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February 2021


snowman19
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15 minutes ago, bluewave said:

This big a swing from the exact date last year is unprecedented. The +AO almost made it to +6. Just ridiculous volatility for two consecutive Februaries.


2020  2  9  5.765
2020  2 10  5.910

035397F3-51D1-4769-880E-B86A82ACE4B8.thumb.gif.23922fdba4f451c815dfc92e24b8e600.gif
 

 

What are your thoughts on the large AO spike? Do you think it will drop again or is this the start of the break down.

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A weak system tracked somewhat farther to the north than had been modeled. As a result, accumulating snow was confined to the north and west of New York City and its nearby suburbs. The 0z HREF did well to catch the shift in snowfall.

Following the departure of this weak system, tomorrow should be partly sunny. Temperatures will run several degrees below normal. Afterward, another light snowfall is possible on Thursday and/or Friday particularly from central Pennsylvania to central New Jersey and southward.

Meanwhile, parts of western Canada experienced near record cold and record cold temperatures. Minimum temperatures included:

Burwash Landing, YT: -49°;Carmacks, YT: -56° (old record: -54°, 2008); Dease Lake, BC: -43° (old record: -28°, 2017); Faro, YT: -50° (old record: -48°, 1979); Norman Wells, NT: -48° Whitehorse, YT: -44°

That frigid air mass will slowly advance eastward and possibly reach the Middle Atlantic and southern New England regions around mid-month. There is some uncertainty as to whether this air mass will move directly into the region sending temperatures into the single digits even in New York City or merely pass nearby delivering a glancing blow with single-digit cold avoiding New York City but affecting areas outside of New York City and Newark. The probability of the latter outcome has increased in recent days.

The Arctic Oscillation (AO) is now severely negative and at its lowest levels in more than five years. It is forecast to rise sharply toward mid-month. A dramatic increase in the AO has sometimes coincided with storminess. Therefore, the February 14-24 period might offer a window of opportunity for a meaningful storm. Details about possible storm tracks or precipitation types are premature at this point.

The ENSO Region 1+2 anomaly was -0.2°C and the Region 3.4 anomaly was -0.7°C for the week centered around February 3. For the past six weeks, the ENSO Region 1+2 anomaly has averaged -0.65°C and the ENSO Region 3.4 anomaly has averaged -1.00°C. La Niña conditions will likely prevail at least through meteorological winter.

The SOI was +30.93 today.

Today, the preliminary Arctic Oscillation (AO) figure was -4.618 today. That is the lowest AO figure since the AO was -4.898 on January 16, 2016.

On February 8 the MJO was in Phase 7 at an amplitude of 2.142 (RMM). The February 7-adjusted amplitude was 2.121.

Based on the latest guidance, no significant stratospheric warming event is likely through the middle of the third week of February.  

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. Since January 1, New York City has picked up 22.0" snow.

Based on sensitivity analysis applied to the latest guidance, there is an implied 84% probability that New York City will have a colder than normal February. February will likely finish with a mean temperature near 32.3°.

 

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13 hours ago, bluewave said:

All the guidance continues the -AO Greenland block until further notice. Looks like a -AO gradient pattern in the immediate future. You can see the MJO 7 influence with the flat SE Ridge. 

0E0B052E-4CB4-4EF6-9623-34701319F854.thumb.png.6c448564ff28093c620b08e50032aaeb.png

209C6FF7-363B-4BCF-A290-B1D76E70CDDA.thumb.png.719e09047f454716873ff2e2d4030b8e.png

 

suppression is also in play (a reverse gradient pattern?) as the next storm will miss us to the south.

 

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20 hours ago, gravitylover said:

Fairy Dust or Diamond Dust. I love that stuff. I've seen it accumulate an inch or two in the mountains when it's really cold, ultimate fluff. It's the residual moisture freezing out of the air and it tends to happen after a warm(ish) sunny day with really low RH. As the snow surface melts a bit the humidity in the lowest levels shoots way up and then the sun goes down and it's a rapid drop the dust starts to freeze out around 10-15*.

Can it also happen during the day?  I love that stuff too, seeing it makes me feel like I'm dreaming lol.  I hope we get to see it this winter, it's very rare down here!

 

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Will update all on-going threads by 830AM except the recap of the 9th around 1030AM. OBS thread for tonight has posted. Snow and ice coming to LI the next 6 days, multiple events. The event of the 18th-19th seems warmer but significant as well and that may end this precarious balance of multiple minor-moderate events with a subfreezing cold pool in a portion of our subforum. In other words, more seasonable temps with the EPS and GEFS considerably on how much loss of the the -NAO/-AO but both are the trending milder, especially after the 18th. I have no skill determining which one prevails nor the impact of the MJO phase, but I think via NAEFS, that we're good for snow and ice in the subforum for another 8 days with a warmer trend for the 18th event. 

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39 minutes ago, wdrag said:

Will update all on-going threads by 830AM except the recap of the 9th around 1030AM. OBS thread for tonight has posted. Snow and ice coming to LI the next 6 days, multiple events. The event of the 18th-19th seems warmer but significant as well and that may end this precarious balance of multiple minor-moderate events with a subfreezing cold pool in a portion of our subforum. In other words, more seasonable temps with the EPS and GEFS considerably on how much loss of the the -NAO/-AO but both are the trending milder, especially after the 18th. I have no skill determining which one prevails nor the impact of the MJO phase, but I think via NAEFS, that we're good for snow and ice in the subforum for another 8 days with a warmer trend for the 18th event. 

Walt, snowfall for 6 consecutive days on Long Island?

 

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7 minutes ago, LibertyBell said:

Walt, snowfall for 6 consecutive days on Long Island?

