SCE SAI often have this relaxation period in December. The effects of SCE SAI induced blockiness mostly peak in the mid winter period thus not concerned at all and would even be a little concerned if this relaxation period did not occur. Sometime in the latter Half of December will feature the reloading of blockiness.

[illinois]

Winters with high SCE SAI often have this relaxation period in December. The effects of SCE SAI induced blockiness mostly peak in the mid winter period thus not concerned at all and would even be a little concerned if this relaxation period did not occur. Sometime in the latter Half of December will feature the reloading of blockiness.

Very good point 76, 79 and 02 featured relaxation following colder than average stretches in late November or early December. For the winter weather enthusiasts seems like a positive development.

[michsnowfreak]

The exceptional cold produced some of the coldest readings in at least a decade in many parts of the Midwest and East and the coldest temperatures so early in the season in at least 25 years in many of those locations. A quick summary is below:

 

This is an excellent chart don! I didnt even realize this was Detroits coldest November temp since 1978, nor the earliest to hit 11F! Im the local stats guy, I better get on my toes as winter has begun

[donsutherland1]

This is an excellent chart don! I didnt even realize this was Detroits coldest November temp since 1978, nor the earliest to hit 11F! Im the local stats guy, I better get on my toes as winter has begun

It was very impressive. Hopefully, it will be fun winter with lots of snow and cold.

[michsnowfreak]

It was very impressive. Hopefully, it will be fun winter with lots of snow and cold.

Hopefully! Its just an awesome feeling to know that severest winter anyone alive here has ever seen may be followed by another harsh winter (I was SO sure we were due for a mild winter, but the signs at least say not this year).

 

With 3.7" of snow in November, Detroit is at 81.9" on the calendar year. This ties with 1881 for 2nd snowiest calendar year on record, just 0.7" away from the record of 82.6" set just in 2008. Obviously barring an unforeseen absence of winter, that record just set a few years ago looks to be broken again. Oh the snowy times we are in

 

5 snowiest calendar years for Detroit

1.) 82.6" - 2008

2.) 81.9" - 1881

2.) 81.9" - 2014 thru Nov 23

4.) 75.3" - 1974

4.) 75.3" - 2005

[uncle W]

Hopefully! Its just an awesome feeling to know that severest winter anyone alive here has ever seen may be followed by another harsh winter (I was SO sure we were due for a mild winter, but the signs at least say not this year).

 

With 3.7" of snow in November, Detroit is at 81.9" on the calendar year. This ties with 1881 for 2nd snowiest calendar year on record, just 0.7" away from the record of 82.6" set just in 2008. Obviously barring an unforeseen absence of winter, that record just set a few years ago looks to be broken again. Oh the snowy times we are in

 

5 snowiest calendar years for Detroit

1.) 82.6" - 2008

2.) 81.9" - 1881

2.) 81.9" - 2014 thru Nov 23

4.) 75.3" - 1974

4.) 75.3" - 2005

these are the good ole days for sure...the east coast isn't doing bad either...Philadelphia is averaging over 40" the last five years...they can go snowless for the next five years and still end up average for the decade...

[michsnowfreak]

these are the good ole days for sure...the east coast isn't doing bad either...Philadelphia is averaging over 40" the last five years...they can go snowless for the next five years and still end up average for the decade...

Wow thats incredible.

 

Detroit is averaging 59.7" over the last 7 winters. That is about 18" above normal. With our location and the Great Lakes influence, we are less susceptible to the extremes that east coast winters can bring (ie, our snowiest winters wont look as impressive compared to average...nor will our crappiest winters look as terrible compared to average...as such extremes in Philly, New York or even Boston)....so to be holding a foot and a half above normal for 7 years is unchartered waters. If you go back to 2002, the 12 year average is 52.9", so about a foot above average..considering we use 30-year normals, that is NO small sample size (and does include a few clunkers). Quality control from ncdc should be interesting when the next set of norms comes out

 

Detroit snowfall - since 2002-03....1981-2010 avg 42.7"....130-year avg approx 41"

2013-14: 94.9"

2012-13: 47.7"

2011-12: 26.0"

2010-11: 69.1"

2009-10: 43.7"

2008-09: 65.7"

2007-08: 71.7"

2006-07: 30.3"

2005-06: 36.3"

2004-05: 63.8"

2003-04: 24.1"

2002-03: 60.9"

[donsutherland1]

 

If one looks at the latest CFSv2 forecast for December, one finds a “torch-type” outcome across virtually all of North America. Such an outcome would be enough to steal all the joy associated with Hanukkah and Christmas. However, the latest teleconnection forecasts suggest the development of a PNA+/AO- regime in the longer-range.

