December 2017 Discussions & Observations Thread

[NEG NAO]

1 minute ago, Paragon said:

This is how it usually works.  Where did you see hour by hour?  It's a general statement.  On transition days the high is almost always in the early hours and temperatures drop throughout the day.  Anyone who gets into specifics at this range is foolish.

 

how do you know for sure Monday is going to be the transition day ?

[Paragon]

1 minute ago, NEG NAO said:

how do you know for sure Monday is going to be the transition day ?

What other day do you think it's likely to be?  That's where most of the guidance has been, other than a few blips here and there.

 

[NEG NAO]

5 minutes ago, Paragon said:

What other day do you think it's likely to be?  That's where most of the guidance has been, other than a few blips here and there.

 

still have to determine if the blips are actually blips - transition of temps to much colder could easily happen Sunday night and Monday morning could be close to freezing or below - we won't know for sure for at least 2 more days - guidance has had a history the last few weeks of not coming up with the right solution until 2 or 3 days out....

[Paragon]

1 minute ago, NEG NAO said:

still have to determine if the blips are actually blips - transition of temps to much colder could easily happen Sunday night and Monday morning could be close to freezing or below - we won't know for sure for at least 2 more days - guidance has had a history the last few weeks of not coming up with the right solution until 2 or 3 days out....

Perhaps.  Though if the transition happens Sunday night, we could still get that cheap high in the 40s at like 1 or 2 am lol with temps falling during the day.

 

[The Plowsman]

still have to determine if the blips are actually blips - transition of temps to much colder could easily happen Sunday night and Monday morning could be close to freezing or below - we won't know for sure for at least 2 more days - guidance has had a history the last few weeks of not coming up with the right solution until 2 or 3 days out....

More like 1 hr out lol

[NEG NAO]

3 minutes ago, The Plowsman said:

31 minutes ago, NEG NAO said:

still have to determine if the blips are actually blips - transition of temps to much colder could easily happen Sunday night and Monday morning could be close to freezing or below - we won't know for sure for at least 2 more days - guidance has had a history the last few weeks of not coming up with the right solution until 2 or 3 days out....

More like 1 hr out lol

true - anyways here is the 18Z GEFS 2M temps Christmas morning - temps stay steady in the low 30's during the day then crash in the evening

[Paragon]

What has the Euro been showing?  We should wait for the 0z runs, I like to use just the 0z and 12z runs which is when all the models are sync'ed up.

GFS has a tendency of rushing through pattern changes and has a cold bias.

 

Today for instance, we set a new record high on Long Island and it was close to 60 at LGA.

If it's not going to snow, this is the perfect weather.

 

[LongBeachSurfFreak]

49 minutes ago, NEG NAO said:

true - anyways here is the 18Z GEFS 2M temps Christmas morning - temps stay steady in the low 30's during the day then crash in the evening

Wow that’s epic coast to coast cold. We haven’t seen anything like that in a while. Almost like all the cold has dislodged into NA

[uncle W]

Dec. 1831...coldest on record...NYC averaged 22.2...-2.7 lower than the lowest December in Central Park...Average came from Fort Columbus on Governors Island NY...I found a daily record from Erasmus Hall in Brooklyn NY...Highs and lows are the morning observation and afternoon observation...Highs and lows could be a little higher or lower each day...

day max...min...snow...depth...

01... 32.....23.....T.......1"

02... 32.....23.....0.......1"

03... 26.....22.....0.......1"

04... 30.....20.....2"......3"

05... 25.....14.....0.......3"

06... 25.....15.....0.......3"

07... 26.....14.....0.......3"

08... 28.....20.....0.......3"

09... 32.....24.....0.......3"

10... 30.....20.....0.......2"

11... 35.....20.....0.......1"

12... 27.....18.....0.......1"

13... 25.....16.....0.......1"

14... 23.....17.....1"......2"

15... 21.....13.....2"......4"

16... 25.....11.....0.......4"

17... 26.....11.....T.......4"

18... 17.......9.....0.......4"

19... 26.....18.....0.......4"

20... 26.....18.....0.......4"

21... 38.....24.....0.......2"

22... 24.....10.....0.......2"

23... 24.......8.....0.......2"

24... 38.....26.....2"......2" might have started as rain...

