My Winter Outlook 2010-11

[Isotherm]

It's a shame this thread is gone as there was a lot of good, informative posts from people. I'm going to post it again here so we can look back at the end of the winter.

http://www.easternuswx.com/bb/index.php?/topic/239941-my-winter-outlook-2010-11/

NAO/AO/QBO/Solar

The NAO has been consistently negative since the spring of 2008, with only a handful of interruptions on the positive side. What has been causing this plummet in NAO values over the past few years? There are multiple mechanisms at work, and I believe that the Sun is/has ultimately been a major driver of the NAO.

Solar eruptions are linked to the North Atlantic Oscillation. Dr Theodor Landscheidt, a successful solar forecaster, showed how variations in solar output, solar wind, geomagnetic activity, galactic cosmic rays, among other periodicities, impact the modality of the NAO.

Geomagnetic activity indices measure the affect of solar eruptions on Earth. Note the figure below; a strong correlation was found between the geomagnetic aa index and the NAO index over the past half century. Early in the period, particularly prior to 1955, geomagnetic activity had a significant impact on the stratosphere but not the troposphere. However, since then, its impact extended down into the troposphere. Studies have speculated that as the Sun has become more active, with increasing irradiance/output by the mid 1900s, its impact on the troposphere strengthened. For the period 1970-2000, the correlation coefficient for the geomagnetic aa and the NAO was 0.93, an outstanding correlation.

Galactic cosmic rays (GCR) have been shown to have a strong inverse correlation to geomagnetic activity and thus the NAO. The concept in a nutshell is as follows: in times of high geomagnetic activity, the solar wind is stronger, which prevents a significant amount of galactic cosmic rays from reaching the Earth’s surface. When geomagnetic activity is lower in conjunction with a weaker solar wind, more GCR can penetrate through the atmosphere. Since GCR are an ionizing radiation, they act as a sort of nuclei for cloud formation, particularly low level clouds. Thus, surface cloudiness increases and global temperatures generally cool when GCR are high. There is likely a connection between increases/decreases in cloud cover over the Atlantic (via variations in GCR) and the NAO.

Below is the comparison of NAO and GCR values since 1950. Note the strong negative correlation.

When comparing the solar sunspot cycles to geomagnetic activity, notice there is a pretty significant lag between the maxima/minima of each. In terms of correlation with NAO values, geomagnetic activity and GCR have higher correlations than the sunspot curve itself (although the latter is important as well).

If we take a look at the following geomagnetic Ap index graph, its strong correlation to the NAO becomes apparent (geomagnetic Ap index is correlated almost perfectly with the aa index). The NAO relative minima periods of the mid 50s, the 60s-early 70s, late 70s, mid 80s, mid/late 90s, and right now correlate to the lower Ap values. The NAO relative maxima periods of the early 60s, mid 70s, early and late 80s, early-mid 90s, and the mid 2000s correlate to the higher Ap values. The NAO and Ap index curves are very well correlated over the past 40-50 years.

In summation, since 1950, we have seen an intensifying correlation between geomagnetic activity and the NAO index, possibly due to a strengthening stratospheric vortex post 1970 (Thompson, et al 2000), With that being said, what about the QBO and other NAO forcing mechanisms? The solar factors, namely geomagnetic activity and GCR provide a fairly strong argument that NAO values will remain on the negative side for this upcoming winter. In addition, the Sun is probably main driver of low NAO values since 2008, as shown above.

In terms of the QBO – it is known that the westerly phase tends to promote a stronger polar vortex and the easterly phase weakens the vortex (much like the effect of geomagnetic fluctuations on the polar vortex). However, which is more important in terms of NAO modality – QBO or geomagnetic activity?

Let’s take a look at some select years in the past few decades, and examine the states of both the QBO and geomagnetic ap index, and their corresponding impact on the NAO phase.

1972-73

1973-74

1974-75

1979-80

1983-84

1988-89

1989-90

1991-92

1993-94

2000-01

All of the above years featured a -QBO (easterly), yet all winters (DJF) had a +NAO average. If we look at the geomagnetic ap index for those winters, they all featured either high or rising values.

1977-78

1978-79

2008-09

All of these years featured a +QBO (westerly), yet the winters had a –NAO average. The geomagnetic ap index was either low or decreasing during those seasons.

