HPC AM Discussion

[donsutherland1]

Don,

Yes that was the one I was referring to Feb 23-24.

Phase 3, Amplitude 2.1 for 2/23, 24, and 25.

[donsutherland1]

BTW did only one of those Norfolk snowstorms make it up to NYC with accum snow?

I wish one of them had. Neither storm brought accumulating snow to NYC. A few days after the latter event, a trace of snow was recorded in NYC.

[Gibbsfreeenergy]

Although I have enormous respect for the expertise and outstanding work done by HPC (and am rooting for the operational Euro solution to verify), I do raise a caveat. Although general climatology would tend to favor the Euro, moderate/strong La Niña climatology does not. Just a small difference in timing when a phase takes place or if it does would have a substantial impact on the outcome. It is no coincidence that since 1871, there have been only two KU-type storms (December 1909 and January 2000) when the ENSO Region 3.4 anomaly was -1 or below. None of those storms brought 10" or more snow in all of the big cities running from Richmond to Boston (RIC, DCA, PHL, NYC, BOS). Although one cannot rule out what would be an unprecedented event for the 1871-present timeframe were the operational 0z Euro to verify, historical odds are against it. That the ECMWF ensemble guidance has shifted south and eastward and a number of other models are well east of the Euro adds to this sense of caution.

I think the overuse of La Nina the last month when there have been very few La Nina aspects about this pattern has been a mistake. The rising AAM levels through November and into early December, coupled with crazy amount of blocking, have really made La Nina take a back seat. Given this, I am not sure how relevant Nina is at this present time. Actually, I can make the argument that Nina like trends would suggest a higher likelihood for northwest trends....backward of what occurred lat weekend, and if this misses, backward of this event as well.

I will say though, the rapid decline in AAM presently is finally showing signs of having an impact on the pattern in the Medium range.There might even be a lakes cutter or two ?in the 6-15 day period.

[Ender]

I think the overuse of La Nina the last month when there have been very few La Nina aspects about this pattern has been a mistake. The rising AAM levels through November and into early December, coupled with crazy amount of blocking, have really made La Nina take a back seat. Given this, I am not sure how relevant Nina is at this present time. Actually, I can make the argument that Nina like trends would suggest a higher likelihood for northwest trends....backward of what occurred lat weekend, and if this misses, backward of this event as well.

I will say though, the rapid decline in AAM presently is finally showing signs of having an impact on the pattern in the Medium range.There might even be a lakes cutter or two ?in the 6-15 day period.

I was just going to post, in retraction to my sarsasm about Nina climo...something's not right with this Nina. California has been deluged. That's not exactly typical.

[billgwx]

Although I have enormous respect for the expertise and outstanding work done by HPC (and am rooting for the operational Euro solution to verify), I do raise a caveat. Although general climatology would tend to favor the Euro, moderate/strong La Niña climatology does not. Just a small difference in timing when a phase takes place or if it does would have a substantial impact on the outcome. It is no coincidence that since 1871, there have been only two KU-type storms (December 1909 and January 2000) when the ENSO Region 3.4 anomaly was -1 or below. None of those storms brought 10" or more snow in all of the big cities running from Richmond to Boston (RIC, DCA, PHL, NYC, BOS). Although one cannot rule out what would be an unprecedented event for the 1871-present timeframe were the operational 0z Euro to verify, historical odds are against it. That the ECMWF ensemble guidance has shifted south and eastward and a number of other models are well east of the Euro adds to this sense of caution.

Agree, not from an index-based perspective but just by looking at the model data. The ECMWF idea of a perfect northern/southern stream phase just seems unlikely to me...looks a lot like that ECMWF hiccup late last week that wound up a 970-ish low inside the 40/70 benchmark when most of its other runs remained suppressed. A big dump for NYC metro is not necessarily a lock per the 00Z ECMWF ensmean and even the 00Z GFS shifted NW by the traditional 125 miles, but the snow bunny in me likes the Rausch prog that puts OKX in the sweet spot.

[A-L-E-X]

I was just going to post, in retraction to my sarsasm about Nina climo...something's not right with this Nina. California has been deluged. That's not exactly typical.

I remember a few years ago we had an el nino in which cali bearly got any rain lol. I guess climatology is trumped by variance, even in ENSO.

[donsutherland1]

I think the overuse of La Nina the last month when there have been very few La Nina aspects about this pattern has been a mistake. The rising AAM levels through November and into early December, coupled with crazy amount of blocking, have really made La Nina take a back seat. Given this, I am not sure how relevant Nina is at this present time. Actually, I can make the argument that Nina like trends would suggest a higher likelihood for northwest trends....backward of what occurred lat weekend, and if this misses, backward of this event as well.

I will say though, the rapid decline in AAM presently is finally showing signs of having an impact on the pattern in the Medium range.There might even be a lakes cutter or two ?in the 6-15 day period.

IMO, the persistent and recent extreme blocking has basically dominated December. I'm just using the La Niña climatology with respect to the risk of a KU-type storm. I believe a moderate snowfall is still on the table and the 0z ECMWF mean can adjust either somewhat west or east. I'm just not buying into the operational ECMWF and believe the recent shift eastward in the EC ensemble mean is a warning sign that the models with a less impressive solution may have a better grasp of at least some details that could be critical.