25... 34.....26.....1"......2" White Christmas...

26... 30.....20.....1"......3"

27... 25.....18.....0.......3"

28... 29.....21...10"....13"

29... 33.....24.....0.....13"

30... 24.....13.....0.....13"

31... 32.....18.....2"....13"

http://www.glenallen... Eastern US.pdf

[Paragon]

2 hours ago, uncle W said:

Dec. 1831...coldest on record...NYC averaged 22.2...-2.7 lower than the lowest December in Central Park...Average came from Fort Columbus on Governors Island NY...I found a daily record from Erasmus Hall in Brooklyn NY...Highs and lows are the morning observation and afternoon observation...Highs and lows could be a little higher or lower each day...

day max...min...snow...depth...

01... 32.....23.....T.......1"

02... 32.....23.....0.......1"

03... 26.....22.....0.......1"

04... 30.....20.....2"......3"

05... 25.....14.....0.......3"

06... 25.....15.....0.......3"

07... 26.....14.....0.......3"

08... 28.....20.....0.......3"

09... 32.....24.....0.......3"

10... 30.....20.....0.......2"

11... 35.....20.....0.......1"

12... 27.....18.....0.......1"

13... 25.....16.....0.......1"

14... 23.....17.....1"......2"

15... 21.....13.....2"......4"

16... 25.....11.....0.......4"

17... 26.....11.....T.......4"

18... 17.......9.....0.......4"

19... 26.....18.....0.......4"

20... 26.....18.....0.......4"

21... 38.....24.....0.......2"

22... 24.....10.....0.......2"

23... 24.......8.....0.......2"

24... 38.....26.....2"......2" might have started as rain...

25... 34.....26.....1"......2" White Christmas...

26... 30.....20.....1"......3"

27... 25.....18.....0.......3"

28... 29.....21...10"....13"

29... 33.....24.....0.....13"

30... 24.....13.....0.....13"

31... 32.....18.....2"....13"

http://www.glenallen... Eastern US.pdf

Unc, how far back do your records go? For snowfall and temps?  Anything close to 100" of snow in New York City in a season from the 1800s?  Or monthly average temp in the teens?  I think the PA Weather Book mentioned it a couple of times and had the coldest low back during the 1700s when New York City remained below zero all day and was near -20 for the low.  Also had a three foot snowstorm in New York City with temps near 0.

 

[NEG NAO]

[LongBeachSurfFreak]

54 minutes ago, Paragon said:

Unc, how far back do your records go? For snowfall and temps?  Anything close to 100" of snow in New York City in a season from the 1800s?  Or monthly average temp in the teens?  I think the PA Weather Book mentioned it a couple of times and had the coldest low back during the 1700s when New York City remained below zero all day and was near -20 for the low.  Also had a three foot snowstorm in New York City with temps near 0.

 

That was basically a different climate period with the peak of the little ice age. I have read about fairs being held on the frozen NY harbor which is unthinkable today. Also that the ocean itself froze for several miles out. 

Anyone have the temp for feb 15? I would like to see how it compares to that 22.

[Paragon]

6 minutes ago, LongBeachSurfFreak said:

That was basically a different climate period with the peak of the little ice age. I have read about fairs being held on the frozen NY harbor which is unthinkable today. Also that the ocean itself froze for several miles out. 

Anyone have the temp for feb 15? I would like to see how it compares to that 22.

Could you imagine a glacier being parked on the South Shore of the Island?  I'm sure you could still surf in the winter, but you'd be ice skating or ice fishing in Reynolds Channel and the Great South Bay in the winter!

 

BTW woohoo ISLANDERS ARE BACK ON LONG ISLAND WHERE THEY BELONG

and not that far from me lol.

 

The two arctic outbreaks in December 1917 and February 1934 were so extreme that they are like a flashback to how winters were in the 1700s and 1800s.  Even the coldest days of that earlier era were only a couple of degrees colder than those two days.

 

 

[SnowGoose69]

11 minutes ago, Paragon said:

Could you imagine a glacier being parked on the South Shore of the Island?  I'm sure you could still surf in the winter, but you'd be ice skating or ice fishing in Reynolds Channel and the Great South Bay in the winter!

