Winter 2014-2015 Medium-Term Discussion

[Ottawa Blizzard]

I've noticed some similarities between this Fall and that of 1984. November 1984 was chilly in southern Ontario, while December 1984 was a blowtorch. January 1985 turned frigid.

[JBG]

As much as one pster said I was "in 1972-3" the similarity seems eery. Little snow, lots of drizzle, and the chance of a minor shot of cold in the last week. That was followed by the "pattern change" everyone wants but it was to dry and frigid, followed by another torch, followed by more dry and frigid, followed by La Niña. Thoughts?

[donsutherland1]

Some morning thoughts...

 

1. The long-awaited pattern change is now unfolding. The GFS and to a lesser extent ECMWF favor a possible Arctic intrusion after January 4. The largest impact would be across the Northern Plains and Great Lakes regions with a lesser impact farther south and east. By the time the pattern eases, numerous cities in the Northern Plains, Great Lakes region, southern Ontario, southern Quebec, and into New England, will likely have experienced their coldest reading so far this winter.

 

2. The energetic subtropical jet may also begin to relax sometime in the January 10-15 timeframe.

 

3. The AO forecast has grown even uglier. If that forecast is accurate, no KU-type East Coast snowstorms will be likely through January 15. The Great Lakes region (including southern Ontario) would still have a better chance at experiencing a significant snowfall, but probably not a blockbuster event. Lighter snows and perhaps a moderate event during the colder period cannot be ruled out, especially across parts of New England. Washington, DC provides a good example of the importance of an AO-/PNA+ pattern for snowfall in the Mid-Atlantic region in January. For the 1950-2014 period, Washington, DC has averaged a measurable snowfall once every 10.0 days in January. With an AO-/PNA+ pattern, it has averaged such a snowfall once every 8.2 days. With an AO+/PNA- pattern, it has averaged such a snowfall once every 11.7 days. 

 

4. The ECMWF continues to suggest a possible weak stratospheric warming event (confined to between 10 hPa and 30 hPa) and centered largely in the vicinity of 90°N). If the current forecast stands, one probably won't see much lasting impact on the polar vortex. It should be noted that Sudden Stratospheric Warming (SSW) events can develop on very short notice. At the same time, not every winter experiences such an event. Moreover, some of the SSW events occur in response to a period of sustained and severe blocking, which has not been the case so far. Consequently, there is no assurance that the current winter will see such an event.

[GaWx]

Some morning thoughts...

 

4. The ECMWF continues to suggest a possible weak stratospheric warming event (confined to between 10 hPa and 30 hPa) and centered largely in the vicinity of 90°N). If the current forecast stands, one probably won't see much lasting impact on the polar vortex. It should be noted that Sudden Stratospheric Warming (SSW) events can develop on very short notice. At the same time, not every winter experiences such an event. Moreover, some of the SSW events occur in response to a period of sustained and severe blocking, which has not been the case so far. Consequently, there is no assurance that the current winter will see such an event.

 

 Here is a copy of a post I made just 15 minutes ago in the MidAtlantic thread. I'm posting this here because my take on the progs attached below is that this would actually be a very strong SSW as opposed to just a weak SW:

 

 

 I just saw this chart referred to by Mitch (reattached below) for the first time and am quite surprised it hasn't generated more discussion! In my book, this (assuming verification) would definitely count as a strong SSW. This shows an absolute 90-60N warming of ~37C (see bottom chart; ~40C is about as warm as has occurred) and a warming anomalywise of ~30C at 5 mb over just five days from 12/26 to the 12/31 peak. Per my eyeballs, this 37C absolute warming could very well be a top three strength warming since 1979. That 30C anomaly warming would be at least a top 12 strength SSW based on anomalies (28C+ anomaly warming over a week or so elapsed period) since 1979 and the strongest such warming anomalyise since 1/22/09 (which had ~33C anomaly warming). The reason that it would do better absolutewise is that the sharpest warming of normals occurs between the last few days of Dec. and the first couple of days of Jan as per the attached chart, which cuts down some on the anomaly warming. For all of my data, I use this source:

 

http://www.cpc.ncep.noaa.gov/products/stratosphere/strat-trop/

 

 So, I'd love to see more discussion about this. There is no doubt in my mind that IF this forecast verifies that it would count as a SSW and one of the strongest ones (possibly top 3) based on absolute warming since at least 1979. Now, whether or not its effects on the pattern/PV/AO are sig. or not is a whole other Q. Based on the past, I'm not so sure of this as it seems to widely vary. Regardless, I have read that it can take 3+ weeks for its main effects to occur.

