Winter 2013-14 medium range discussion

[donsutherland1]

On the warm side, Atlanta has had a low temperature of 65° so far today. The daily record high minimum temperature is 60°, which was set in 1998. If today's figure holds, that would be the second warmest minimum temperature on record for Atlanta in December, tied with 65° on 12/1/1991 and just behind 68° on 12/2/1991.

[donsutherland1]

A further note on Denver, which has so far had a reading of -15° today, tying the daily mark set in 1972:

 

In terms of days on which the temperature fell to -10° or lower prior to December 5, the only prior days were during the 19th century. Those dates, including yesterday's reading are:

 

11/28/1877 -10°

11/29/1877 -18°

11/30/1877 -10°

 

11/17/1880 -14°

11/18/1880 -12°

11/29/1880 -10°

 

11/27/1887 -14°

 

12/4/2013 -13°

[Isotherm]

A further note on Denver, which has so far had a reading of -15° today, tying the daily mark set in 1972:

 

In terms of days on which the temperature fell to -10° or lower prior to December 5, the only prior days were during the 19th century. Those dates, including yesterday's reading are:

 

11/28/1877 -10°

11/29/1877 -18°

11/30/1877 -10°

 

11/17/1880 -14°

11/18/1880 -12°

11/29/1880 -10°

 

11/27/1887 -14°

 

12/4/2013 -13°

 

 

 

That's extremely impressive. Basically need to go back to (almost)  the tail end of the little ice age. Near off the charts -EPO pulse coupled with a strong -PNA will do that.

[donsutherland1]

That's extremely impressive. Basically need to go back to (almost)  the tail end of the little ice age. Near off the charts -EPO pulse coupled with a strong -PNA will do that.

I agree. It's a really extraordinary cold shot. It will be interesting to see the list of all the records tied or broken.

[donsutherland1]

The ensemble data continues to show a retrograding ridge that could lead to the EPO's going neutral and then possibly positive after mid-month. In response, a milder pattern could set in across at least parts of the CONUS. Moreover, it appears that the possible pattern change could be hemispheric in nature.

 

For example, both the ensembles and also partial teleconnection cases indicate a much warmer regime could set in across northern Europe where coming days will very likely produce readings 1-2 standard deviations below normal.

 

 

While nothing is cast in stone yet, there continue to enough signals to watch for a possible pattern change down the road. For now one of the most extreme early-season Arctic air masses in North America in recent years is making weather headlines.

[usedtobe]

Cold Air Now Arriving in the Pacific Northwest, Does Snow Lie in the Future?

 

At 10 pm PST, the temperature at Seattle stood at 37° and is likely to approach or reach freezing by morning. Even colder readings will occur during the following days.

 

Now that the much anticipated cold air is arriving, the all-important question concerns whether it will snow. Both the 12/2 18z and 12/3 0z runs of the GFS have suggested the potential for an extended snowfall event. The GFS Forecast and Reforecast ensembles have both had a precipitation signal for some time.

 

 

In addition, the December 2008 cold outbreak, which has shown up in multiple runs of the GFS ensembles' objective analogs and in the partial teleconnection cases, featured two weeks of cold, along with snow. From December 13 through December 26, 13.9" snow fell. The biggest storm dumped 6.6" during the 12/20-22 timeframe.

 

The synoptic pattern is very likely to feature an EPO-/PNA- combination through at least the first two weeks of December. Such a pattern accounts for the overwhelming share of Seattle's 6" or greater snowstorms. The AO, which is highly important when it comes to Mid-Atlantic snowstorms is much less of a factor in the Pacific Northwest.

 

Below are a scatter diagram, AO/PNA and EPO/PNA charts for Seattle's 6" or greater snowstorms.

 

 

Needless to say, such a pattern does not guarantee snowfall, but it is the kind of pattern that is most favorable for such events. Odds probably favor at least some accumulation of snow in Seattle and Spokane and possibly Portland before the cold period ends.

Don, really nice post and research.   Those are the kinds of graphs that easily tell the story.  I'd guess most of the events also were with a negative PDO. 

[easternsnowman]

The ensemble data continues to show a retrograding ridge that could lead to the EPO's going neutral and then possibly positive after mid-month. In response, a milder pattern could set in across at least parts of the CONUS. Moreover, it appears that the possible pattern change could be hemispheric in nature.

 

For example, both the ensembles and also partial teleconnection cases indicate a much warmer regime could set in across northern Europe where coming days will very likely produce readings 1-2 standard deviations below normal.

 

 

While nothing is cast in stone yet, there continue to enough signals to watch for a possible pattern change down the road. For now one of the most extreme early-season Arctic air masses in North America in recent years is making weather headlines.

Sooner or later it has to change because it can't get any colder!

[donsutherland1]

Don, really nice post and research.   Those are the kinds of graphs that easily tell the story.  I'd guess most of the events also were with a negative PDO. 

Thanks Wes. Yes, most did occur with a negative PDO. It will be interesting to see if Seattle winds up with a snowier than normal December by the time the extended period of cold ends. Not every such pattern produced, but at least the odds are higher than if one were dealing with a PNA+ or EPO+.