Thus, in 13/40 years since 1970 the QBO and NAO were inversely correlated and did not follow the expected signal (+QBO/+NAO, -QBO/-NAO). So 67.5% of years followed the expected QBO/NAO combination. However, the geomagnetic ap index-NAO correlation since 1970 was quite a bit higher.

The QBO and geomagnetic ap index appear to have a relationship, which is not surprising; solar activity impacts stratospheric circulations/patterns. With that being said, geomagnetic activity appears to be more important than the QBO in terms of connection to NAO modality. In times of lower geomagnetic activity and –QBO, the –NAO potential is likely enhanced significantly. An example of this is last winter, 2009-10, a blockbuster snow winter over the Mid atlantic due to an active southern stream and sustained blocking.

The question is – what will happen next winter? We have a +QBO, moderate to strong La Nina, and record low geomagnetic activity. There’s no doubt in my mind regarding the solar effect on the NAO over the past couple years. In fact, the NAO has remained negative this autumn even with an intense Nina and +QBO. In 1955, we had a strong nina and +QBO until January 1956. The latter part of the winter turned slightly negative QBO. Geomagnetic activity dropped significantly in the mid 50s, which IMO was a major forcing in the significant –NAO of the 1955-56 winter.

Another NAO forcing mechanism is the Atlantic multidecadal oscillation (AMO). If we compare the NAO and AMO curves over the past several decades, there’s an apparent connection between the upswing and downswing of the AMO, and NAO values. Notice how the NAO averaged positive after the AMO minima of 20s and the 70s, while the NAO averaged negative after the AMO maxima of the mid/late 40s, and the mid 2000s. The NAO has been trending more negative over recent years, and this fits the overall AMO cycle as well. The NAO has its own decadal cycle as shown in the first image, and the curve is trending down since 2000, but the unprecedented solar factor is definitely aiding in the sustained negative NAO since 2008.

Therefore, the NAO factors for the upcoming winter are as follows: mod-strong La Nina, +QBO, declining AMO decadal cycle, declining NAO decadal cycle, record low geomagnetic activity, etc. Based upon the discussion above, I believe the solar influence is probably the most influential of all factors. However, the powerful Nina will be a factor fighting against the development of sustained blocking this winter, which will likely keep the NAO from being anywhere near as low as it was last winter, (when the El Nino and –QBO enhanced it).

With that said, I believe it is probable that a weakly negative NAO will persist for the winter season regardless of the powerful Nina. Since the AO has a strong correlation with the NAO, I anticipate a near-neutral AO, with spells of negative and positive (although not too positive).

PDO/PNA/EPO/ENSO

The Pacific signaling should easier to determine compared to the Atlantic this year. We currently have a powerful, basin wide La Nina event, with the latest region 3.4 reading at -1.5c, which is considered borderline strong.

The Pacific Decadal Oscillation (PDO) is clearly negative, with the September value coming in a -1.61 per the JISAO data. La Nina’s with strongly negative PDO’s tended to be more common in the 1950-1975 period, when the PDO decadal phase was negative. Over the past several years, the PDO downswing has returned. The onset was noticeable in the moderate El Nino of 2006-07, as the PDO was very low for a warm ENSO event. However, the PDO has been trending down since the late 90s, gradually.

Looking at the SSTA profile, the Pacific set-p is one that favors MJO waves remaining in the early octants (2-6), as very cold water pushing into ENSO region 4 could aid in halting their progression eastward across the tropical Pacific. The Gulf of Alaska is about near normal on its northern periphery and down the Pac NW coast, but colder than normal further SW. This Pacific regime generally supports a negative PNA/positive EPO pattern, with a vortex in the Gulf of Alaska, enhancing the jet into the NW US.

Forecast models – the latest CFS has ENSO region 3.4 within strong territory should the middle part of the winter, prior to weakening by Feb/March (typical of Nina climo). The ECMWF is in solid consensus with the CFS idea; region 3.4 numbers hovering in the -1.5c to -2.0c range for the better part of the winter, before becoming moderate late winter.

Therefore, I believe it is possible that this La Nina event will peak strong in the trimonthlies, meaning we’ll see three months with region 3.4 SSTA at -1.5c or lower. It’s not out of the question a couple weekly readings fall as low as -1.8c to -2.0c. So no doubt we have a powerful La Nina on our hands, whether it peaks at -1.5c or -2.0c, it’s going to be a major play in United States weather (as well as globally).

