Medium Range Discussion Winter 2011-12

[Ottawa Blizzard]

the 12z run of the GFS is beautiful for cold in the east from February 5th on, and would appear to depict what JB was saying might happen in his video. Knowing our luck though it's probably overdone.

[ORH_wxman]

I think the risk for a KU type event is elevated in this pattern...certainly way more than the pattern we have seen for the last 8 weeks. I won't predict what the temp anomalies will be in the east for the entire month, but during the period of Feb 5-Feb 18 or so...I believe there will be a shot at a larger east coast winter event.

"Elevated" risk does not mean likely, but it means a much greater chance than the miniscule chance of such an event in an average pattern or certainly in the pattern we've seen. Some of the similar patterns in the objective CPC analogs of the GEFS and GGEM ensembles were that of large storms in Jan 1961, Feb 1995, Feb 1996, Jan 2005, and Feb 2006, There were also many patterns listed that were amplified but did not produce, but such is the nature of these types of patterns, some of them produce and some don't.

The one mitigiating factor that would create a little more pause for such an event would be the NAO...we lack a nice NAO block. But as displayed in the events listed above, such an NAO block is not necessary to get a storm...it simply increases the odds.

[BethesdaWX]

the 12z run of the GFS is beautiful for cold in the east from February 5th on, and would appear to depict what JB was saying might happen in his video. Knowing our luck though it's probably overdone.

The Euro, JMA, UKMET, and GEFS ensembles all seem to have a healthy MJO wave now, suggesting higher amplitude into the sexy octants 8-3. GEFS keeps us in octant 6 longer while the rest get us into octant 7 within 5 days.

[Chris L]

I think the risk for a KU type event is elevated in this pattern...certainly way more than the pattern we have seen for the last 8 weeks. I won't predict what the temp anomalies will be in the east for the entire month, but during the period of Feb 5-Feb 18 or so...I believe there will be a shot at a larger east coast winter event.

"Elevated" risk does not mean likely, but it means a much greater chance than the miniscule chance of such an event in an average pattern or certainly in the pattern we've seen. Some of the similar patterns in the objective CPC analogs of the GEFS and GGEM ensembles were that of large storms in Jan 1961, Feb 1995, Feb 1996, Jan 2005, and Feb 2006, There were also many patterns listed that were amplified but did not produce, but such is the nature of these types of patterns, some of them produce and some don't.

The one mitigiating factor that would create a little more pause for such an event would be the NAO...we lack a nice NAO block. But as displayed in the events listed above, such an NAO block is not necessary to get a storm...it simply increases the odds.

Some heavy hitters for the east coast, there, Will. (the analogs). I really think we can certainly get an event of that power.

[uncle W]

with the AO below -4 is a good sign...I think it will get even lower and the NYC area will get a cold wave or snowstorm or both before March...If the AO stays minus then March might have more snow/cold...I don't think we will get a storm or as cold as the last two years but I think the biggest snow of the season and coldest temperature is a head of us...

[donsutherland1]

Don,

What analogs are you using/weighting the highest right now? I'm curious how the large scale progression in those years compares to what we've seen this year.

1998-99 probably compares closest winter to what has been seen so far this winter but does not necessarily mean that February would be identical to February 1999. 1955-56 has been a rising analog especially with the recent developments related to the AO, 1975-76 is another analog year, and smaller contributions were taken from 1970-71 and 1995-96. What happened in the past 1-2 months is one factor, but a small one. How the pattern has evolved in the current month is far more important factor e.g., the breakdown of the AO+ regime is a key development. Then assumptions about various parameters for the month ahead is another. Adjustments are then made given my confidence in a variety of ensemble solutions (ENSO, MJO, anomalies, etc.) and also the observed decadal temperature trend in various parts of North America.

FWIW, the monthly map for February based on the latest objective analog years (1957, 1970, 1980, 1983, 1986, 1993, 1998, and 2005) also shows widespread warm anomalies. The possible message from that composite is that the objective analogs might be highlighting a period of cold embedded in a larger period of warmth. Time will tell.

