2013 Fall Medium Range Discussion

[ayuud11]

Don,

Any comments on this? http://www.cpc.ncep.noaa.gov/products/intraseasonal/temp10anim.gif

[donsutherland1]

Don,

Any comments on this? http://www.cpc.ncep.noaa.gov/products/intraseasonal/temp10anim.gif

 

I believe that 10 mb warming lends confidence in the idea that the EPO will probably be predominantly negative for at least the next week or two.

[donsutherland1]

Some evening thoughts...

 

1. No major changes with respect to snow-starved Washington, DC. My thinking inclusive of the 0z NAM and GFS with weight given to the 12z ECMWF is that metro Washington will probably see a 4"-8" snowfall. Nearby Dulles International Airport will likely see 8"-14". If something closer to the NAM verifies, even larger amounts would be possible.

 

2. The two biggest March storms since 1840 brought 12" to Washington. The more recent of those two storms occurred on March 27-28, 1891. The March 28, 1891 edtion of The Washington Post wrote:

 

Everybody thought spring had come. The ladies were getting their Easter bonnets, the maple trees were pushing out their tender green buds, and some of the early-flowering shrubs in the parks were almost ready to open their tiny red and yellow blooms. Then this blizzard came along. The freezing wind, with its load of wet, clinging snow, made the maple tree buds shiver and shake till they fell off onto the sloppy pavements. The tardy Easter buyer had to postpone her shopping excursion. The rubber overshoes that had been thrown away were brought out again. The soft little ***** willows over in the Eastern Branch marshes that were just pushing their dainty blonde heads out of the green pods were soaked through and covered with the wet snow and then knocked off into the mud by the heavy raindrops with which the northeast wind pelted them. The flower buds on the shrubs in the parks were wrenched off by the wind and, falling in the wet grass, were soon covered up by the snow.

 

Parts of western Virginia saw much larger amounts of snow. Some 30 inches accumulated at Winchester.

 

3. Odds of at least an appreciable to perhaps signifcant snowfall in the northern Mid-Atlantic and New England that I placed at one-in-three this morning have increased. There is some possibility that the storm might wind up as a KU snowstorm (if the 0z NAM is reasonably accurate). One of the leading analog cases for March cited in #631 was 1960, so it will be interesting to see if such a storm develops. Certainly, at least portions of the Middle Atlantic region will very likely receive a significant March snowfall.

[uncle W]

Some evening thoughts...

 

1. No major changes with respect to snow-starved Washington, DC. My thinking inclusive of the 0z NAM and GFS with weight given to the 12z ECMWF is that metro Washington will probably see a 4"-8" snowfall. Nearby Dulles International Airport will likely see 8"-14". If something closer to the NAM verifies, even larger amounts would be possible.

 

2. The two biggest March storms since 1840 brought 12" to Washington. The more recent of those two storms occurred on March 27-28, 1891. The March 28, 1891 edtion of The Washington Post wrote:

 

Everybody thought spring had come. The ladies were getting their Easter bonnets, the maple trees were pushing out their tender green buds, and some of the early-flowering shrubs in the parks were almost ready to open their tiny red and yellow blooms. Then this blizzard came along. The freezing wind, with its load of wet, clinging snow, made the maple tree buds shiver and shake till they fell off onto the sloppy pavements. The tardy Easter buyer had to postpone her shopping excursion. The rubber overshoes that had been thrown away were brought out again. The soft little ***** willows over in the Eastern Branch marshes that were just pushing their dainty blonde heads out of the green pods were soaked through and covered with the wet snow and then knocked off into the mud by the heavy raindrops with which the northeast wind pelted them. The flower buds on the shrubs in the parks were wrenched off by the wind and, falling in the wet grass, were soon covered up by the snow.

 

Parts of western Virginia saw much larger amounts of snow. Some 30 inches accumulated at Winchester.

