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January 2021 General Discussions & Observations Thread


Stormlover74
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In coming days, a positive to strongly positive EPO will coincide with a negative to strongly negative AO. Since 1950, there were 13 cases where the EPO was +1.000 or above while the AO was -1.500 or below for at least three consecutive days during the January 1-20 period. In 3 cases, the Arctic block extended southward into the Middle Atlantic region (January 1-4, 1955; January 15-17, 1998; and, January 1-3, 2003). 

The composite pattern is one that favors above to much above normal temperatures and little or no snowfall through at least the first 10 days of January in much or all of the Middle Atlantic Region and southern New England. Central and Upstate New York, along with central and northern New England would have greater opportunities for snowfall.

Based on the latest guidance, there is a growing possibility that New York City’s Central Park could have a mean temperature of 40° or above during the January 1-10 period. There have been 20 prior cases since record-keeping began in 1869.

It still appears possible that the January 10-15 period could mark a transition to a potentially snowier pattern. The key will be the continuation of Arctic blocking. 

Following such warm starts to January, 60% of the above cases saw less than 2” snow during the second half of January. However, in the 30% of cases with 4” or more snow during the second half of January, the AO was predominantly negative. Half of those cases saw 10” or more snow during the second half of January (1907, 1966, and 2005).

Although a continuation of Arctic blocking cannot ensure a snowy second half of January—1998 is one such exception, largely on account of the super El Niño—the general absence of such blocking has seen little or no snowfall during the January 16-31 period following such warm starts to January.

Things to watch for going forward if a snowy second half of January is likely:

Continuation or reinforcement of the persistent AO- regime

Development of a trough underneath the block that extends into the Middle Atlantic region

The coldest air in the hemisphere will likely be focused on Europe on account of what increasingly looks like a polar vortex-splitting major stratospheric warming event. Severe cold’s migration to Europe does not mean that snowfall will be lacking.

In the meantime, inspired by the work of Hooralph, here’s a sortable table of New York City’s 10” or greater snowstorms (1950-present):

https://public.tableau.com/profile/don.sutherland#!/vizhome/NYC10Snowstorms1950-Present/Dashboard1

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4 hours ago, Wentzadelphia said:

Thought this was interesting. I knew I had seen a similar H5 looking map. The event shown on today’s 12z euro looks really similar to December 18-20 1995. Any older people on here remember that one?

E2098B81-A099-413A-AEBE-B5C3A5FEE442.png

A7A46AAE-9ADB-45BA-9F57-351895384D44.gif

Yeah it was a good example of terrible pacific good Atlantic with a snow event.  I always show that event as an example of what a -NAO does 

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Likewise, wishing everyone a Happy New Year and to add another topic later today for Jan 8-9.  Just need time to think it through. Ensembles are timid despite 00z/1 GFS parallel, EC and GGEM on board. Will probably add the topic this afternoon but leave room for blocking forcing system too far south of us- ie a miss.  I don't think it's a miss but I'm sure we can all envision how this might fail. Later, Walt

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7 hours ago, Rjay said:

I think NYC finishes January +3 but with multiple snow threats.  Pretty crazy to think about.   

Yea, +3 in January can snow. I’m really at a loss to explain where the twitterologists are getting this super cold arctic pattern from. Is it possibly a snow pattern in January if we can pop a +PNA? Yea. Arctic, “polar vortex” death pattern? Not even close, there’s no cross-polar flow. Wishcasting galore right now

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December ended at 39.2[+1.7].

The first 8 days of January are averaging 41degs.(36/45).         Making it 36degs., or +3.0.

Snow dates on various models, runs are 3rd.,9th and 12th.        Probably not real as amounts/dates playing musical chairs.

The Strat Warming is looking like a Fail as all TeleConnections except the WPO are getting less favorable by mid-month.      Jan. 09-17 is averaging 37(32/41), or just 4 degrees better than the above Jan. 01-08---and one of those four degrees is climatological anyway.

1609480800-V0W1lEm4zFA.png

.........and Oh Yes:     Happy Warm Year.

36*(65%RH) here at 6am.        35* at 7am.     41* by 10am.        43* by 2pm.        40* by 10am.

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1 hour ago, snowman19 said:

Yea, +3 in January can snow. I’m really at a loss to explain where the twitterologists are getting this super cold arctic pattern from. Is it possibly a snow pattern in January if we can pop a +PNA? Yea. Arctic, “polar vortex” death pattern? Not even close, there’s no cross-polar flow. Wishcasting galore right now

No one is expecting an arctic pattern as far as I can tell. 

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9 hours ago, Rjay said:

I think NYC finishes January +3 but with multiple snow threats.  Pretty crazy to think about.   

Yeah, we could easily finish with above normal January snowfall and a warm departure. Islip averaged 38.0° in March 2018 and finished with 31” of snow. The NYC average in January is 32.6°. So March 2018 temperatures in a January would have been +5.4. It really comes down to getting a favorable Pacific and storm track with just cold enough for snow. February 2017 was another example on Long Island. Islip recorded 14.7”of snow at an average temperature of 37.8. NYC was able to go to 10.4” in December with a 39.3 average temperature. That’s why I think that we’ll continue to experience great snowstorms even as the winters continue to warm. We showed  a few winters ago that we could go 40/40. 
 

 

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15 minutes ago, snowman19 said:

That is a very ugly PAC. EPO floodgates wide open

The retrograding block will also have a MJO 3-6 standing wave. We could very well go +EPO/+PNA/-AO/-NAO. So a high water content heavy wet snow for the storms that are cold enough. Maybe a continuation of the tree damage theme as branches could snap under the weight of the snow. 

AC956BCF-0537-41ED-B5B8-1BCC640A56C2.thumb.png.b20c5b2dc80cc5da0684fe80c8abb313.png

 

 

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Morning thoughts...

Clouds will increase this morning. The line of precipitation currently stretching from central Virginia northwestward into Indiana will reach the region this afternoon or evening. Some mixed or frozen precipitation is possible far north and west of New York City. Elsewhere, periods of rain are likely. Temperatures will likely reach the lower 40s across much of the region. Afterward, temperatures could hold steady or slowly rise overnight. Likely high temperatures include:

New York City (Central Park): 43°
Newark: 44°
Philadelphia: 44°

The first 10 days of January will likely feature much above normal temperatures. Afterward, a somewhat colder and potentially snowier pattern could evolve.

30-Day Verification:

New York City (Central Park):
Average daily forecast: 43.4°
Average temperature: 43.8°
Average error: 1.3°

Newark:
Average daily forecast: 44.6°
Average temperature: 44.5°
Average error: 1.2°

Philadelphia:
Average daily forecast: 45.1°
Average temperature: 45.2°
Average error: 1.3°

 

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