[donsutherland1]

Climatology Associated with Central Pacific-Centered El Niño Events:
Typically, such events have featured widespread cold in the eastern U.S. To define a Central or Western Pacific-centered El Niño, I took all El Niño years in which the ratio of December-February ENSO Region 1+2 anomalies to ENSO Region 3.4 anomalies came to +0.50 or less. To date, Winter 2009-10’s ratio is +0.075. The following winters met that criteria: 1957-58, 1958-59, 1963-64, 1965-66, 1968-69, 1969-70, 1977-78, 1987-88, 1991-92, 2002-03, and 2004-05.

The February composite temperature anomaly was:
http://img.photobucket.com/albums/v327/donsutherland1/ENSO12212009-2.png

The one risk would be the evolution of the current central Pacific-based El Niño into a basinwide event, as happened when the ENSO Region 1+2 anomalies spiked in Winter 1991-92. That outcome is increasingly unlikely. The January 13 anomaly for that region was +0.3°. Meanwhile, ENSO Region 3.4 had ticked down to +1.7°C. In short, the current moderate El Niño appears to be fading slowly and there is no indication of a transformation to a dreaded basinwide winter-killer event.

December Severe Blocking:
In my thread concerning severe blocks (AO reached -3. or below) in December with an ENSO Region 3.4 anomaly of +0.5°C or warmer, it was noted that there were six years that saw such blocks: 1958, 1963, 1968, 1969, 1976, and 1977. 5/6 (83%) cases saw a negative AO in February:

February 1959: +2.544
February 1964: -0.575
February 1969: -3.114
February 1970: -1.325
February 1977: -2.010
February 1978: -3.014

The composite February temperature anomaly for those years was:
http://img.photobucket.com/albums/v327/donsutherland1/CompF596469707778.png

February 1959 featured cold only in New England. The other years saw widespread cold across much of the East.

Major Mid-Winter Warming (MMW) of the Stratosphere:
From Karin Labitzke and Barbara Naujokat, Freie Universitaet Berlin, a Major-Midwinter Warming (MMW) is defined as follows:

Major Midwinter Warmings occur mostly in January-February. In addition to warming of the north polar region and reversal of the meridional temperature gradient, they are also associated with a breakdown of the polar vortex, which is replaced by a high. That is, the definition of a Major Midwinter Warming requires not only the warming but also a total change of circulation. The definition of a breakdown of the polar vortex is that the usual westerlies in the Arctic at 10 hPa are replaced by easterlies so that the centre of the vortex moves south of 60-65°N. The vortex is either displaced entirely or split into two.

The latest computer modeling shows:

A reversal of the zonal winds beyond the critical 10 mb level by 192 hours:
http://img.photobucket.com/albums/v327/donsutherland1/Stratforecast01182010192h.gif

A shift in the polar vortex (though not a split) south of 65°N latitude:
http://img.photobucket.com/albums/v327/donsutherland1/VortexECMWF01182010.gif

The bottom line is that while it had become quite clear on the modeling that a sudden stratospheric warming (SSW) event was about to unfold, there had been some debate as to whether it would reach the magnitude of an MMW. Past experience following some severe blocking episodes suggested that odds leaned toward a significant stratospheric warming event. The 1/18/2010 12z guidance has thrown its weight toward an MMW, as the extent of warming and shifting of the polar vortex meet the classic definition of an MMW.

Such events often result in renewed blocking that can persist for up to 60 days. Should such blocking develop and persist, it would fit the climatology associated with severe blocking episodes (AO of -3 or below) that developed in December.

The Extreme Case: February 1958, 1969, and 1978
What could a February with widespread cold, an active subtropical jet, and significant and persistent blocking look like? February 1958, 1969, and 1978 offer perhaps a sketch of the extreme parameter.

The composite 500 mb height anomalies for the Northern Hemisphere were:
http://img.photobucket.com/albums/v327/donsutherland1/Feb195819691978Hts.gif

The composite U.S. temperature anomaly was:
http://img.photobucket.com/albums/v327/donsutherland1/Feb195819691978.png

Those winters had in common:

• Widespread cold in the East
• Generally warmer than normal readings west of the Continental Divide
• Above to much above normal precipitation in California, the Gulf Coast
• Drier than normal conditions in the Midwest
• 1 or more KU snowstorms

If one examines the superensemble guidance centered on January 30, 2010, one finds 3 of the 10 analogs are: January 28, 1958, January 16, 1969, and January 26, 1969. Three other analogs are January 26, 1966, January 22, 1967, and February 1, 1983. All of those analog years saw a KU snowstorm. Five of them had such a snowstorm no later than 3 weeks after the analog date. The median and mean figures were 13 days.

