Medium Range Discussion Winter 2011-12

[winterymix]

The persistence of the absence of blocking and continuing warmth has led to some forecasts being revised toward the warmer side for this winter.

Interesting comments, as expected, from Don S.

The GFS ensembles suggest an unrelenting zonal-flow upper air firehose courtesy of the Pacific region throughout this month.

In recent winters when we have witnessed the same pattern, it has been terribly stubborn to break down and give way to

a blocking pattern. Those calling for a better pattern in mid-January or even Groundhog Day may easily verify. Sad for

Eastern snow lovers but could be helpful for the national economy. DCA could book < 10 inches of snow this winter.

[donsutherland1]

It's the gfs and 312 hours out so it must be a lock!

You misunderstood Winterymix's point. His point is that the kind of pattern that is in place can be very slow to break down i.e., 1998-99, 2006-07, etc. The GFS ensembles reflect that situation.

Of course, things can change. But, to date, each time the modeling has tried to portray an Arctic outbreak, things have shifted and the outbreak did not materialize.

[Srain]

While there remains some differences regarding the track, a rather potent Winter Storm appears to be taking shape for the Southern Rockies/Southern Plains Sunday-Tuesday (December 18-20). Some totals of 4 inch+ snowfall totals may be expected from as the cold core 5H low tracks across Northern Mexico and on E along the Red River Valley. Areas under the trowal may well see higher totals as the slow moving system treks ENE.

[easternsnowman]

You misunderstood Winterymix's point. His point is that the kind of pattern that is in place can be very slow to break down i.e., 1998-99, 2006-07, etc. The GFS ensembles reflect that situation.

Of course, things can change. But, to date, each time the modeling has tried to portray an Arctic outbreak, things have shifted and the outbreak did not materialize.

I think someone said that patterns usually take around 60 days to breakdown. I believe last year was an example of that 60 day timeline. My point was that long range models have been wrong for the most part especially lately. In 2006-2007 I would of had above normal snow if it was'nt for the sleet storms.

[donsutherland1]

While there remains some differences regarding the track, a rather potent Winter Storm appears to be taking shape for the Southern Rockies/Southern Plains Sunday-Tuesday (December 18-20). Some totals of 4 inch+ snowfall totals may be expected from as the cold core 5H low tracks across Northern Mexico and on E along the Red River Valley. Areas under the trowal may well see higher totals as the slow moving system treks ENE.

Srain,

Very nice discussion. I agree with you. The guidance + past experience with similar patterns during La Niña events suggests that the rest of December will generally see below normal to near normal readings in those areas. Opportunities for winter weather should be present. Overall, it should be a fun pattern for winter weather lovers in those areas.

[Srain]

Srain,

Very nice discussion. I agree with you. The guidance + past experience with similar patterns during La Niña events suggests that the rest of December will generally see below normal to near normal readings in those areas. Opportunities for winter weather should be present. Overall, it should be a fun pattern for winter weather lovers in those areas.

Thanks Don. The greatest benefit that we are seeing is the reducing of the ongoing drought across Texas and Oklahoma. With the active pattern many areas for the first time since summer are dropping below Exceptional Drought status (D4) as inflow to our lakes increases.

[donsutherland1]

I think someone said that patterns usually take around 60 days to breakdown. I believe last year was an example of that 60 day timeline. My point was that long range models have been wrong for the most part especially lately. In 2006-2007 I would of had above normal snow if it was'nt for the sleet storms.

Unfortunately, when the signals on the teleconnections are ambiguous e.g., weak PNA signal, there can be a lot of uncertainty. Situations where there is a decisive EPO, PNA, and AO signal are not the norm. Occasionally, one signal can be so extreme that it overwhelms the others. Placement of height anomalies can be critical in the absence of such decisive or extreme situations and it is difficult to pinpoint such anomalies in the medium-range and beyond. ENSO evolution also has an impact.

[donsutherland1]

Thanks Don. The greatest benefit that we are seeing is the reducing of the ongoing drought across Texas and Oklahoma. With the active pattern many areas for the first time since summer are dropping below Exceptional Drought status (D4) as inflow to our lakes increases.