 

BTW woohoo ISLANDERS ARE BACK ON LONG ISLAND WHERE THEY BELONG

and not that far from me lol.

 

The two arctic outbreaks in December 1917 and February 1934 were so extreme that they are like a flashback to how winters were in the 1700s and 1800s.  Even the coldest days of that earlier era were only a couple of degrees colder than those two days.

 

 

There will be a few attempted lawsuits before it happens for sure but it’ll happen  

[Morris]

55/45 today. +13.5

[NorthShoreWx]

3 hours ago, uncle W said:

Dec. 1831...coldest on record...NYC averaged 22.2...-2.7 lower than the lowest December in Central Park...Average came from Fort Columbus on Governors Island NY...I found a daily record from Erasmus Hall in Brooklyn NY...Highs and lows are the morning observation and afternoon observation...Highs and lows could be a little higher or lower each day...

day max...min...snow...depth...

01... 32.....23.....T.......1"

02... 32.....23.....0.......1"

03... 26.....22.....0.......1"

04... 30.....20.....2"......3"

05... 25.....14.....0.......3"

06... 25.....15.....0.......3"

07... 26.....14.....0.......3"

08... 28.....20.....0.......3"

09... 32.....24.....0.......3"

10... 30.....20.....0.......2"

11... 35.....20.....0.......1"

12... 27.....18.....0.......1"

13... 25.....16.....0.......1"

14... 23.....17.....1"......2"

15... 21.....13.....2"......4"

16... 25.....11.....0.......4"

17... 26.....11.....T.......4"

18... 17.......9.....0.......4"

19... 26.....18.....0.......4"

20... 26.....18.....0.......4"

21... 38.....24.....0.......2"

22... 24.....10.....0.......2"

23... 24.......8.....0.......2"

24... 38.....26.....2"......2" might have started as rain...

25... 34.....26.....1"......2" White Christmas...

26... 30.....20.....1"......3"

27... 25.....18.....0.......3"

28... 29.....21...10"....13"

29... 33.....24.....0.....13"

30... 24.....13.....0.....13"

31... 32.....18.....2"....13"

http://www.glenallen... Eastern US.pdf

1" or more snowcover every day of December in NYC.  That doesn't happen much in Caribou.  Different times...

[nzucker]

32 minutes ago, NorthShoreWx said:

1" or more snowcover every day of December in NYC.  That doesn't happen much in Caribou.  Different times...

Only 5 days had a max temperature of >32F. That's incredible. 

[brooklynwx99]

I am very interested in the Dec 28-Jan 2 timeframe for a major EC winter storm. There is a consistent signal for Pacific energy (perhaps a cutoff ULL) moving onto the WC after Christmas with energy traversing the country. I am aware that these are OP runs at range, but ensembles are supportive of the timeframe as well. Modeling has been very stable considering the lead.

There will most likely be an anomalous antecedent airmass with Arctic HP nosing into the Great Plains and SE Canada. This will provide confluence and CAD, locking in cold air. 

The energy from the Pacific will interact with the STJ, injecting more moisture into the atmosphere. This will help to juice up the overrunning potential, which will be a feature of this pattern. 

The mixture of the moist warm air and dry arctic air will produce dynamic conditions. It would almost certainly lead to a large area of prolific precipitation. One of the reasons why I am pretty bullish about this time period is that an large overrunning event really fits the pattern. Usually storms are not favorable given a certain pattern, but the well-established anomalous cold airmass and STJ injection is a recipe for trouble.

However, this assumes that the modeling is picking up the pattern correctly. Due to the unanimous agreement among both statistical data and modeling, I can safely assume that the models have a clue regarding the general longwave features for this period. Now, we will see.

As many of the experts on this forum have said, patience will prove very important in this pattern. I think that we have a good shot of it paying off in the coming weeks. Let’s keep the disco going. 

[Cobalt]

DT's take on the potential 27th-30th event

 

[CIK62]

Next 8 days down to average 37degs., or about 2degs. AN.

[bluewave]

It will come down the the post Christmas Arctic cold to tip the monthly temperature departures back to below normal. Temps through the 19th are close to normal for most of the area. Just goes to show how easy it is to get to above normal snowfall here with temps breaking even through the 19th.

