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Mid to Long Term Discussion 2020


jburns
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A lot of moving pieces for the system next week. One thing to pay attention to this far out more so than fantasy maps and exact placement of precip as modeled is the mode of cold air transport. This cannot be emphasized enough that even the best runs the last 2 days, especially east of the mountains, are highly dependent on the ~1040 mb High able to efficiently push cold air in-time to meet with the precip. This cold-chasing rain approach very rarely works out especially when the cold is coming from the NW. A backdoor front with cold air established in the NE usually works better (CAD). THAT being said, this is one of the strongest highs we've seen modeled this season. If we can get a long-duration overunning event, those can work in this setup. An amped low can also work to pull and manufacture some of it's own cold air (But we all know the mid level implications of an amped SE storm with marginal cold to begin with). Verdict: this situation is borderline at best. The Euro appeared to be onto something with runs yesterday before going to suppression city today. But the storm is still there. It did not lose it. GFS obviously was more in line with the EURO runs, but is delayed with the cold air (likely not incorrect). This is probably our best "threat" this season, but it has much less going for it than it does going against it and that's just the truth.

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1 hour ago, ILMRoss said:

Focus on Thursday. Thursday is a no frills, overrunning event where the atmosphere is hair trigger sensitive to disturbances due to the thermal gradient. The closing coastal needs a lot more to go right. Focus on Thursday.

Yeah, the problem is there may no energy to work with.  The euro took a step toward the gfs in wanting to hang the energy back in the SW.  Always something...especially so this winter.  I don't think it's dead yet but the euro suite (including the EPS) makes me think this is going the way everything else has this winter. 

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Here's the 12z GFS.  There are two key shortwaves in the northern stream (top left panel).  The first is in the eastern Great Lakes at the start of the loop.  That's the table setter with the cold high pressure coming in behind it (behind the eastern U.S. cold front).  The next one drops down from Montana into NE Colorado - this works to keep the flow more southwesterly across the south.  I've noticed a trend in recent model runs to have this shortwave drop a bit farther to the southwest, which is what is needed to get the overrunning precip going.  Having that wave drop into the southwest and then hope it spins and comes out at just the right time is a riskier play (as ILMROSS referenced earlier).  That wave also links up with waviness in the subtropical jetstream.  Note on the bottom left panel how the moisture blows up in Texas before heading east.  The ICON had a very similar look to the GFS, but it was a close miss with the storm over the SE.

This GFS run though no doubt has some good qualities to it.

y7hDbKf.gif

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2 minutes ago, Extreme NEGA said:

Pretty sure this has been asked before but what does Dendritic growth mean on the soundings?

Typically the area on a sounding where the temp is between -10C and -20C. You want to see if that region is saturated or not. This is the temp range for optimal snow growth and the microphysics involved in that.

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Just now, Extreme NEGA said:

Pretty sure this has been asked before but what does Dendritic growth mean on the soundings?

There's a range of temps at which dendrites grow (which create very high ratio snows). Ideally you want the area of greatest lift, to fall within this zone to get dendrites. On tropical tidbits, the orange bars on the left tell you how much lift there is at that level.

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