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February Medium/Long Range Thread


stormtracker
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BTW wanted to post what I've noticed over the years in terms of trajectory of storms on guidance and when they are most and least likely to adjust north v south.  The angles are just symptoms on the models of the underlying reasons but since its easier to just see the angle of precip then to analyze those factors for most people its a cheat code kind of thing.  

Angles.thumb.png.a2e75ad9d88412a751abd7802132637e.png

The lines above represent the angle of the precip.  

Green is the angle most likely to adjust north.  This is typical of a wave approaching from the SW, its mature enough to get precip up into the TN valley and its also gaining some amplitude as represented by the fact the precip is gaining latitude east of the mountains some.  This combo is the most likely wave to adjust northwest.  Guidance most often underestimates the northward extent of precip and the ability of the wave to push the thermal boundary north as it amplifies in this type of setup.  

Red is not a setup that often adjusts for the better if you are north of the precip and want that "north trend".  Red often indicates a wave that is not amplifying, or not amplifying enough to offset a hostile cold press on the north of it.  This trajectory is most likely to adjust south actually.  Even in extreme examples like Feb 5 2010, it didn't hurt us, but that is an example that adjusted south some at the end...my friend in north central NJ was expecting 6-10" on the northern fringe and got 1".  That storm, even as strong as it was, made absolutely no northern adjustment the final 48 hours and if anything adjusted south some at the last minute.  The two waves this year that were fails for northern MD had this trajectory also.  The two March 2014 storms both trended south some from 72 hours out and they were also examples of this trajectory.  January 2019 was another example.  This in my experience are least likely to trend north and are more likely to sink south some at the end.  

The Orange line is a problem because systems tend to adjust NORTH not WEST.  A west trend actually requires a faster developing system and that actually goes against model bias that often phases and begins the amplification process of a late developing east coast storm too soon.  9/10 this trajectory will not end will if you are west of the precip on guidance 72 hours out...it probably won't adjust west significantly.  

There are exceptions to these 3 rules...nothing is 100%, wish it was that easy...Jan 2000 is a great example that broke the orange line rule.  But these are generally when we can expect a north v a south trend MOST often based on the trajectory, which again is a cheat to factors causing that trajectory which make a north v south adjustement on guidance more or less likely.  

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Just now, Heisy said:

I’m pretty impressed how decent it snows even with the late phase on the euro, good sign. Really hope we could find a way to get a closer tuck


.

If it's like the Ukie, and I haven't looked closely, north and west precip may be from tpv interaction. 

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Don't forget about us poor folks in the middle who are on the line of missing the jack to our SE but close enough to get a more respectable total vs the desolate souls to the NW. Middle children need love too

I moved to Leesburg to get closer to you and to get more snow. Each goal has betrayed me
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