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November 2018 Discussions & Observations Thread


Rtd208
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On 11/16/2018 at 9:54 AM, PB COLTS NECK NJ said:

If we do the grand tour into 7 /8 / 1 with amplitude , the month of December should end up cold and snowy.

 

As it is starting with the back few days of November into the 1st 10 days or so should feature a major E/C storm.

 

Prob 2 legit shots before the 15th.

 

Phase diagram of the MJO index from the operational GFS

 

 

There is a chance that a 2 wave scenario materializes before the 10th or so.  I know many would settle for one , but the loading phase at 500 a week or so prior to snowmaggedon showed some similarities about 10 days ago , so the following 10 to 15 days will be the period to watch.

 

A mid month warm up is on the way , the question is for how long ? 

 

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To date, 2018 has generally ranked among the 10 wettest years on record in much of the region. Total rainfall and 2018’s ranking for select cities follow:

Allentown: 60.68” (3rd)
Atlantic City: 61.91(3rd)
Bridgeport: 54.40” (8th)
Cooperstown, NY: 55.55” (5th)
Elmira, NY: 54.91” (1st)
Hamburg, PA: 71.33” (1st)
Harrisburg: 61.32” (2nd)
Islip: 57.64” (5th)
New York City: 59.02” (9th)
Newark: 52.38” (12th)
Philadelphia: 55.14” (5th)
Port Jervis, NY: 58.88” (5th)
Scranton: 57.82” (2nd)
Shirley, NY: 55.92” (1st)
Shrub Oak, NY: 60.85” (3rd)
Upton, NY: 65.25” (1st)

New York City will likely see 2018 rank among its five wettest years on record. Some implied probabilities based on historical and 1971-2017 December precipitation:

Rank or Amount:
4th (65.11”, 1989): Historic Data: 8%; 1971-2017 Data: 18%
65.00” or more: Historic Data: 9%; 1971-2017 Data: 19%
62.50” or more: Historic Data: 53%; 1971-2017 Data: 62%
5th (61.67”, 2007): Historic Data: 71%; 1971-2017 Data: 75%
6th (61.21”, 1975): Historic Data: 79%; 1971-2017 Data: 81%
7th (60.92”, 1990): Historic Data: 84%; 1971-2017 Data: 85%
60.00” or more: Historic Data: 94%; 1971-2017 Data: 93%
8th (59.89”, 2006): Historic Data: 94%; 1971-2017 Data: 93%

New York City’s December Precipitation Records:
Least: 0.25”, 1955
Most: 9.98”, 1973

Snowfall across the region has also been much above normal to date.  For the most part, the distribution of snowfall from the upper Midwest eastward to the Middle Atlantic and New England regions suggests that the overall idea of a snowy winter remains on track.

Years were filtered based on snowfall-to-date through November 30 for the following thresholds:

Albany: 6” or more
Boston: Measurable < 3”
Chicago: 3” or more
Detroit: 3” or more
New York City: 2” or more
Philadelphia: 0.5” or more
Portland: 4” or more

The most common matches excluding Chicago and Detroit were: 1892, 1896, 1898, 1938, and 1967.

When Chicago and Detroit were added to the sample, the most common matches were 1892, 1896, 1898, and 1967

Weighted averages were constructed as follows: All common years from the sample that included Chicago and Detroit were given 150% weight. 1938 was given 100% weight.

Weighted average seasonal snowfall for select cities was as follows:

Baltimore: 25.3”
Boston: 53.6”
New York City: 41.5”
Philadelphia: 32.6”
Washington, DC: 28.5”

None of those years were El Niño years. A Central Pacific-based El Niño typically sees enhanced precipitation and snowfall.  Thus, my thinking from my winter idea remains unchanged. My thoughts on seasonal snowfall were as follows:

Albany: 70”-80”
Baltimore: 30”-40”
Binghamton: 85”-95” (a 100” figure is looking more likely now)
Boston: 55”-65”
New York City: 45”-55”
Newark: 45”-55”
Philadelphia: 40”-50”
Providence: 50”-60”
Scranton: 50”-60”
Washington, DC: 25”-35”

Finally, as the calendar turns to December, consistent with numerous snowy winter cases, I continue to expect December to feature above normal snowfall. My guess is that New York City has a good chance of receiving 6” or more snow and some possibility of picking up 10” or more snow for the month. Perhaps the highest probability of snow will exist during the first two weeks of the month. There’s some chance that the last week of the month might also feature a rising risk of snowfall as the pattern becomes more volatile toward the end of the milder regime.

As often happens, a 2-3 week period of milder weather could develop. Based on a combination of the forecast teleconnections and EPS, the timing for the onset of this milder period will probably be around mid-month +/- 3 days.

Currently, the Pacific sea surface temperature anomalies closely resemble those seen in 2002, particularly in the Gulf of Alaska region. Warm anomalies in that region typically favor an EPO-. Through the first 25 days of November, the EPO was negative 72% of the time. In November 2002, the EPO was negative 70% of the time. However, during the December 10, 2002-January 6, 2003 period, the EPO went positive for 26/28 (93%) days. The EPO is forecast to go positive around December 7. The EPO then went negative on January 7. It was negative during the remaining 43/53 (81%) days of meteorological winter. Considering the sea surface temperature anomalies in the Pacific, I remain confident that the EPO will return to predominantly negative values after a positive period (the latest EPS weeklies hint at the return of a neutrall to negative EPO around January 10). As the EPO is a critical piece of my overall winter thoughts, I am not overly concerned by the current teleconnection forecast.

P.S. A post-script is in order. Bear in mind that a warm outlook on the 3-4-week EPS is no more or less likely to verify than the cold outlook it replaces or vice versa. At 3-4 week lead times, forecasting accuracy is not materially different from assuming seasonal outcomes.

 

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2 hours ago, IrishRob17 said:

Don’t count it, you don’t want to drop your average snowfall number ;)

It failed what I've always* called the snowball test. If you can make a snowball from it, there's no way around counting it.

*I've never called it that before now, but the second best time to plant a tree etc...

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1 hour ago, NJwx85 said:

Good chance at some snow tomorrow afternoon/night with the clipper system. NAM is further North but the RGEM/GFS are further South.

BL is marginal along the coast but it could come down decently for a few hours, especially North and West.

 

p7oSL1h.png

So, Probably some light accumulations up to 1 inch possible? Or will it be a quick dusting then melt?

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Last day of Nov. averaging 40degs., about 3degs. BN.

Month to date is  -3.4[44.5].    Nov. should end at  -3.3[44.4].

All 8 days are averaging 42degs , or 1deg. AN.

GFS/CMC gives us little to talk about after the warm rain Sun.   EPS likes Dec. 9.  GEFS has a 50/50 chance of a total of 3" by mid-month.

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Owing to narrow fgen forcing, good jet config and steep lapse rates aloft, this could be a very localized overperformer (1-2") this afternoon, probably terrain-favored as NJwx alluded to yesterday. Could be a surprise in/near the city too despite the warm layers in the soundings.

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