January 2021 General Discussions & Observations Thread

[bluewave]

NYC has a shot at its 3rd latest first low under 20° this weekend. The average first date since 2000 was 12-24. Just goes to show the lack of cold this winter so far.

 

KNYC   GFSX MOS GUIDANCE   1/21/2021  0000 UTC                       
 FHR  24| 36  48| 60  72| 84  96|108 120|132 144|156 168|180 192      
 THU  21| FRI 22| SAT 23| SUN 24| MON 25| TUE 26| WED 27| THU 28 CLIMO
 X/N  44| 35  45| 25  34| 19  37| 24  40| 26  38| 28  39| 26  36 24 38

Frost/Freeze Summary for NY CITY CENTRAL PARK, NY
Each section contains date and year of occurrence, value on that date.
Click column heading to sort ascending, click again to sort descending.

Year	Last	Value	First	Value	Season Length
1931	02-15 (1931)	16	02-16 (1932)	18	365
2001	02-22 (2001)	17	02-05 (2002)	19	347
2012	01-22 (2012)	18	01-22 (2013)	13	365
1974	02-15 (1974)	18	01-15 (1975)	17	333
1981	03-18 (1981)	17	01-09 (1982)	17	296

 

[donsutherland1]

Morning thoughts...

An area of clouds may move across parts of the region this morning, but the afternoon should be mostly sunny throughout the region. Temperatures will likely reach the lower to perhaps middle 40s in most of the region. Likely high temperatures around the region include:

New York City (Central Park): 42°

Newark: 44°

Philadelphia: 45°

A strong cold front could bring another period of light snow or flurries on Friday.

[wdrag]

Good Morning--- wasn't sure where to place this... I'd like a little immediate visibility for this written conversation with the ECMWF yesterday and then you take and run with it as you wish---just strongly recommend that we are are realistic about limitations of snowfall-snow depth on the EC model.  This speaks only of the ECMWF and EPS.  As some of us know there has been discussion about various vendor depictions of snowfall.  

My recommendation is to take the lower value of EC snowfall.  Snow depth on the EC is a good lower end check and may in some ways if initing at zero depth, represents a total positive snow depth change as seen via tropical tidbits, which I like to use as a baseline for accumulations.  However, I'm still unsure how sleet is treated in some of the vendor depictions but if it's 10 to 1...its wrong, probably ~70% inflated. 

Here is how the ECMWF group handles snow/rain/ice pellets (PL or sleet in the USA-) Note the UK calls a rain-snow mix as sleet, a different approach there.  I'll place this in the Model Thread as well so it's there as a reference for the future. 

 

Ice pellets are not stored as such in the model but reach the ground as a mixture of rain and snow, and it is the proportions of those that are present, and the type of surface onto which the ice pellets are falling, that will determine how the accumulation on the ground works. Similarly if there is already snow on the surface, then it depends on how deep the snow there is modelled to be, what it's density is, and what the air and snow temperatures are. In short there is a lot of scope for forecast snow depth on the ground to go wrong, and this is particularly true if you have ice pellets or (UK style) sleet falling, or if there is already a lot of snow on the ground. And known (extraneous) systematic errors in the handling of snow depth on the ground, relating mainly to there being only 1 snow layer currently in the IFS, do not help at all. So unfortunately there really is no rule of thumb (like 10:1), and this evidently stems from many issues. Ordinarily ice pellets would, I think, change snow depth on the ground via a ratio that is rather less than 10:1, but that is about all I can say.

The deterministic ECMWF model (HRES) and the ensemble (ENS) both behave as described above.

So I doubt this is the answer you were hoping for, but anyway please feel free to read further on such topics in either the Forecast User Guide (e.g. here: https://confluence.ecmwf.int/display/FUG/9.7+Precipitation+Types - second sub-section in particular), or in our listing of known model issues (here: https://confluence.ecmwf.int/display/FCST/Known+IFS+forecasting+issues)

[lee59]

24 minutes ago, bluewave said:

NYC has a shot at its 3rd latest first low under 20° this weekend. The average first date since 2000 was 12-24. Just goes to show the lack of cold this winter so far.

