The Medium Range Thread

[NittanyWx]

am, you have any links for any good peer-reviewed articles relating to mountain torquing and/or MJO forcing?

I'd be interested in this as well.

[wxmx]

You can try this:

http://web.lmd.jussieu.fr/~flott/publications.html

This paper focuses on the solar aspects and influence on climate, but touches stuff like MT and AO.

http://www.agci.org/dB/PDFs/10S1_LGray_SolarInfluencesCLimate.pdf

[am19psu]

I'm feeling pretty bullish on March starting out like a lion across the Northern Tier of the U.S., with Arctic intrusions across the Northern Plains, Great Lakes and Northeast being common through the Ides of March. The establishment of the Hudson Bay vortex in concert with a tropically forced ridge over the Aleutians/GoA should do the trick. The questions are how far south will the cold get and whether the cold will be timed correctly to produce snow. I think places like MSP, MKE, DTW, ALB, and ORH should do well through the first two weeks of the month. ORD, IND, CMH, PIT, and PHL should be in the battle ground. I'd expect those places to see a pattern of warm/wet followed by cold/dry.

[Mikehobbyst]

So in emoticon talk:

ALB to Boston =

NYC and vicinity = or and sitting on the fence

Philly to DC = forget the and get use to Time to stop

[am19psu]

The Euro weeklies came in way different than other medium range guidance, showing a torch for the Eastern U.S. through mid-month. I'm not on board with that forecast at all. There might be short periods of warmth, but the overall pattern north of 40N should be cooler than normal, I'd think.

[Ji]

No signs of anything colder than normal till about march 8-10

[am19psu]

No signs of anything colder than normal till about march 8-10

For you? Yeah. North of the PA Turnpike is a much different story.

[Ellinwood]

The Euro weeklies came in way different than other medium range guidance, showing a torch for the Eastern U.S. through mid-month. I'm not on board with that forecast at all. There might be short periods of warmth, but the overall pattern north of 40N should be cooler than normal, I'd think.

"Torch" through mid-month certainly a possibility in the Mid-Atlantic and Southeast... I would favor aboves over belows for the region overall, with cooler trends towards the end.

[VAwxman]

The Euro weeklies came in way different than other medium range guidance, showing a torch for the Eastern U.S. through mid-month. I'm not on board with that forecast at all. There might be short periods of warmth, but the overall pattern north of 40N should be cooler than normal, I'd think.

My guess is that most of NE even will be on the + side of the normal line for first half of March. I don't mind the weeklies actually, in that the best chance for stronger cold into the CONUS is probably toward the middle third of the month or beyond. Not that I'm highly confident in any details though.

[am19psu]

"Torch" through mid-month certainly a possibility in the Mid-Atlantic and Southeast... I would favor aboves over belows for the region overall, with cooler trends towards the end.

Yeah, I think the Mid-Atlantic will be warm, but I'd have thought that ORD/DTW/LGA/BOS would be on the cool side except for next weekend.

My guess is that most of NE even will be on the + side of the normal line for first half of March. I don't mind the weeklies actually, in that the best chance for stronger cold into the CONUS is probably toward the middle third of the month or beyond. Not that I'm highly confident in any details though.

Interesting. I would have thought the ridge over the Aleutians and the potential for ridging over the North Atlantic would lead to cooler temps across the Northern CONUS. But I'm a noob at this, so I'm happy to be wrong. More than anything, I'm happy some other people decided to chime in.

[Ellinwood]

Yeah, I think the Mid-Atlantic will be warm, but I'd have thought that ORD/DTW/LGA/BOS would be on the cool side except for next weekend.

I just re-read the posts, and I found that the clarification to my confusion was answered in one of your replies already. Reading comprehension fail for me

[VAwxman]

Yeah, I think the Mid-Atlantic will be warm, but I'd have thought that ORD/DTW/LGA/BOS would be on the cool side except for next weekend.