[donsutherland1]

Sooner or later it has to change because it can't get any colder!

 

I agree. North America has seen two exceptionally cold air masses, one just prior to the U.S. Thanksgiving Day holiday, and the current one. The bigger question concerns whether the outcome following the pattern change, assuming it unfolds, will prove to be persistent.

[tacoman25]

This is certainly among the coldest air masses so early in the season in Denver.

 

However, the -5° figure is from Denver International Airport, but the record only goes back to 1995 there. At Stapleton Airport, where records used to be kept (records go back to 1948 there), there were 7 dates prior to December 5 when the temperature fell below -5°, including November 9-10, 1950 with a temperature of -8°. The lowest Denver area record prior to December 5 per Threadex is -18° on November 29, 1877.

 

I think you misread. The -13 yesterday was the lowest temperature before Dec 5 for Denver airport records. Previous was -8, which as you pointed out happened in Nov 1950 and a couple other times.

[donsutherland1]

I think you misread. The -13 yesterday was the lowest temperature before Dec 5 for Denver airport records. Previous was -8, which as you pointed out happened in Nov 1950 and a couple other times.

I did. I assumed that the figure was for Denver overall, for which DEN is now the official site of record, not specifically the DEN site. I regret the error.

[tacoman25]

I did. I assumed that the figure was for Denver overall, for which DEN is now the official site of record, not specifically the DEN site. I regret the error.

 

No worries. It looked like you thought I had said -5, not Dec 5.

[Ottawa Blizzard]

Hoping that some of that western cold and snow can make its way east! It's looking like that could happen next week. In order to be impressive for early December in Toronto in my books I'd need to see highs at least in the upper teens.

[easternsnowman]

I agree. North America has seen two exceptionally cold air masses, one just prior to the U.S. Thanksgiving Day holiday, and the current one. The bigger question concerns whether the outcome following the pattern change, assuming it unfolds, will prove to be persistent.

If it does I feel it will pretty much kill winter for NYC south.

[SnoSki14]

It feels like everyone thinks we will torch soon, but it's still incredible difficult to know that with any certainty.

JB's -WPO/+EPO combination looked interesting and we would avoid torching. I also heard mets discussing that the low heights in the GOA region/+EPO are not torching us because of a split flow that still allows polar air to come down and undercut the GOA trough.

Also the PV is closer to us, which is also offsetting the warm air.

[donsutherland1]

It feels like everyone thinks we will torch soon, but it's still incredible difficult to know that with any certainty.

JB's -WPO/+EPO combination looked interesting and we would avoid torching. I also heard mets discussing that the low heights in the GOA region/+EPO are not torching us because of a split flow that still allows polar air to come down and undercut the GOA trough.

Also the PV is closer to us, which is also offsetting the warm air.

While I believe the odds have increased that a milder pattern lies ahead sometime after mid-month once the EPO goes neutral or positive, I'm not sure about the magnitude of the warmth. A lot will depend on the other synoptic details. I can't rule it out either. However, if an EPO+/AO+ regime develops and then persists for an extended period of time, the probability of at least a period of much above normal temperatures would increase.

[donsutherland1]

Hoping that some of that western cold and snow can make its way east! It's looking like that could happen next week. In order to be impressive for early December in Toronto in my books I'd need to see highs at least in the upper teens.

It might be tough for Toronto to have a day with a maximum temperature in the teens, but at least the possibility is on the table as per the GFS, which is showing a high of near -7°C next Thursday. Unfortunately, that's still a week away so there's a lot of latitude for change.

[Ji]

It might be tough for Toronto to have a day with a maximum temperature in the teens, but at least the possibility is on the table as per the GFS, which is showing a high of near -7°C next Thursday. Unfortunately, that's still a week away so there's a lot of latitude for change.

Ur really trying to make it warm. What's if it's the year where the warm is always 10 days away

[donsutherland1]

Ur really trying to make it warm. What's if it's the year where the warm is always 10 days away

 

The colder and preferably snowier the outcome, the happier I'll be.

 

P.S. Enjoy Sunday's snowfall.

[Ji]

The colder and preferably snowier the outcome, the happier I'll be.

 

P.S. Enjoy Sunday's snowfall.

your wish might come true.

 

[Jonger]

Its the opposite of the last two winters, this year the warmth shows up 15 days out and just keeps getting pushed back.

[QcSevereWx]

Its the opposite of the last two winters, this year the warmth shows up 15 days out and just keeps getting pushed back.

Cold and dry,... would you prefer mild and snowy ?

[donsutherland1]

December 16-22, 2013 Thoughts:

 

Historical experience argues for the EPO to go neutral or positive within a week after mid-month, but the ensembles show a rise but do not conclusively agree on that outcome. As a consequence, my thoughts assume an EPO that is a compromise (neutral to somewhat negative through the duration of the period in question.

 

There are also some differences between the GFS ensembles and the reforecast ensembles. Considering the existence of somewhat of a disconnect between the objective analogs based on the GFS ensembles and the outcome for the ensembles themselves, as well as the reforecast ensembles showing more cold air in Canada, I suspect that the reforecast ensembles probably are closer to reality. The ensembles may be reducing the expanse of cold anomalies in Canada a little more quickly.

