March Medium Range Discussion

[jm1220]

Yea I feel bad for the DC crew.  They are still paying for 09-10, and this year it has been especially painful as places to their west have had a pretty good year.  My town (Staunton, VA, 150mi SW of DC) has gotten about 30" this year, right around avg for them.

We really lucked out here in putting up an OK but torturing season. If everything was shifted another 50 miles or so NE, we would be where Philly is, at less than 10"(?) for the season. Goes to show how it can be a lot easier to put together decent events here than just to our SW. It would be really nice if we could eek out one more event to top the year off.

[NEG NAO]

12Z GFS snow accumulation

 

http://raleighwx.americanwx.com/models/gfs/12zgfssnowdepth084.gif

[Allsnow]

Big storm coming end of next week on gfs

[donsutherland1]

and what type of events coincided here with the AO that low in mid to late March ?

 

1958 saw a KU event that coincided with severe late March blocking. Near misses occurred in 1984 and 1996.

 

For those who are unaware, the Arctic Oscillation (AO) has now been negative for 38 consecutive days. It is extremely likely to be negative for at least 40 consecutive days and likely to be negative for at least 50 consecutive days.

 

 

The kind of severe blocking being forecast to develop in coming days is rare. Hence, to obtain a larger sample, I looked at all blocks of at least 30 days of duration that saw the AO fall to at least -3 or below in March. Later, I narrowed for those that had durations of 40 days or longer and 50 days or longer. I also took a look at those that saw the AO fall to -4 or below on or after March 1 (the 1996 block reached peak severity on 4/4).

 

The following table shows total snowfall for the March 16-31 timeframe for the larger sample and three smaller subsets discussed above for New York City (NYC):

 

 

The table provides a general idea. Areas such as northern New Jersey and the Hudson Valley would do better.

 

The table provides only a general overview. The exact pattern and whether storminess is present will be key. Right now, it is probably safe to argue that there is an above to perhaps much above climatological probability that the general NYC area will see some accumulation of snow during the second half of March. The 0z EMCWF and 0z, 6z, and 12z GFS all point to possible opportunities.

[earthlight]

hi Jon

i read your post with awe. ridiculous setup for late march.

you said two winters ago that you love to see the setup in order before the players are on the field because it makes the model solution believable. having said that, do you have enough faith in the gfs or ggem to keep the interest? even though the solutions make sense, its hard not to think we are being mindbended again.

 

I don't yet, but that's solely due to the fact that all of the model guidance (even the ensembles) have been struggling immensely with the timing and positioning of features inside 120 hr. This isn't that uncommon with big blocking events and as don posted above we have the AO starting to rapidly fall now. That being said, I think the potential is higher than normal for a winter weather event across parts of the Northeast with that specific wave. The models have shown it pretty consistently. It just will come down to the positioning of the big upper low to our north and the exact timing of the shortwave coming into the west coast.

[earthlight]

Big storm coming end of next week on gfs

 

The upper level low over the Northeast looks too suppressive to me, on this run.

[Allsnow]

End of next week holds the most promise. Very active stj. Need the ull to slowly move out

[earthlight]

1958 saw a KU event that coincided with severe late March blocking. Near misses occurred in 1984 and 1996.

 

For those who are unaware, the Arctic Oscillation (AO) has now been negative for 38 consecutive days. It is extremely likely to be negative for at least 40 consecutive days and likely to be negative for at least 50 consecutive days.

 

 

The kind of severe blocking being forecast to develop in coming days is rare. Hence, to obtain a larger sample, I looked at all blocks of at least 30 days of duration that saw the AO fall to at least -3 or below in March. Later, I narrowed for those that had durations of 40 days or longer and 50 days or longer. I also took a look at those that saw the AO fall to -4 or below on or after March 1 (the 1996 block reached peak severity on 4/4).

 

The following table shows total snowfall for the March 16-31 timeframe for the larger sample and three smaller subsets discussed above for New York City (NYC):

 

 

The table provides a general idea. Areas such as northern New Jersey and the Hudson Valley would do better.

