Winter 2012-13 (DJF) Forecast

[uncle W]

Good forecast. I agree with the analogs you selected. 2006 is a very good match to this year, not only in terms of ENSO but also sensible weather in the U.S. and Northern Hemisphere and global SST patterns. I especially liked 1994 and 2006, since they both featured a negative DJFM mean PDO. 1994 was also a close match for QBO to date, which brings me to my next point. I wouldn't worry to much about the negative QBO at this point. It appears we've reached the biennial peak of the easterly phase and will be rapidly rising towards the positive, westerly phase by winter. It was pointed out to me that the QBO is a decent predictor of NAO, and the two closest matches to this year's pattern are 1994 and 2001 -- which were both disaster winters. 1994 is also a good ENSO analog, and 2001 not horrible to this point (was positive-neutral during the summer, but then dropped).

Here's a chart showing what I mean re: the QBO. The blue is observed QBO value for January 1993 through December 1994 (i.e. leading to the winter of 1994-95), the red is observed QBO for January 2011 through August 2012 (the most recent 20 months), and the green shows January 2000 through December 2001 (i.e. leading to the winter of 2001-02). As you can see, the current cycle has closely tracked the 2000-01 and 1993-94 events to date. What this suggests to me is that QBO will probably be positive (westerly phase) by sometime during the winter. I'm not sure if it will be there by December, but almost certainly by February. Historically, the negative, easterly phase has ranged from 11 to 19 months. So far, this cycle, there has already been 14 months below zero. There are three more months before December, which would mean we'd be at 17 months at that time. So it would take something not previously observed, to not see the QBO reach the positive phase by February.

if those analogs work out this is what December temperatures will look like...probably very little snow if any for NYC in December...Both February's were colder than average with one good wintry event...

[Rainshadow]

Good forecast. I agree with the analogs you selected. 2006 is a very good match to this year, not only in terms of ENSO but also sensible weather in the U.S. and Northern Hemisphere and global SST patterns. I especially liked 1994 and 2006, since they both featured a negative DJFM mean PDO. 1994 was also a close match for QBO to date, which brings me to my next point. I wouldn't worry to much about the negative QBO at this point. It appears we've reached the biennial peak of the easterly phase and will be rapidly rising towards the positive, westerly phase by winter. It was pointed out to me that the QBO is a decent predictor of NAO, and the two closest matches to this year's pattern are 1994 and 2001 -- which were both disaster winters. 1994 is also a good ENSO analog, and 2001 not horrible to this point (was positive-neutral during the summer, but then dropped).

Here's a chart showing what I mean re: the QBO. The blue is observed QBO value for January 1993 through December 1994 (i.e. leading to the winter of 1994-95), the red is observed QBO for January 2011 through August 2012 (the most recent 20 months), and the green shows January 2000 through December 2001 (i.e. leading to the winter of 2001-02). As you can see, the current cycle has closely tracked the 2000-01 and 1993-94 events to date. What this suggests to me is that QBO will probably be positive (westerly phase) by sometime during the winter. I'm not sure if it will be there by December, but almost certainly by February. Historically, the negative, easterly phase has ranged from 11 to 19 months. So far, this cycle, there has already been 14 months below zero. There are three more months before December, which would mean we'd be at 17 months at that time. So it would take something not previously observed, to not see the QBO reach the positive phase by February.

Entropy, is this 30mb qbo?

[Ellinwood]

WINTER FORECAST UPDATE

My original forecast from August had to basically be thrown out due to a few key factors.

1. ENSO faltering. While the positive trends have recovered, there was a major misstep in the trend as the values for most of the ENSO regions started to fall. The latest data indicates that the positive trend has resumed, which led me to go with an ENSO value bordering on positive neutral and weak Nino for DJF. A new ENSO prediction means new analogs, which can be found at the end of the post.

2. Siberian snow cover. As you can see from the graphic below, significant gains have been made in Siberia compared to the start of the month. <a href="http://voices.washin...a.html">Studies show a correlation</a> between positive snow cover trends over Siberia and cooler temperatures across eastern North America.

3. The North Atlantic Oscillation (NAO). The NAO has generally been negative since May, and it shows no signs of going positive any time soon. A -NAO helps pull cold air into the eastern U.S. during the winter months.

Along with this new data, I also used the PDO and AMO signals to help weight my analog years.

The monthly breakdown:

Winter 2012-2013:

ANALOGS:

in [year (weight)] format

1976-77 (more)

1958-59 (more)

1952-53 (more)

2003-04 (less)

1990-91 (less)

1979-80 (less)

1960-61 (less)

NOTE: Anomalies are against 1981-2010 normals.

[winterymix]

This idea is a toggle of polarity.

Last year, we had that incessant warmth and the outlook here

is for very assertive cold anomalies

[JoMo]

That's a very large dry area across a lot of the country. Can you give any specific reasoning for why it is such a large area?

