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Rtd208

February 2018 Discussions & Observations Thread

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Back on January 10, I had been concerned that the 500mb pattern evolution shown on some of the ensemble members could lead to a temporary AO+ period in the January 20-25 period.

https://www.americanwx.com/bb/topic/50695-january-2018-discussions-observations-thread/?do=findComment&comment=4768918

Today (1/26), the AO has gone positive (+0.244), so the timing was somewhat off. To date, the AO has averaged -0.204 for winter 2017-18. 60% days have had negative values (23% with values of -1.000 or below) and 40% days have had positive values (14% with values of +1.000 or above).

The AO is forecast to return to negative values in coming days. Needless to say, the AO cannot be forecast in a skillful fashion beyond two weeks. So the AO’s going positive shortly a day later than the timeframe I had noted is more a matter of chance related to the 500 mb pattern evolution than skill.

There is strong consensus on the guidance that the AO will go negative after a short period of positive values. The GEFS suggest that by the middle or latter part of the first week in February, the AO could be strongly negative and the PNA could be positive to strongly positive.

Such a pattern would favor colder than normal temperatures and a higher than climatological probability of measurable snowfall. Some quick statistics for the February 1-15, 1981-2010 climate period for New York City (NYC):

All dates:
Mean temperature: 34.0°
% days with high temperatures of 50° or above: 19%
% days with low temperatures < 20°: 21%
Ratio of days with low temperatures < 20° to days with high temperatures of 50° or above: 1.1 : 1

% days with measurable snowfall: 11.1%
% days with 1” or more snowfall: 7.3%
% days with 2” or more snowfall: 5.6%
% days with 4” or more snowfall: 2.9%

n=450 days

AO -3 to -1 and PNA +0.5 to +1.5:
Mean temperature: 31.9°
% days with high temperatures of 50° or above: 20%
% days with low temperatures < 20°: 60%
Ratio of days with low temperatures < 20° to days with high temperatures of 50° or above: 3.0 : 1

% days with measurable snowfall: 20.0%
% days with 1” or more snowfall: 15.6%
% days with 2” or more snowfall: 13.3%
% days with 4” or more snowfall: 8.9%

n=75 days

In sum, should a pattern that is reasonably consistent with the longer-range forecast in the AO and PNA develop, February would have the potential to be colder and snowier (possibly much snowier) than average.

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ok since the next legitimate significant  snowstorm threat is coming up Feb.2 let's discuss it in here for now - both Canadian and Euro deliver a MECS

gem_asnow_us_30.png

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2 hours ago, bluewave said:

February looks to start out with a classic gradient pattern. This pattern should feature wintry overrunning potential as waves of low pressure ride NE along the stalled out cold front.

 

gfs-ens_T2maMean_us_7.thumb.png.74a48821dd1110e69c33237912d20d84.png

Where the front exactly stalls is the question as far as who gets what. 

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The 1981-2010 average monthly temperature for February is 35.7...so far the 2011-17 Febs are averaging 34.9...the fifty year period from 1930 to 1979 averaged 33.1...take out the 1950's and it averaged 32.6...the 60's and 70's averaged 32.6...long term since 1880 is near 32.7...

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the coldest February's since 1960...

year...ave temp...max...min...

2015.....23.9........43.......2

1979.....25.5........57.......0

1978.....27.2........41.....10

2007.....28.2........49.......8

1963.....28.3........51......-2

1968.....28.9........49.......5

1967.....29.2........60.......4

2003.....30.1........50.......8

1994.....30.6........62.......7

1993.....30.8........56.......7

1980.....31.4........57.....12

1972.....31.4........62.......9

1995.....31.6........54.......6

2014.....31.6........56.......9

1974.....31.7........61.....11

1962.....31.8........56.......4

1986.....32.0........48.....18

1973.....32.5........58.......7

1969.....32.6........44.....17

1964.....32.9........52.....19

1970.....33.0........57.......9

2010.....33.1........46.....17

1987.....33.2........52.......4

1977.....33.5........57.......8

1965.....33.9........61.....13

1996.....33.9........62.......5

2013.....33.9........55.....17

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So all night long the storm roared on:
The morning broke without a sun;
…All day the hoary meteor fell;
And, when the second morning shone,
We looked upon a world unknown…
A universe of sky and snow!
--John Greenleaf Whittier

To date, winter 2017-18 has been colder and snowier than normal. December featured a widespread early-season snowstorm that dumped 4” or more snow from Philadelphia to Boston. Such a snowstorm has often been a harbinger of an especially snowy winter (mean NYC seasonal snowfall for the 7 prior cases since 1950: 46.0”). Severe and prolonged cold gripped the region from late December into early January. An offshore storm exploded into a superstorm bringing more than a foot of snow across parts of Long Island and more than 6” in large parts of the New York City Metro area. Then, a January thaw set in, interrupted occasionally by transient shots of cold.