 

 

[DaculaWeather]

You can see the warming on the far right.

 

 

 

 

 

 

[GaWx]

 Watch at the following link as the attached anomaly (not absolutes) chart of today should warm very sharply over the next ~4 days in the upper right side probably centered on/near 2-5 hPa/mb) (assuming the forecast noted in my post just above this verifies closely):

 

Link to this anomaly chart that is updated daily:

 

 http://www.cpc.ncep.noaa.gov/products/stratosphere/strat-trop/gif_files/time_pres_TEMP_ANOM_OND_NH_2014.gif

 

It is now at ~+9C for the warmest anomaly. IF it reaches the brown or gray colors (another ~19C+ of anomaly warming), it would qualify as a top 12 SSW since 1979 per my criterium (28C+ based on anomalies).

 

Edit: Sorry, Steve. I just saw that you posted the same thing lol.

 

[DaculaWeather]

 Watch at the following link as the attached anomaly (not absolutes) chart of today should warm very sharply over the next ~4 days in the upper right side probably centered on/near 2-5 hPa/mb) (assuming the forecast noted in my post just above this verifies closely):

 

Link to this anomaly chart that is updated daily:

 

 http://www.cpc.ncep.noaa.gov/products/stratosphere/strat-trop/gif_files/time_pres_TEMP_ANOM_OND_NH_2014.gif

 

It is now at ~+9C for the warmest anomaly. IF it reaches the brown or gray colors (another ~19C+ of anomaly warming), it would qualify as a top 12 SSW since 1979 per my criterium (28C+ based on anomalies).

 

Edit: Sorry, Steve. I just saw that you posted the same thing lol.

 

StratTempAnomOND_NH_2014AsOf122814.gif

Brilliant minds think alike. :-)

[Srain]

The Medium Range guidance continues to advertise a very strong Arctic air mass dropping S from the Canadian Prairies into much of the West and Plains. An anomalous 1060mb+ Arctic High with its origin from Northern Siberia continues to settled S across the North Pole and will drop into the Inter Mountain West and Central Plains early tomorrow and push further S spreading a very dense and shallow Arctic air mass deep into the Lower Colorado River Valley as well as the lee side of the Rockies into the Southern Plains into the NW Gulf Coast. This Arctic High is near or slightly below 3 standard deviations below normal for this time of year. The pattern coincides with a +PDO/-EPO Regime.

 

 

A very cold positive tilted upper trough will extend from Southern California/Southern Arizona where a cold core 5H low will wrap up into a closed core upper low after the Arctic air arrives into Brownsville and Houston on the 30^th into early New Year’s Eve. As the cold core 5H low and trough begin to meander E, embedded short waves will ride NE from the Eastern Pacific setting the stage for warm air to overrun the shallow dense very cold air at the surface. This sort of pattern is a typical Winter Storm setup for extended periods of light freezing drizzle/freezing rain very far S along and N of the I-10 Corridor of Texas and heavy higher elevation snow across the Southern Rockies. This is a classic case of the operational numerical guidance under estimating the dense, shallow very cold air at the surface. We are witnessing all sort of issues from the current storm and much weaker forecasted cold air where sleet and freezing rain is falling this morning where nothing but a cold rain was forecast. The 700mb flow is expected to be easterly creating cold air damming and upslope snow across the Front Range of the Central and Southern Rockies that may extend into Kansas, Western Oklahoma, West Texas, and the Panhandle.

 

Depending of the eventual evolution of the close core upper low as it track E later next week, the potential is present for a major Ice Storm across the Southern half of Texas extending NE into the Tennessee Valley and possibly the Mid Atlantic. The wild card will be for any potential Coastal low/trough development near Brownsville New Year’s Day and moving NE.  It will be interesting to see exactly how this potential Winter Storm develops as we end 2014 and ring in the New Year.

 

 

 

[donsutherland1]

 Here is a copy of a post I made just 15 minutes ago in the MidAtlantic thread. I'm posting this here because my take on the progs attached below is that this would actually be a very strong SSW as opposed to just a weak SW:

 

 