 

3. Odds of at least an appreciable to perhaps signifcant snowfall in the northern Mid-Atlantic and New England that I placed at one-in-three this morning have increased. There is some possibility that the storm might wind up as a KU snowstorm (if the 0z NAM is reasonably accurate). One of the leading analog cases for March cited in #631 was 1960, so it will be interesting to see if such a storm develops. Certainly, at least portions of the Middle Atlantic region will very likely receive a significant March snowfall.

always a great read Don...March 28th is my birthday and the biggest storm on that date was in 1984...March 28th 1891 had no measurable snow for NYC...Another storm that gave DC a lot of snow and NYC a little was in 1942 around the same date...I'm hoping for a 1984 type event over the other two...TWT...

[donsutherland1]

always a great read Don...March 28th is my birthday and the biggest storm on that date was in 1984...March 28th 1891 had no measurable snow for NYC...Another storm that gave DC a lot of snow and NYC a little was in 1942 around the same date...I'm hoping for a 1984 type event over the other two...TWT...

Thanks Uncle W.

 

The "Palm Sunday Snowstorm" of March 1942 was one of Washington's biggest late-season snowstorms. It brought 11.5" to Washington.

 

Some photos: http://wintercenter.homestead.com/photo1942.html

 

Hopefully, we'll get a March 1984-type event before the season is finished. It does appear that the upcoming storm will be modest in and around the City (probably 2"-4" would be my guess at this time). Washington still looks to be on track for a 4"-8" snowfall, after having received just 1.5" to date.

[donsutherland1]

Some mid-day thoughts...

 

The AO is currently -3.767. That's the lowest AO reading in March since March 21, 2006 when the AO fell to -3.822. Consistent with long-duration severe blocks that developed around the time the current blocking regime developed, the present block will end no earlier than the March 10-20 timeframe.

 

Once the block ends, it remains to be seen whether it will be followed by a sustained absence of blocking or a temporary pause before a new blocking regime develops. 1962 saw the block followed by a prolonged general absence of blocking. In contrast, 2001 saw another shorter-lived severe block develop before a general absence of blocking was sustained. Depending on the evolution of blocking, the pool of cold could retreat to the Plains States while shrinking or much of the rest of March could also break out on the cold side of normal in the eastern third of the U.S., along with southern Ontario and perhaps southern Quebec.

 

The 500 mb height anomalies forecast on the GFS ensembles continue to resemble the March 5-7, 1962 event with the 500 mb trough shifting somewhat to the north and east of the 1962 one. As a result, I continue to expect that Washington, DC (DCA) will likely see 4"-8" snow making for a period of good sleighing on Capitol Hill. Sterling, Virginia and westward to the Blue Ridge should see 8"-14" with some higher amounts. However, with the storm's best dynamics likely remaining offshore, the northern Mid-Atlantic region will likely see lesser accumulations, not to mention see a greater share of precipitation in the liquid form. NYC and nearby suburbs will probably see 2"-4" snow. There is risk that amounts could be lighter there. For parts of the East and Ohio Valley, including areas missing out on the upcoming storm, the 3/5-8 storm likely will not be the last system to bring an opportunity for snow.

 

With the EPO likely to be generally negative into the third week of March and the blocking continuing into or through that week, the risk of an Arctic outbreak remains higher than usual for March.

 

Finally, as the pattern continues to evolve, I continue to think that another snowstorm is possible in the Plains States. In fact, the 12z GFS is now hinting at such a possibility in its extended range. That model is showing 1.17" qpf for Kansas City during the 3/16 0z through 3/18 oz timeframe, with a large share of that precipitation being in the frozen form.

[Ottawa Blizzard]

Some mid-day thoughts...

 

The AO is currently -3.767. That's the lowest AO reading in March since March 21, 2006 when the AO fell to -3.822. Consistent with long-duration severe blocks that developed around the time the current blocking regime developed, the present block will end no earlier than the March 10-20 timeframe.

 

Once the block ends, it remains to be seen whether it will be followed by a sustained absence of blocking or a temporary pause before a new blocking regime develops. 1962 saw the block followed by a prolonged general absence of blocking. In contrast, 2001 saw another shorter-lived severe block develop before a general absence of blocking was sustained. Depending on the evolution of blocking, the pool of cold could retreat to the Plains States while shrinking or much of the rest of March could also break out on the cold side of normal in the eastern third of the U.S., along with southern Ontario and perhaps southern Quebec.