The month ahead will likely become the crown jewel of winter 2017-18, at least in terms of snowfall. Cities including Albany, Boston, New York, Philadelphia, and Washington will likely see above to much above normal monthly snowfall.

The MJO will progress through Phase 7 during the first week of February and a trough will march eastward until it locks in over eastern North America for much of the rest of the month (possibly around 2/10 +/- 2 days).

It appears likely that a pattern with an above to much above climatological probability of snowfall will persist through much of February and possibly into the opening of March. Typically, La Niña winters with a PDO+ tend to be snowier than normal, especially when December experiences above normal snowfall. In addition, three of the seven PDO+ winters that saw the first week of February begin with an MJO in Phase 7 coupled with an AO-/PNA+ were exceptionally snowy.

Overall, the likely long-duration pattern that should hold through much of February favors above to much above normal snowfall. Monthly snowfall in the 12”-18” range appears reasonable. The potential exists for more than 20” across parts of the area, including New York City.

Further, 60% of the La Niña-PDO+ winters featured a snowstorm with 12” or more in NYC. That has not occurred this winter, but it could be possible during the upcoming February as the MJO advances through Phases 7, 8, and 1. Phase 1 could offer the highest probability of a large snowstorm. Possible timing might favor the second or third week of February. The possibility of an AO-/PNA+ pattern around mid-February further highlights the timeframe in question.

Finally, in terms of temperatures, my guess is that February will have a mean temperature of around 34.0° +/- 0.5°. The potential for an even colder monthly average temperature exists, especially if a period of severe cold moves into the region. Considering the extent and magnitude of cold likely to cover two-thirds of Canada, any significant to major snowstorm would have the potential to bring a severely cold air mass into the region as it departs. There is a possibility that winter 2017-18 could become the first La Niña winter within the 1950-present period to see single-digit low temperatures in New York City in December, January, and February. The last such winter to feature such cold in all three months was winter 1933-34 (based on reconstructed ENSO data). 

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It is disingenuous to say this has been a colder than normal winter thus far.

You are using extreme cold to negate an extended period of above normal temps. Jan will barely end below normal. It only does because of 10 days of extreme cold.

There hasnt been a flake of snow on the ground or in air since mid month and we have spent two weekends in the 50s. This past weekend we were in the 50s for more than 24 hours straight.

It is like using a statistical mean when a statistical median would be a better representation of the facts.

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18 minutes ago, jfklganyc said:

It is disingenuous to say this has been a colder than normal winter thus far.

You are using extreme cold to negate an extended period of above normal temps. Jan will barely end below normal. It only does because of 10 days of extreme cold.

There hasnt been a flake of snow on the ground or in air since mid month and we have spent two weekends in the 50s. This past weekend we were in the 50s for more than 24 hours straight.

It is like using a statistical mean when a statistical median would be a better representation of the facts.

Sure, if we were using median for the rest of the years of record, and the mean for this year, it would be disingenous. Unless of course youve analyzed the remaining years of data already and found that all the other below normal months had 15+ days of below normal temps. ;)

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54 minutes ago, jfklganyc said:

It is disingenuous to say this has been a colder than normal winter thus far.

You are using extreme cold to negate an extended period of above normal temps. Jan will barely end below normal. It only does because of 10 days of extreme cold.

There hasnt been a flake of snow on the ground or in air since mid month and we have spent two weekends in the 50s. This past weekend we were in the 50s for more than 24 hours straight.

It is like using a statistical mean when a statistical median would be a better representation of the facts.

I don't believe "disingenuous" is a fair characterization.