With regards to the Pacific North American index (PNA), 9/11 moderate to strong La Nina’s featured a negative PNA average for the winter (DJF). 1999-2000 and 2007-08 were the only two years that had a positive PNA. Over the past 6 months, the PNA has largely been positive. In fact, it’s somewhat unusual for this to be happening. 7/11 moderate to strong La Nina’s featured a –PNA in the August-October period. The years that didn’t were 1954, 1998, 1999, and 2007. But 1954 and 1998 shifted to a –PNA by the winter time. Based upon the intensity of this La Nina event and the declining PDO, I believe the PNA will average negative for the winter, although not strongly so, as I’m expecting some fierce resistance on the Atlantic side. The EPO should be opposite the PNA sign, with the likelihood of troughiness in Gulf of Alaska pretty high.

Putting it all together

An interesting pattern may unfold this winter, with the potential high for the NAO averaging on the negative side for DJF, and the AO not as positive as it normally would with the present ENSO regime. However, we have a strong La Nina event in place, and that will undoubtedly play a significant role in the temperature/precipitation distribution across the United States. It’s going to be a bit difficult to analog this winter, or compare it to previous years, as there aren’t many similarities. We have an unprecedented solar set-up with record low geomagnetic activity; we have a –QBO shifting slightly positive in the means, a strong La Nina, and a relatively favorable Atlantic SSTA pattern. Big time conflicts between the Pacific and Atlantic signal fighting for dominance may be the name of the game this winter. The Pacific trying to torch much of the nation, which will surely happen at times, and the NAO overwhelming parts of the US with colder than normal temps and snowfall. 1954-55, 1955-56 are probably the best overall analogs for 2010-2011 IMO. Both occurred in a relative geomagnetic minimum with negative NAO values, both were at a similar place PDO/AMO wise, and both were mod-strong La Nina events (1955-56 was very strong like this one may be). 1973-74 would be up near the top if the solar/NAO fit with this year, but it doesn’t. 1970-71 is pretty good but the La Nina this year will be quite a bit stronger, thus warmer than that winter.

December should be the coldest month relative to normal in the Northeast, with colder anomalies continuing to hold on in January with a favorable NAO pattern. February should be the warm month with the Nina induced SE-ridge going wild, pushing above normal temps further west. Overall, DJF temp departures probably won’t be as warm as most strong La Nina’s, with the more favorable Atlantic regime expected. As for precipitation and storm tracks – there’s likely to be a mixture this winter. We’ll see a good amount of lakes-cutters and inland runners producing Ohio Valley and Northern New England snow, but in times of –NAO, we could see northern stream Miller B clippers dive southward and produce snow in the I-95 corridor. I anticipate December 15th-January 15th to be the snowiest relative to normal for most of the Eastern I-95 corridor, Richmond to Boston. The biggest snows for interior/NNE may be in February with warmer temps but also plentiful precipitation.

Forecast for NYC

Temps

December: -1 to -2

January: 0 to -1

February: +1 to +2

Overall: 0 to -1

Snowfall: 25-32” (near normal)

Bonus cities snowfall:

Philly: 15-22”

Washington DC: 8-15”

Boston: 50-57”

[Isotherm]

[uncle W]

good luck again and thanks for the e mail...

[JBG]

I hope this long-term outlook bears out. I am always suspicious though when forecasters try to find reasons that a strong La Niña winter can produce good snowfalls. Most of them, as our resident historian Uncle Wx1 points out were disappointing.

Again, I hope that this winter is the exception that proves the rule.

[New England Storm]

Great Job as always, I hope this works out.

[HM]

I just wanted to bump this thread because back on Eastern, Isotherm and I got into a good discussion about the solar factors. It is becoming clear, based on the 27-day averaged solar wind, that this winter is failing to come back up to even the 07-08 levels. Therefore, this winter's NAO is likely to average negative, and probably significantly negative. Even if we break a while mid-winter, I think think it comes back big time in March anyway. Also, wanted to send a kudos to Okie as well.

Attached is the graphic and it has become pretty clear that this isn't going to touch 07-08. If it did, I think the NAO would be less of a factor this winter...