 

KNYC   GFSX MOS GUIDANCE   1/21/2021  0000 UTC                       
 FHR  24| 36  48| 60  72| 84  96|108 120|132 144|156 168|180 192      
 THU  21| FRI 22| SAT 23| SUN 24| MON 25| TUE 26| WED 27| THU 28 CLIMO
 X/N  44| 35  45| 25  34| 19  37| 24  40| 26  38| 28  39| 26  36 24 38

Frost/Freeze Summary for NY CITY CENTRAL PARK, NY
Each section contains date and year of occurrence, value on that date.
Click column heading to sort ascending, click again to sort descending.

Year	Last	Value	First	Value	Season Length
1931	02-15 (1931)	16	02-16 (1932)	18	365
2001	02-22 (2001)	17	02-05 (2002)	19	347
2012	01-22 (2012)	18	01-22 (2013)	13	365
1974	02-15 (1974)	18	01-15 (1975)	17	333
1981	03-18 (1981)	17	01-09 (1982)	17	296

 

I can see it getting later and later and one reason is the heat island. The city has put up many large skyscrapers in the past 10 years and it has expanded east into Brooklyn and Queens. This morning for example, Central Park is 28 and most suburbs were in the teens. I was down to 17. 

[lee59]

7 minutes ago, lee59 said:

I can see it getting later and later and one reason is the heat island. The city has put up many large skyscrapers in the past 10 years and it has expanded east into Brooklyn and Queens. This morning for example, Central Park is 28 and most suburbs were in the teens. I was down to 17.  The city can only stay as low as the suburbs when there is strong cold fronts with a lot of wind, and that has not been happening.

 

[the_other_guy]

Has anybody else noticed how warm it’s been relative to forecast from five days ago?

This week was never supposed to be in the low to mid 40s, but that is where we have been thus far...even with cold front passage.

This is turning out to be a very mild January.

[the_other_guy]

33 minutes ago, lee59 said:

I can see it getting later and later and one reason is the heat island. The city has put up many large skyscrapers in the past 10 years and it has expanded east into Brooklyn and Queens. This morning for example, Central Park is 28 and most suburbs were in the teens. I was down to 17. 

Yes that is a big part of it. But a warmer, more humid climate is the other (larger) piece.

NYC just doesnt get cold at night anymore, sadly.

 

[MJO812]

17 hours ago, Allsnow said:

Euro ensemble mean snowfall for next week is 10 inches between 3 storms 

Check out the 0z run

Hopefully it pans out

[CIK62]

0Z Snow Summary:   1/26 ------ 1/30to 2/01

GFS           0" ,    13"

CMC         0",        0"   indeed no precip!

EURO       5",        0"

CLOWN Model-------????????????????????

12Z GFS does little to further any snow and less to further Arctic air intrusion.        It ends up at 60 degrees  after two weeks of nothingness.      22 degrees at best.

12Z CMC is colder and brings back some snow of 6" for the 26th.

12z EURO still 5",   0"

18z GFS is another Nothing Burger.            However it is a 15" Jackpot on the 28th/29th for Roanoke, VA.!

CLOWN Model-------to be announced after the event------actually refer to the above if you can not wait.

 

[bluewave]

2 hours ago, lee59 said:

I can see it getting later and later and one reason is the heat island. The city has put up many large skyscrapers in the past 10 years and it has expanded east into Brooklyn and Queens. This morning for example, Central Park is 28 and most suburbs were in the teens. I was down to 17. 

We know that this isn’t the heat island since the warm minimums are uniform across the whole region. All our stations are in the top 3 or 4 for warmest minimums through January 21st. Even places like BTV still haven’t dropped below 0°. Same lack of cold across urban, suburban, and rural stations.

Time Series Summary for WESTCHESTER CO AP, NY
Click column heading to sort ascending, click again to sort descending.

Rank	Ending Date	Lowest Min Temperature Oct 1 to Jan 21	Missing Count
1	2007-01-21	16	0
-	2002-01-21	16	0
2	1950-01-21	15	52
3	2013-01-21	14	1
4	2021-01-21	13	1
-	2020-01-21	13	2
-	1995-01-21	13	34

 

Time Series Summary for IGOR I SIKORSKY MEMORIAL AIRPORT, CT
Click column heading to sort ascending, click again to sort descending.

Rank	Ending Date	Lowest Min Temperature Oct 1 to Jan 21	Missing Count
1	2002-01-21	18	0
2	2021-01-21	17	1
3	2020-01-21	15	0
-	2013-01-21	15	0
-	2007-01-21	15	0
-	1995-01-21	15	0
-	1993-01-21	15	0
-	1991-01-21	15	0
-	1987-01-21	15	0
-	1975-01-21	15	0

 

Time Series Summary for NY CITY CENTRAL PARK, NY
Click column heading to sort ascending, click again to sort descending.