NYC...-0.4...LGA...+0.1...JFK...-0.9...ISP...0.0...BDR...+0.2...EWR...-0.2

[doncat]

1 hour ago, bluewave said:

It will come down the the post Christmas Arctic cold to tip the monthly temperature departures back to below normal. Temps through the 19th are close to normal for most of the area. Just goes to show how easy it is to get to above normal snowfall here with temps breaking even through the 19th.

NYC...-0.4...LGA...+0.1...JFK...-0.9...ISP...0.0...BDR...+0.2...EWR...-0.2

-0.6° here thru yesterday.

[bluewave]

1 hour ago, doncat said:

-0.6° here thru yesterday.

You should tick up a few points closer to + through this weekend. But then fall back below normal with the cold arriving after Christmas.

[donsutherland1]

The large-scale pattern evolution described on Monday (https://www.americanwx.com/bb/topic/50504-december-2017-discussions-observations-thread/?do=findComment&comment=4707215) has changed little since that time. In general, a powerful EPO block is expected to develop. That block will then expand into the AO region, triggering the development of a negative AO (for which support is now growing on the GEFS). The AO is currently at a preliminary December 2017 high of +2.700. The PNA is likely to remain neutral (somewhat positive or negative). Its current preliminary value is +0.301 and it has been positive through December so far. What has changed is that the guidance has moved back to the somewhat earlier passage of the cold front to on or just before the 25th. Further, the guidance is starting to become more favorable toward a renewed PNA+ in the extended range. In January an AO-/PNA+ combination is associated with a higher frequency of snowfall, including significant snowfall (6” or more) in the Middle Atlantic and southern New England areas.

Applying sensitivity analysis to the latest modeled data, the probability of a colder than normal December has increased. This is the result of the guidance moving into agreement concerning a post-25th Arctic outbreak.

Monthly Mean Temperature for NYC Through:
12/19 38.9°
12/20 39.0°-39.2° (12/18 estimate: 38.4°-39.0°)
12/25 38.5°-40.0° (12/18 estimate: 38.6°-40.2°)
12/31 35.1°-37.5° (12/18 estimate: 35.9°-38.4°)

Estimated probability of a below normal monthly anomaly: 63%

The latest data has reinforced my confidence that December has not yet seen its coldest readings in such cities as Bridgeport, New York, and Newark (lowest temperatures respectively 16°, 20°, and 17°). I also expect additional snowfall at all three locations before the month has ended. It remains possible that all three cities will wind up with monthly snowfall at or above 10”. Right now, I believe the relatively snowless 6z run of the GFS is an outlier given the forecast pattern. I believe the EPS and ECMWF have a better handle on the long-range.

Further, my case preference for this winter has been and remains 2000-01 (with a possibility of a 2010-11 outcome in terms of snowfall). Late December 2000 featured cold with a sizable snowfall in parts of the Middle Atlantic region on December 30-31. While a big snowfall rivaling that outcome isn’t necessarily on the table, the idea of at least a moderate snowfall most definitely is. Currently, the 0z ECMWF shows a potential storm that could deliver such a snowfall near the end of December followed by a fresh surge of Arctic air.

For the winter as a whole, the Middle Atlantic and southern New England regions still remain on course for above to possibly much above average snowfall.

[White Gorilla]

4 hours ago, donsutherland1 said:

The large-scale pattern evolution described on Monday (https://www.americanwx.com/bb/topic/50504-december-2017-discussions-observations-thread/?do=findComment&comment=4707215) has changed little since that time. In general, a powerful EPO block is expected to develop. That block will then expand into the AO region, triggering the development of a negative AO (for which support is now growing on the GEFS). The AO is currently at a preliminary December 2017 high of +2.700. The PNA is likely to remain neutral (somewhat positive or negative). Its current preliminary value is +0.301 and it has been positive through December so far. What has changed is that the guidance has moved back to the somewhat earlier passage of the cold front to on or just before the 25th. Further, the guidance is starting to become more favorable toward a renewed PNA+ in the extended range. In January an AO-/PNA+ combination is associated with a higher frequency of snowfall, including significant snowfall (6” or more) in the Middle Atlantic and southern New England areas.