I agree. Hopefully, the reversal of the drought will continue throughout the winter and beyond.

[donsutherland1]

DCA could book < 10 inches of snow this winter.

FWIW, my 2011-2012 seasonal snowfall guesses for the NEWX seasonal snowfall contest included:

Baltimore: 12.5"

Boston: 37.4"

New York City: 12.1"

Newark: 16.1"

Philadelphia: 13.5"

Providence: 28.5"

Washington, DC:

...DCA: 10.0"

...IAD: 13.5" (sorry Ji)

The guesses were submitted back in November. They include anything that might have fallen in October. December snowfall will provide a good clue as to whether the guesses are on track. Unfortunately, the absence of snowfall suggests that certain figures might even have to be lowered further. There is a distinct and growing possibility that BWI, DCA, IAD, NYC, and PHL could all see less than 10" seasonal snowfall. Hopefully, that won't happen, but it is a concern.

[Kevin Druff]

Don -- what's your background? You're obviously very knowledgeable and widely respected on the board, but not red-tagged. Is that by choice? Or, is meteorology simply a post-career profession?

TIA!

P.S. I just stumbled on to your photo archive page. The next time I go to my mom's, I will try to find the pictures from the January 1996 blizzard in Staunton. I have a picture of our split rail fence almost entirely buried by snow.

[Srain]

The medium/long range guidance continues to advertise an active pattern across the S Plains. While there is still some differences regarding the eventual track, Sunday-Tuesday suggest a potent Winter Storm could produce snowfall in the range of 4-8 inches under the trowal. Just beyond during the pre Holiday period, yet another upper low develops and it appears this feature may come further S as a stronger short wave trough in the northern jet drops S into the N Rockies/N Plains bringing yet another chance for wintry mischief in the Thursday-Saturday timeframe. There are hints of a Coastal low developing along the Texas Coast with the second disturbance, so the week leading up to the long weekend Holiday period will need to be monitored.

[am19psu]

The medium/long range guidance continues to advertise an active pattern across the S Plains. While there is still some differences regarding the eventual track, Sunday-Tuesday suggest a potent Winter Storm could produce snowfall in the range of 4-8 inches under the trowal. Just beyond during the pre Holiday period, yet another upper low develops and it appears this feature may come further S as a stronger short wave trough in the northern jet drops S into the N Rockies/N Plains bringing yet another chance for wintry mischief in the Thursday-Saturday timeframe. There are hints of a Coastal low developing along the Texas Coast with the second disturbance, so the week leading up to the long weekend Holiday period will need to be monitored.

Yup, if you want a white Christmas, head to ABQ or AMA. Good analysis, Steve.

[donsutherland1]

The medium/long range guidance continues to advertise an active pattern across the S Plains. While there is still some differences regarding the eventual track, Sunday-Tuesday suggest a potent Winter Storm could produce snowfall in the range of 4-8 inches under the trowal. Just beyond during the pre Holiday period, yet another upper low develops and it appears this feature may come further S as a stronger short wave trough in the northern jet drops S into the N Rockies/N Plains bringing yet another chance for wintry mischief in the Thursday-Saturday timeframe. There are hints of a Coastal low developing along the Texas Coast with the second disturbance, so the week leading up to the long weekend Holiday period will need to be monitored.

Very nice discussion, Srain.

I believe that the current pattern will persist at least through the remainder of December.

[donsutherland1]

Below is a chart that shows, among other things, temperature anomalies based on an AO in the +1 to +2 range; PNA in the -0.75 to +0.75 range, ENSO R3.4 anomalies in the -1.50 to -0.75 range, for the 12/20-31 timeframe (1950-2010) to gain insight into the likely anomalies for the upcoming 12/24-31 timeframe.

In general, based on the above composites, even as the pattern is the type that could allow a cold shot into the East, with its greatest impact from the Mid-Atlantic region northward, warm anomalies will again likely outduel the cold ones.

Since that time, the ensembles have shifted. They now favor an AO in the +1 to +3 range. However, they also favor a positive PNA (0 to +1). A few ensemble members push the PNA beyond +1 for a brief period of time.