February 2010:
Right now, it is a little too soon to argue for an extreme outcome. It is also premature to suggest that February 2010 will be identical to any one of the three extreme cases described above. Nonetheless, the combination of ENSO climatology, historic experience following severe December blocks, and likely imminent MMW all suggest that February will likely see:

• Significant and persistent blocking with numerous days on which the AO is < -2
• Widespread cold in the East
• An active subtropical jet

Together, these factors suggest that February 2010 will likely be cold and stormy. Where the heaviest snows fall will depend on the synoptic setup for those events. However, given that numerous very snowy winters have seen excessive snows in December in the Mid-Atlantic and southern New England regions, February could wind up very snowy in the Washington, DC to Boston region and a KU snowstorm is a distinct possibility.

[Radders]

Nicely presented and very informative. Thanks for taking the time to write this up.

[Huffwx]

Do you get tired of the "well done Don"...you do such a great job putting these write ups together.

Search a little harder and find more Jan 66 matches. Magical down here in VA, 40 inches in 2 weeks.

[CapeCodWeather.Net]

Don,
As always a great presentation of information. If the old rating system were still available, I'm sure you'd earn many a +1.

[ezweather]

Don,

As always great post. I would recommend this post be pinned for reference. This is invaluable information in that what you bring to the table in longterm potential hazardous weather outlooks. Its something that I will note for the webcasts I do on short and long term hazardous outlooks.

Excellent post and let's see what happens. I know we are all hungry for 1 or 2 KU events.

[cbw123]

Great write up, February's almost always become the best month in regards to snow and cold during el ninos.

[Jim Hughes]

Don, There's a reason why when you look at the Berlin data, or the NCEP data, it shows the zonal wind strength at 60N. This is where most experts look in regards to the 10mb PV strength and MMW's. It's not 80-90N. Mind you this doesn't mean that it is unimportant. Or even not a good indicator of what lies down the road. But these are two different issues.

[srainhoutx]

Don, I thank you for taking the time to put together a very informative and educational post. Many of our members have come to learn some very valuable information regarding signals of long range forecasting. The interaction between the Pros as well as knowledgeable members is what makes this board so great. Kudos to all that add quality input to Don's information as well. Our future forecasters are peaking their interest from this type of commentary and that will serve us well in the years to come.

[weathafella]

Don, you are amazing in your knowledge and your presentation. Thank you!

[Typhoon_Tip]

donsutherland1, on 19 January 2010 - 08:27 PM, said:

Climatology Associated with Central Pacific-Centered El Niño Events:
Typically, such events have featured widespread cold in the eastern U.S. To define a Central or Western Pacific-centered El Niño, I took all El Niño years in which the ratio of December-February ENSO Region 1+2 anomalies to ENSO Region 3.4 anomalies came to +0.50 or less. To date, Winter 2009-10’s ratio is +0.075. The following winters met that criteria: 1957-58, 1958-59, 1963-64, 1965-66, 1968-69, 1969-70, 1977-78, 1987-88, 1991-92, 2002-03, and 2004-05.

The February composite temperature anomaly was:
...

The one risk would be the evolution of the current central Pacific-based El Niño into a basinwide event, as happened when the ENSO Region 1+2 anomalies spiked in Winter 1991-92. That outcome is increasingly unlikely. The January 13 anomaly for that region was +0.3°. Meanwhile, ENSO Region 3.4 had ticked down to +1.7°C. In short, the current moderate El Niño appears to be fading slowly and there is no indication of a transformation to a dreaded basinwide winter-killer event.

December Severe Blocking:
In my thread concerning severe blocks (AO reached -3. or below) in December with an ENSO Region 3.4 anomaly of +0.5°C or warmer, it was noted that there were six years that saw such blocks: 1958, 1963, 1968, 1969, 1976, and 1977. 5/6 (83%) cases saw a negative AO in February:

February 1959: +2.544
February 1964: -0.575
February 1969: -3.114
February 1970: -1.325
February 1977: -2.010
February 1978: -3.014

The composite February temperature anomaly for those years was:
...

February 1959 featured cold only in New England. The other years saw widespread cold across much of the East.

Major Mid-Winter Warming (MMW) of the Stratosphere:
From Karin Labitzke and Barbara Naujokat, Freie Universitaet Berlin, a Major-Midwinter Warming (MMW) is defined as follows:

Major Midwinter Warmings occur mostly in January-February. In addition to warming of the north polar region and reversal of the meridional temperature gradient, they are also associated with a breakdown of the polar vortex, which is replaced by a high. That is, the definition of a Major Midwinter Warming requires not only the warming but also a total change of circulation. The definition of a breakdown of the polar vortex is that the usual westerlies in the Arctic at 10 hPa are replaced by easterlies so that the centre of the vortex moves south of 60-65°N. The vortex is either displaced entirely or split into two.

The latest computer modeling shows:

A reversal of the zonal winds beyond the critical 10 mb level by 192 hours:

A shift in the polar vortex (though not a split) south of 65°N latitude:

The bottom line is that while it had become quite clear on the modeling that a sudden stratospheric warming (SSW) event was about to unfold, there had been some debate as to whether it would reach the magnitude of an MMW. Past experience following some severe blocking episodes suggested that odds leaned toward a significant stratospheric warming event. The 1/18/2010 12z guidance has thrown its weight toward an MMW, as the extent of warming and shifting of the polar vortex meet the classic definition of an MMW.

