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Monday 12/2 Threat Disco


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Just now, OceanStWx said:

I definitely agree that was a real warm outlier, but I did want to highlight one nice thing about the 3km NAM. It explicitly forecasts snow ratios based on hydrometeor type. Snow ratios change according to the rime factor. The higher the rime factor the close to pure sleet you are getting. 

This example from the latest 3 km shows reflectivity and rime factor. Over NNE there is reflectivity but no rime factor (=pure snow). As you move SW you get more and more riming. 

Webp.net-gifmaker%205_zpswffoz8us.gif

 

> 5 rime factor (cyan into the warm colors) is typically graupel and sleet. The NAM will use snow ratios anywhere from 5:1 for graupel down to 2:1 for sleet. Between the no riming and factor of 5 you get ratios from 3:1 to 8:1. It definitely produces a more realistic looking snowfall map in situations where mixing is forecast to occur.

3K been steadfast at getting some of the WAA snow this far north, Before the SLP takes off.

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1 minute ago, OceanStWx said:

I definitely agree that was a real warm outlier, but I did want to highlight one nice thing about the 3km NAM. It explicitly forecasts snow ratios based on hydrometeor type. Snow ratios change according to the rime factor. The higher the rime factor the close to pure sleet you are getting. 

This example from the latest 3 km shows reflectivity and rime factor. Over NNE there is reflectivity but no rime factor (=pure snow). As you move SW you get more and more riming. 

Webp.net-gifmaker%205_zpswffoz8us.gif

 

> 5 rime factor (cyan into the warm colors) is typically graupel and sleet. The NAM will use snow ratios anywhere from 5:1 for graupel down to 2:1 for sleet. Between the no riming and factor of 5 you get ratios from 3:1 to 8:1. It definitely produces a more realistic looking snowfall map in situations where mixing is forecast to occur.

Is rime factor only available in AWIPS?

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Just now, EastonSN+ said:

What's funny is every model except the Canadian models skip some part of CT. 

We shall see, rarely are the bands EXACTLY where modeled.

If I were only able to see the model output for my county, I'd probably be delighted to get a few inches in early December. But seeing everyone around me getting thrashed while we choke subsidence makes me feel cosmically punished, like I have some sins i forgot to atone for. 

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Just now, dendrite said:

I’m enjoying tracking this one. I feel like this system has some tricks up its sleeve...whether that results in something favorable or not for us.

Looks to be coming together late in the game for us, Moreso here as the SLP looks to bomb in the GOM on the last couple model cycles.

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2 minutes ago, OceanStWx said:

There's a lot of bust potential on the NE side if that WAA washes out too soon.

It seems the 3k has been the only model that has had it, Others do not, But looks like the high and the block are not as strong either it seems to allow the further north progression, Still an eternity up here as some of the first flakes don't look to fly for another 36 hrs or so or longer.

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3 minutes ago, dendrite said:

I’m enjoying tracking this one. I feel like this system has some tricks up its sleeve...whether that results in something favorable or not for us.

Yup, these larger storms often have some kind of surprise.  My favorite is double the snow but the most common one is pingfest showing up early.

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Just now, dendrite said:

Where do you calculate the greatest omega to be?

just N or NW of the lows...which on cod it didn't really appear that way. 

Look at the 700VV on Cod...has the strongest within the 282m contour.

Anyways I think its more of a contour thing...looks like cod does every 3m and TT does every 4m...so adding in an extra contour on Cod I suppose it's fine. 

But regarding the posts about the snow hole in CT...CT sucks on serious subsidence/dry air on the NAM 

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8 minutes ago, Hoth said:

If I were only able to see the model output for my county, I'd probably be delighted to get a few inches in early December. But seeing everyone around me getting thrashed while we choke subsidence makes me feel cosmically punished, like I have some sins i forgot to atone for. 

Lol right.

 

Im not buying the NAM one bit.  Not cuz it skips me(CT), but because it literally gives every other direction/area the goods...but one.   I just don’t see that happening.  If it skipped CT and places West and NW and SW...and then went over to the NE..that’d be much more believable.  But not this stupidity.  

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Just now, weatherwiz said:

just N or NW of the lows...which on cod it didn't really appear that way. 

Look at the 700VV on Cod...has the strongest within the 282m contour.

Anyways I think its more of a contour thing...looks like cod does every 3m and TT does every 4m...so adding in an extra contour on Cod I suppose it's fine. 

But regarding the posts about the snow hole in CT...CT sucks on serious subsidence/dry air on the NAM 

Yup and it’s not just the nam showing dry air either. 

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Just now, dryslot said:

Looks to be coming together late in the game for us, Moreso here as the SLP looks to bomb in the GOM on the last couple model cycles.

That secondary low that forms off of ACY really gets elongated and the isobars get “pulled” back as it tries to escape as the H5 ULL trails well behind. That’s an inv trough look as the PVA moves in aloft to kink those sfc isobars and form a convergence zone. There’s other forcing mechanisms also going on in the midlevels to our SW. Eventually H5 catches up and we get a new sfc low that sorta goes bonkers and gets pulled back in toward ENE like one of those classic blizzard loops before the whole shebang moves out. I just think it’s going to be a mess to figure out after the WAA portion. I’m not really stressing over any solutions...just sitting back and seeing how it’ll play out.

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1 minute ago, WinterWolf said:

Lol right.

 

Im not buying the NAM one bit.  Not cuz it skips me(CT), but because it literally gives every other direction the goods...but one.   I just don’t see that happening.  If it skipped CT and places West and NW and SW...and then went over to the NE..that’d be much more believable.  But not this stupidity.  

Amen, Wolf. And yet I keep getting flashbacks to that static subby hole in southern RI in March '13. It happens. Heck, it happened to me two years ago when Ray got his 30" and I got like 2.5". Let's hope it's wrong.

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Just now, dendrite said:

That secondary low that forms off of ACY really gets elongated and the isobars get “pulled” back as it tries to escape as the H5 ULL trails well behind. That’s an inv trough look as the PVA moves in aloft to kink those sfc isobars and form a convergence zone. There’s other forcing mechanisms also going on in the midlevels to our SW. Eventually H5 catches up and we get a new sfc low that sorta goes bonkers and gets pulled back in toward ENE like one of those classic blizzard loops before the whole shebang moves out. I just think it’s going to be a mess to figure out after the WAA portion. I’m not really stressing over any solutions...just sitting back and seeing how it’ll play out.

I've been pretty much sold on 4" or so but the ceiling is a lot higher today, So we just continue to watch like i have been.

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2 minutes ago, dendrite said:

That secondary low that forms off of ACY really gets elongated and the isobars get “pulled” back as it tries to escape as the H5 ULL trails well behind. That’s an inv trough look as the PVA moves in aloft to kink those sfc isobars and form a convergence zone. There’s other forcing mechanisms also going on in the midlevels to our SW. Eventually H5 catches up and we get a new sfc low that sorta goes bonkers and gets pulled back in toward ENE like one of those classic blizzard loops before the whole shebang moves out. I just think it’s going to be a mess to figure out after the WAA portion. I’m not really stressing over any solutions...just sitting back and seeing how it’ll play out.

You can really see the model rip some sort of vorticity or PV through Delmarva and back into SNE at the end of the run. That's when you really see precip rates increased across SNE/CNE.

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