NYC/PHL December 24-27 Potential - Part 2

[NEG NAO]

I can't understand why everyone is certain the EURO is going to verify being the western outlier - considering its still 5 days away and with its know Bias. I would think a GFS/Canadian/EURO compromise would be the safest way to go right now to avoid the BIG letdown if the EURO trends east with 48 - 72 hours.

(Hope this post doesn't get deleted like the last one I wrote a few days ago )

[SnowGoose69]

The Euro is getting way too much love, there is no doubt about that but given its nailed these big events before thats probably why...if this was a El Nino or weak Nina I'd feel better...getting a storm of that magnitude in a strong Nina would be like a 1 in 10,000 year occurrence.

[Rainshadow]

The Euro is getting way too much love, there is no doubt about that but given its nailed these big events before thats probably why...if this was a El Nino or weak Nina I'd feel better...getting a storm of that magnitude in a strong Nina would be like a 1 in 10,000 year occurrence.

Based on Philly snow climatology more like 1 in 101 or 1 in 127.

[NorEaster27]

Euro ensembles are pretty far SE of the OP:

http://moe.met.fsu.edu/cgi-bin/ecmwf-ensmeantc2.cgi?time=2010122200&field=Sea+Level+Pressure&hour=Animation

[am19psu]

I know I am the only one looking at it, but it's troubling to me that the reforecast ensembles are soooo far OTS with this.

[NorEaster27]

OP Euro vs the world is deja vu....

[NorEaster27]

The Euro is getting way too much love, there is no doubt about that but given its nailed these big events before thats probably why...if this was a El Nino or weak Nina I'd feel better...getting a storm of that magnitude in a strong Nina would be like a 1 in 10,000 year occurrence.

very much agreed, its not like the Euro nailed the last "storm." Like I said last night I am amazed everyone is running with the Euro when it has little to no support among other models. This is another threading the needle situation. For the past storng Ninas on record, we never had a KU east coast storm.

[blizzardof09]

The consistency of the euro the past several days makes it very hard for it be gone against. Last night the nam/gfs was trending towards the european solution as the southern s/w was slowing down and was allowing for more phasing, didn't do it but it was very close. Today' 12z gfs and 12z european will determine if the european holds serve and the gfs follows it again, if it does it has to be considered that the european has the right idea since the shortwave will or close to coming onshore in the west and the sampling will be a lot better.

.

[A-L-E-X]

I know I am the only one looking at it, but it's troubling to me that the reforecast ensembles are soooo far OTS with this.

If this is the case, a snowstorm for Cape Cod might even be a bit too generous.

[A-L-E-X]

Based on Philly snow climatology more like 1 in 101 or 1 in 127.

Tony, when we are talking about "big storms" are we referring to 10" or greater in at least three of the five I-95 major cities? (Which is what qualifies for KU event, I think.)

[am19psu]

If this is the case, a snowstorm for Cape Cod might even be a bit too generous.

I'm certainly not implying they're right - I'd go with the Euro ensemble - but it also doesn't make me feel warm and fuzzy inside.

[A-L-E-X]

I'm certainly not implying they're right - I'd go with the Euro ensemble - but it also doesn't make me feel warm and fuzzy inside.

It's a very fragile scenario and there is a huge margin for error, youre in a very unenviable position with this.

It's too bad that most of the general public doesnt get to see the inner workings, because if they did, they wouldnt mock forecast "busts." With a situation like this, getting it "right" is a minor miracle lol.

[Rainshadow]

Tony, when we are talking about "big storms" are we referring to 10" or greater in at least three of the five I-95 major cities? (Which is what qualifies for KU event, I think.)

Alex, only locally in Philly, December 25-26, 1909 only moderate or strong la nina season event that was over one foot.

[LVblizzard]

HPC has been hugging the idea of an east coast blizzard for days now.