 

The table provides only a general overview. The exact pattern and whether storminess is present will be key. Right now, it is probably safe to argue that there is an above to perhaps much above climatological probability that the general NYC area will see some accumulation of snow during the second half of March. The 0z EMCWF and 0z, 6z, and 12z GFS all point to possible opportunities.

 

Thanks Don, great research.

 

I think its is safe to say that there will be plenty of storminess. After the storm cuts to our northwest this weekend (it actually redevelops over New England, but the primary is way too far north for most interests here), it looks like there will be an elongating upper level low over the Northeast US.

 

The models are very consistent in keeping an active flow of energy coming out of the Pac NW after that. With a renewed cold air source just to our north and developing strong blocking, I think the potential is very high that someone sees a winter weather event as well. It could be the system around 180 hours, or it could even be after that. We won't know many more details until we get closer -- and I think the forecast guidance is going to struggle in ironing out the details of such a highly anomalous pattern.

[Allsnow]

Things are going to get very interesting around here next week

[Allsnow]

Going off surface maps on the 12z gfs you would think its mid January

[uncle W]

the 1984 near miss on 3/28-29 was a major storm with 2.5" of precip...3-4" of slush in the city but 26" of snow in Tobyhanna Pa...1980 had two noreasters on the 13th-14th and 31st that brought some snow with it...1984's storm had temperatures just above freezing most of the storm...Big storms are still possible this time of year...

[SnoSki14]

I can't guarantee a big snow event, I can't say what kind of negative departures we will have or how the storms will play out, I can guarantee that we will not be seeing any big time spring warmth for a long time, 60F or higher is a long reach right now, even 50+ is going to be a struggle.

[jm1220]

Things are going to get very interesting around here next week

We still have to rely on timing as John said. Blocking makes it so that S/W's can have a better shot at phasing, through a slower flow and by forcing the northern stream to dive instead of staying fast/progressive. But the block has to develop in the right way and at the right time-12/26/10 was a great example. Without that mammoth block the storm would never have happened, and almost didn't happen anyway. If that block were weaker the streams would have stayed separate for longer, and the storm would have likely been more progressive.

[earthlight]

We still have to rely on timing as John said. Blocking makes it so that S/W's can have a better shot at phasing, through a slower flow and by forcing the northern stream to dive instead of staying fast/progressive. But the block has to develop in the right way and at the right time-12/26/10 was a great example. Without that mammoth block the storm would never have happened, and almost didn't happen anyway. If that block were weaker the streams would have stayed separate for longer, and the storm would have likely been more progressive.

 

Agreed on all counts. One encouraging thing is that the ensembles really keep a dominant blocking ridge through the 228 hour period, and it's not just a positive height anomaly. There is very good agreement on a pretty large-scale block developing across much of Greenland into North Central Canada through that period. So I think we will have multiple opportunities to work with. There will be plenty of energy coming out of the Pacific.

 

You can loop through this and see what I mean...it really is impressive.

 

http://www.meteo.psu.edu/~fxg1/ENSHGTAVGNH_6z/ensloopmref.html

[SnoSki14]

I still find it odd how much the gfs cuts the system for early next week although the latest run showed more of a redeveloping coastal, though it wouldn't make a difference.

I'm guessing the lack of digging with primary and the blocking setting up a bit late is why the outcome isn't different.

[earthlight]

I still find it odd how much the gfs cuts the system for early next week although the latest run showed more of a redeveloping coastal, though it wouldn't make a difference.

I'm guessing the lack of digging with primary and the blocking setting up a bit late is why the outcome isn't different.

 

That primary low is very far northwest. It's not necessarily "cutting" but the blocking hasn't really had an effect on the height field across the CONUS by that time. So instead of that shortwave being forced to dig southeast through the Central US, there is actually a bit of  SE Ridge response.

 

Not all is lost, though. All of the medium range models have a very similar piece of energy coming out of the Pac NW by 120-144 hours, and by that time, there is a significant amount of blocking and cold air available.

 

It's just a matter of time.

[donsutherland1]

Thanks Don, great research.

 

I think its is safe to say that there will be plenty of storminess. After the storm cuts to our northwest this weekend (it actually redevelops over New England, but the primary is way too far north for most interests here), it looks like there will be an elongating upper level low over the Northeast US.