NWS assesses whether months and seasons are colder than normal based on mean, not median temperatures (using the 1981-2010 period). When the NWS comes out with its report at the end of the season, its conclusion will be based on the mean anomaly during meteorological winter. I referenced means, because that's the standard by which the NWS measures things.

Setting that aside to look at things from two different perspectives:

1. To date, NYC has seen 53% of days (12/1/2017-1/28/2018 come out colder than normal). So, even as the thaw has been impressive, a small majority of days have actually been colder than normal to date.

2. Using median temperatures, the median 12/1-1/28/1981-2010 temperature is 36.0°. The median temperature for the same period this winter was 35.0°. The median temperature so far is running 1.0° below the median for the 1981-2010 climate period.

The latest NOAA map on surface temperature anomalies (12/1/2017-1/27/2018):

 

Anomalies12012017-01272018.jpg

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1 hour ago, donsutherland1 said:

I don't believe "disingenuous" is a fair characterization.

NWS assesses whether months and seasons are colder than normal based on mean, not median temperatures (using the 1981-2010 period). When the NWS comes out with its report at the end of the season, its conclusion will be based on the mean anomaly during meteorological winter. I referenced means, because that's the standard by which the NWS measures things.

Setting that aside to look at things from two different perspectives:

1. To date, NYC has seen 53% of days (12/1/2017-1/28/2018 come out colder than normal). So, even as the thaw has been impressive, a small majority of days have actually been colder than normal to date.

2. Using median temperatures, the median 12/1-1/28/1981-2010 temperature is 36.0°. The median temperature for the same period this winter was 35.0°. The median temperature so far is running 1.0° below the median for the 1981-2010 climate period.

The latest NOAA map on surface temperature anomalies (12/1/2017-1/27/2018):

 

Anomalies12012017-01272018.jpg

many winters had one month of very cold while the other two were mild...it added up to an average winter...2000-01 was similar but didn't have a cold February...2006-07 had 30 of the 90 day met winter average 26 degrees...the other 60 days averaged 41 degrees and it ended up above normal...so far there are 20 days with a max 32 or lower...that's already more than average...

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4 minutes ago, PB COLTS NECK NJ said:

Perfect Weeklies , 30 days. 

Trough centered in the east thru early March.

 

Lots of potential for sure. If we can get some Atlantic blocking to accompany this pattern it could be an epic month ahead.

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2 hours ago, uncle W said:

many winters had one month of very cold while the other two were mild...it added up to an average winter...2000-01 was similar but didn't have a cold February...2006-07 had 30 of the 90 day met winter average 26 degrees...the other 60 days averaged 41 degrees and it ended up above normal...so far there are 20 days with a max 32 or lower...that's already more than average...

I agree with you. February will almost certainly add to the number of days with high temperatures of 32° or lower.

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3 hours ago, donsutherland1 said:

I don't believe "disingenuous" is a fair characterization.

NWS assesses whether months and seasons are colder than normal based on mean, not median temperatures (using the 1981-2010 period). When the NWS comes out with its report at the end of the season, its conclusion will be based on the mean anomaly during meteorological winter. I referenced means, because that's the standard by which the NWS measures things.

Setting that aside to look at things from two different perspectives:

1. To date, NYC has seen 53% of days (12/1/2017-1/28/2018 come out colder than normal). So, even as the thaw has been impressive, a small majority of days have actually been colder than normal to date.

2. Using median temperatures, the median 12/1-1/28/1981-2010 temperature is 36.0°. The median temperature for the same period this winter was 35.0°. The median temperature so far is running 1.0° below the median for the 1981-2010 climate period.

The latest NOAA map on surface temperature anomalies (12/1/2017-1/27/2018):

 

Anomalies12012017-01272018.jpg

I give you credit for calculating the median, which is,in fact, below normal.

 

Im not disputing the use of mean and median when comparing todays statistics with prior years.

 

What I was saying is that characterizing January as below normal is a bit disingenuous when we look at a historical perspective of BN Januarys. 

It involves the third coldest stretch on record, followed by a warm up that nearly negated the negative departure. 

A record stretch of cold followed by a decimal point negative departure in context to historical below normal Januarys is a discussion point.

I was skiing in the Catskills on grass this past Wednesday.

It was 56 degrees In Hastings on Hudson  two hours after sunset on Saturday.