 

Nevertheless, the outcome suggests milder conditions will likely become more widespread across the CONUS during the period, though parts of the northern tier could still wind up colder than normal. A cold shot, particularly early in the period could impact the East.

 

Below are charts showing the ENSO+teleconnection cases, teleconnection cases excluding ENSO, the reforecast ensembles, and most recent run of the NAEFS:

 

Overall, my thoughts err on the colder side across parts of the Northern tier of the CONUS for the overall anomalies during the period. Specifically, my thoughts are as follows:

 

 

Canada: Almost all of Canada would wind up with cold anomalies for the period as a whole.

 

Pacific Northwest, Northern Plains, Great Lakes region, New England: Somewhat cooler than normal.

 

Southwest, Central/Southern Plains, Mid-Atlantic: Generally warmer than normal, but the northern Mid-Atlantic could wind up near to normal.

 

Southeast/Gulf Coast: Warmer to possibly much warmer than normal.

[donsutherland1]

Today, Portland, OR had a high temperature of 30°. That was Portland's first subfreezing day since November 23, 2010 when the temperature also topped out at 30°. It was also the 2nd lowest daily maximum reading on record, tied with 1956. The record is 27°, which was set in 1972.

 

In addition, Portland picked up 0.5" snow. That was the second largest snowfall for this date, tied with 1994. The daily record is 2.0", which was set back in 1942.

[tacoman25]

Today, Portland, OR had a high temperature of 30°. That was Portland's first subfreezing day since November 23, 2010 when the temperature also topped out at 30°. It was also the 2nd lowest daily maximum reading on record, tied with 1956. The record is 27°, which was set in 1972.

 

In addition, Portland picked up 0.5" snow. That was the second largest snowfall for this date, tied with 1994. The daily record is 2.0", which was set back in 1942.

 

Areas further south in OR did much better for snow. Eugene, OR picked up close to 6".

[thenewbigmack]

December 16-22, 2013 Thoughts:

 

Historical experience argues for the EPO to go neutral or positive within a week after mid-month, but the ensembles show a rise but do not conclusively agree on that outcome. As a consequence, my thoughts assume an EPO that is a compromise (neutral to somewhat negative through the duration of the period in question.

 

There are also some differences between the GFS ensembles and the reforecast ensembles. Considering the existence of somewhat of a disconnect between the objective analogs based on the GFS ensembles and the outcome for the ensembles themselves, as well as the reforecast ensembles showing more cold air in Canada, I suspect that the reforecast ensembles probably are closer to reality. The ensembles may be reducing the expanse of cold anomalies in Canada a little more quickly.

 

Nevertheless, the outcome suggests milder conditions will likely become more widespread across the CONUS during the period, though parts of the northern tier could still wind up colder than normal. A cold shot, particularly early in the period could impact the East.

 

Below are charts showing the ENSO+teleconnection cases, teleconnection cases excluding ENSO, the reforecast ensembles, and most recent run of the NAEFS:

 

 

Don,

 

I haven't been on this forum in a while, but it's great to see you posting regulary. As you're aware, it's been quite cold over in my neck of the woods (NW Wa), but unfortunately it wasn't snow filled like I was hoping. It's currently 19* with decent winds out of the north and a wind chill of 9*.

 

Anyways, I was wondering what your thoughts were regarding the timeframe immediately following the one above. I don't have access to the Euro weeklies, but Brett Anderson's interpretations for the 23rd-29th timeframe shows cold and snow immediately north of the Canadian border. By this time, it looks as if the MJO will be returning to the Indian Ocean. If the AO continues to remain positive and the EPO continues to remain negative, history presents us with strong signal for a SE Ridge and a -PNA pattern. You've mentioned that the EPO is likely to head towards neutral soon, the forecasts just don't reflect this yet (Not saying you're wrong at all though). 

 

 

If we were in fact to have an MJO over the IO with a -EPO/+AO combo, here's what the anomaly chart would look like. Would love to hear your input on whether you see this as a possiblity or not. Thanks!

 

[GaWx]

Savannah, GA, tied its alltime December record yesterday with 83. Record go back to 1874!

[JoMo]

thenewbigmack, The 500 MB setup you posted is very similar to what the 00z Euro Ensemble Mean shows towards the 20th and 21st. There's higher heights NW of Alaska but the overall look is very similar. 

[donsutherland1]

This morning's low temperature at Havre, MT has so far been -39°. That reading is its third consecutive daily record low temperature and its coldest reading during the 2000-present period.

 

Its readings for the past two days have been:

 

12/5 High: -14° (broke daily record of -12°, 1880); Low: -28° (broke daily record of -27°, 1956)

12/6 High: -13°; Low: -38° (broke daily record of -31°, 1972

 

The 12/5 high was also the lowest high temperature during the 2000-present period

[donsutherland1]

Savannah, GA, tied its alltime December record yesterday with 83. Record go back to 1874!

That's very impressive.