With respect to the cutter idea, I agree. I suspect that if there is a storm around New Year's Day +/- 1-2 days, odds might even favor such a solution.

[mattie g]

Yup, exceptionally, exceptionally unusual. In fact, when did it last happen? I know it has..but pretty darn unusual. Especially in mid winter. Of course, it's happened, or come close to happening, on the Euro a couple times already this December.

Didn't it happen with (at least) one of the big MA storms last year?

I know I've seen a visible sat image of it recently - just can't remember which one storms it was.

[A-L-E-X]

Agree, not from an index-based perspective but just by looking at the model data. The ECMWF idea of a perfect northern/southern stream phase just seems unlikely to me...looks a lot like that ECMWF hiccup late last week that wound up a 970-ish low inside the 40/70 benchmark when most of its other runs remained suppressed. A big dump for NYC metro is not necessarily a lock per the 00Z ECMWF ensmean and even the 00Z GFS shifted NW by the traditional 125 miles, but the snow bunny in me likes the Rausch prog that puts OKX in the sweet spot.

OKX always seems to be the sweet spot for snow on Long Island lol.

[thegreatdr]

HPC does not receive the individual 00z ECMWF/00z Canadian ensemble member plots or the 00z ECMWF ensemble mean until 10-11z. Still, even without these advantages, on average, the night and day shifts verify pressure-wise quite similarly from days 3-7. Sometimes day shift outperforms night shift, and other times night shift outperforms day shift. Until this past month, the old 12z ECMWF ensemble mean was scoring similarly to the 00z GEFS mean available to night shift. We'll know more in a week about this particular event, as the pressure verification lags by about one calendar day.

DR

That may be true, I have seen the briefer internal discussions come out as early as 3 am. I don't know the ending time of that shift, but it does start before 11 pm.

[donsutherland1]

...but the snow bunny in me likes the Rausch prog that puts OKX in the sweet spot.

That makes two of us.

[A-L-E-X]

IMO, the persistent and recent extreme blocking has basically dominated December. I'm just using the La Niña climatology with respect to the risk of a KU-type storm. I believe a moderate snowfall is still on the table and the 0z ECMWF mean can adjust either somewhat west or east. I'm just not buying into the operational ECMWF and believe the recent shift eastward in the EC ensemble mean is a warning sign that the models with a less impressive solution may have a better grasp of at least some details that could be critical.

With respect to the cutter idea, I agree. I suspect that if there is a storm around New Year's Day +/- 1-2 days, odds might even favor such a solution.

Don, are you still on board with major blocking returning in early Jan?

[Rainshadow]

I think the overuse of La Nina the last month when there have been very few La Nina aspects about this pattern has been a mistake. The rising AAM levels through November and into early December, coupled with crazy amount of blocking, have really made La Nina take a back seat. Given this, I am not sure how relevant Nina is at this present time. Actually, I can make the argument that Nina like trends would suggest a higher likelihood for northwest trends....backward of what occurred lat weekend, and if this misses, backward of this event as well.

I will say though, the rapid decline in AAM presently is finally showing signs of having an impact on the pattern in the Medium range.There might even be a lakes cutter or two ?in the 6-15 day period.

Nina or not, the quadrant that the gwo is currently in has historically been a dud for big ticket events in PHL since 1958 (as far back as I can get them on the CDC site).

[Rainshadow]

HPC does not receive the individual 00z ECMWF/00z Canadian ensemble member plots or the 00z ECMWF ensemble mean until 10-11z. Still, even without these advantages, on average, the night and day shifts verify pressure-wise quite similarly from days 3-7. Sometimes day shift outperforms night shift, and other times night shift outperforms day shift. Until this past month, the old 12z ECMWF ensemble mean was scoring similarly to the 00z GEFS mean available to night shift. We'll know more in a week about this particular event, as the pressure verification lags by about one calendar day.

DR

Thanks, I wasn't sure if you made it to this site, glad to see you here.

[Gibbsfreeenergy]

Nina or not, the quadrant that the gwo is currently in has historically been a dud for big ticket events in PHL since 1958 (as far back as I can get them on the CDC site).

I don't have access to plots since I am on vaca, but would be interesting to see what those GWO plots show for a composite pattern vs what is progged currently. My initial guess is a disconnect, but I cant be sure without my plots.

[isohume]

I don't know, seems a little optimistic to me...almost skewed.

[thegreatdr]

I heard at work the other day that my name had come up on this board, so I figured I might as well join up, again.

DR

Thanks, I wasn't sure if you made it to this site, glad to see you here.

[Rainshadow]

I don't have access to plots since I am on vaca, but would be interesting to see what those GWO plots show for a composite pattern vs what is progged currently. My initial guess is a disconnect, but I cant be sure without my plots.

Could very well be (the cdc gwo phase site says it should be milder east) as its not been very nina-like.

[donsutherland1]

Don, are you still on board with major blocking returning in early Jan?