The PNA, not AO, will likely be the big driver of how things shape up during the 12/24-31 timeframe. A PNA that averages > +1 would have the potential to overwhelm the impact of the AO and produce a colder outcome in the East. Right now, that is not the most likely scenario. However, a cold shot could coincide with a brief push beyond +1.

Below is a chart that shows two scenarios for the same ENSO conditions listed above and an AO in the +1 to +3 range. They were taken from all of December (1950-2010) to enlarge the sample size. The chart on the left shows the most likely PNA outcome (0 to +1). Notice the warmth is consistent with the charts at the top of this message. The chart on the right shows a scenario for a +1 to +3 PNA.

In sum, despite a possible cold shot, the 12/24-31 period still looks to wind up on the warm side of normal. However, were the PNA to rise beyond what is currently modeled, a colder outcome would be possible.

[showmethesnow]

The chart on the left shows the most likely PNA outcome (0 to +1). Notice the warmth is consistent with the charts at the top of this message. The chart on the right shows a scenario for a +1 to +3 PNA.

Did you by any chance glance into what the precip anomalies would be in both cases? By looking at the temp anomalies I am guessing the one on the left probably suggests a wetter Midwest to East coast whereas the one on the right probably suggests a drier Midwest to East coast? Basically warm/wet or a cold/dry options?

[donsutherland1]

Did you by any chance glance into what the precip anomalies would be in both cases? By looking at the temp anomalies I am guessing the one on the left probably suggests a wetter Midwest to East coast whereas the one on the right probably suggests a drier Midwest to East coast? Basically warm/wet or a cold/dry options?

The chart on the left had wet anomalies running from eastern Texas across the Gulf States out through the Mid-Atlantic region and then eastern New England. The Midwest and Great Lakes area saw normal precipitation. The chart on the right, was dry throughout most of the East. Hence, mild/wet and cold/dry were the two scenarios shown, with the former being more likely.

[Srain]

Interesting pattern via the Euro...

[donsutherland1]

Just a few quick notes:

1. The Southern Plains snowstorm for the 12/18-20 period will be a headline story. It will probably be one of this winter's highlight storms. Given the guidance, I expect some areas will experience blizzard conditions. Even as I watch the system from the nose-bleed seats far in the East, it will be fascinating to see things unfold.

2. Recent runs of the GFS ensembles have really backed off on the rise in the PNA. The consensus is for a 0 to +1 figure for the 12/24-31 timeframe, but some ensemble members take the PNA somewhat negative. The "spike" shown by a few is gone. No members take it above +1. As a result, the Pacific Northwest, which has enjoyed a cold late autumn/early winter, but is in the midst of a mild period, could see a return toward colder weather beginning in the next 7-10 days.

3. The setup suggests that some of the runs of the operational GFS have probably been overdone in terms of cold during the 12/24-31 period. The model could subsequently back off and the overall 12/24-31 period, despite a cold shot or two, will probably wind up somewhat warmer than normal in the East.

4. Winter will likely maintain its grip on portions of the U.S. being impacted by the upcoming blizzard, with the cold outdueling the warmth for the remainder of this month.

[Srain]

Just a few quick notes:

1. The Southern Plains snowstorm for the 12/18-20 period will be a headline story. It will probably be one of this winter's highlight storms. Given the guidance, I expect some areas will experience blizzard conditions. Even as I watch the system from the nose-bleed seats far in the East, it will be fascinating to see things unfold.

2. Recent runs of the GFS ensembles have really backed off on the rise in the PNA. The consensus is for a 0 to +1 figure for the 12/24-31 timeframe, but some ensemble members take the PNA somewhat negative. The "spike" shown by a few is gone. No members take it above +1. As a result, the Pacific Northwest, which has enjoyed a cold late autumn/early winter, but is in the midst of a mild period, could see a return toward colder weather beginning in the next 7-10 days.

3. The setup suggests that some of the runs of the operational GFS have probably been overdone in terms of cold during the 12/24-31 period. The model could subsequently back off and the overall 12/24-31 period, despite a cold shot or two, will probably wind up somewhat warmer than normal in the East.

4. Winter will likely maintain its grip on portions of the U.S. being impacted by the upcoming blizzard, with the cold outdueling the warmth for the remainder of this month.