[mitchnick]

yep, even the short term NAM doesn't want to loose the -NAO

http://www.nco.ncep.noaa.gov/pmb/nwprod/analysis/namer/nam/00/index_500_m_loop.shtml

[Isotherm]

I just wanted to bump this thread because back on Eastern, Isotherm and I got into a good discussion about the solar factors. It is becoming clear, based on the 27-day averaged solar wind, that this winter is failing to come back up to even the 07-08 levels. Therefore, this winter's NAO is likely to average negative, and probably significantly negative. Even if we break a while mid-winter, I think think it comes back big time in March anyway. Also, wanted to send a kudos to Okie as well.

Attached is the graphic and it has become pretty clear that this isn't going to touch 07-08. If it did, I think the NAO would be less of a factor this winter...

HM, thanks for the comments!

The Sun's behaviour has truly been amazing over the past three years, and it's still throwing us some curveballs. The NAO certainly responded well to the low solar environment, and it looks to continue on the negative side through the better part of January. Honestly the NAO has been a bit more negative than even I anticipated, and December will turn out slightly colder than I thought. This winter really goes to show that at least for Northeast/GL forecasting, the fluctuations of the NAO/AO generally hold more weight than any other signal, including ENSO. Although the backdrop of the strong la nina pattern is seen in sensible weather patterns nationwide, the NAO/AO modality can significantly "mute" and even overpower the ENSO regime.

I still believe February will end up being the warmest month relative to normal, with a stronger SE ridge trying to assert itself. Then as you noted, it's quite possible March is interesting w/ tthe weakening nina and a resurgence in high latitude blocking.

This is a bit off-topic, but with this continued low solar environment, and the overall direction of global decadal phases (trending -PDO and -NAO), the upcoming winters could be very interesting in the US. We'll eventually get some higher SSN's but essentially the damage has been done in terms of the effects this long minimum will have on cooling global climate, but that's for another discussion.

[Isotherm]

yep, even the short term NAM doesn't want to loose the -NAO

http://www.nco.ncep....00_m_loop.shtml

Pretty amazing to see the ridiculous staying power of the -NAO since 2008. Two consecutive winters with record blocking don't happen by chance that's for sure. There were other drivers but if we didn't have this low solar/geomag environment I'd be willing to bet the NAO would have been neutral or positive so far this winter.

[tacoman25]

HM, thanks for the comments!

The Sun's behaviour has truly been amazing over the past three years, and it's still throwing us some curveballs. The NAO certainly responded well to the low solar environment, and it looks to continue on the negative side through the better part of January. Honestly the NAO has been a bit more negative than even I anticipated, and December will turn out slightly colder than I thought. This winter really goes to show that at least for Northeast/GL forecasting, the fluctuations of the NAO/AO generally hold more weight than any other signal, including ENSO. Although the backdrop of the strong la nina pattern is seen in sensible weather patterns nationwide, the NAO/AO modality can significantly "mute" and even overpower the ENSO regime.

I still believe February will end up being the warmest month relative to normal, with a stronger SE ridge trying to assert itself. Then as you noted, it's quite possible March is interesting w/ tthe weakening nina and a resurgence in high latitude blocking.

This is a bit off-topic, but with this continued low solar environment, and the overall direction of global decadal phases (trending -PDO and -NAO), the upcoming winters could be very interesting in the US. We'll eventually get some higher SSN's but essentially the damage has been done in terms of the effects this long minimum will have on cooling global climate, but that's for another discussion.

Your forecast and trust in the solar influence is bearing out well....but judging from your maps, the East south of NYC is going to be more than slightly colder than you thought for December.

[Isotherm]

Your forecast and trust in the solar influence is bearing out well....but judging from your maps, the East south of NYC is going to be more than slightly colder than you thought for December.

Tacoman, yeah the blocking has been so historic that the 0 to -1 and -2 to -3 areas should have probably been switched. The US-Canadian border won't be far from normal but the SE US will end up well below normal. I wish I had gone more bullish on the NAO overwhelming the SE ridge completely in December, but that's in the past now. Either way I'm happy I didn't go warm/blowtorch this winter. I forget but what was your take on the NAO this winter?

[HM]

HM, thanks for the comments!