[ace0927]

The Euro is getting way too much love, there is no doubt about that but given its nailed these big events before thats probably why...if this was a El Nino or weak Nina I'd feel better...getting a storm of that magnitude in a strong Nina would be like a 1 in 10,000 year occurrence.

the only caveat is- we only have 75-100 years of true record keeping. So it would be 1 in a 100 and there is no way to know what truely happened 200 yrs ago or 1000 years ago, only assumptions can be made....crazier stuff has happened like 3 KU's in one season (ala last yr and 60-61)

[A-L-E-X]

Alex, only locally in Philly, December 25-26, 1909 only moderate or strong la nina season event that was over one foot.

Wow, that was one of the storms Don was talking about and that was one of our mod-strong la nina neg el nino analogs we were looking at (besides 1909-10, the others were 1916-17, 1917-18, 1955-56). Dec 1909 was a big snow for NYC also-- one of those super charger clippers that exploded into a Miller B just offshore, I believe. (That's what this was supposed to be a few days ago too!)

I guess that Jan 2000 and Feb 1989 then qualify as "near misses?"

[cnjraider]

I'm certainly not implying they're right - I'd go with the Euro ensemble - but it also doesn't make me feel warm and fuzzy inside.

You have a tough forecasting job my friend. I am not a met, but I have been following the weather in the central nj area since the early "60"s. I can't remember ever witnessing a storm coming up the coast from that far south and east. I am not saying it can't happen, but if I were a betting man, I would give it little chance. I know there is no science to what I just stated, but history can be a good teacher as well. For the snow lovers, I wish you all nothing but the best.

[SnowGoose69]

Wow, that was one of the storms Don was talking about and that was one of our mod-strong la nina neg el nino analogs we were looking at (besides 1909-10, the others were 1916-17, 1917-18, 1955-56). Dec 1909 was a big snow for NYC also-- one of those super charger clippers that exploded into a Miller B just offshore, I believe. (That's what this was supposed to be a few days ago too!)

I guess that Jan 2000 and Feb 1989 then qualify as "near misses?"

February 1989 would have easily been a 1-2 foot storm everywhere, it missed by around 100-150 miles...thats probably the best chance during a strong Nina at least the last 40-50 years.

[phlwx]

Glad to see nothing has really changed this morning. I'm still thinking SNE is going to get 12+, but our region is up in the air (except E LI). Pending discussions with colleagues, I'm thinking I'll back off my snow totals from NYC to DCA by half.

What are you thinking of the Canadian outcome? That seems to be a bit more realistic than last night's Euro run....

[Tiburon]

I know I am the only one looking at it, but it's troubling to me that the reforecast ensembles are soooo far OTS with this.

Maybe it's just me, but it looks like the 120hr mean has the surface low tracking to the benchmark...I mean, that looks about 150 E of Wallops Island. Unless we're talking about SNE and NNE, if you're in the MA, that has you pretty damn well in the game.

[am19psu]

What are you thinking of the Canadian outcome? That seems to be a bit more realistic than last night's Euro run....

That's the direction I'm leaning, though I'm probably still a bit more bullish closer to the coast in the Delmarva and Jersey than the CMC verbatim.

[Rainshadow]

Wow, that was one of the storms Don was talking about and that was one of our mod-strong la nina neg el nino analogs we were looking at (besides 1909-10, the others were 1916-17, 1917-18, 1955-56). Dec 1909 was a big snow for NYC also-- one of those super charger clippers that exploded into a Miller B just offshore, I believe. (That's what this was supposed to be a few days ago too!)

I guess that Jan 2000 and Feb 1989 then qualify as "near misses?"

Alex,

Yes PHL just had under 10" in Jan 2000 (also March 1956) and Feb 1989 was the ultimate near miss.

[A-L-E-X]

Ok, so we can put March 1956 on our list too-- but was ENSO 3.4 still under -1.0 at that time or had the la nina weakened by then, Tony?

[A-L-E-X]

February 1989 would have easily been a 1-2 foot storm everywhere, it missed by around 100-150 miles...thats probably the best chance during a strong Nina at least the last 40-50 years.

I was thinking that also-- I think we have to catalog the near misses along with the hits because sheer random variability could have made the difference with that kind of small margin.

[Rainshadow]

Ok, so we can put March 1956 on our list too-- but was ENSO 3.4 still under -1.0 at that time or had the la nina weakened by then, Tony?

Different interpretations I'm sure, but it was a strong la nina at the start of that winter.