 

The models are very consistent in keeping an active flow of energy coming out of the Pac NW after that. With a renewed cold air source just to our north and developing strong blocking, I think the potential is very high that someone sees a winter weather event as well. It could be the system around 180 hours, or it could even be after that. We won't know many more details until we get closer -- and I think the forecast guidance is going to struggle in ironing out the details of such a highly anomalous pattern.

 

I fully agree with you. It will be interesting to see how things turn out in the end. Certainly, there's a lot more potential than we've seen in a number of years.

[IsentropicLift]

The 12z JMA is very amplified with the threat for early next week

 

http://grib2.com/jma/CONUS_JMA_500_GPHTMPVORT_144HR.gif

[Allsnow]

Hr 144 big storm getting going. Ull looks suppressive to our north. That needs to get out or drift ne

[Allsnow]

Hr 162 is close but it looks to miss se. Too much ull

[RUNNAWAYICEBERG]

kinda reminds me of the suppressive ull from the other week with the big stalled cutoff low...as we got closer, it wasnt as strong and more NE than projected.

[Allsnow]

Yes ots hr 168 on the euro

[MJO812]

The ULL is further northeast on this run. We need it more northeast so the storm will have a chance to come up. Big potential with a lot of energy running around.

[RUNNAWAYICEBERG]

the block over the greenie land strengthens thus pressing down on the ull in the NE. if it could just loosen up a bit, the ull moves NE more. deff a timing issue here.

[IsentropicLift]

The Euro at day 10 has another big storm on the horizon

 

http://www.meteo.psu.edu/~fxg1/ECMWF0.5_12z/f240.gif

[Dsnowx53]

That primary low is very far northwest. It's not necessarily "cutting" but the blocking hasn't really had an effect on the height field across the CONUS by that time. So instead of that shortwave being forced to dig southeast through the Central US, there is actually a bit of SE Ridge response.

Not all is lost, though. All of the medium range models have a very similar piece of energy coming out of the Pac NW by 120-144 hours, and by that time, there is a significant amount of blocking and cold air available.

It's just a matter of time.

Yeah, blocking of this magnitude is usually a ticking time bomb. Often times, the first wave or two misses, but something eventually materializes. We had to be pretty patient with the March 8 event, but eventually we got something. And despite the time of year, the upcoming pattern actually looks much more favorable. Better airmass, better Pacific, and more favorably oriented blocking. Something's got to give.

[earthlight]

Yeah, blocking of this magnitude is usually a ticking time bomb. Often times, the first wave or two misses, but something eventually materializes. We had to be pretty patient with the March 8 event, but eventually we got something. And despite the time of year, the upcoming pattern actually looks much more favorable. Better airmass, better Pacific, and more favorably oriented blocking. Something's got to give.

 

The Euro ensembles have a really interesting signal post 200 hours. The block retrogrades and then drops into Central Canada, while Pac NW vort is moving through the Central US. This almost forces the elongated upper level low over Southeast Canada to phase into the Central US vort. On the Euro ensembles this occurs a little farther east, but the entire pattern looks like it might support a huge storm around that time frame.

 

You can see something similar occurring towards the end of the 12z Canadian. Look how the upper level low moved westward from Southeast Canada and is now positioning itself to interact with the Central US vort. The Canadian actually takes this really far west and drops it in over the Plains. I think that is pretty unlikely...but just throwing out some ideas as we move forward.

 

The Euro ensembles really got my interest from 180-220 hours.

 

http://www.meteo.psu.edu/~fxg1/CMC_12z/f168.gif

[earthlight]

...and following along the script, the 18z GFS is retrograding the ULL and dropping it into the Central US trough like a few of us were talking about.

 

http://www.meteo.psu.edu/~fxg1/AVN_18z/f168.gif

[Zelocita Weather]

Major hit on the 18z gfs next Friday/Saturday...great pattern

[Allsnow]

...and following along the script, the 18z GFS is retrograding the ULL and dropping it into the Central US trough like a few of us were talking about.

http://www.meteo.psu.edu/~fxg1/AVN_18z/f168.gif

I was talking to isotherms about the ull for this setup. Need to give it 3-4 days as models will move it around. Look how march 8th ended up