 I just saw this chart referred to by Mitch (reattached below) for the first time and am quite surprised it hasn't generated more discussion! In my book, this (assuming verification) would definitely count as a strong SSW. This shows an absolute 90-60N warming of ~37C (see bottom chart; ~40C is about as warm as has occurred) and a warming anomalywise of ~30C at 5 mb over just five days from 12/26 to the 12/31 peak. Per my eyeballs, this 37C absolute warming could very well be a top three strength warming since 1979. That 30C anomaly warming would be at least a top 12 strength SSW based on anomalies (28C+ anomaly warming over a week or so elapsed period) since 1979 and the strongest such warming anomalyise since 1/22/09 (which had ~33C anomaly warming). The reason that it would do better absolutewise is that the sharpest warming of normals occurs between the last few days of Dec. and the first couple of days of Jan as per the attached chart, which cuts down some on the anomaly warming. For all of my data, I use this source:

 

http://www.cpc.ncep.noaa.gov/products/stratosphere/strat-trop/

 

 So, I'd love to see more discussion about this. There is no doubt in my mind that IF this forecast verifies that it would count as a SSW and one of the strongest ones (possibly top 3) based on absolute warming since at least 1979. Now, whether or not its effects on the pattern/PV/AO are sig. or not is a whole other Q. Based on the past, I'm not so sure of this as it seems to widely vary. Regardless, I have read that it can take 3+ weeks for its main effects to occur.

 

 StratWarmingProg122714.gif

To be sure, the 12/27 run is more impressive than the 12/26 one I had viewed. Still, I'd be more comfortable if a larger section of the 60N-90N region from 30 hPa or higher had readings in the vicinity of -30°C or above.

 

 

The new charts have increased the prospects of a SSW event, but let's see if the data holds up and there is, in fact, a large-scale warming and a switch in the zonal wind fluxes.

[Isotherm]

This is going to be a very close call, but right now, if the ECMWF guidance is correct, we definitely see a minor to moderate stratospheric warming event, though not officially major.

 

The definition of a major warming is when the 10mb zonal wind at 65N latitude reverses and becomes easterly for more than 5 consecutive days.

 

Per the current ECMWF, zonal winds reverse to an easterly direction for 3 days at 65N and probably at least 3-5 days for 70-90N. Nevertheless, whether we attain a major warming or not, the perturbation occurring / moderate intensity warming will be sufficient to help induce a more negative tropospheric AO mode as January presses onward.

 

Unless current forecasts improve, it appears we might have a near-miss for the major warming classification.

 

 

As shown below, we try to go easterly for a few days at 10mb/65N, then begin to go westerly again at that level / latitude.

 

[Isotherm]

Here's an example of one of the most impressive SSW events in the past several years. Note the reversal to strong easterly zonal winds in the 65N / 10mb cross section.

 

 

[donsutherland1]

On 12/26, I noted that the EPO is forecast to fall strongly negative in coming days and then remain predominantly negative through the next 15 days. Periodic runs of the operational GFS have brought some of the Arctic air into the U.S.

 

The EPO is now negative and it should continue to fall sharply over the next few days. At the same time, the GFS has had decent run-to-run continuity with respect to Arctic air coming eastward after January 5. For the first time, the 12/28 12z run of the ECMWF delivers an Arctic shot all the way to the Mid-Atlantic and New England regions.

 

In short, it still remains premature to write off Winter 2014-15.

[jdrenken]

 Here is a copy of a post I made just 15 minutes ago in the MidAtlantic thread. I'm posting this here because my take on the progs attached below is that this would actually be a very strong SSW as opposed to just a weak SW:

 

 

 I just saw this chart referred to by Mitch (reattached below) for the first time and am quite surprised it hasn't generated more discussion! In my book, this (assuming verification) would definitely count as a strong SSW. This shows an absolute 90-60N warming of ~37C (see bottom chart; ~40C is about as warm as has occurred) and a warming anomalywise of ~30C at 5 mb over just five days from 12/26 to the 12/31 peak. Per my eyeballs, this 37C absolute warming could very well be a top three strength warming since 1979. That 30C anomaly warming would be at least a top 12 strength SSW based on anomalies (28C+ anomaly warming over a week or so elapsed period) since 1979 and the strongest such warming anomalyise since 1/22/09 (which had ~33C anomaly warming). The reason that it would do better absolutewise is that the sharpest warming of normals occurs between the last few days of Dec. and the first couple of days of Jan as per the attached chart, which cuts down some on the anomaly warming. For all of my data, I use this source:

 

http://www.cpc.ncep.noaa.gov/products/stratosphere/strat-trop/

 

 So, I'd love to see more discussion about this. There is no doubt in my mind that IF this forecast verifies that it would count as a SSW and one of the strongest ones (possibly top 3) based on absolute warming since at least 1979. Now, whether or not its effects on the pattern/PV/AO are sig. or not is a whole other Q. Based on the past, I'm not so sure of this as it seems to widely vary. Regardless, I have read that it can take 3+ weeks for its main effects to occur.