Rank	Ending Date	Lowest Min Temperature Oct 1 to Jan 21	Missing Count
1	2013-01-21	22	0
2	2021-01-21	20	1
-	2002-01-21	20	0
-	1932-01-21	20	0
3	1987-01-21	19	0
-	1980-01-21	19	0
-	1908-01-21	19	0

 

Time Series Summary for ISLIP-LI MACARTHUR AP, NY
Click column heading to sort ascending, click again to sort descending.

Rank	Ending Date	Lowest Min Temperature Oct 1 to Jan 21	Missing Count
1	2013-01-21	20	0
2	2021-01-21	17	1
	2020-01-21	17	0
-	2007-01-21	17	0
3	1995-01-21	16	0

 

Time Series Summary for Burlington Area, VT (ThreadEx)
Click column heading to sort ascending, click again to sort descending.

Rank	Ending Date	Lowest Min Temperature Oct 1 to Jan 21	Missing Count
1	2016-01-21	2	0
-	2002-01-21	2	0
2	2021-01-21	1	1
-	1932-01-21	1	0

[mikem81]

2 hours ago, MJO812 said:

Check out the 0z run

Hopefully it pans out

Most looks to be after the 28th.... About 3-5 inches from the 26th storm

[Allsnow]

Snow mean for next week on the eps is 10-12 inches 

[mikem81]

4 minutes ago, Allsnow said:

Snow mean for next week on the eps is 10-12 inches 

Its through Feb 5th

[Allsnow]

2 minutes ago, mikem81 said:

Its through Feb 5th

Yes, through the 2nd it’s 8-9 inches. Highest it’s been since the December storm 

[Allsnow]

+pna/-NAO/cold in the central US at the end of the eps today 

[Allsnow]

5 minutes ago, bluewave said:

Yeah, looks like the EPS wants to warm back up again after February 2nd. So let’s make the most of our window of opportunity for snowfall from Jan 25 to around Feb 2nd. EPS has been targeting this period for best wintery potential for a while now.

Jan 25 to Feb 1

Feb 2 to Feb 8

 

 

Yep. Probably a cutter during that timeframe as the pattern breaks down. Looks like we reshuffle the pac and NAO to start the 2nd week of February 

[wdrag]

I agree on the above 2 by Bluewave et al 5th-Feb 2.  Snowfall that I see on the 12zEPS is about 8" NYC and 10-12" central PA through Feb 5. 

fwiw and am ot intent on threading for a couple of days til we see more consensus for the 25th-26th,  12z/21 NAEFS for the 28th has a nice 12-18 hour snow event NJ-down to central VA. Pretty impressive on the NAEFS.  

[EastonSN+]

Weeklies keep the negative NAO through Feb 22.

The week of the 15th through 22 looks nice with no SE ridge and -NAO placed further north. Also a small rise in PNA. Perhaps this would be the pattern break down week with a great chance of a pattern break down storm?

Also per Twitter rumblings of another PV split. So maybe a negative NAO through Feb.

[Allsnow]

Just now, EastonSN+ said:

Weeklies keep the negative NAO through Feb 22.

The week of the 15th through 22 looks nice with no SE ridge and -NAO placed further north. Also a small rise in PNA. Perhaps this would be the pattern break down week with a great chance of a pattern break down storm?

Also per Twitter rumblings of another PV split. So maybe a negative NAO through Feb.

Shh...Don’t tell @snowman19 he is waiting on his Niña February 

[Tatamy]

12z NAEFS at 180 hours

 

[bluewave]

26 minutes ago, Allsnow said:

Yep. Probably a cutter during that timeframe as the pattern breaks down. Looks like we reshuffle the pac and NAO to start the 2nd week of February 

I wonder what would have to happen for us to get extended cold like we saw in 13-14 and 14-15 again?

[Rjay]

7 hours ago, MJO812 said:

Check out the 0z run

Hopefully it pans out

 

I should ban storm vista snowfall maps.  Did they change their algo a couple of years ago?  I remember they would show like 2-4" when other maps showed 6-10".  Now it seems like they went full weenie with their algorithm.   