[Lee]

This morning, the AO was -4.441. That is the lowest AO reading since December 19, 2010 when the AO was -4.695. Since 1950, there were 14 prior cases on which the AO fell to -4.000 or below in January. In 13/14 (93%) of those cases, the AO averaged < 0 in February. February 1959 was the lone exception. In 11/14 (79%) of those cases, the AO averaged -1.000 or below in February. In 6/14 (43%) of those cases, the AO averaged -2.000 or below in February. Hence, this latest data gives me strong confidence that the AO will average negative in February, and possibly -1.000 or below.

What is likely to be unprecedented for January 2012 is that none of the prior cases during which the AO fell to -4.000 or below in January had a January AO average > -1.000. The highest January average among those cases was -1.204 in January 1956. January 2012 has had an average AO of +0.069 (1/1-1/29). The month will likely finish with an average AO of -0.200 to -0.100. February 1956 had a monthly AO average of -2.029. Nevertheless, February 1956 saw the eastern portion of the U.S. have warmer than normal readings. Some of the data used for my February 2012 guess was based on February 1956.

Excellent stuff from you this Winter Don! Not that you've not always been a huge asset to the board anyway:).

There is one thing I am a little curious about and that is the '56 analogue. Yeah, taken as the CFS 2 depicts it as of now, that would be about as perfect an analogue one could use. AND, the CFS 2 has been almost stellar this winter, so might just work out great. But, what about the preceding month's pattern? January has been somewhat different than that of 1956. Normal to cool anomalies over most of the east, while being drier as well, as opposed to 2012 , as you know, mild and wet over much of the area.

It is possible i.m.o the difference in such a large area of soil moisture could change the February pattern outcome from that of '56; change LP intensity / track even if a similar 5h setup occurs.

I'm sure the ao/nao was the reason for the pattern difference then as some other indices were similar, of which I'm sure the '56 analogue was derived from.

So, the point I'm trying to make is, even if the CFS is right and we come up with a similar feb.56 pattern, I wouldn't expect it to be as pronounced. Of which from what I can gather, you are not expecting it to be.

[Srain]

The 12Z Euro has trended slower with the trough and the upper air disturbance for later in the week. HPC has tasked WSR (Winter Storm RECON) mission for the Pacific that include C-130 flights from Alaska and a possible G-IV mission from HI. We should see guidance settle on a sensible solution with that additional data in the days ahead.

WEATHER RECONNAISSANCE FLIGHTS

CARCAH, NATIONAL HURRICANE CENTER, MIAMI, FL.

0115 PM EST SUN 29 JANUARY 2012

SUBJECT: WINTER STORM PLAN OF THE DAY (WSPOD)

VALID 30/1100Z TO 31/1100Z JANUARY 2012

WSPOD NUMBER.....11-060

I. ATLANTIC REQUIREMENTS

1. NEGATIVE RECONNAISSANCE REQUIREMENTS.

2. OUTLOOK FOR SUCCEEDING DAY.....NEGATIVE.

II. PACIFIC REQUIREMENTS

1. FLIGHT ONE -- TEAL 72

A. P54/ DROP 8 (45.0N 166.0W)/ 31/0000Z

B. AFXXX 08WSC TRACK54

C. 30/1830Z

D. 17 DROPS AS PUBLISHED ON TRACK

E. AS HIGH AS POSSIBLE/ 31/0600Z

2. SUCCEEDING DAY OUTLOOK:

A. POSSIBLE TEAL C-130J MISSION FOR

P56/ DROP 9 (44.3N 151.0W)/ 01/0000Z.

B. POSSIBLE NOAA G-IV MISSION FOR

P56/ DROP 9 (44.3N 151.0W)/ 01/1200Z.