The Sun's behaviour has truly been amazing over the past three years, and it's still throwing us some curveballs. The NAO certainly responded well to the low solar environment, and it looks to continue on the negative side through the better part of January. Honestly the NAO has been a bit more negative than even I anticipated, and December will turn out slightly colder than I thought. This winter really goes to show that at least for Northeast/GL forecasting, the fluctuations of the NAO/AO generally hold more weight than any other signal, including ENSO. Although the backdrop of the strong la nina pattern is seen in sensible weather patterns nationwide, the NAO/AO modality can significantly "mute" and even overpower the ENSO regime.

I still believe February will end up being the warmest month relative to normal, with a stronger SE ridge trying to assert itself. Then as you noted, it's quite possible March is interesting w/ tthe weakening nina and a resurgence in high latitude blocking.

This is a bit off-topic, but with this continued low solar environment, and the overall direction of global decadal phases (trending -PDO and -NAO), the upcoming winters could be very interesting in the US. We'll eventually get some higher SSN's but essentially the damage has been done in terms of the effects this long minimum will have on cooling global climate, but that's for another discussion.

Hey, look...I have seen a lot of forecasts for December and not too many were correct. However, there were some that were more correct than others by going colder. So don't beat yourself up. Just remember that, if you are planning on a dominating -NAO monthly signal, to put your coldest anomalies in the south...that's what I did for December and what I kept warning everyone about...but it is hard to make many critiques to your forecast here because your solar based NAO call was superb and I would certainly pay money for your thoughts.

I agree with everything you said, as far as the rest of the winter. -EPO will begin mid JAN and that will transition us into a RNA styled pattern by early Feb. The NAO is starting to have me convinced something goes down Jan 14-17, although it may be something that ends up out to sea if the block is portrayed correctly.

[Mitchel Volk]

The -NAO and AO may stem from global warming. Warmer SST s and less Artic ice may contribute to the above normal 500MB heights over the key regions. In addition, the temperatures over Baffen Island and western Greenland are amazing high these two past winters. I also notcie some of the global warming models also painted this scenario too. Just a thought.

[nzucker]

The -NAO and AO may stem from global warming. Warmer SST s and less Artic ice may contribute to the above normal 500MB heights over the key regions. In addition, the temperatures over Baffen Island and western Greenland are amazing high these two past winters. I also notcie some of the global warming models also painted this scenario too. Just a thought.

Then why was the NAO/AO record positive when the Earth was warming the fastest between 1978-1998?

Why was the -NAO/-AO pattern so prevalent when the Earth was cooling in the 50s and 60s?

Doesn't really add up..

[Mitchel Volk]

That is linear thinking; the atmosphere do not act that way. The 1950's and 60's are way different from the past 10 years to present, actually 1993 to present. The storms, snowfalls of late are unpresidented and record breaking. I grew up during the 1960's and it was stormy; but not like this. The coastal northeast are breaking snowfall records like there is not tommorow. Last winter storms and this one had central pressures that are amazing low for this latitude again and again. I know 1960 and 1969 had pressures of 966, and 972. But we were close to or lower then that many times last winter and this one was down to 962 at least. I do think storms are getting stronger in the northeast as we progress towards a warmer climate.

[nzucker]

That is linear thinking; the atmosphere do not act that way. The 1950's and 60's are way different from the past 10 years to present, actually 1993 to present. The storms, snowfalls of late are unpresidented and record breaking. I grew up during the 1960's and it was stormy; but not like this. The coastal northeast are breaking snowfall records like there is not tommorow. Last winter storms and this one had central pressures that are amazing low for this latitude again and again. I know 1960 and 1969 had pressures of 966, and 972. But we were close to or lower then that many times last winter and this one was down to 962 at least. I do think storms are getting stronger in the northeast as we progress towards a warmer climate.

My town near NYC had three 18"+ snowfall events in Winter 60-61. We ended with 90" on the winter compared to an average of 35". That's not extreme?

The strong storms are due to the powerful NAO/AO block that allows ULLs to develop farther south than normal. We haven't seen a solar minimum like this since 1810 so we are in unprecedented territory regarding how the solar minimum affects the blocking that produces such Nor'easters.

[okie333]

My town near NYC had three 18"+ snowfall events in Winter 60-61. We ended with 90" on the winter compared to an average of 35". That's not extreme?

The strong storms are due to the powerful NAO/AO block that allows ULLs to develop farther south than normal. We haven't seen a solar minimum like this since 1810 so we are in unprecedented territory regarding how the solar minimum affects the blocking that produces such Nor'easters.

