Medium Range Discussion Summer 2012

[mnweather]

Might need a fall thread now instead.

[Riptide]

It doesn't feel like fall, and the record low sea ice levels will keep it warm well into November. It will be like last year, anomalous heat followed by snowstorms; no transitional period per se.

[nzucker]

It doesn't feel like fall, and the record low sea ice levels will keep it warm well into November. It will be like last year, anomalous heat followed by snowstorms; no transitional period per se.

The sea ice is a minor factor in fall temperatures here. We're much too far from the Arctic to see large amounts of fall warming based on declines in sea ice, in the way that Barrow and other towns nearer the ice pack have seen.

For example, since the sudden fall in sea ice in 2007, October has averaged just slightly above normal across much of the US, with warmth in the Northeast and Upper Midwest balanced by cool in the Southeast and Pacific Northwest. 2007 itself is the only year that stands out to me as a ridiculously warm fall:

Although I agree that the sea ice may be a minor factor in keeping recent autumns a little milder, it doesn't preclude having a transition season. Personally, I think that much bigger factors in the recent fall warmth are the +AMO tendency which keeps higher SSTs to our east in the Atlantic, the lack of snow cover at northern latitudes (related to sea ice but not the same), and to the greatest degree, luck. It also is important to realize that we've had some cold spells in the last few autumns, such as the Sept/Oct 2009 couplet which featured mid-October snows just to our north (months were -1.2 and -1.6 at KNYC in that order), and of course the October storm last year. October and November 2008 finished -1.5 and -1.2, with Central Park not getting above freezing on 11/22/08, a notable cold snap.

[donsutherland1]

It doesn't feel like fall, and the record low sea ice levels will keep it warm well into November. It will be like last year, anomalous heat followed by snowstorms; no transitional period per se.

Arctic amplification, which is now being seen in early fall on account of the low sea ice extent, has a regional (Arctic) not hemispheric impact. Where a wider impact may be felt is that a warmer Arctic is resulting in cold air masses being somewhat less expansive and less severe than would otherwise be the case. However, the resulting cold/warm anomalies depend on the synoptic pattern.

[uncle W]

NYC has not seen a freezing temperature in November since 2008...It averaged 35 degrees for the monthly minimum the last three years...Normal/average is in the mid to upper 20's...it seems like the cold season is getting shorter on both ends of the winter..

[Ottawa Blizzard]

Historically, isn't mid to late Fall below average temperature wise in an El Nino, even if the winter ends up warm? I refer people to the Falls of 1997 and 2002. Taking those into account, I can't see how Fall will end up a blowtorch, as Environment Canada seems to be forecasting. I remember they forecasted a torch back in 2002, but then had to "rethink" their forecast after a very cold mid and late October.

[toronto blizzard]

Environment Canada always forecasts warm weather anyway so I wouldn't put much stock into their forecasts

[CoastalWx]

Thought I'd spark up the thread a bit with some interesting things going forward.

The models really show the pattern amplifying with a Siberian ridge, western Canadian ridge, and NATL ridge. This basically drives a series of troughs into the Plains. As far as what is causing it, I can't really put a finger on it, other than it's just a natural pattern change...perhaps maybe helped by MJO trying to go towards weak P7 and a rise in Global AAM tendency. In any case, could be a series of stronger cold fronts plunging into the Plains. Not sure if much cooler wx makes it past the GL in this pattern as the heart of cooler air is forced south into the Plains.

GEFS 11-15 day avg 500 anomalies.

[trapperman]

Thanks CoastalWx. I've been posting about this repeatedly in the Lakes forum and been repeatedly getting bashed by the warministas. Now both the ops and the ensembles show it. I like. The plains need some of this after the utter agony they've been through this summer.

[CoastalWx]

Thanks CoastalWx. I've been posting about this repeatedly in the Lakes forum and been repeatedly getting bashed by the warministas. Now both the ops and the ensembles show it. I like. The plains need some of this after the utter agony they've been through this summer.

I suppose it is possible the pattern does not come out like this if recent trends have any say, but at least it's a change for the Plains.

[NJwinter23]

Thought I'd spark up the thread a bit with some interesting things going forward.