[Ottawa Blizzard]

1998-99 probably compares closest winter to what has been seen so far this winter but does not necessarily mean that February would be identical to February 1999. 1955-56 has been a rising analog especially with the recent developments related to the AO, 1975-76 is another analog year, and smaller contributions were taken from 1970-71 and 1995-96. What happened in the past 1-2 months is one factor, but a small one. How the pattern has evolved in the current month is far more important factor e.g., the breakdown of the AO+ regime is a key development. Then assumptions about various parameters for the month ahead is another. Adjustments are then made given my confidence in a variety of ensemble solutions (ENSO, MJO, anomalies, etc.) and also the observed decadal temperature trend in various parts of North America.

FWIW, the monthly map for February based on the latest objective analog years (1957, 1970, 1980, 1983, 1986, 1993, 1998, and 2005) also shows widespread warm anomalies. The possible message from that composite is that the objective analogs might be highlighting a period of cold embedded in a larger period of warmth. Time will tell.

This January couldn't have been more different in Toronto compared to 1999 however. January 1999 was among Toronto's snowiest ever.

[donsutherland1]

This January couldn't have been more different in Toronto compared to 1999 however. January 1999 was among Toronto's snowiest ever.

Ottawa Blizzard,

I was only referring to the distribution of warm anomalies. I should have been more specific.

[donsutherland1]

Thanks Lee.

1956 is among a number of cases that I used in coming up with my February idea. I give some weight to past months, a lot of weight to the current month, and also factor in my expectations for the coming month. I'll be curious to see if 1956 remains relevant for March, as March 1956 was a fun month for cold and snow.

[Ottawa Blizzard]

Ottawa Blizzard,

I was only referring to the distribution of warm anomalies. I should have been more specific.

No problem

[mitchnick]

Thoughts for the 2/8-15/2012 Timeframe:

For the first time this winter, my medium-term forecast shows cold anomalies in the eastern U.S., southern Ontario, and southern Quebec. There is risk that a warmer outcome could still unfold and much will depend on the Arctic Oscillation. Currently, there is a huge spread among the ensemble members for the AO.

The following chart shows (clockwise):

1. The composite temperature anomalies for ENSO Region 3.4 anomalies in the -1.45°C to -0.65°C range, an AO in the -1.25 to -0.25 range, and the PNA in a +0.25 to +1.25 range.

2. The 1/29/2012 0z GFS Ensemble forecast of the Arctic Oscillation.

3. Composite temperature anomalies for MJO Phase 8 (Amplitude 1-2) during La Niñas in February.

4. The Objective Analogs centered on 2/9 rolled forward 3 days (GFS ensembles).

The 1/29/2012 run of the CFSv2 is even more aggressive on the February warm anomalies (virtually all of the U.S. and Canada, including Alaska).

Don, the fact that the model has Alaska very warm causes pause. Though possible, rarely do you see Alaska way above normal along with the lower 48s. Something ain't right there. Seems to me it's one or the other.

[Feb]

I think the risk for a KU type event is elevated in this pattern...certainly way more than the pattern we have seen for the last 8 weeks. I won't predict what the temp anomalies will be in the east for the entire month, but during the period of Feb 5-Feb 18 or so...I believe there will be a shot at a larger east coast winter event.

"Elevated" risk does not mean likely, but it means a much greater chance than the miniscule chance of such an event in an average pattern or certainly in the pattern we've seen. Some of the similar patterns in the objective CPC analogs of the GEFS and GGEM ensembles were that of large storms in Jan 1961, Feb 1995, Feb 1996, Jan 2005, and Feb 2006, There were also many patterns listed that were amplified but did not produce, but such is the nature of these types of patterns, some of them produce and some don't.

The one mitigiating factor that would create a little more pause for such an event would be the NAO...we lack a nice NAO block. But as displayed in the events listed above, such an NAO block is not necessary to get a storm...it simply increases the odds.

Nice post Will. I wish you would post more outside of the NE forum. Of course seeing that you live there i understand but you are one of the most knowledgeable mets on this board and i appreciate your thoughts.