 

 

Such an outcome would favor the development of a trough in eastern North America with associated cold anomalies in that area. The latest run of the GFS ensembles shows the possible development of such an outcome at the end of its range. The just-completed 11/26/2014 12z run of the GFS also hints at a return to cooler conditions in the extended range.

 

 

All said, I remain wary of the CFSv2 idea given the forecast teleconnections and 500 mb pattern. Moreover, it should be noted that even the 10/31 run of the CFSv2 showed warm anomalies across almost all of North America for November. To put it mildly, even as sleet is pinging in parts of the NYC metro area and snow is falling not far outside the city, November has worked out differently. Therefore, my guess is that a colder pattern could begin to develop toward or just before mid-month.

[Ottawa Blizzard]

 

If one looks at the latest CFSv2 forecast for December, one finds a “torch-type” outcome across virtually all of North America. Such an outcome would be enough to steal all the joy associated with Hanukkah and Christmas. However, the latest teleconnection forecasts suggest the development of a PNA+/AO- regime in the longer-range.

 

 

Such an outcome would favor the development of a trough in eastern North America with associated cold anomalies in that area. The latest run of the GFS ensembles shows the possible development of such an outcome at the end of its range. The just-completed 11/26/2014 12z run of the GFS also hints at a return to cooler conditions in the extended range.

 

 

All said, I remain wary of the CFSv2 idea given the forecast teleconnections and 500 mb pattern. Moreover, it should be noted that even the 10/31 run of the CFSv2 showed warm anomalies across almost all of North America for November. To put it mildly, even as sleet is pinging in parts of the NYC metro area and snow is falling not far outside the city, November has worked out differently. Therefore, my guess is that a colder pattern could begin to develop toward or just before mid-month.

Don, would you see December 1993 as being a possible analog? That year saw a relatively mild December before severed cold moved in around the 21st.

[donsutherland1]

Don, would you see December 1993 as being a possible analog? That year saw a relatively mild December before severed cold moved in around the 21st.

My guess is that the evolution toward a colder pattern will likely occur earlier in December than it did in 1993. Atlantic blocking didn't commence until after the first week in December in 1993. The ensembles suggest an earlier onset of Atlantic blocking this time around.

[donsutherland1]

For those who are interested, Earthlight has a great discussion about the possible pattern change for December in the NYC sub forum. The discussion can be found here.

[scottmartin49]

For those who are interested, Earthlight has a great discussion about the possible pattern change for December in the NYC sub forum. The discussion can be found here.

Been reading over there- glad there's a 'non-regional' forum for sure. Wish fulfillment will always get in the way of accurate forecasting, and hanging mid-range hopes on the MJO with larger signals running counter seems dubious at best.

 

CPC's gone 'decidedly uncertain'- at least until Sunday http://www.cpc.ncep.noaa.gov/products/predictions/long_range/fxus07.html  

anyone here have a better read on things?

[Ottawa Blizzard]

I was just looking through volume two of David Ludlum's "Early American Winters" and came across the winter of 1855-1856, which was apparently very mild in both the Midwest and northeast right up until the solstice only to turn frigidly cold for January, February and March. Part of me wonders if it will be a similar set-up this year. Ludlum's book is so interesting as it includes an overview of every winter at Fort Snelling in Minnesota from the 1820s to the 1870s showing the reader how the winters varied greatly; in the mid to late 1820s, for example, the Midwest apparently had a string of very mild "non- winters".

[GaWx]

I was just looking through volume two of David Ludlum's "Early American Winters" and came across the winter of 1855-1856, which was apparently very mild in both the Midwest and northeast right up until the solstice only to turn frigidly cold for January, February and March. Part of me wonders if it will be a similar set-up this year. Ludlum's book is so interesting as it includes an overview of every winter at Fort Snelling in Minnesota from the 1820s to the 1870s showing the reader how the winters varied greatly; in the mid to late 1820s, for example, the Midwest apparently had a string of very mild "non- winters".

 

 

According to a source whose link is now dead (so I can no longer link to the data; it was a MN website), 1855-6 was El Nino fwiw. Here is what I had copied:

 

 

 “Both the 1824-1825 and 1877-1878 winters coincided with El Nino/Southern Oscillation (ENSO) episodes [Quinn, 1978], periodic warmings of the far away Equatorial Pacific Ocean that have been linked to anomalous weather conditions in higher latitudes (e.g., heavy winter rainfall in Southern California or mild winters in the Upper Midwest.  Other Quinn identified ENSO's that encompass the 1820-1869 period of study include 1819-20, 1821-22, 1828-29, 1832-33, 1837-38, 1844-45, 1845-46, 1850-51, 1852-53, 1855-56, 1857-58, 1864-65, and 1868-69."

 

So, this list claims that 14 of the 50 winters were El Ninos. That is 28% of them, which is about right.