Correct, and definitely makes sense within physics. Pressure is the weight of air on the earth. Matter is neither created nor destroyed, barring nuclear reactions (which have a very negligible effect on the weight of air on Earth). Thus total weight is constant. Thus, average pressure on Earth is constant (around 1013.25mb when converted to sea level equivalent). If a huge high pressure region forms in the Arctic, then by definition the pressure in the mid-latitudes must be lower (although the tropics or Southern Hemisphere could have the lower pressure instead, this rarely happens in practice due to the wind currents involved).

[Absolute Humidity]

Perhaps were seeing GW influence our temps a bit here, not a lot, but just enough to keep are lows from dipping to normal - 2 deviations one wouldexpect during a typical cold snap, at least for the mid atlantic per GFS and Euro I recall some -20 + 850's in the medium range bust last year. Sure it was cold, but nothing at all like I would expect when comparing to just a few winters a dacade or two ago. Also mybe this slight heat increase is having a role in juicing up our storms, thus giving the atmosphere the ability to hold more moisture at a warmer temp than colder?

[Isotherm]

Hey, look...I have seen a lot of forecasts for December and not too many were correct. However, there were some that were more correct than others by going colder. So don't beat yourself up. Just remember that, if you are planning on a dominating -NAO monthly signal, to put your coldest anomalies in the south...that's what I did for December and what I kept warning everyone about...but it is hard to make many critiques to your forecast here because your solar based NAO call was superb and I would certainly pay money for your thoughts.

I agree with everything you said, as far as the rest of the winter. -EPO will begin mid JAN and that will transition us into a RNA styled pattern by early Feb. The NAO is starting to have me convinced something goes down Jan 14-17, although it may be something that ends up out to sea if the block is portrayed correctly.

HM, thanks so much for the kind words.

Yeah the NAO has certainly shaked things up this winter and made a strong nina very interesting. Your Dec call on anomaly placement was spot on. Let's hope we get a repeat of the blizzard, but this time to include the entire east coast.

[Isotherm]

Perhaps were seeing GW influence our temps a bit here, not a lot, but just enough to keep are lows from dipping to normal - 2 deviations one wouldexpect during a typical cold snap, at least for the mid atlantic per GFS and Euro I recall some -20 + 850's in the medium range bust last year. Sure it was cold, but nothing at all like I would expect when comparing to just a few winters a dacade or two ago. Also mybe this slight heat increase is having a role in juicing up our storms, thus giving the atmosphere the ability to hold more moisture at a warmer temp than colder?

My thinking is we're 1) Heading back into a favorable global regime in terms of declining PDO, NAO, and AMO, much like the 50s and 60s, 2) However, global temperatures are warmer now than they were back then (regardless of the reasons) So essentially we have a conducive pattern for big storms but with more available energy in the atmosphere due to warmer temps, which could possibly be aiding in enhancing the baroclinicity / gradient along the east coast, fueling these monsters. While the 60s were very stormy, here in CNJ I've had an average of 1 12"+ storm every winter since 2000. 01-02, 06-07, 07-08 didn't have any, but I had 4 in 09-10. That's just incredible. The NAO/AO is a major part of it, but a think the straw that breaks the camel's back so to speak may be the warmer globe.

[Absolute Humidity]

My thinking is we're 1) Heading back into a favorable global regime in terms of declining PDO, NAO, and AMO, much like the 50s and 60s, 2) However, global temperatures are warmer now than they were back then (regardless of the reasons) So essentially we have a conducive pattern for big storms but with more available energy in the atmosphere due to warmer temps, which could possibly be aiding in enhancing the baroclinicity / gradient along the east coast, fueling these monsters. While the 60s were very stormy, here in CNJ I've had an average of 1 12"+ storm every winter since 2000. 01-02, 06-07, 07-08 didn't have any, but I had 4 in 09-10. That's just incredible. The NAO/AO is a major part of it, but a think the straw that breaks the camel's back so to speak may be the warmer globe.

Agreed, exaclty, totally regardless of why it warmer, I've never seen storms as juiced as these have been in the last 13 months. Its as if our typical 4 - 8" event is now a MECS/HECS. Still waiting for our BECS. Its coming, just a matter of when.