[Allsnow]

21 minutes ago, bluewave said:

I wonder what would have to happen for us to get extended cold like we saw in 13-14 and 14-15 again?

I have no idea at this point. We did have extended cold in December 2017 into January 2018. I believe that was all -epo/+pna driven 

[bluewave]

9 minutes ago, Allsnow said:

I have no idea at this point. We did have extended cold in December 2017 into January 2018. I believe that was all -epo/+pna driven 

Something really flipped after the super El Niño. We did get that impressive cold stretch from late December 2017 into early January 2018. But the record warmth that followed with the 80° in February boosted the winter temperature departure to above average. 

[forkyfork]

a rare trend

[Cfa]

Later sunsets becoming noticeable now, sky still blue at almost 5, a month ago it’d be black.

[Allsnow]

8 minutes ago, forkyfork said:

a rare trend

Artic air getting trapped under the block?

[MJO812]

Weeklies keep blocking right through  February 

[forkyfork]

Just now, Allsnow said:

Artic air getting trapped under the block?

just a colder shot than what it looked like initially 

[donsutherland1]

Temperatures again rose into the lower 40s across much of the region today. The remainder of the week will be fair and seasonably cold. A much colder air mass will arrive for the weekend. Parts of the region could struggle to reach freezing on Saturday and Sunday.

Meanwhile, Nunavut experienced another day with near record and record high temperatures. High temperatures included:

Eureka: -4° (just missed its daily record from 1985 by 0.2°C)
Grise Fiord: 16° (old record: 9°, 1985)
Iqaluit: 32°
Kimmirut: 35° (old record: 23°, 2003)
Pangnirtung: 30° (old record: 24°, 2007)
Qikiqtarjuaq: 13° (old record: 12°, 2013)
Resolute: 9°

The abnormal warmth will likely continue in Nunavut through Saturday.

As Arctic blocking persists, next week could feature two opportunities for snowfall. The earlier event (January 25-27 timeframe) will likely focus its heaviest snows on the Philadelphia to New York City area. The latter event (January 28-29 timeframe) will likely focus its heaviest snows on the Washington, DC to Philadelphia area. A widespread significant snowfall (6" or above) still appears relatively unlikely. A light or moderate snowfall (2"-4" or 3"-6") remains more likely. However, some of the guidance suggests that the second storm could rapidly intensify, so there is a greater degree of uncertainty for that event in terms of amounts.

AO-/PNA- patterns typically do not produce significant or major snowstorms for the Middle Atlantic or southern New England regions in late January or early February. During the January 20-February 7, 1950-2020 period, there have been 5 storms that brought 4" or more snow to at least two of the following cities--Boston, New York City, or Philadelphia--during an AO-/PNA- pattern. None of those storms brought 6" or more snow to two or more of those cities. Therefore, until the potential events are within 72 hours or less and the guidance suggests otherwise, the base case is against a widespread significant or major snowfall.

Afterward, the evolution of the AO will determine whether potential for measurable snow events will continue into February.

The ENSO Region 1+2 anomaly was -0.3°C and the Region 3.4 anomaly was -1.2°C for the week centered around January 13. For the past six weeks, the ENSO Region 1+2 anomaly has averaged -0.73°C and the ENSO Region 3.4 anomaly has averaged -1.08°C. La Niña conditions will likely prevail at least through meteorological winter.

The SOI was -1.27 today. That is the first negative value since November 23, 2020 when the SOI was -7.83.

Today, the preliminary Arctic Oscillation (AO) figure was -2.510.

On January 20 the MJO was in Phase 6 at an amplitude of 0.682 (RMM). The January 19-adjusted amplitude was 0.424.

Following a significant stratospheric warming event, the stratosphere is now cooling. The cooling will likely accelerate during the second half of January. As is typical for vortex-splitting events, the major piece of the polar vortex migrated to Eurasia. The end result has been an absence of severe cold in much of North America.

The significant December 16-17 snowstorm during what has been a blocky December suggests that seasonal snowfall prospects have increased especially from north of Philadelphia into southern New England. At New York City, there is a high probability based on historic cases that an additional 20" or more snow will accumulate after December. Were blocking to disappear, snowfall prospects would diminish.

Based on sensitivity analysis applied to the latest guidance, there is an implied 91% probability that New York City will have a warmer than normal January. January will likely finish with a mean temperature near 35.0°.