The models really show the pattern amplifying with a Siberian ridge, western Canadian ridge, and NATL ridge. This basically drives a series of troughs into the Plains. As far as what is causing it, I can't really put a finger on it, other than it's just a natural pattern change...perhaps maybe helped by MJO trying to go towards weak P7 and a rise in Global AAM tendency. In any case, could be a series of stronger cold fronts plunging into the Plains. Not sure if much cooler wx makes it past the GL in this pattern as the heart of cooler air is forced south into the Plains.

GEFS 11-15 day avg 500 anomalies.

I've also been watching this signal on the models for quite some time coastal. Earlier last week the ensembles started showing a good signal for a trough in the aleutians and a ridge around the Northwest NA coast in the 11-15...I figured a stronger down stream trough would eventually be realized over the Central U.S...Not really sure what is causing the amplified pattern either. I'd guess the transition season we are entering makes it more difficult to diagnose the causes for weather patterns. For one, the MJO is being registered in phase 4 of late, and this correlates to the modeled pattern quite well in September. Not sure what to make of the glaam signal which continues to sit in the negative state with quite the variability in tendency of late...you could try and argue the onset of weak el nino is tied into it, but between the -glaam state and the lack of any -SOI signal, I find it hard to back that.

19967 2012 8 31 -0.84 -0.77

19968 2012 9 1 -0.89 0.30

19969 2012 9 2 -0.78 1.06

19970 2012 9 3 -0.70 -0.45

19971 2012 9 4 -0.88 -1.63

19972 2012 9 5 -1.04 -0.59

19973 2012 9 6 -1.04 -0.17

19974 2012 9 7 -1.09 -0.41

19975 2012 9 8 -1.04 1.84

[trapperman]

We all know how accurate CPC maps can be, but they certainly are on board, and if this is anywhere near accurate, some of that precip in northern MN and the UP, maybe even northern wisco would be of the frozen kind, at least sleet.

[CoastalWx]

I've also been watching this signal on the models for quite some time coastal. Earlier last week the ensembles started showing a good signal for a trough in the aleutians and a ridge around the Northwest NA coast in the 11-15...I figured a stronger down stream trough would eventually be realized over the Central U.S...Not really sure what is causing the amplified pattern either. I'd guess the transition season we are entering makes it more difficult to diagnose the causes for weather patterns. For one, the MJO is being registered in phase 4 of late, and this correlates to the modeled pattern quite well in September. Not sure what to make of the glaam signal which continues to sit in the negative state with quite the variability in tendency of late...you could try and argue the onset of weak el nino is tied into it, but between the -glaam state and the lack of any -SOI signal, I find it hard to back that.

19967 2012 8 31 -0.84 -0.77

19968 2012 9 1 -0.89 0.30

19969 2012 9 2 -0.78 1.06

19970 2012 9 3 -0.70 -0.45

19971 2012 9 4 -0.88 -1.63

19972 2012 9 5 -1.04 -0.59

19973 2012 9 6 -1.04 -0.17

19974 2012 9 7 -1.09 -0.41

19975 2012 9 8 -1.04 1.84

Yeah the signal from those two previous features you mentioned are pretty weak. I just find it interesting that this pattern appears to be taking hold and could drive quite the cool shot into the Plains.

[tacoman25]

Yeah the signal from those two previous features you mentioned are pretty weak. I just find it interesting that this pattern appears to be taking hold and could drive quite the cool shot into the Plains.

Preceded by the warning shot front this week. Highs the next couple days will struggle to get warmer than the low 60s here, after being near 90 the past couple days. Heavy snow expected in parts of the high country.

The long, hot summer for the central U.S. appears to be coming to an abrupt end.

[SpartyOn]

Environment Canada always forecasts warm weather anyway so I wouldn't put much stock into their forecasts

But..they have been generally spot on with numerous forecast.

[The_Global_Warmer]

I will pass on getting chilly September weather so parts of the arctic can get torched.

Day 6-10, 500MB Height anomaly's.

11-15 day, H5 anomaly's.