A-L-E-X,

I've noted that the GFS ensembles have hinted at it (though the site showing the individual ensemble forecasts seems to have a problem beyond 1/1). My thought had been that the AO could actually go positive during the first week in January +/- a few days. December superblock experience would suggest the former. La Niña experience (albeit with somewhat weaker La Niñas and weaker blocking) would suggest the latter, which would then translate into a generally cold January. I want to see more data before embracing the former idea. I do believe that strong blocking will return later this winter (probably late February/early March).

[Yeoman]

Although I have enormous respect for the expertise and outstanding work done by HPC (and am rooting for the operational Euro solution to verify), I do raise a caveat. Although general climatology would tend to favor the Euro, moderate/strong La Niña climatology does not. Just a small difference in timing when a phase takes place or if it does would have a substantial impact on the outcome.

I would agree until you look at the record breaking precip in CA.. There is a larger factor than La Nina at play in this pattern..

[Ginx snewx]

Quite interesting that the Cali rains broke records in several cities set in Dec 1970

[donsutherland1]

I would agree until you look at the record breaking precip in CA.. There is a larger factor than La Nina at play in this pattern..

The Niña is just one factor. The persistent and recently extreme blocking has dominated and led to some un-Niña-like situations. The timing of the phasing will be crucial in determining whether a KU-type event unfolds. Historical odds + the trend in the ECMWF ensembles + various other models (GFS, GGEM, UKMET) all suggest that the KU idea is probably not the most likely solution. Much as I'd prefer to see the ECMWF idea verify, the recent trend in the ECMWF ensembles/GGEM/UKMET and general continuity in the GFS suggest that the ECMWF might not have the best handle on a critical detail(s). I also believe that the ECMWF's bias in holding back energy may also be contributing at least somewhat to its recent solutions.

[easternsnowman]

The Niña is just one factor. The persistent and recently extreme blocking has dominated and led to some un-Niña-like situations. The timing of the phasing will be crucial in determining whether a KU-type event unfolds. Historical odds + the trend in the ECMWF ensembles + various other models (GFS, GGEM, UKMET) all suggest that the KU idea is probably not the most likely solution. Much as I'd prefer to see the ECMWF idea verify, the recent trend in the ECMWF ensembles/GGEM/UKMET and general continuity in the GFS suggest that the ECMWF might not have the best handle on a critical detail(s). I also believe that the ECMWF's bias in holding back energy may also be contributing at least somewhat to its recent solutions.

It's not like;y to get a KU in a moderate or strong nina, but who would of predicted 3 KU's last year....these are unusual times.

[Rainshadow]

The Niña is just one factor. The persistent and recently extreme blocking has dominated and led to some un-Niña-like situations. The timing of the phasing will be crucial in determining whether a KU-type event unfolds. Historical odds + the trend in the ECMWF ensembles + various other models (GFS, GGEM, UKMET) all suggest that the KU idea is probably not the most likely solution. Much as I'd prefer to see the ECMWF idea verify, the recent trend in the ECMWF ensembles/GGEM/UKMET and general continuity in the GFS suggest that the ECMWF might not have the best handle on a critical detail(s). I also believe that the ECMWF's bias in holding back energy may also be contributing at least somewhat to its recent solutions.

Don,

Until the energy gets out of the desert southwest, one has to be wary of this, I agree.

[Rainshadow]

Quite interesting that the Cali rains broke records in several cities set in Dec 1970

Ironically (maybe not) also in a nina winter.

[J.Mike]

I know that HM (Accuweather) dumping the GFS in favor of the Euro causes snickers here, but he's not the only one:

NYC NWS: THE GFS WAS AN EXTREME SOUTHERN OUTLIER EVEN AMONGST ITS ENSEMBLE MEMBERS WITH THIS STORM AND ITS SOLUTION HAS BEEN DISCARDED AT THIS TIME.

[WBRE Wx]

Don,

Until the energy gets out of the desert southwest, one has to be wary of this, I agree.

Interesting though that the new 36-hour GFS is actually slower with the feature coming into New Mexico than last night's 48 hour Euro!

[donsutherland1]

I know that HM (Accuweather) dumping the GFS in favor of the Euro causes snickers here, but he's not the only one:

NYC NWS: THE GFS WAS AN EXTREME SOUTHERN OUTLIER EVEN AMONGST ITS ENSEMBLE MEMBERS WITH THIS STORM AND ITS SOLUTION HAS BEEN DISCARDED AT THIS TIME.

IMO, the GFS may be too suppressed. Yesterday, I liked a compromise between the ECMWF ensemble mean and the GFS ensemble mean. I believe the 12/22 0z ECMWF ensemble mean is a reasonable idea and there could be some adjustment either east or west from that.

[Bluescat1]

Ironically (maybe not) also in a nina winter.

Tony have you changed your do or die time from Thursday 12Z yet?

[Guest someguy]

The GGEM and NOGAPS have 4D-VAR and the euro ensembles do not agree with the OP....

this is 100% wrong

if you dont know what you are talking about please stop

to begin with the 0z ggem still has a major low near the coast

and the Nogaps -- the no clue -- has far worst resolution .