 

The 500 mb height anomalies forecast on the GFS ensembles continue to resemble the March 5-7, 1962 event with the 500 mb trough shifting somewhat to the north and east of the 1962 one. As a result, I continue to expect that Washington, DC (DCA) will likely see 4"-8" snow making for a period of good sleighing on Capitol Hill. Sterling, Virginia and westward to the Blue Ridge should see 8"-14" with some higher amounts. However, with the storm's best dynamics likely remaining offshore, the northern Mid-Atlantic region will likely see lesser accumulations, not to mention see a greater share of precipitation in the liquid form. NYC and nearby suburbs will probably see 2"-4" snow. There is risk that amounts could be lighter there. For parts of the East and Ohio Valley, including areas missing out on the upcoming storm, the 3/5-8 storm likely will not be the last system to bring an opportunity for snow.

 

With the EPO likely to be generally negative into the third week of March and the blocking continuing into or through that week, the risk of an Arctic outbreak remains higher than usual for March.

 

Finally, as the pattern continues to evolve, I continue to think that another snowstorm is possible in the Plains States. In fact, the 12z GFS is now hinting at such a possibility in its extended range. That model is showing 1.17" qpf for Kansas City during the 3/16 0z through 3/18 oz timeframe, with a large share of that precipitation being in the frozen form.

Don, do you think Toronto has a shot at one final 2-4" storm?

[andyhb]

Not sure if this has been mentioned or not, but another SSW episode looks to be in progress over E Asia...

 

[donsutherland1]

Don, do you think Toronto has a shot at one final 2-4" storm?

I believe Toronto has a good shot at such a storm.

[donsutherland1]

At 4 pm CST, 6.0" snow had fallen at Chicago's O'hare Airport, breaking the daily record of 3.8" that had been set in 1999. That brought the monthly snowfall figure to 6.7".

 

Snow-liquid ratios had been running above 12:1. Since then, an additional 0.15" precipitation had fallen. That would put Chicago's daily snowfall close to 8". As a result, it is likely that Chicago has already had its biggest March snowfall since March 1-2, 2002 when 9.1" fell. March 2013 is also likely Chicago's snowiest March since 2002 when 11.2" snow had accumulated. It is plausible that by the end of the month, Chicago could have its highest March snowfall since 1999 when the monthly figure came to 18.2"

 

Overall, the significant March snowfall is a welcome development in a city that suffered through an historic snowfall drought.

[donsutherland1]

Chicago Update...

 

As of 9 pm CST, Chicago's O'hare Airport had picked up 9.1" snow. Chicago's monthly figure of 9.8" is its highest March total since 2002 when 11.2" fell.

[donsutherland1]

Evening thoughts…

 

Everything remains in place for a major late-season Mid-Atlantic snowstorm, along with a significant snowfall across part of New England. Already, Chicago saw 9.1” snow through 9 pm CST, as a snowy month in the Great Lakes, Ohio Valley, Mid-Atlantic, and New England regions, along with southern Ontario and southern Quebec appears to be evolving.

 

From #631 (February 19):

 

FWIW, the current mix of analog cases suggests the potential for a snowy March in parts of the Mid-Atlantic region and New England. The Ohio Valley, southern Ontario and southern Quebec would likely seek their most snowfall in March since 2011. 

March snowfall for select cities based on the analog cases (weighted for frequency of cases): 

 

Boston: 9.7" (snowiest since 2009)

Cleveland: 10.8" (snowiest since 2011)

Montreal: 26.0 cm/10.2" (snowiest since 2011)

New York City: 7.2"  (snowiest since 2009)

Toronto: 21.7 cm/8.5" (snowiest since 2011)

Washington, DC: 6.8" (snowiest since 1999); excluding 1960: 2.2" (snowiest since 2009)

 

…What the above figures are useful in illustrating is the big picture idea that March could be snowier than usual in the Mid-Atlantic and New England regions and that the Ohio Valley and parts of southern Canada should see a much snowier March than last winter.