 

I don't think I implied that, did I? Snows 11th, probably later 13-14 (snow to ice?), 16th.  There is still an outside chance we'll see more snow than modeled for the 12th but will count on that southwest of LI. The way I see it, 3 of those 6 days will see some sort of snow accumulation whatever it is. 

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The next 8 days are averaging 24degs.(18/29), or -10.0.

Up to 10" of snow possible over the next 10 days, via the major models.

27*(63%RH) at 6am/7am here.      30* by 10am.     31* at 11am.      32* by 12:30pm.    33* at 1pm.      35* at 2pm.       36* at 3pm.

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2 hours ago, LibertyBell said:

Can it also happen during the day?  I love that stuff too, seeing it makes me feel like I'm dreaming lol.  I hope we get to see it this winter, it's very rare down here!

 

Yes but it has to be, or have been, sunny enough to cause evaporation and really still air too so that the crystals can form and precipitate out. 

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Morning thoughts...

Today will be partly to mostly cloudy and somewhat colder than normal. Temperatures will likely top out in the lower and middle 30s in most of the region. Likely high temperatures around the region include:

New York City (Central Park): 32°

Newark: 34°

Philadelphia: 35°

A weak system will pass eastward across the Middle Atlantic region. It could bring a small accumulation of snow to New York City and its nearby northern suburbs. The northward extent of 1”-3” snows will likely be across central New Jersey.

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Not sure what to make of the weeklies and ensembles. NAO stays negative throughout however EPO goes positive and some guidance floods the country with above normal temps after 240 (GEPS). Definate troughing over Alaska which should flood country with Pac air. However, unlike January where Canada was void of any Arctic air, this go around it should take a while to remove the dense cold air from Eastern Canada. I guess worst case is we eventually go back to the Jan pattern with a better source region.

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14 minutes ago, EastonSN+ said:

Not sure what to make of the weeklies and ensembles. NAO stays negative throughout however EPO goes positive and some guidance floods the country with above normal temps after 240 (GEPS). Definate troughing over Alaska which should flood country with Pac air. However, unlike January where Canada was void of any Arctic air, this go around it should take a while to remove the dense cold air from Eastern Canada. I guess worst case is we eventually go back to the Jan pattern with a better source region.

And remember models often rush a pattern change....that'll buy us another week to 10 days.    This is working out nicely-wouldn't mind if the pattern broke around 3/10 and we headed into spring.

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Looks like our first -5 AO reading during a La Niña February. The other 3 Februaries were El Niño years.

2-14-10...-5.132....2-6-10....-5.205....Niño 3.4....+1.5

2-5-78.....-5.291....................................................+0.7

2-13-69....-5.285...................................................+1.1

10DBFC99-72DD-4BAB-80F5-2B3879B2ADD0.gif.5e7146aaf22545ddb837ead6a848ac03.gif
 

 

 

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2020-21 noted for snowstorms...

winters with a -5sd ao...

winter.......AO min. date......winter noted for...

1976-77...-7.433...01/15/1977...severe cold...

1969-70...-6.365...03/05/1970...severe cold...

1984-85...-6.226...01/19/1985...severe cold...

2009-10...-5.821...12/21/2009...snowstorms...

2012-13...-5.688...03/20/2013...Feb snowstorm...

1977-78...-5.291...02/05/1978...Jan/Feb snowstorms...

1968-69...-5.282...02/13/1969...Feb snowstorm...

2010-11...-5.172...12/18/2010...snowstorms...

1965-66...-5.130...01/28/1966...late Jan snowstorm...

1962-63...-5.010...01/21/1963...severe cold...

2015-16...-4.916...01/17/2016...Jan snowstorm...

2000-01...-4.854...02/25/2001...Dec snowstorm...

1959-60...had a -5sd in Nov...March snowstorm

2002-03...had a -5sd in Oct...snowy winter...

 

 

feb 2 10 21 ao.gif

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The T's that were showing for NYC last week for the mid-month period seem set to happen in Texas et al instead---as even Houston gets to 0* apparently.

Not even single digit hits here.

This is in Houston.      Maybe elevation is playing a role here.       Hard to believe this is really 2M above sea level.

1612936800-3XDhq5MuBZY.png

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3 hours ago, CIK62 said:

The T's that were showing for NYC last week for the mid-month period seem set to happen in Texas et al instead---as even Houston gets to 0* apparently.

Not even single digit hits here.

This is in Houston.      Maybe elevation is playing a role here.       Hard to believe this is really 2M above sea level.

1612936800-3XDhq5MuBZY.png

the potential result of this incredible anomaly:

image.thumb.png.0b7112227404989ffae17b4410a051af.png

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7 hours ago, bluewave said:

Looks like our first -5 AO reading during a La Niña February. The other 3 Februaries were El Niño years. So it’s no surprise that the models continue the -AO pattern.

2-14-10...-5.132....2-6-10....-5.205....Niño 3.4....+1.5

2-5-78.....-5.291....................................................+0.7

2-13-69....-5.285...................................................+1.1

10DBFC99-72DD-4BAB-80F5-2B3879B2ADD0.gif.5e7146aaf22545ddb837ead6a848ac03.gif
 

 

 

2001 was close (2000-01 la nina)

2000-01...-4.854...02/25/2001...Dec snowstorm...

from Uncle

How many la ninas have had a -5 SD at some point in the winter?

I saw 10-11 is also in the list, but that one was in late December

 

 

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9 hours ago, wdrag said:

I don't think I implied that, did I? Snows 11th, probably later 13-14 (snow to ice?), 16th.  There is still an outside chance we'll see more snow than modeled for the 12th but will count on that southwest of LI. The way I see it, 3 of those 6 days will see some sort of snow accumulation whatever it is. 

I'm seeing comparisons to Feb 1994 (which also occurred on the same date), but much shorter duration and less extreme than that

 

 

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