Applying sensitivity analysis to the latest modeled data, the probability of a colder than normal December has increased. This is the result of the guidance moving into agreement concerning a post-25th Arctic outbreak.

Monthly Mean Temperature for NYC Through:
12/19 38.9°
12/20 39.0°-39.2° (12/18 estimate: 38.4°-39.0°)
12/25 38.5°-40.0° (12/18 estimate: 38.6°-40.2°)
12/31 35.1°-37.5° (12/18 estimate: 35.9°-38.4°)

Estimated probability of a below normal monthly anomaly: 63%

The latest data has reinforced my confidence that December has not yet seen its coldest readings in such cities as Bridgeport, New York, and Newark (lowest temperatures respectively 16°, 20°, and 17°). I also expect additional snowfall at all three locations before the month has ended. It remains possible that all three cities will wind up with monthly snowfall at or above 10”. Right now, I believe the relatively snowless 6z run of the GFS is an outlier given the forecast pattern. I believe the EPS and ECMWF have a better handle on the long-range.

Further, my case preference for this winter has been and remains 2000-01 (with a possibility of a 2010-11 outcome in terms of snowfall). Late December 2000 featured cold with a sizable snowfall in parts of the Middle Atlantic region on December 30-31. While a big snowfall rivaling that outcome isn’t necessarily on the table, the idea of at least a moderate snowfall most definitely is. Currently, the 0z ECMWF shows a potential storm that could deliver such a snowfall near the end of December followed by a fresh surge of Arctic air.

For the winter as a whole, the Middle Atlantic and southern New England regions still remain on course for above to possibly much above average snowfall.

I am pleased to hear about snow and cold probabilities but I just want to take a minute to applaud you, Don, as one of the most informative, intelligent, scientifically minded, balanced, and level headed weather posters I have ever seen.  Your thoughtful analyses are so thorough and descriptive. I was told you are not a pro met, but geez, yo ssure sound like one!  And it is not just "sounding".... Your knowledge is very impressive and broad.  I am so grateful for your contributions here. 

[donsutherland1]

1 hour ago, White Gorilla said:

I am pleased to hear about snow and cold probabilities but I just want to take a minute to applaud you, Don, as one of the most informative, intelligent, scientifically minded, balanced, and level headed weather posters I have ever seen.  Your thoughtful analyses are so thorough and descriptive. I was told you are not a pro met, but geez, yo ssure sound like one!  And it is not just "sounding".... Your knowledge is very impressive and broad.  I am so grateful for your contributions here. 

Thank you for the very kind compliments. Have a great Holiday season.

[White Gorilla]

6 minutes ago, donsutherland1 said:

Thank you for the very kind compliments. Have a great Holiday season.

You too! 

[swataz]

The Canadian has a pretty close call for Christmas Day around here, albeit rain as the primary form of precipitation. 

How reliable is that model lately?

[PB COLTS NECK NJ]

On 12/14/2017 at 7:18 AM, PB GFI said:

2 M temps are BN everyday on the EPS on North day 10 thru 15.

There is a lot of HP in the pattern and plenty that will nose in.

We have a 3 day issue 18th - 21st where LP is cutting through W Canada so that will be a reset.

The MJO goes into 8 around the 21st time frame ,  so later in the period look for that weak SE ridge to get weaker 

Ahhh Reddunce ?

Written on the 14th , so the 10.- 15 

The 24th - 29th will solidly BN Check 

A weaker SE ridge check , that we really took apart because at this time people were buying 60 and rain 

A cutter and we warm for 3 days check 

MJO into 8 around the 21st check 

We would have to reset after there waa a neg in W Canada from the 18 - 21 and the cutter is 2 days later and the warm up is 3 days as the rest really flows.

You guys have to realize ,  people do real work and score their work and this board has a delusional poster that no one corrects , you drive away good posters and their forecasts.

Clean this turd up 

 

I think it snows on Christmas day for most on the board , I hope you guys enjoy it.

 

 

 

 

[PB COLTS NECK NJ]

Normal is 42/36

The call was for 3 days AN then BN from the 24 - 29

Joe , I need to see the 10 day torch and your 60 and rain for Christmas  ? 

We are BN from the 24th on