 

To date, monthly snowfall figures are as follows:

 

Boston: Trace (My estimate: 5”-10” in the upcoming storm)

Cleveland: 2.8”

Montreal: 8.4 cm (3.3”)

New York City: Trace (My estimate: 2”-4” but a close call for more)

Toronto: 0.4 cm (0.2”)

Washington, DC: 0.0” (My estimate: 4”-8” for DCA; IAD should see 8”-14”)

 

When it comes to Boston, only 10 years beginning in 1892 have seen the February-March snowfall amount to 40” or more. After recording 34.0” in February (5^th highest February snowfall on record), Boston is within reach of 40” for the two-month total. The 10^th highest February-March total is 43.3” in 1978. Before March 2013 ends, I believe Boston has a good chance at surpassing that figure. Only three years saw Boston record 50” or more snow in the February-March timeframe. As I suspect that there could be at least another opportunity for snowfall this month, there is some chance that Boston could reach 50” for the two-month total.

 

The combination of strong blocking (AO-) and an EPO- for perhaps the next two weeks suggests a potent pattern that could feature an Arctic outbreak and an opportunity for snowfall. The latest objective analogs from the GFS ensembles centered around March 16 include March 17, 1958 and March 1, 1960, dates that came shortly before major snowstorms.

[andyhb]

I know I have my own (and others do as well), but any thoughts on severe season Don?

[donsutherland1]

I know I have my own (and others do as well), but any thoughts on severe season Don?

My early thoughts are that severe weather will probably be less than normal this month and also during April. There might be more hope for April, as uncertainty in my analog pool is greater, but odds still seem to favor less than normal activity at this point in time.

[donsutherland1]

Some late afternoon thoughts...

 

My thoughts concerning the ongoing storm have proved wrong in DCA and IAD. A look at actual temperature profiles shows that the column from 850 mb to the surface was forecast to be too cool on both the GFS and NAM. The same holds true with respect to LGA. Hence, even as the 12z and 18z runs of the NAM are aggressive on snowfall potential for the metro NYC area, I believe the amounts being shown on the "clown maps" will likely be confined either to the circus or the realm of fantasy.

 

In that context, my guess concerning storm total snowfall for NYC (2"-4") may well prove to be too high given the consistent cold bias shown on the modeled soundings leading up to the storm. In short, the odds in what was already a fairly marginal situation to begin with are probably tilted more so toward liquid precipitation than accumulating snow for the metropolitan NYC area and adjacent suburbs. Some accumulation is still possible, but it might be difficult for NYC to move much beyond the low-end of my range barring better model performance with respect to the column.

[andyhb]

My early thoughts are that severe weather will probably be less than normal this month and also during April. There might be more hope for April, as uncertainty in my analog pool is greater, but odds still seem to favor less than normal activity at this point in time.

 

Yeah, the middle of March looks like a dud at this time, I know several people (including myself) who were banking on late March to the first/second week of April for something, although I know Tony in the C/W thread went with around May 4th as his first high risk.

 

Cheers for the input , although it's a bit discouraging (lol), especially after the shut down early last year (After April 14th, essentially). I'm curious to know what analog pool you are looking at.

 

I am wondering if the impressive stratospheric warming event in January had anything to do with the parade of troughs onto the West Coast through late Jan into Feb. A pattern like that in April/May would likely result in multiple significant severe weather outbreaks (relating to the current SSW episode strengthening as we speak and the increase in mountain torque coinciding with it).

[donsutherland1]

Andy,

 

My top analogs for March included 1960, 1965 and, to a lesser extent, 2006. 1965 did have a major tornado outbreak in April. Going into April 1965 has been fading, but the mix doesn't contain years that one would be looking for i.g., 1974, 1982, 1996, etc. A few dates for 1982 had been showing up recently, but not enough to make the analog a significant one for me. I'll have more confidence in the analog pool by mid-month and things could change from where they stand now.

[andyhb]

Yeah, 1960 had a big outbreak in the Plains in May, 2006 had two significant events at the beginning of the month and was largely a dud after that (ala last year a bit). Other years I'd be looking for (for April) are 1956, 2011, 1998, 1984 and 1979. May and June are obviously more prolific in terms of the number of years, and I have my doubts that the season will completely shut down after April this year.

[andyhb]

Not sure if Mike is around to answer this, but is there an archive of these maps somewhere? By the way, that's a pretty impressive anomaly over Western Asia and Northern/Eastern Africa.

 

[donsutherland1]

Some afternoon thoughts...