[Srain]

HPC Afternoon Final Update:

AFTN MODEL AND ENS GUIDANCE CONTINUES UNDERMINE ANY ALREADY LOW

CONFIDENCE IN ANY RELIABLE SOLUTION OVER MUCH OF CONUS AS

GFS/UKMET/CMC/ECMWF HAVE GONE BACK TO YESTERDAYS 12Z SOLUTIONS OF

LEAVING BEHIND SIGNIFICANT ENERGY IN SWRN CONUS WITH THE CMC/UKMET

AND ECMWF HAVING THE STRONGEST MID LEVELS AND AT THE SFC FORMING A

SFC LOW IN THE SRN PLAINS TO GLFMEX REGION THEN MOVING INTO THE

SOUTHEAST AND MID ATLC REGIONS. GFS WHILE LEAVING BEHIND MORE OF A

MID LEVEL LOW IN THAT REGION SHEARS IT OUT AND HAS THE DIGGING NRN

STREAM THE DOMINANT FEATURE. THIS RESULTS IN A NRN STREAM SHORTWVE

AND LOW REFORMING FROM THE OH VALLEY TO THE NC COAST BUT SHIFTING

EWD WELL OFFSHORE. THE VERY LARGE SPREAD OF SOLUTIONS AND

UNCERTAINTY AND A GREAT WEATHER AND SOCIAL POTENTIAL IMPACT IN

WHATEVER SOLUTION TURNS OUT TO BE CORRECT WARRANTS A WINTER STORM

PACIFIC RECON WHICH WILL BE FLOWN EARLY THIS WEEK. AFTN FINALS

WILL NOT BE CHANGED BASED ON THE RECENT 12Z RUNS. THERE IS

SIMILARITY TO YESTERDAYS 12Z RUNS WHICH QUICKLY CHANGED OVERNIGHT.

[Amped]

The Euro, JMA, UKMET, and GEFS ensembles all seem to have a healthy MJO wave now, suggesting higher amplitude into the sexy octants 8-3. GEFS keeps us in octant 6 longer while the rest get us into octant 7 within 5 days.

Holy crap. Is that Austrailia and New Zeland that get flooded in phase 7.

[cooling climate]

This morning, the AO was -4.441. That is the lowest AO reading since December 19, 2010 when the AO was -4.695. Since 1950, there were 14 prior cases on which the AO fell to -4.000 or below in January. In 13/14 (93%) of those cases, the AO averaged < 0 in February. February 1959 was the lone exception. In 11/14 (79%) of those cases, the AO averaged -1.000 or below in February. In 6/14 (43%) of those cases, the AO averaged -2.000 or below in February. Hence, this latest data gives me strong confidence that the AO will average negative in February, and possibly -1.000 or below.

What is likely to be unprecedented for January 2012 is that none of the prior cases during which the AO fell to -4.000 or below in January had a January AO average > -1.000. The highest January average among those cases was -1.204 in January 1956. January 2012 has had an average AO of +0.069 (1/1-1/29). The month will likely finish with an average AO of -0.200 to -0.100. February 1956 had a monthly AO average of -2.029. Nevertheless, February 1956 saw the eastern portion of the U.S. have warmer than normal readings. Some of the data used for my February 2012 guess was based on February 1956.

Obviously the stratospheric warming is now having a big impact and is likely to over the coming weeks.

[donsutherland1]

Don, the fact that the model has Alaska very warm causes pause. Though possible, rarely do you see Alaska way above normal along with the lower 48s. Something ain't right there. Seems to me it's one or the other.

I agree, Mitchnick. I suspect that Alaska will wind up colder than normal for February. I would not be surprised if the CFSv2 returns to a cold scenario in Alaska tomorrow or Tuesday, as it had in some earlier runs.

[packbacker]

I agree, Mitchnick. I suspect that Alaska will wind up colder than normal for February. I would not be surprised if the CFSv2 returns to a cold scenario in Alaska tomorrow or Tuesday, as it had in some earlier runs.

Don - Why are the weekly CFSv2 so different than the monthly for Feb? The weekly CFSv2 have colder ST anomalies in east for most of Feb via weeklys but the monthly is a torch....