Interesting. I would have thought the ridge over the Aleutians and the potential for ridging over the North Atlantic would lead to cooler temps across the Northern CONUS. But I'm a noob at this, so I'm happy to be wrong. More than anything, I'm happy some other people decided to chime in.

I think the energy coming in from the GOA low isn't allowing the PV to sink far enough south in eastern Canada, and the north Atlantic ridge gets shoved more toward Iceland rather than Greenland. We do get variability in NE though, but not sure it's enough for first half of month to get on the below side of the normal line. If the big high anomaly holds near / over AK though, at some point we will get a period where we pay for that, though strongest cold would be favored more toward the middle of the nation. 6z operational shows the worst case scenario. Really need to get the tropical forcing currently in the WPAC to shift eastward and contribute to the "colder" signal from the recent huge MT spike, rather than fighting against it.

[domenic]

6z and the 12z operational are showing below normal anomalies that -10 to 35 degrees below normal. what are the chances of this coming true?

[am19psu]

I'm not entirely sure how to interpret the current GWO state, but it looks to me like we're in Stage 4 of the GSDM right now. If this a transition similar to the Weickmann and Berry paper, we ought to see a lot of severe wx threats through the first ten days of March and the second half of the month is going to be cold in the Northeast and Great Lakes.

[easternsnowman]

I'm not entirely sure how to interpret the current GWO state, but it looks to me like we're in Stage 4 of the GSDM right now. If this a transition similar to the Weickmann and Berry paper, we ought to see a lot of severe wx threats through the first ten days of March and the second half of the month is going to be cold in the Northeast and Great Lakes.

Withy that scenerio which I think will happen....it means at least anyone fron the M/D line north has a shot at snow.

[domenic]

I'm not entirely sure how to interpret the current GWO state, but it looks to me like we're in Stage 4 of the GSDM right now. If this a transition similar to the Weickmann and Berry paper, we ought to see a lot of severe wx threats through the first ten days of March and the second half of the month is going to be cold in the Northeast and Great Lakes.

The lastest model runs are showing a warm-up from march 13 and 14 th.To me it seems that the week of the12th thru the 18th will be above avg. in the N.E. and great lakes.

DO you think that the polar jet will dig that far south to allow cold air into N.E. and G.L region?

[Ji]

the EURO looks putrid for the east Coast from NYC down to DC

[domenic]

the EURO looks putrid for the east Coast from NYC down to DC

what days are you talking about,warm or cold ????

[am19psu]

The lastest model runs are showing a warm-up from march 13 and 14 th.

I'm not sure which model runs you are talking about. The GEFS and ECENS both show cool anomalies through Mar 13 then going to near normal, which often happens at the end of runs due to model spread.

In the Philly thread, Vawxman (who is way better than me at medium range forecasting) thinks the strongest cold anomalies won't head east until the last 7-10 days of the month.

[wxmx]

Top 10 coldest March for some parts of the N Plains?

[VAwxman]

My guess is that most of NE even will be on the + side of the normal line for first half of March. I don't mind the weeklies actually, in that the best chance for stronger cold into the CONUS is probably toward the middle third of the month or beyond. Not that I'm highly confident in any details though.

Well most of the East did wind up on the + side of normal for March 1-15, though it was not a blowtorch by any means. We do see better chances for chill now in modeling starting middle of next week as NAO goes negative. The final few days of the month are anybody's guess at this stage.

*Map courtesy of MDA

[ApacheTrout]

Well most of the East did wind up on the + side of normal for March 1-15, though it was not a blowtorch by any means. We do see better chances for chill now in modeling starting middle of next week as NAO goes negative. The final few days of the month are anybody's guess at this stage.

*Map courtesy of MDA

Neat map. The warm temps in the Adirondacks and cold temps in Vermont reflect storm paths west of the Adirondacks (I think). Bu what would explain the below normal temperature islands in Ohio and North Carolina?

[am19psu]

Am I nuts for thinking the AO forecasts are off for mid-month?

vs.