 

1. The AO remains below -3 for the 4th consecutive day (-3.310). Blocking is forecast to continue into the extended period.

 

2. Yesterday saw a big bust with my thoughts around the Washington, DC area (in part due to lower precipitation than the qpf and, more importantly, the thermal profile winding up warmer than had been modeled).

 

3. It still appears possible that my thoughts (#668 and #674) concerning New York City (storm total snowfall of 2"-4") and Boston (storm total snowfall 5"-10") might verify, particularly given the latest run of the ECMWF. The latter city has the better chance of verifying. Boston needs 7.2" snow to reach 50" for the 2012-13 season.

 

4. There appears to be a growing likelihood that the last 5-10 days of the month could wind up on the mild side of normal in the eastern third of the U.S., with the Plains States perhaps receiving another shot of cold air.

[nschiraldi]

Looks like the GWO will continue to evolve around the phase space as the MJO begins to come out into the W.Pac (GEFS forecasts are live again!). Also, its interesting to note the poleward transport of AAM (consistent with progression of MJO convection..perhaps a little slow in timing) in forecast for mid March/early Apri. Resurgence of strong zonal mean westerlies in mid-latitudes could make things interesting for the central/eastern US. These zonal mean westerlies are dynamically supportive of another blocking episode...

 

Much of the northern hemisphere blocking has been due to the result of slow eastward propagation of tropical convection over the IO/maritime continent. A composite analysis of slow eastward propagation tropical convection (.5-4 m/s phase speed) shows the dominance of the ridge over N.H. on intraseasonal time scales. It's not until the convection gets out into the W.Pac and closer to the dateline that a trough emerges in the traditional NAO blocking region. We've observed this pattern for much of this winter!

 

Just some food for thought...

Nick

 

 

[Heisy]

Don,

 

The EURO is showing a pretty good pattern in the day 7-10 range. Do you like this time period for a late season snowfall in the East? 

[thunderbolt]

Looks like the GWO will continue to evolve around the phase space as the MJO begins to come out into the W.Pac (GEFS forecasts are live again!). Also, its interesting to note the poleward transport of AAM (consistent with progression of MJO convection..perhaps a little slow in timing) in forecast for mid March/early Apri. Resurgence of strong zonal mean westerlies in mid-latitudes could make things interesting for the central/eastern US. These zonal mean westerlies are dynamically supportive of another blocking episode...

 

Much of the northern hemisphere blocking has been due to the result of slow eastward propagation of tropical convection over the IO/maritime continent. A composite analysis of slow eastward propagation tropical convection (.5-4 m/s phase speed) shows the dominance of the ridge over N.H. on intraseasonal time scales. It's not until the convection gets out into the W.Pac and closer to the dateline that a trough emerges in the traditional NAO blocking region. We've observed this pattern for much of this winter!

 

Just some food for thought...

Nick

 

 

welcome to the board ( nice poast)

[donsutherland1]

Don,

 

The EURO is showing a pretty good pattern in the day 7-10 range. Do you like this time period for a late season snowfall in the East? 

 

Highzenberg,

 

There is potential. But with the seasonal transition toward spring further underway, the room for error is shrinking. If the pattern unfolds as the ECMWF has suggested with the polar vortex possibly approaching or even dropping into the region, the opportunity for another late-season snowfall would increase. Certainly, I think New England, parts of the Midwest, Ohio Valley and Ontario and Quebec should see additional snowfall. For NYC and Philadelphia, it will  be more of a challenge, but the ECMWF's pattern would hold some promise.

[Ed Lizard]

Semi-OT, and may wind up deleted.  But Donald Sutherland is credited with pictures in a book (the second edition of a book my wife game me as newlyweds) I got for Christmas, ( second edition birthday) and in the context of the book, it is "our" Donald Sutherland.

 

He has always been one of the more respected non-red tags as he deserves, but he almost deserves an honorary tag as the forum's best poster.

 

Especially after the NAM poem.

[donsutherland1]

Semi-OT, and may wind up deleted.  But Donald Sutherland is credited with pictures in a book (the second edition of a book my wife game me as newlyweds) I got for Christmas, ( second edition birthday) and in the context of the book, it is "our" Donald Sutherland.

