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February Winter Storm Prospects


WeatherX

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Well, looking at this from what john and wil are saying, i totally see there perspective of east/west and what they mean vs what i mean. I am really speaking about, as Will says, the north atlantic ridge. The east based blocks he shows are not what I am referring to, and I now see my verbage is not proper since clearly those east based blocks are successful and show up in several of the best storms. I will have to be careful of this moving forward.

And I found that reanalysis website, great stuff.

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Well, looking at this from what john and wil are saying, i totally see there perspective of east/west and what they mean vs what i mean. I am really speaking about, as Will says, the north atlantic ridge. The east based blocks he shows are not what I am referring to, and I now see my verbage is not proper since clearly those east based blocks are successful and show up in several of the best storms. I will have to be careful of this moving forward.

And I found that reanalysis website, great stuff.

This one in case you were on a different one

http://www.esrl.noaa.gov/psd/data/composites/day/

N ATL ridge is generally bad for big snowstorms...east based blocks like a UK block can work...but again the block is only one part of the equation. You still need other pieces to work. If you notice on those composites...all of them have a robust 50/50 low forming or already formed. That is the biggest key...DT used to harp on this back in the day and he is correct...the 50/50 low might be the most important synoptic piece of the puzzle with any shortwave amplifying into the east...and its almost always there. Always an exception or two, but its a staple of KU events as it keeps the high pressure anchored over Canada or New England in the more suppressed events.

Feb '83 actually succeeded with a N ATL ridge...but it was decently amplified.

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0z GFS has a coastal hugger for the area. Looks like it starts off as snow and then changes to rain as the low gets closer. SNE gets hammered. Another solution by the GFS.

Surface temps are upper 30's and 540 line is north of city. Maybe some sleet or mangled mix. Then mostly rain.

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The track is better than 18z. Not sure why the GFS is so warm.

The H5 progression, quite frankly, is pretty disgusting and unfavorable as depicted. H5 vort closes off in the central Plains, propagates northeast into IN/OH, driving the surface low pretty far north, attempting to erode the sfc cold. Then the vort becomes an open wave thereafter as it reaches the east coast, the exact opposite of what we want (an ideal progression would be a potent s/w moving W-E through the Plains, tilting negative and closing off once it nears PA/MD/VA to get bombogenesis going). This synoptic set-up produces a stronger primary low, then weaker secondary as H5 opens up and the sfc ridge to the north helps to dry it out.

This will change 50 more times, and we do have some positives on that map. The 50/50 low is in place prior to the storm, with some height rises edging up into sern Greenland, plentiful sfc high pressure over sern Canada, and a ridge out west. It's just that the actual short wave evolution is very disorganized and convoluted; models having great difficultly handling this nern s/w and the large disparity between runs should continue for another 1-2 days at least.

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The H5 progression, quite frankly, is pretty disgusting and unfavorable as depicted. H5 vort closes off in the central Plains, propagates northeast into IN/OH, driving the surface low pretty far north, attempting to erode the sfc cold. Then the vort becomes an open wave thereafter as it reaches the east coast, the exact opposite of what we want (an ideal progression would be a potent s/w moving W-E through the Plains, tilting negative and closing off once it nears PA/MD/VA to get bombogenesis going). This synoptic set-up produces a stronger primary low, then weaker secondary as H5 opens up and the sfc ridge to the north helps to dry it out.

This will change 50 more times, and we do have some positives on that map. The 50/50 low is in place prior to the storm, with some height rises edging up into sern Greenland, plentiful sfc high pressure over sern Canada, and a ridge out west. It's just that the actual short wave evolution is very disorganized and convoluted; models having great difficultly handling this nern s/w and the large disparity between runs should continue for another 1-2 days at least.

Thanks; your post provided some good explanation.

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The 00z GFS setup was not great, but it was definitely less terrible than the 18z run. If we can get this northern stream feature farther south or to come in quicker, the surface low will deepen rapidly and cold air will get involved. 6 hours or so earlier and this run would have been a major hit for our area -- but there's too much warm air advection as it is.

http://www.meteo.psu.edu/~gadomski/AVN_0z/f174.gif

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Well, looking at this from what john and wil are saying, i totally see there perspective of east/west and what they mean vs what i mean. I am really speaking about, as Will says, the north atlantic ridge. The east based blocks he shows are not what I am referring to, and I now see my verbage is not proper since clearly those east based blocks are successful and show up in several of the best storms. I will have to be careful of this moving forward.

And I found that reanalysis website, great stuff.

No hard feelings at all...I just wanted to clear it up to avoid any confusion. It can be deceptive when you're looking at maps and trying to differentiate between a east based -NAO and anything else. Typically I find the East Based NAO's to be centered near the N Atlantic and Iceland with the ridge axis pointed that way..similar to the graphics Will posted. Here's another.

East+Based+-NAO.png

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The 00z GFS setup was not great, but it was definitely less terrible than the 18z run. If we can get this northern stream feature farther south or to come in quicker, the surface low will deepen rapidly and cold air will get involved. 6 hours or so earlier and this run would have been a major hit for our area -- but there's too much warm air advection as it is.

http://www.meteo.psu.edu/~gadomski/AVN_0z/f174.gif

I agree with this. That low really bombs east of Boston. Couple hours earlier could really help out the coastal areas.

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Agree -- and check out the mid level ridge over the Rockies that just sags east beginning at 120. Does us no good at all.

Yep, the ridge pushing eastward across southern Canada forces a sort of "pinch off" to the south, ultimately closing the H5 low and ruining the downstream snow potential. We'll have to see if that's a feature on future runs (the H5 ridge bulging ewd); if so, we may have problems with the H5 low closing off earlier than we'd like. Plenty of time ahead luckily.

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East Based Negative NAO(s) are generally tougher to provide a classic KU event for the entire East Coast, am I right there?

Yes. Generally the further west the block is oriented the better. Dec 09 - Dec 11 was essentially as good as one can get, with the core of pos height anomalies actually SW of Greenland, teleconnecting to the low height field maximum directly underneath, over the East Coast.

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Stop there.

OP run beyond this range is totally useless...esp in this pattern change. Even the first wave is useless...it keeps changing every run.

It has become a joke. The magnitude of the changes at 84-102 hours is ridiculous...you can only imagine what's going on as these changes are rolled forward into the medium range. Just horrible run to run continuity.

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It has become a joke. The magnitude of the changes at 84-102 hours is ridiculous...you can only imagine what's going on as these changes are rolled forward into the medium range. Just horrible run to run continuity.

Its fruitless to watch it. That's why I said "wake me up on Monday if it still shows it" eons ago.

Not sure that event applies now. Might have to wait until Tuesday.

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Its fruitless to watch it. That's why I said "wake me up on Monday if it still shows it" eons ago.

Not sure that event applies now. Might have to wait until Tuesday.

I'm just glad the models are still agreeing on a big time PNA ridge through the medium term. That's one thing that hasn't changed. I would be much more concerned if they were waffling on that.

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