[tacoman25]

Tacoman, yeah the blocking has been so historic that the 0 to -1 and -2 to -3 areas should have probably been switched. The US-Canadian border won't be far from normal but the SE US will end up well below normal. I wish I had gone more bullish on the NAO overwhelming the SE ridge completely in December, but that's in the past now. Either way I'm happy I didn't go warm/blowtorch this winter. I forget but what was your take on the NAO this winter?

Believe me, like just about everyone else I wish I had gone more bullish on blocking this winter. I actually made a preliminary winter forecast that had the East about as cold or maybe slightly colder than yours, but chickened out and decided to side more with Nina climo for the East (except February, which I had cooler than many outlooks). My actual winter forecast suggested a weakly negative/neutral NAO. Oops.

My main analogs have actually performed quite well overall (1916-17, 1950-51, 1955-56, and 1970-71)...if I had followed them to a T my forecast would have turned out better (nationally).

[Isotherm]

Believe me, like just about everyone else I wish I had gone more bullish on blocking this winter. I actually made a preliminary winter forecast that had the East about as cold or maybe slightly colder than yours, but chickened out and decided to side more with Nina climo for the East (except February, which I had cooler than many outlooks). My actual winter forecast suggested a weakly negative/neutral NAO. Oops.

My main analogs have actually performed quite well overall (1916-17, 1950-51, 1955-56, and 1970-71)...if I had followed them to a T my forecast would have turned out better (nationally).

Tacoman, yeah our analogs were pretty similar. My top 3 were 55-56, 54-55, and 70-71, all cold La Ninas across the northern tier. If I had followed my top analog 55-56 perfectly, I would've nailed the SE US very cold departures but decided to err on the side of caution, going with colder further north up the East Coast in December. I like the way my Jan outlook looks right now, with a N-S gradient pattern in the cold/warm anomlies, but we'll see.

My main worry right now is I didn't go cold enough for the DJF period, although I went slightly below avg for the Northeast. Also, the pattern we have reloading within the next couple weeks is one that can send many areas above their seasonal snowfall normal.

Either way, the main point of my outlook this year was to try to convince people that the solar factor is/will be a lot bigger player than many think WRT the NAO/AO and consequently NA sensible wx, so I'm glad that's been working out well.

[Isotherm]

Forecast for NYC

Temps

December: -1 to -2

January: 0 to -1

February: +1 to +2

Overall: 0 to -1

Snowfall: 25-32” (near normal)

Bonus cities snowfall:

Philly: 15-22”

Washington DC: 8-15”

Boston: 50-57”

Ok, so here we are heading into the second half of the meteorological winter season. Thus far, NYC has been below to well below avg temps since December 1st, with DEC finishing at -4.5 below normal, and January likely to finish cold, although not as cold relative to normal as December.

For February - if NYC saw another colder than normal month, it would only be the 9th time since 1950 where all three winter months, DJF, were colder than avg in NYC area.

Years that featured a cold Dec/Jan/Feb:

1961-62

1962-63

1968-69

1969-70

1976-77

1977-78

1995-96

2002-03

Note the clustering in the 1960s, coinciding nicely with the decadal low points of the PDO, AMO, and NAO (everything in a negative phase w/ the globe cooler overall). Another small couplet in the late 70s, coinciding with the PDO reversal to positive and residual strong -NAO blocking. Thereafter, we only had two lone years, 95-96, and 02-03, with all three months DJF cold in NYC.

Statistically speaking, there's about an 87% chance that February 2011 will NOT be colder than normal, based upon what has transpired this winter so far. In addition, not that the following factor matters much in this winter, but mod/strong La Nina climatology also argues against a cold February.

Furthermore, the NAO/AO blocking of the past couple months looks to at least relax by late Jan into early Feb, with values closer to neutral. That should take a lot of the arctic air off the playing field in the South and Eastern US. The wildcard is the PNA, which also contrary to strong nina climo, looks to be positive for the forseeable future (conducive for east coast troughiness). Putting all this together, I believe the magnitude of the cold will lessen as we head into February, but my original call of +1 to +2 is probably too warm. If I had to make a revision, I'd go not far from normal, but still on the plus side, 0 to +1.

However, this winter has proven to be unlike any other snowfall wise for a mod/strong La Nina. My snowfall forecast for NYC, which I thought was pretty bullish at the time (considering NYC's snowiest strong nina winter produced in the 30-35" range for snowfall). But considering we've already reached that range, it's apparent to me another historic winter is in store snowfall wise in the tristate area.