 

He has always been one of the more respected non-red tags as he deserves, but he almost deserves an honorary tag as the forum's best poster.

 

Especially after the NAM poem.

Thank you for the very kind words. I'm just happy to be able to contribute here and to learn from so many who are very knowledgeable.

[donsutherland1]

Some evening thoughts...

 

1. The AO is forecast to drop to between -4 and -3 around the 3/20-24 timeframe, while the PNA is forecast to go weakly negative.

 

2. The 500 mb anomalies associated with those teleconnections for the second half of March is shown below:

 

 

3. In terms of winter weather threats, there were 6 years that saw such an AO-PNA combination since 1950. 50% saw at least some measurable snow in Boston and New York City in the period running from 5 days before to 5 days after that combination; 33% saw some measurable snow in Philadelphia; and, 17% saw some measurable snow in Washington, DC. There was one KU snowstorm during those years (the March 1958 storm).

 

In short, even as climatology becomes increasingly tilted against snow in the Mid-Atlantic and New England areas, the kind of pattern forecast on the ensembles suggests higher than climatological potential for at least some snowfall. Favored regions would be the northern Mid-Atlantic and New England areas. That's not anything close to a certainty, but at least there's some potential on the table. One can't say that for most years and it is a marked contrast from last March when the "summer in March" episode lay just ahead.

[toronto blizzard]

Some evening thoughts...

 

1. The AO is forecast to drop to between -4 and -3 around the 3/20-24 timeframe, while the PNA is forecast to go weakly negative.

 

2. The 500 mb anomalies associated with those teleconnections for the second half of March is shown below:

 

 

3. In terms of winter weather threats, there were 6 years that saw such an AO-PNA combination since 1950. 50% saw at least some measurable snow in Boston and New York City in the period running from 5 days before to 5 days after that combination; 33% saw some measurable snow in Philadelphia; and, 17% saw some measurable snow in Washington, DC. There was one KU snowstorm during those years (the March 1958 storm).

 

In short, even as climatology becomes increasingly tilted against snow in the Mid-Atlantic and New England areas, the kind of pattern forecast on the ensembles suggests higher than climatological potential for at least some snowfall. Favored regions would be the northern Mid-Atlantic and New England areas. That's not anything close to a certainty, but at least there's some potential on the table. One can't say that for most years and it is a marked contrast from last March when the "summer in March" episode lay just ahead.

How about Toronto,Don? Snow chances higher than normal?

[donsutherland1]

How about Toronto,Don? Snow chances higher than normal?

Toronto is not finished. 40% of the analog cases saw Toronto pick up 12.5 cm or more snow in the period running 5 days before to 5 days after the teleconnection combinations cited above. 1 of those years saw more than 20 cm snow fall. All 6 cases had at least light snow in the aforementioned period.

[donsutherland1]

Strong blocking continues...

 

The Arctic Oscillation (AO) was -1.889. That marked the 35th consecutive day on which the AO was negative.

 

The latest GFS ensembles have grown even more impressive on the restrengthening of the ongoing blocking. They are are suggesting that the AO could fall to between -5 and -4.

 

 

The historic 500 mb pattern with such intense blocking would suggest that even after considering the seasonal migration of the jet, suppression might be at least an equal risk to a cutting system.

 

 

If the block materializes as shown on the GFS ensembles, the 240-hour cutter could just as easily be directed toward the Ohio Valley with secondary development perhaps in the vicinity of the Delmarva or toward the Middle Atlantic coast. This will be something to watch should the AO begin to tank.

 

Moreover, with the PNA forecast to be somewhat negative, that's also favorable for a colder outcome at this point in time. 5/6 (83%) of the March-April KU snowstorms commenced with the PNA below 0.

 

Consistent with the forecast teleconnections, 3 of the 10 dates shown on the objective analogs centered around March 23 come from March 1958 (3/7/1958, 3/13/1958, and 3/20/1958).

 

In sum, an area running from the Midwest (including Chicago which has now emerged from its historic snow drought) across the Ohio Valley into New England, northward across southern Ontario and southern Quebec, and probably at least the northern Mid-Atlantic region likely has not seen its last snowfall.