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12/10-11 Disco / Obs - Rain/Snow/Wind Event


nj2va
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41 minutes ago, Terpeast said:

Yeah, that's probably closer to reality given the sfc temps. Not trying to be a downer, but I'm always reserved on anafronts

this really isnt an anafrontal event anymore, the reason why we're getting sm snow on recent runs is bc of a secondary coastal low forming and undergoing surface cyclonegenesis which throws moisture nw back into the cold sector, this isnt cold front trying to catch up to precip

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Hrrr 18z looks significantly more amplified v 12z. Nice trend. NAM looks a mess at 18z which isn’t uncommon it’s bouncy AF. 
 

Which brings me to…what is NCEPs high res short range flag ship model of choice now anyways???  They stopped updating the NAM and SREF years ago. Which was fine they’re ancient and probably outlived the usefulness of tweaking their core at this point. But they were never replaced.  The HRRR isn’t any more reliable and seems mostly ignored. The ARW FV3 I don’t think ever became operational (unless I missed that) and is largely absent in any forecast discussion. The RRFS has been in development for years and still isn’t operational. Frankly in most discussions of short range Synoptics they still talk about the euro and gfs mostly. So…what exactly is the current preferred high res short range guidance? Any of the pros in this area want to chime in? 

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9 minutes ago, DarkSharkWX said:

this really isnt an anafrontal event anymore, the reason why we're getting sm snow on recent runs is bc of a secondary coastal snow forming and undergoing surface cyclonegenesis which throws moisture nw back into the cold sector, this isnt cold front trying to catch up to precip

This. That 500 low goes negative a low forms over South Carolina

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7 minutes ago, stormy said:

The 18z NAM finally comes to it's senses. It was on steroids..

I’d be careful using the NAM to sniff out trends. First of all which one?  The 3k is still amplified. 12k shat the bed. 6z the 3k did that. Both haven’t been updated in forever and jump around even worse than most high res guidance.   Frankly over the last few years I’ve found I would have been better off simply ignoring the NAMs completely.  Now if the other 18z guidance comes in like that…but so far all we have is the HRRR and it went the other way and is more amplified. 

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5 minutes ago, psuhoffman said:

NAM looks a mess at 18z which isn’t uncommon it’s bouncy AF. 

Looking at the vorticity and can't really understand why the output is worse, 18z appears (to me) more negatively tilted vs 12z. It also has a further south low and a larger area of snow on the backside of the front. Looks like there is almost a bit of a precip hole but not sure why that is (.5 qdf after changeover vs .7). I know its just one run but I want to understand the process better. 

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Just now, SnowenOutThere said:

Looking at the vorticity and can't really understand why the output is worse, 18z appears (to me) more negatively tilted vs 12z. It also has a further south low and a larger area of snow on the backside of the front. Looks like there is almost a bit of a precip hole but not sure why that is (.5 qdf after changeover vs .7). I know its just one run but I want to understand the process better. 

Are we discussing the 12k or 3k?  They are significantly different 

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1 minute ago, SnowenOutThere said:

Sorry meant to specify 3k compared to its 12z run.

The changes on the 3k are mostly noise imo. A lot of the missing snow from 12z was from that ridiculous deform band that was putting down like 3”/hr totals. Instead of one mega band the 18z has several more transient bands. The super band was kinda an unlikely outcome but synoptically I didn’t see a huge difference.  The 18z is more amplified and slower. I actually like the 18z 3k better regardless of the less impressive clown maps. That deform band isn’t something it’s going to get right anyways outside like 12 hours and otherwise absent that one thing the 18z run was better imo. 

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5 minutes ago, DarkSharkWX said:

nam 12k still looks good, 500mb wise i think they both improved, slightly more held back but same tilt and more amped

12k northern and southern jet was considerably more amped

namconus_z500_vort_us_fh39_trend.gif

12z was more amplified than the 18z 12knam. The less impressive surface outcome was actually consistent with its upper levels. BUT it’s the NAM and the 3k and HRRR went the other way so until I see more reliable guidance trend less amplified I wouldn’t take it too seriously. 

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16 minutes ago, psuhoffman said:

I’d be careful using the NAM to sniff out trends. First of all which one?  The 3k is still amplified. 12k shat the bed. 6z the 3k did that. Both haven’t been updated in forever and jump around even worse than most high res guidance.   Frankly over the last few years I’ve found I would have been better off simply ignoring the NAMs completely.  Now if the other 18z guidance comes in like that…but so far all we have is the HRRR and it went the other way and is more amplified. 

I can't find any disagreement with what you say. The 12k dropped 10:1 snowfall from 7" to 2" for my area and dropped total rainfall from 3.15" to 1.63".   It amps more toward the coast and shifts precip. footprint which has been a 6 month pattern.

Yes, the 3k is still amplified with snow but drops rainfall for me from 2.59" to 1.11".

I agree with your thoughts about a short range model with more reliability. 

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It’’s amazing how consistent the euro has been for 5 runs. There has been a slight trend to go more negative the last 2 runs (good) but overall the euros been a rock with all other guidance converging on it. 
IMG_0185.thumb.gif.320207f9ccc27fa66738ae39d366eb10.gif
This is one of the reasons I still find the euro useful in short range. I’ll use the high res to pick out meso features but this lends confidence that the general idea here is becoming pretty locked in. Of course this is a very marginal setup wrt Tempe so now cast issues with the exact Tempe and banding will have a huge impact. 1-2 degrees and where a meso band sets up is the difference between 1-2” of wet paste and white rain. But this consistency combined with the meso models converging towards it makes me confident the idea of a more amplified negative tilt wave is correct. So at least we are in the game.  Like I said I use it as a baseline to judge everything else. 
 
BTW 1-3” of wet snow is better than 2-4” of dry snow imo. The wet snow sits on top the grass better and sticks to everything.  Looks a lot nicer. 

Agreed. Thats what I meant about using it to see whether or not it’s holding the same general evolution in the short range. For me, it’s more about the minute details. I don’t think it does as well as some meso models when it comes to pinpointing bands, but it is definitely still a good sign when the euro holds strong.


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