[tacoman25]

Looks quite cold for western Europe next week, too. Record cold fairly likely for much of the Midwest if the 0z GFS verifies.

People on here would be going nuts if this pattern developed 3 months from now.

[tacoman25]

It doesn't feel like fall, and the record low sea ice levels will keep it warm well into November. It will be like last year, anomalous heat followed by snowstorms; no transitional period per se.

It will sure feel like fall in a lot of places next week.

Believe it or not, the Arctic ice extent does not control your local weather.

[SVT450R]

Looking good.

[trapperman]

Not that they are to be trusted any more than the Euro weeklies, but the extended 06z GFS and 12z both bring shot after shot of cold into the plains until the end of September. That would be quite something...

[tacoman25]

Not that they are to be trusted any more than the Euro weeklies, but the extended 06z GFS and 12z both bring shot after shot of cold into the plains until the end of September. That would be quite something...

The 0z GFS had the same thing. Very consistent modeling for now.

[trapperman]

The 0z GFS had the same thing. Very consistent modeling for now.

Stationary PAC NW 588 DM high pressure. Haven't seen that for a long time...

[trapperman]

Honestly now I have never seen 2 models in better agreement out to 240 hours than the 12z runs of the Euro and GfS today. Right down to the EPac coast closed low at 240. Shot after shot of 0 or below 850s into the upper midwest.

[tacoman25]

The 12z Euro continues the theme of a series of intense cold fronts sweeping through the Midwest over the next 7-10 days.

[tacoman25]

Today's 12z Euro is just as bullish on the incoming early fall cold snap, if not more so. Lots of cold records should fall, and perhaps even some snow in MN and the U.P. of MI.

0c line gets to northern MN in 48 hrs, and makes it down to Detroit at 96 hrs. Then the second cold front gets it into Iowa at 168 hrs.

-4C makes it to northern Lake Superior at 72 hrs, and far northern MN again at hour 168.

[icebreaker5221]

I think the overall cold pattern for the central and eventually eastern 1/2 of the country will persist for at least another 2 weeks. Models tend to be too quick in breaking down blocking patterns, and this one looks to be here to stay. A recurving Typhoon Samba, as well as a couple prospective recuvers further down the line (~a week from now?), teleconnects with further east coast troughing.

Also, MJO has continued to progress quite steadily (albeit weakly) through phases 4 and 5, despite some recent model predictions to slow or stall altogether. I believe it will slow a little, but remains progressive enough to reach phase 1 in 8-12 days. Phases 1 and 2 are both cold phases in the fall, so if the MJO continues to propagate into phase 2 and perhaps continues to slow, we could be talking a fairly long-lived cool spell.

[Met1985]

I think the overall cold pattern for the central and eventually eastern 1/2 of the country will persist for at least another 2 weeks. Models tend to be too quick in breaking down blocking patterns, and this one looks to be here to stay. A recurving Typhoon Samba, as well as a couple prospective recuvers further down the line (~a week from now?), teleconnects with further east coast troughing.

Also, MJO has continued to progress quite steadily (albeit weakly) through phases 4 and 5, despite some recent model predictions to slow or stall altogether. I believe it will slow a little, but remains progressive enough to reach phase 1 in 8-12 days. Phases 1 and 2 are both cold phases in the fall, so if the MJO continues to propagate into phase 2 and perhaps continues to slow, we could be talking a fairly long-lived cool spell.

Ya kind of what the latest GFS was showing today. How long has it been since we saw a pattern alike this. Very refreshing.

[tacoman25]

Ya kind of what the latest GFS was showing today. How long has it been since we saw a pattern alike this. Very refreshing.

September 2010 had a somewhat similar, though less amplified pattern for a week or two. Got pretty darn cold in the upper Midwest with that one. This one looks to have much more widespread cool weather.

Before that, October 2009 was the last major/extended fall cold snap for many places, and that one was a real doozy.

[Powerball]

I would definitely loved to have a pattern like this in December...

[SoCoWx]

No hope for the east coast then? Cold air is nice, when it's here. But the models seem to want to keep the immediate coast locked in more of a late Summer/early Fall pattern, rather than a full on Autumnal regime.