[A-L-E-X]

That's the direction I'm leaning, though I'm probably still a bit more bullish closer to the coast in the Delmarva and Jersey than the CMC verbatim.

The 0z euro ensembles (which seem to have the highest verification scores over the long term) had this thing 150 miles SE of the BM-- so your call for sne would work out well. We'd just be on the fringe of the moderate snow here in southwestern long island.

[Rainshadow]

Since this storm is still stuck in @120 hr land, Here is the statistical odds for any given storm in a moderate or strong la nina @ PHL since 1949-50. This was done by Mark at our office yesterday:

The discussion that follows applies to PHL.

Tony had thirteen winters from the 1949-50 winter onward analagous to this winter in his data set, and there were four snow events during those winters with an accumulation of six or more inches.

It turns out that there were 113 measurable snow events during those winters. A measurable snow event was defined as either a day of greater than or equal to a tenth of an inch of snow or, whenever it happened, consecutive days each with greater than or equal to a tenth of an inch of snow. In other words, three days in a row of measurable snow counted as one event.

That comes out to an average of about 8.7 snow events per analogue winter.

Also, given that a snow event will occur, the chances of it resulting in six or more inches of snow is about 3.5 percent, and the chances of it resulting in ten or more inches of snow approaches zero percent (notice that I didn't say, "is zero percent.").

So, based on the analogue winters, the occurrence of snow is not rare, but the occurrence of a lot of snow in any given event is.

[SnoSki14]

Long range is looking ugly again, looks like the Nina is roaring back once more. I wouldn't be surprised if this was our last big threat for the season. How amazing that despite the setup aloft looking very different from last weekend, the track is nearly identical to that big bust. But what are you going to do, at least I won't have to do any shoveling or watch out for black ice.

[A-L-E-X]

Since this storm is still stuck in @120 hr land, Here is the statistical odds for any given storm in a moderate or strong la nina @ PHL since 1949-50. This was done by Mark at our office yesterday:

The discussion that follows applies to PHL.

Tony had thirteen winters from the 1949-50 winter onward analagous to this winter in his data set, and there were four snow events during those winters with an accumulation of six or more inches.

It turns out that there were 113 measurable snow events during those winters. A measurable snow event was defined as either a day of greater than or equal to a tenth of an inch of snow or, whenever it happened, consecutive days each with greater than or equal to a tenth of an inch of snow. In other words, three days in a row of measurable snow counted as one event.

That comes out to an average of about 8.7 snow events per analogue winter.

Also, given that a snow event will occur, the chances of it resulting in six or more inches of snow is about 3.5 percent, and the chances of it resulting in ten or more inches of snow approaches zero percent (notice that I didn't say, "is zero percent.").

So, based on the analogue winters, the occurrence of snow is not rare, but the occurrence of a lot of snow in any given event is.

Tony, what about the probabilistic occurrence of 1.0" or greater snowfall events-- I guess thats the minimum definition of "snow cover."

BTW was 2000-01 a weak or mod la nina winter? I see the Millenium storm analog being mentioned now and then (also *gulp* March 2001 lol.)

[cnjraider]

Since this storm is still stuck in @120 hr land, Here is the statistical odds for any given storm in a moderate or strong la nina @ PHL since 1949-50. This was done by Mark at our office yesterday:

The discussion that follows applies to PHL.

Tony had thirteen winters from the 1949-50 winter onward analagous to this winter in his data set, and there were four snow events during those winters with an accumulation of six or more inches.

It turns out that there were 113 measurable snow events during those winters. A measurable snow event was defined as either a day of greater than or equal to a tenth of an inch of snow or, whenever it happened, consecutive days each with greater than or equal to a tenth of an inch of snow. In other words, three days in a row of measurable snow counted as one event.

That comes out to an average of about 8.7 snow events per analogue winter.

Also, given that a snow event will occur, the chances of it resulting in six or more inches of snow is about 3.5 percent, and the chances of it resulting in ten or more inches of snow approaches zero percent (notice that I didn't say, "is zero percent.").

So, based on the analogue winters, the occurrence of snow is not rare, but the occurrence of a lot of snow in any given event is.