A “below normal Jan” statistic Without discussing the number 50°+ days thus far Doesn’t paint a picture of what this winter has been about. 

I look forward to the return of the trough For February...let’s hope it pans out. 

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On 1/29/2018 at 8:27 PM, jfklganyc said:

I give you credit for calculating the median, which is,in fact, below normal.

 

Im not disputing the use of mean and median when comparing todays statistics with prior years.

 

What I was saying is that characterizing January as below normal is a bit disingenuous when we look at a historical perspective of BN Januarys. 

It involves the third coldest stretch on record, followed by a warm up that nearly negated the negative departure. 

A record stretch of cold followed by a decimal point negative departure in context to historical below normal Januarys is a discussion point.

I was skiing in the Catskills on grass this past Wednesday.

It was 56 degrees In Hastings on Hudson  two hours after sunset on Saturday.

A “below normal Jan” statistic Without discussing the number 50°+ days thus far Doesn’t paint a picture of what this winter has been about. 

I look forward to the return of the trough For February...let’s hope it pans out. 

Nov / Dec / Jan have been below BN 

So should Feb , not sure anyone needs to paint a picture that is inaccurate.

The 8 days of 50 s were beaten by the 10 days of below freezing 

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8 minutes ago, jfklganyc said:

I give you credit for calculating the median, which is,in fact, below normal.

 

Im not disputing the use of mean and median when comparing todays statistics with prior years.

 

What I was saying is that characterizing January as below normal is a bit disingenuous when we look at a historical perspective of BN Januarys. 

It involves the third coldest stretch on record, followed by a warm up that nearly negated the negative departure. 

A record stretch of cold followed by a decimal point negative departure in context to historical below normal Januarys is a discussion point.

I was skiing in the Catskills on grass this past Wednesday.

It was 56 degrees In Hastings on Hudson  two hours after sunset on Saturday.

A “below normal Jan” statistic Without discussing the number 50°+ days thus far Doesn’t paint a picture of what this winter has been about. 

I look forward to the return of the trough For February...let’s hope it pans out. 

Grass? Wall to wall snow pack in southern Vermont even at my house at 1600’. 

Its almost impossible for us to have a wall to wall cold winter. Even back in the early 1900s the coldest winters had warm periods. As many have said this isn’t Labrador. With that said, a good febraury will give this winter the impression of being a cold and snowy winter. I’m a few inches from normal on the island. That included a 14” true blizzard. If we can hold on into March we could be talking about one of the greats. 

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12 minutes ago, LongBeachSurfFreak said:

Grass? Wall to wall snow pack in southern Vermont even at my house at 1600’. 

Its almost impossible for us to have a wall to wall cold winter. Even back in the early 1900s the coldest winters had warm periods. As many have said this isn’t Labrador. With that said, a good febraury will give this winter the impression of being a cold and snowy winter. I’m a few inches from normal on the island. That included a 14” true blizzard. If we can hold on into March we could be talking about one of the greats. 

Plenty of bare spots in the woods all over Vermont where there is no snowmaking

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12 minutes ago, qg_omega said:

Plenty of bare spots in the woods all over Vermont where there is no snowmaking

To be fare the house is on a north facing ridge. South facing slopes do have bare spots and the valleys are pretty snowless.

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7 minutes ago, NorthShoreWx said:

I took this photo on Saturday at 3500 feet in the Catskills.

 

20180127_140356s1000.jpg.14670446357c3f3324395ac2f2c043d8.jpg

Just curious, where in the Catskills is it 3,500 feet? I have a house at 1,600 feet there never thought it went above 2,500.

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Just now, sferic said:

Just curious, where in the Catskills is it 3,500 feet? I have a house at 1,600 feet there never thought it went above 2,500.

There are 35 summits in the Catskills over 3500 feet.  This photo was on the east side of Lone Mountain.  It is a trail-less peak and we were bushwhacking.

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8 hours ago, NorthShoreWx said:

There are 35 summits in the Catskills over 3500 feet.  This photo was on the east side of Lone Mountain.  It is a trail-less peak and we were bushwhacking.

Im impressed! And thank you for photo

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18 hours ago, Rtd208 said:

 

I hate it when they say northern 1/3 of the country and then make it seem like we aren't in the northern 1/3 when we are

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