Such events often result in renewed blocking that can persist for up to 60 days. Should such blocking develop and persist, it would fit the climatology associated with severe blocking episodes (AO of -3 or below) that developed in December.

The Extreme Case: February 1958, 1969, and 1978
What could a February with widespread cold, an active subtropical jet, and significant and persistent blocking look like? February 1958, 1969, and 1978 offer perhaps a sketch of the extreme parameter.

The composite 500 mb height anomalies for the Northern Hemisphere were:

The composite U.S. temperature anomaly was:

Those winters had in common:

• Widespread cold in the East
• Generally warmer than normal readings west of the Continental Divide
• Above to much above normal precipitation in California, the Gulf Coast
• Drier than normal conditions in the Midwest
• 1 or more KU snowstorms

If one examines the superensemble guidance centered on January 30, 2010, one finds 3 of the 10 analogs are: January 28, 1958, January 16, 1969, and January 26, 1969. Three other analogs are January 26, 1966, January 22, 1967, and February 1, 1983. All of those analog years saw a KU snowstorm. Five of them had such a snowstorm no later than 3 weeks after the analog date. The median and mean figures were 13 days.

February 2010:
Right now, it is a little too soon to argue for an extreme outcome. It is also premature to suggest that February 2010 will be identical to any one of the three extreme cases described above. Nonetheless, the combination of ENSO climatology, historic experience following severe December blocks, and likely imminent MMW all suggest that February will likely see:

• Significant and persistent blocking with numerous days on which the AO is < -2
• Widespread cold in the East
• An active subtropical jet

Together, these factors suggest that February 2010 will likely be cold and stormy. Where the heaviest snows fall will depend on the synoptic setup for those events. However, given that numerous very snowy winters have seen excessive snows in December in the Mid-Atlantic and southern New England regions, February could wind up very snowy in the Washington, DC to Boston region and a KU snowstorm is a distinct possibility.

Wonderful presentation Don - I love it! I've been waiting for this.

To add to the stratosphere discussion, currently there is an impressive emerging warm anomaly: http://www.cpc.noaa....JFM_NH_2010.gif

Question now is whether this warm anomaly is actively propagating downward in altitude within the polar vortex. We need another 14 days or so to determine that. If it kisses the tropopause the correlation on -AO (and probable -NAO) is much better for obvious reasons. That said, propagation time is a 20 day affair.

[ptb127]

Great post Don! Thank you so much for your imput!

[EastWxWatcher92]

I hope it works Don..for a winter that had so much potential and an unbelievable setup...it's been one huge disappointment.

[relic_hunter]

EastWxWatcher92, on 19 January 2010 - 11:45 PM, said:

I hope it works Don..for a winter that had so much potential and an unbelievable setup...it's been one huge disappointment.

why in the name of all that is holy would you clutter Mr. Sutherland's thread with your pathetic post? (and as such prompt my continued cluttering by necessitating this post to you)

[Thunderbolt]

Hi Don, very nice work, I always look forward to reading your posts. If its any consulation, I just wanted to let you know Mr. Anderson from Accuweather interpretation of the european monthly came out for the month of february, it looks like its in your corner with colder than normal for the east coast and above normal snowfall for the middle atlantic and up the coast!!!!

Keep up the good work!
Chris

[Jebman]

Thanks Don. This is one of your best ever. You are a meteorological rock star, a gentleman and a scholar.

[Varicweather]

Don,
Clear and very informative foercast on what may happen. Thanks for sharing! E-wall seems to be in your corner with
the GFS ushering in the cold air quicker. Like December, perhaps the pattern begins with a snowstorm. Ewall mean 500mb
heights support your view:



 12010 0z.gif (97.58K)
Number of downloads: 7

[winterymix]

Thanks, Don. Each winter seems to have its own individual personality.
The current winter has more than a minimal interest in serving up blue plate specials.
The February special seems to be the Maison de Don KU platter with side dishes
of slush, sleet, salted roads and icy blasts for dessert. YUM!

[Psalm 148:8]

Excellent!! I learned something! YEA! I now know what MMW is...seeing that it is being referenced lately...with each excellent post such as this one,I further my knowledge...bit by bit...thanks for writing a well informed, understandable (not too technical) post.. :thumbsup:

[donsutherland1]

The forecast MMW remained on track on the ECMWF. As John noted in a follow-on post, it will take some time for the warming to propagate to the troposphere, typically around 20 days.

In addition, the 6z GFS ensembles have swung toward a NAO-/EPO- regime for the extended range. I suspect that the operational GFS and, to a lesser extent, the GFS ensembles will continue to shift around for a time before locking in on the return of sustained blocking, sustained cold, and growing opportunities for snow from the Great Lakes region eastward to the Mid-Atlantic/New England regions.

P.S. Thanks all for the kind words.

[GreensboroWx]

I really enjoy reading/learning from your posts. Keep up the good work!