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Extremely cold next week with bare ground.


Mikehobbyst

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Looks like highs in the low teens Tuesday and Wednesday for the NYC area with lows near 7-12 degrees, without snow cover. This is one of those unmodified cA regimes with pure import from Quebec and direct north wind discharge. This will actually be serious for water main and pipe ruptures due to deep freeze into the ground for 2-3 days without snow cover. We really needed snowcover right now with this cA regime coming over bare ground and supporting 15-19 degree highs without snow cover, With snow it would have been 8-14 degree highs and -3 to 2 degree lows. We'll be watching rapid dormancy and any remaining green in the lawns get fully browned due to deep ground freeze. No snowstorms yet either,

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With the obvious exception of practically the entire pattern, the intensity of the cold spell can be compared to that of 12/14/10, and would actually be stronger than last December if the ECM is correct... that cold spell also brought highs in the 20s, and with this case, highs in the low-mid 20s are looking reasonable for much of the area as well. The winds are also something to watch, as combined with the low temps, most of the area could easily see wind chills in the single digits, perhaps sub-zero further inland.

Dec 14, 2010 cold spell:

post-1753-0-57342700-1325173040.gif

0z ECMWF forecast for this cold spell:

post-1753-0-81905100-1325173044.gif

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GFS gets 504dm heights over the NW suburbs on the GFS. This outbreak seems to be getting slightly colder on the models.

It's an interesting trend that this year, the models seem to be trending towards stronger cold spells, not towards less cold. The same happened 2 weekends ago when the NAM/GFS had highs in the low-mid 30s a few days earlier, with actual high temps only in the upper 20s to 30 degrees. The GFS shows 2m temps in the lower 20s at 18z Wednesday, which adding a few degrees to account for any possible cold bias still gives a high of nearly 25 degrees. It'll be interesting to see in this case if the GFS is too cold or if it's actually on the right track with temperatures.

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Highs would be in the teens on Tuesday if the models are correct right now. The blast of cold air originally traverses the Midwest before sweeping in on Monday, but the real peak of the cold air drops in and funnels from the north out of Quebec on Tuesday. That -20 air would not be modified greatly in my opinion.

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I say highs will be in the 25-30 F range with lows 13-18 F with single digits well inland and probably 10-15 F on Long Island. The GFS always overplays the cold in a artic outbreak. Upton says upper 20's to lower 30's and lows in the teens to near 20 F for the city. I do believe it will probably a few degrees than what Upton is says but I doubt teens for highs in NYC. Mid to upper 20's seem to be more realistic with lows in the teens in coastal areas and single digits inland. Wednesday will probably be few degrees warmer with highs in the upper 20's to near 30.

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I say highs will be in the 25-30 F range with lows 13-18 F with single digits well inland and probably 10-15 F on Long Island. The GFS always overplays the cold in a artic outbreak. Upton says upper 20's to lower 30's and lows in the teens to near 20 F for the city. I do believe it will probably a few degrees than what Upton is says but I doubt teens for highs in NYC.

Everyone stayed in the 20s all day with that last push of cold we had with full sunshine and no snowcover anywhere and 850s were not anywhere near as cold as all models are currently predicting for the next cold shot.

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I say highs will be in the 25-30 F range with lows 13-18 F with single digits well inland and probably 10-15 F on Long Island. The GFS always overplays the cold in a artic outbreak. Upton says upper 20's to lower 30's and lows in the teens to near 20 F for the city. I do believe it will probably a few degrees than what Upton is says but I doubt teens for highs in NYC. Mid to upper 20's seem to be more realistic with lows in the teens in coastal areas and single digits inland.

Normally, I'd agree with you, but not this year.

Nearly every cold shot weve had, I've been lower than what Upton and the models predicted. I think it may just be the 'thing' this year.

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most of NYC's coldest temperatures zero or below came with some snow cover...I doubt we see anything close to that but here are the coldest outbreaks and what snow depth if any was on the ground...bare ground events in red...

since 1917-18...

12/28-1/4 1917-18...-13...2-3" snow depth...

2/5/1918...-6...6" snow depth...

12/20/1919...-1...1" snow depth...

2/1/1920...-1...3" snow depth...

2/17/1922...-2...4" snow depth...

1/28/1925...-2...10" snow depth...

1/27/1927...-1...bare ground...

12/30/1933...-6...9" snow depth...

2/9/1934...-15...3" snow depth...

1/28/1935...-1...10" snow depth...

1/23/1936...-3...5" snow depth...

12/20/1942...-4...1" snow depth...

2/15/1943...-8...2" snow depth...

1/31/1948...0...9" snow depth...

2/3/1955...0...3" snow depth...

1/15/1957...0...bare bround...

2/2/1961...-2...8" snow depth...

2/8/1963...-2...bare ground...

1/9/1968...-1...3" snow depth...

1/23/1976...-1...1" snow depth...

1/17/1977...-2...6" snow depth...

2/18/1979...0...3" snow depth...

12/25/1980...-1...less than 1" snow depth...

1/17/1982...0...5" snow depth...

1/21/1985...-2...3" snow depth...

1/19/1994...-2...5" snow depth...

1/27/1994...0...7" snow depth...

1/10/2004...1...bare ground...

1/16/2004...5" snow depth...

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I don't think 850s are cold enough for NYC to get even close to 0F...we were around -24C 850s in January 2009 with snow cover and Central Park only got to 6F for a minimum. This time, 850s are 4-5C warmer, there's a lack of deep snow cover to the north, and there's nothing on the ground at all in the metro area. I would forecast low-mid 20s for highs with lows in the low teens for Central Park on Tuesday, perhaps a bit milder on Wednesday. Suburban areas, especially out towards the LI Pine Barrens, should see lows in the single digits to near zero.

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I don't think 850s are cold enough for NYC to get even close to 0F...we were around -24C 850s in January 2009 with snow cover and Central Park only got to 6F for a minimum. This time, 850s are 4-5C warmer, there's a lack of deep snow cover to the north, and there's nothing on the ground at all in the metro area. I would forecast low-mid 20s for highs with lows in the low teens for Central Park on Tuesday, perhaps a bit milder on Wednesday. Suburban areas, especially out towards the LI Pine Barrens, should see lows in the single digits to near zero.

The lowest temperatures in NYC will occur on the windy CAA nights especially when it is funneling from due north down the Hudson. So snow cover in NYC proper wouldn't make a difference in my opinion since were not talking about radiational cooling parameters here. The journey of the cold air across bare versus snow covered ground would make a big difference like you said. And in this case despite the lack of deep snow in the immediate northern suburbs, I still dont think the airmass is modified greatly on its track down from eastern Quebec. (see behind the secondary arctic front Tuesday morning). With that being said, I'm with you as far as the 850 temps just not being cold enough for a reading like that Tuesday morning. I would not rule out a 8-9 degree reading just yet, but low teens is probably spot on (given the model forecasts are correct)

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