[Ellinwood]

That's a very large dry area across a lot of the country. Can you give any specific reasoning for why it is such a large area?

Part of the precipitation pattern can be derived from the background ENSO signal, which, even though it is weak, could/should have some influence on the overall pattern.

I would hypothesize that some of the ridging over the western U.S. helps with the drier regime over the Southwest to central Rockies, and a storm track that dives from western Canada into the south-central Plains would not transport much moisture with it east of the Rockies. Once the disturbance reaches the southern Plains, it re-develops and pulls in some Gulf moisture, allowing for normal to wet conditions along the Gulf. This also acts to cut off Gulf moisture transport the north-central U.S. to the Great Lakes. As the storm track curves back to the northeast, it brings some of the moisture up along the East Coast.

With the exception of 1979-80, there was actually a pretty strong correlation between the analog years on a seasonal level.

EDIT: Looking at the monthly level, December appears quite dry across most of the U.S. (with more normal conditions along the East Coast). January has wetter conditions in the Northwest and Florida, with some dryness lingering in the Southwest, central Plains and western Midwest. February shifts the wetter conditions into the north-central U.S. and western Gulf as drier conditions sit over the central Plains, southern Midwest and northeastern U.S.

[WinterWxLuvr]

WINTER FORECAST UPDATE

My original forecast from August had to basically be thrown out due to a few key factors.

1. ENSO faltering. While the positive trends have recovered, there was a major misstep in the trend as the values for most of the ENSO regions started to fall. The latest data indicates that the positive trend has resumed, which led me to go with an ENSO value bordering on positive neutral and weak Nino for DJF. A new ENSO prediction means new analogs, which can be found at the end of the post.

2. Siberian snow cover. As you can see from the graphic below, significant gains have been made in Siberia compared to the start of the month. <a href="http://voices.washin...a.html">Studies show a correlation</a> between positive snow cover trends over Siberia and cooler temperatures across eastern North America.

3. The North Atlantic Oscillation (NAO). The NAO has generally been negative since May, and it shows no signs of going positive any time soon. A -NAO helps pull cold air into the eastern U.S. during the winter months.

Along with this new data, I also used the PDO and AMO signals to help weight my analog years.

The monthly breakdown:

Winter 2012-2013:

ANALOGS:

in [year (weight)] format

1976-77 (more)

1958-59 (more)

1952-53 (more)

2003-04 (less)

1990-91 (less)

1979-80 (less)

1960-61 (less)

NOTE: Anomalies are against 1981-2010 normals.

I hope you're right about Dec/Jan. I'd much rather have winter during those two months. First half of Feb can be good, but after that winter events tend to be slop fests.

[Snow_Miser]

Ellinwood,

Nice discussion and forecast.

Quick question on your precipitation chart. I apologize if this has been asked already.

What anomaly constitutes as being "dry" and "wet" in your precipitation maps? What constitutes as "normal?"

[Bob Chill]

Seems a lot of us are looking at the 76-77 analog. It would be precarious to assume record breaking cold potential this year but a similar ul pattern is possible. 76-77 was crazy cold but it was also dry. Sometimes too much of a good thing isn't good. At least when it comes to precip. If we do get a crazy -ao/nao combo then just about all of us on the EC will be shivering under blue skies. Lake effect areas would do fairly well if the pattern developed in Dec when the difference between air and water temps would be at their highest.

Here's what Dec 76 looked like @ 500mb:

[Ellinwood]

Ellinwood,

Nice discussion and forecast.

Quick question on your precipitation chart. I apologize if this has been asked already.

What anomaly constitutes as being "dry" and "wet" in your precipitation maps? What constitutes as "normal?"

It's pretty arbitrary... I don't have any set percentages for them. I just use the precip maps to give people the general idea of what to expect. As a guideline, you could use the "very dry" for under 50%, "dry" for 50-85%, "wet" for 115-150% and "very wet" for over 150%. Again, they aren't set numbers, but maybe I could add specified ranges in future outlooks.

[scottmartin49]

Seems a lot of us are looking at the 76-77 analog. It would be precarious to assume record breaking cold potential this year but a similar ul pattern is possible. 76-77 was crazy cold but it was also dry. Sometimes too much of a good thing isn't good. At least when it comes to precip. If we do get a crazy -ao/nao combo then just about all of us on the EC will be shivering under blue skies. Lake effect areas would do fairly well if the pattern developed in Dec when the difference between air and water temps would be at their highest.

Here's what Dec 76 looked like @ 500mb:

Seeing this already- flow has been easterly off Ontario for the last month. It's already cooling down though, with what warmth there is left pooling on the Eastern shore. Near continuous moisture showing up on the Montague doppler, but ground temps are still holding up, so no snow.

http://www.coastwatc...chive/o2/Nov05/