 

 StratWarmingProg122714.gif

 

The best question is to determine where the core of cold gets dumped...and the severity.

[blizzardof96]

Here's an example of one of the most impressive SSW events in the past several years. Note the reversal to strong easterly zonal winds in the 65N / 10mb cross section.

 

 

I was always under the impression that a major SSWE is classified as an event where the 60N/10mb U wind anomaly reverses to easterly for at least five days. Do you have any papers that support the 65N/10mb idea? Thanks.

[InstantWeatherMaps]

I don't think this is "weak" by any definition of the word.

 

[donsutherland1]

I don't think this is "weak" by any definition of the word.

 

Recent runs have grown more impressive. Currently, it is still a possible moderate event, as the 60N wind anomaly is not forecast to switch. Maybe future runs will show such a development.

[GaWx]

The link below is showing sharp warming of anomalies continuing above the 10 mb level of the stratosphere. There was about a 4C anomaly warming just since yesterday's released map to ~+13 C at the warmest anomaly level of 1-2 mb. Watch to see how much warmer it gets over the next 3-5 days as this updates daily. If that prog that Mitchnick posted Saturday in the MidAtlantic forum and that I copied into this thread were to verify, I'd expect to see some brown colors (+28 to +32) at least near the 5 mb level within 3-5 days, which would make it a top 12 strong SSW since at least 1979 based on that criterion, alone. Let's see how much warmer it actually gets. Keep in mind that normals in those strat levels warm rather sharply in late Dec./early Jan. meaning absolute warming is actually a fair bit stronger than these anomaly warmings are showing.

http://www.cpc.ncep.noaa.gov/products/stratosphere/strat-trop/gif_files/time_pres_TEMP_ANOM_OND_NH_2014.gif

Edited

[Isotherm]

I was always under the impression that a major SSWE is classified as an event where the 60N/10mb U wind anomaly reverses to easterly for at least five days. Do you have any papers that support the 65N/10mb idea? Thanks.

 

 

I retrieved that definition directly from NOAA.

 

See the following, and click on the link at the top:

 

http://webcache.googleusercontent.com/search?q=cache:DR49JexJ26IJ:ftp://ftp.cpc.ncep.noaa.gov/long/misc/SSW_Poster_new.pdf+&cd=2&hl=en&ct=clnk&gl=us

 

States that 65N / 10mb reversal to easterly for 5+ days is the definition of a major warming event.

[Isotherm]

Latest zonal wind forecast indicates a brief reversal at 65N / 10mb at D 7-8, then resumption of westerly winds D 9-10, though the attack on the vortex continues strongly at 10mb. The attempt in the D7-8 period probably won't result in a major warming, but it looks like it could occur shortly thereafter if the progged bombardment persists.

 

 

Temperatures are progged to continue to warm rapidly at 90N. Definitely a positive sign that we're making significant progress here.

 

[AlaskaETC]

http://theweathercentre.blogspot.com/2014/12/january-long-range-outlook-la-nina.html

 

Not very promising...

[tnweathernut]

http://theweathercentre.blogspot.com/2014/12/january-long-range-outlook-la-nina.html

 

Not very promising...

His header indicates to expect the unexpected.  I think we should just run with that thought.

 

On topic, the long range modeling and ensembles (around 180) appear  to be turning a little in our (eastern US) favor.  Nice ridging out west, nice -EPO, and the PV in eastern/southeastern Canada with big (1040+) highs coming down from western Canada.

[DTWXRISK]

  Folks need to keep in mind  SSW  can affect  OTHER Portions of  the Northern  Hemisphere  besides    eastern US.   SSW  events are   rapidly becoming   over hyped.   The Winter of  2011-12   filled with  talks about SSW   events and when it  hit   central  and eastern and western  Russia and the Ukraine   turned  BITTERLY  cold and snowy  

[GaWx]

Folks need to keep in mind SSW can affect OTHER Portions of the Northern Hemisphere besides eastern US. SSW events are rapidly becoming over hyped. The Winter of 2011-12 filled with talks about SSW events and when it hit central and eastern and western Russia and the Ukraine turned BITTERLY cold and snowy

Agreed 100%. Any one SSW may or may not have a significant impact on the E US or any part of the US and may even have very little effect on the AO, even if very strong. Regardless, I do think they're quite interesting to follow.