[donsutherland1]

Don - Why are the weekly CFSv2 so different than the monthly for Feb? The weekly CFSv2 have colder ST anomalies in east for most of Feb via weeklys but the monthly is a torch....

They use a different base period. The monthly forecast uses the 1982-2010 period. The weeklies use the warmer 1999-2010 period.

[packbacker]

They use a different base period. The monthly forecast uses the 1982-2010 period. The weeklies use the warmer 1999-2010 period.

Ah, thanks for the clarification.

[cbmclean]

Probably a combination of the longer-term warming (the Arctic has consistently been warmer than shown on composites using past data for similar patterns) and the cold air's having drained into parts of Eurasia.

I have a question which is probably more appropriate for the Met 101 forum, but since this thread has veered in this direction recently I would liek to ask it here.

Does anyone have some good information, which they wouldn't mind sharing, about the nature and mechanisms of temperature anomalies in the polar regions during winter especially? During winter here in the midlatitudes, they simple explanation that I usually get from the weather media is that basically whether we get a cold or warm winter depends on how much "arctic" air makes its way down. When large amounts of arctic air heads south, we get cold snaps. When the arctic air is "locked up" in the north, we get mild weather. Sometimes the mechanism of the varying strength of the polar westerlies as described by the AO/NAO is invoked as an explanation etc. This all makes sense: the arctic is the "source" of cold in the boreal winter. What kind of winte ryou get depends on how much or how connected or isolate dyou are from that source.

But what I don't hear about as often is what mechanisms lead to cooler or warmer conditions in arctic itself. Of course, the first-order common sense answer seems to be simple: It would seem that the artci will be cold or warm depending on how much its cold air is shunted down into the lower latitudes. So when the AO is - and large amounts of arctic air is transported to the midlatitudes, the arctic shoudl, on the whoel have a positive temperature anomaly. On the other hand, when the AO is + and the arctic air is kept "locked up" then the arctc should possess a negative temperature anomaly. Is it really that simple?

[ORH_wxman]

They use a different base period. The monthly forecast uses the 1982-2010 period. The weeklies use the warmer 1999-2010 period.

That still doesn't seem to match to me...some of the differences are several degrees celsius...the difference in the base period is tenths of degrees. Not along the lines of a full 1-3 degrees celsius (and in some spots more than that). Unless I miscalculated something.

[ORH_wxman]

That still doesn't seem to match to me...some of the differences are several degrees celsius...the difference in the base period is tenths of degrees. Not along the lines of a full 1-3 degrees celsius (and in some spots more than that). Unless I miscalculated something.

I ran 1999-2010 Feburary versus 1981-2010 (1982-2010 I figured won't be much different)...and the difference is even worse than I thought off the top of my head looking at more crude stats...February has actually cooled quite a bit versus the '81-'10 average in the '99-'10 years.

So that makes it even more of a discrepancy on the CFS weeklies vs monthlies than previously questioned. If the weeklies have it below average versus the colder '99-'10 mean and the monthlies have it above average versus the warmer '82-'10 mean, then there is a great disconnect. The original premise was that the '82-'10 period was colder in February, but that is not the case...at least for the CONUS...I'm sure its warmer up north in the arctic regions though.

Which makes for an interesting question regarding the CFS weekly vs monthly forecasts...and how they do not match up when you add the weeklies together vs the monthly forecast.

[donsutherland1]

That's very interesting Will. Perhaps DTK might have further insight into the CFSv2 on this issue? Having said that, the CFSv2 monthly forecasts are currently in a range that has demonstrated some level of skill, so it will be interesting to see how things turn out.

[donsutherland1]

The AO fell a little further. Today, the AO was -4.464. That is the lowest AO reading since December 19, 2010 when the AO was -4.695.

[dtk]

That's very interesting Will. Perhaps DTK might have further insight into the CFSv2 on this issue? Having said that, the CFSv2 monthly forecasts are currently in a range that has demonstrated some level of skill, so it will be interesting to see how things turn out.