Don, I agree the 12/18-20 period will be the headline story this week. We further S are monitoring the post Holiday Weekend timeframe as the 00Z Euro continues to advertise a very active pattern with U/L activity further S and phasing of the Northern jet short wave activity as well as a noisy STJ. The last week of December could prove interesting for the Southern Plains yet again as suggested by the Operational Euro.

[Srain]

lol...

[wxmx]

I think the 12z GFS is too progressive, beating the E Coast ridge, as it buckles the current pattern, but there's not real reason to do so. There's also little support from it's own ensembles:

The Euro has been digging (and phasing) energy deep in MX, that would be quite a call right now, but at least something similar to what has been happening all season is what I would expect for the 24-28th period, with a winter storm brewing in the SW and NW MX.

[winterymix]

Srain

lol...

What is up with the weird depiction of 850 mb warmth flooding the Pacific NW?

Is it plausible? The entire pattern is quirky, given the SW to NE railroad track of

storms from Old Mexico to Detroit along with Pacific warmth and some sort of

SE ridge. My hunch is this is typical of La Nina. Meteorologist(s) explano, please.

[wxmx]

What is up with the weird depiction of 850 mb warmth flooding the Pacific NW?

Is it plausible? The entire pattern is quirky, given the SW to NE railroad track of

storms from Old Mexico to Detroit along with Pacific warmth and some sort of

SE ridge. My hunch is this is typical of La Nina. Meteorologist(s) explano, please.

Not that typical, unless there's a very strong W Coast ridge, which is somewhat uncommon on Niñas and -PDO (at least amplifying that far south)... look at Jan 8-11th 1967 for an extreme example in a neutral cold ENSO pattern...another one would be late Feb (23-27th) 1894, that was a full fledged Niña....and even to some extent, last early Feb

[Srain]

The 00Z GFS is bound and determined to make the next week worth watching across the Texas and the Southern Plains. Coastal lows and cold air can make for an interesting setup in this region...

[Ed Lizard]

Sorry to sound "how much for Philly" on a one week model forecast unlikely to verify perfectly, but I think a touch of isoallobaric winds at my house would be enough for happy precip, verbatim.

Homina. Saturation in the crystal growth region.

[am19psu]

Looks like the interior Northeast could be setting up for a moderate event for Xmas day. Berkshires FTW?

[donsutherland1]

With the 12/19-23 period getting underway, it is worth re-examining where things stand. Back in this thread on December 8 (#200), I noted that operational GFS, which had a cold outlook, was not supported by its ensembles. I also brought up a composite pattern based on forecast teleconnections. It should be noted that the AO is essentially zero/ever so slightly negative but expected to rebound strongly after coming off a long period of high readings. As a result, the atmosphere still reflects the predominant AO+ state. The PNA is slightly above the expected range, but not high enough to really change things.

The chart in question is below:

From Ryan Maue's website, here are the forecast 5-day temperature anomalies (2 meter for 12/19 through 12/24, which is very close to the period in question):

Those forecast anomalies match up very well with the composite 850 mb temperature anomalies posted on 12/8 for an idea as to how things could work out.

The result is that as the 12/19-23 period gets underway, the warmer scenario is the one that is likely to play out. Should that scenario play out, the "cold" outcome would be yet another false alarm among a growing number that one has seen to date. Until some of the big teleconnections (AO, EPO, PNA) change, one probably won't see big changes in the overall pattern. Instead, cold shots would likely be transient and opportunities for snowfall would be limited and dependent on "threading" the proverbial needle in an unfavorable pattern.

[dom]

Did any notice what gfs operational did on last two days of the run. It has alot of acrtic air heading south.Any thoughts on this?

[HailMan06]

The 00Z GFS is bound and determined to make the next week worth watching across the Texas and the Southern Plains. Coastal lows and cold air can make for an interesting setup in this region...

Is that a 1044 mb high I see over Colorado?

[Geos]

Is that a 1044 mb high I see over Colorado?

Yes!

I was surprised to see the AO at -0.88 today. I think the ridge in central Asia is going to start affecting the AO coming up in a week or two.