And then what that means for temperatures?

[VAwxman]

In the Philly thread, Vawxman (who is way better than me at medium range forecasting) thinks the strongest cold anomalies won't head east until the last 7-10 days of the month.

Yay I got lucky on this one!

[VAwxman]

Am I nuts for thinking the AO forecasts are off for mid-month?

What we are seeing looks like the beginning stages of the Final Warming, initiated by this killer MT spike. But it is important to remember that a true SSW or FW has nothing to do with actual temperatures in the stratosphere by definition, so even though the stratosphere is very warm (maybe even record warm) here in the next 10 days, the actual FW probably has not occured until we get into the 11-15 day time frame. You often see an AO spike just prior to the FW, so in that sense, the AO chart does not really disagree, assuming it would trend down toward day 15 and beyond. It is possible it is too extreme (GFS ensemble is actualy predicting an April AO record), even if the right sign.

[am19psu]

What we are seeing looks like the beginning stages of the Final Warming, initiated by this killer MT spike. But it is important to remember that a true SSW or FW has nothing to do with actual temperatures in the stratosphere by definition, so even though the stratosphere is very warm (maybe even record warm) here in the next 10 days, the actual FW probably has not occured until we get into the 11-15 day time frame. You often see an AO spike just prior to the FW, so in that sense, the AO chart does not really disagree, assuming it would trend down toward day 15 and beyond. It is possible it is too extreme (GFS ensemble is actualy predicting an April AO record), even if the right sign.

Thanks for the info. I assume I should Google Scholar articles on Final Warming so I understand the dynamics of it better?

[VAwxman]

Thanks for the info. I assume I should Google Scholar articles on Final Warming so I understand the dynamics of it better?

Here is the basic definition (which you may already know):

Final Warmings mark the transition from the cold cyclonic vortex in winter to the warm anticyclone centered on the pole in summer. Their intensity varies much and they can be divided into major and minor Final Warmings. The time when the Final Warmings take place - when the westerlies of winter are replaced by the easterlies of summer - also varies a good deal, so they are further divided into early and late Final Warmings.

from this link:

http://strat-www.met.fu-berlin.de/products/cdrom/html/section2-1.html

[CoastalWx]

Thanks for that quick explanation, Brian. Good stuff.

[am19psu]

Here is the basic definition (which you may already know):

Final Warmings mark the transition from the cold cyclonic vortex in winter to the warm anticyclone centered on the pole in summer. Their intensity varies much and they can be divided into major and minor Final Warmings. The time when the Final Warmings take place - when the westerlies of winter are replaced by the easterlies of summer - also varies a good deal, so they are further divided into early and late Final Warmings.

from this link:

http://strat-www.met.fu-berlin.de/products/cdrom/html/section2-1.html

Thanks, Brian. I actually did know the definition, but I don't know how that translates to sensible weather. I'll get to researchin'

[jconsor]

Am I nuts for thinking the AO forecasts are off for mid-month?

And then what that means for temperatures?

Positive AO doesn't always mean warmth in late Mar-April, esp. for the northeast US. However, I do agree that the GFS ensemble is likely a bit overdone on the degree of positive AO in early April.

I found 6 years that had a period of well below normal temps in the northeast US along with an AO averaging at least +1 SD above the mean.

1950: Apr 1-15

1954: Mar 30-Apr 5

1967: Apr 7-30

1972: Apr 1-15

1982: Apr 20-30

1990: Mar 24-31

The early spring +AO periods that are cold in the northeast US tend to have a -EPO, with positive anomalies over AK and/or NW Canada, and a pronounced trough over eastern Canada. They also tend to be La Nina or at least neutral years.

Here is a composite of Apr 6-12, 1950; Mar 24-30, 1990 and Apr 4-9, 1972, 3 of the best examples of this phenomenon. The 500 mb composite isn't too far off from the GFS ensemble 11-15 day forecast.