Well, I know for sure how the monthlies are calculated, so I'll start there (described at http://origin.cpc.nc...wang/cfsv2fcst/):

Every ten days a new set of monthlies are produced based on the previous ten days worth of forecasts (that's a 40 member ensemble right there)...these are the plots labeled E3.

Now, if you want to do a direct comparison from some of the weekly products (such as those available at http://origin.cpc.nc...eaver/cfs_fcst/):

You have to do some mental math to produce a comparable figured...I'll try to demonstrate. Let's take the latest T2m monthly:

Focus on the upper left for Feb. To produce a similar figure from the weeklies, you need to patch together several figures. Start with the plots that are labeled to have used the 28th ICs (weeks 1-2 first):

But that's not the whole ensemble that went into the monthlies (only 16 of the members), so you also need to then include the ones from the ICs on the 24th (again, week 1 forecast):

Now, that's still not the entire ensemble that went into the monthly (the above gives 32 of the 40 members), so you can also include the anomalies from the forecast labeled to have been initialized on the 20th or so (which as a reminder is a running, time-lagged ensemble from the 16 consecutive forecasts). Including the last 16 members will actually give a larger ensemble that into the monthly (so you'd actually have to find a way to construct the bits from half of those members from the 20th).

You then also need to include the 2nd half of Feb, starting again from the 28th:

and then back up to the 24th:

The point I'm trying to make is that it is a 40 member ensemble that goes into the monthlies (only updated every 10 days), whereas only 14 members that go into the weeklies (which are updated daily). I'm pretty sure if I were to go through and carefully reconstruct the monthly from the weeklies, I could do it.

As a last point, I'm 99.99% positive that the same base period/climatology is used for the weekly and monthly products.

[donsutherland1]

Thanks for the explanation, DTK. I believe that addresses the seeming difference.

With respect to the base period, the following language is provided on the daily ensemble runs:

Weeklies: "...The forecast displayed here is the ensemble mean of 16 forecast members from initial conditions of the last 14 days. All anomalies are with respect to the lead dependent model climatology from the hindcast period (1999-2010) without any adjustment."

Monthlies: "...The forecast displayed here is ensemble mean of the latest available 16 or 21 members. All anomalies are with respect to the climatology from entire hindcast period (1982-2010) without any adjustment."

[Ginx snewx]

This is much  better. Nice cool down for 3 weeks in Feb, good to see finally

[BethesdaWX]

I have a question which is probably more appropriate for the Met 101 forum, but since this thread has veered in this direction recently I would liek to ask it here.

Does anyone have some good information, which they wouldn't mind sharing, about the nature and mechanisms of temperature anomalies in the polar regions during winter especially? During winter here in the midlatitudes, they simple explanation that I usually get from the weather media is that basically whether we get a cold or warm winter depends on how much "arctic" air makes its way down. When large amounts of arctic air heads south, we get cold snaps. When the arctic air is "locked up" in the north, we get mild weather. Sometimes the mechanism of the varying strength of the polar westerlies as described by the AO/NAO is invoked as an explanation etc. This all makes sense: the arctic is the "source" of cold in the boreal winter. What kind of winte ryou get depends on how much or how connected or isolate dyou are from that source.

But what I don't hear about as often is what mechanisms lead to cooler or warmer conditions in arctic itself. Of course, the first-order common sense answer seems to be simple: It would seem that the artci will be cold or warm depending on how much its cold air is shunted down into the lower latitudes. So when the AO is - and large amounts of arctic air is transported to the midlatitudes, the arctic shoudl, on the whoel have a positive temperature anomaly. On the other hand, when the AO is + and the arctic air is kept "locked up" then the arctc should possess a negative temperature anomaly. Is it really that simple?

-AO cools the arctic surface via increased radiational cooling/lack of wind, but is warmer from the LT upward, visa versa with the +AO. -AO also tends to increase tropical cloud cover/convection, visa versa with the +AO. I believe that has implications to the total energy budget.