[GaWx]

Here is the latest daily update (as of day 363):

http://www.cpc.ncep.noaa.gov/products/stratosphere/strat-trop/gif_files/time_pres_TEMP_ANOM_OND_NH_2014.gif

Though continuing to warm, this is not warming as fast as that prog from Saturday had suggested. To get a strong SSW, it usually needs to be faster than this (say, ~4 C/day). The warmest anomaly warmed only from ~+12-13 C yesterday to ~+14 C today, only ~1.5 C rise (though absolutes would be warming more due to the rather significant rise in normals in very late December). This not so fast rise tells me that it may not get close to the brown/+28+ threshold that would make it a top 12 SSW per that criterion. However, there's still time, especially if the warming accelerates over the next couple of days. I think that the earliest it would max out would be the map two days from now (for 12/31) and some progs suggest it may not max out for at least a few days after that.

[Isotherm]

Cohen's latest post today acknowledges a SSW / vortex splitting event at the end of the first week of January, and favors the ECMWF evolution of further vortex perturbation which could potentially induce a major SSW event. Says the negative AO should result 1-2 weeks following and persist for at least 6 weeks. The one wildcard is the Barents-Kara sea low which could interfere with wave driving, though of the Northern Hemisphere continents, the presence of this low favors the greatest tropospheric effects / cold drainage in North America and not Europe via -EPO/AK block forcing. Overall, it was a very positive post. Also says that any warm-up in the Eastern US will be transient in the coming weeks.

[thunderbolt]

Until I see the MJO going to more favorable phases as much as I would love to believe him I'm just not buying it right now

[Isotherm]

The 500mb composite for warmer than normal El Nino Januarys since 1975 denotes a strong +EPO / +AO / +NAO pattern with the mean ridge located over SE Canada:

 

 

 

Progged pattern for the first 5 days of January at H5:

 

 

 

Progged pattern for the Jan 5-10th period at H5:

 

 

 

 

Temperature departures for the warm Nino year Januarys:

 

 

 

 

 

Point being, the first 10 days of January don't appear to be following the warm "camp" of analogs for El Nino years, with the most notable difference being the polar opposite NPAC/AK EPO signature.

 

For El Nino's, the time of divergence among years tends to occur in January, that is, we're entering a very telling period in terms of the ultimate fate of the winter. Warm El Ninos tended to continue to blowtorch from December through much of January. Cold El Ninos like 1976, 2002, and 2009, stayed cold for most of the DJF period. Transition El Nino's like 2004, 1986 and 1987 featured a warm Dec and much colder January and February

 

So this winter will be showing its cards shortly, and at least for the next 10 days, it doesn't appear to be moving toward the wire to wire warmth analog camp.

[Amped]

The 500mb composite for warmer than normal El Nino Januarys since 1975 denotes a strong +EPO / +AO / +NAO pattern with the mean ridge located over SE Canada:

 

 

 

Progged pattern for the first 5 days of January at H5:

 

 

 

Progged pattern for the Jan 5-10th period at H5:

 

 

 

 

Temperature departures for the warm Nino year Januarys:

 

 

 

 

 

Point being, the first 10 days of January don't appear to be following the warm "camp" of analogs for El Nino years, with the most notable difference being the polar opposite NPAC/AK EPO signature.

 

For El Nino's, the time of divergence among years tends to occur in January, that is, we're entering a very telling period in terms of the ultimate fate of the winter. Warm El Ninos tended to continue to blowtorch from December through much of January. Cold El Ninos like 1976, 2002, and 2009, stayed cold for most of the DJF period. Transition El Nino's like 2004, 1986 and 1987 featured a warm Dec and much colder January and February

 

So this winter will be showing its cards shortly, and at least for the next 10 days, it doesn't appear to be moving toward the wire to wire warmth analog camp.

 

It really doesn't look that Nino like either.  No real STJ to speak of and the CPC analogs don't bring up too many el ninos.

[wxmx]

It really doesn't look that Nino like either.  No real STJ to speak of and the CPC analogs don't bring up too many el ninos.

Other than FL, the regions with the highest precipitation correlation with an El Niño have been wetter than normal, MX especially. The STJ has been pretty active, although the eastern third of the CONUS has not benefitted much from it.

 

[mrgolf]

Happy new year to everyone!! Ive been reading about the possible SSW event alot of people are talking about. Most of the talk goes over my head to be honest.Models look promising and then they don't. The question I have is what's inhibiting a true SSW or even a major SSW from happening? I've heard the key is wind reversal at 10mb to easterly. I thought we had an easterly -qbo unless its too strong. Lastly,what do we need to watch for that may signal a true SSW that would change the pattern to one that features a -nao and ao? That easterly wind reversal isn't coming easy that's for sure