Updated snowfall for the big cities:

NYC: 50-57"

Boston: 60-67"

Philly: 28-35"

DC: 10-17"

As you can see my largest revision is for NYC. Boston and Philly I've upped by about a foot and DC just about the same as before.

[A-L-E-X]

Iso, if your forecast verifies, you might need to bring another rare analog into the equation-- the first pair of back to back 50" snowfall seasons at NYC since 1916-17 and 1917-18..... and the only time it's happened so far. And interestingly enough, two of the analogs being used once solar is factored into the equation.

BTW how many of those cold winters featured below normal temps for all four cold months-- DJFM?

[Isotherm]

Iso, if your forecast verifies, you might need to bring another rare analog into the equation-- the first pair of back to back 50" snowfall seasons at NYC since 1916-17 and 1917-18..... and the only time it's happened so far. And interestingly enough, two of the analogs being used once solar is factored into the equation.

BTW how many of those cold winters featured below normal temps for all four cold months-- DJFM?

Alex,

Yeah those two years have turned out to be very good analogs for this winter, considering ENSO state, global/solar regime, etc. Of those 8 years, 5 of them had cold Marches too: 1962, 1969, 1970, 1978, and 1996. So it's been about 15 years since the last stretch of colder than normal temps D through M. Let's see if this year changes that! I believe there's a good chance March is cold, however, I'm not convinced February will be below avg in NYC.

[uncle W]

Alex,

Yeah those two years have turned out to be very good analogs for this winter, considering ENSO state, global/solar regime, etc. Of those 8 years, 5 of them had cold Marches too: 1962, 1969, 1970, 1978, and 1996. So it's been about 15 years since the last stretch of colder than normal temps D through M. Let's see if this year changes that! I believe there's a good chance March is cold, however, I'm not convinced February will be below avg in NYC.

my theory is if we don't get the January thaw the second half of the month it will come in February...Last year we had a good thaw (50 on this date last year) and February resumed the snowy cold pattern we had before the thaw...We are getting the coldest temperatures of the winter and a few snowfalls ( I hope ) when we should be getting the January thaw...We could get a long February thaw like we saw in 1961 or one like we had in 1994...1947 also had their thaw in February...1996 had two thaws...One the end of January and the other the end of February...1957-58 also...

[nzucker]

Alex,

Yeah those two years have turned out to be very good analogs for this winter, considering ENSO state, global/solar regime, etc. Of those 8 years, 5 of them had cold Marches too: 1962, 1969, 1970, 1978, and 1996. So it's been about 15 years since the last stretch of colder than normal temps D through M. Let's see if this year changes that! I believe there's a good chance March is cold, however, I'm not convinced February will be below avg in NYC.

I think there's a good chance March comes in colder than normal, as do you. Your forecast has been among the best on this board so far, really great work! We are having another historic winter, and the next two weeks looks to be particularly snowy and bitterly cold now that we've gotten this slop storm out of the way.

[A-L-E-X]

Alex,

Yeah those two years have turned out to be very good analogs for this winter, considering ENSO state, global/solar regime, etc. Of those 8 years, 5 of them had cold Marches too: 1962, 1969, 1970, 1978, and 1996. So it's been about 15 years since the last stretch of colder than normal temps D through M. Let's see if this year changes that! I believe there's a good chance March is cold, however, I'm not convinced February will be below avg in NYC.

I'm also going to ask you to look at some of our really good backloaded winters, since la ninas seem to produce big late season snowfalls. Specifically, looking at 1955-56, 1966-67, 1995-96 and 2005-06.

[A-L-E-X]

I think there's a good chance March comes in colder than normal, as do you. Your forecast has been among the best on this board so far, really great work! We are having another historic winter, and the next two weeks looks to be particularly snowy and bitterly cold now that we've gotten this slop storm out of the way.

I think NYC can make it to 40" of seasonal snowfall by the end of January, which would put them in great shape for back to back 50" snowfall seasons for the only time in their history. You and I had discussed at length about how last winter was not exceptional, not in terms of snowfall (which was great), but in terms of duration of snowcover and in terms of cold air. Looks like this winter has the best of all worlds (so far.)