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The Second Wave: Dec 10 (Model Discussion)


stormtracker

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more Facebook Mets(this is for next weekend though)

 

The weekend event is a good example where the NAO is actually needed, despite all the +NAO snow events we are getting lately. If you are going to amplify a wave like that west of the Appalachians, you better have a -NAO in-place.

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yet we all know the best banding will happen to our west ;)...do you agree, or think this one is a DC east event in terms of max QPF?

 

I remember you in feb 2006, when models showed a s/e event and you were insistent that the best banding would set up nw of DC and you were right..

 

ha.. just answered your question below without seeing this post. Thanks for the Feb 06 memory...

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Facebook mets   :facepalm:

I use my own profile page to discuss storm potentials and my friends get a kick out of it.  I'm just wondering if this would be a better option for some of these other "Met" pages?  I think one big issue is false authenticity.

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I use my own profile page to discuss storm potentials and my friends get a kick out of it.  I'm just wondering if this would be a better option for some of these other "Met" pages?  I think one big issue is false authenticity.

Send them all to Ji's page, he is the best.

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The better ratio component / 700-500mb fronto band should still favor N/W areas seeing the max snow, even though modeled QPF is highest SE or where averaging between two areas is occurring. Maybe Wes can elaborate there.

 

Zoomed in at 12z tomorrow on GFS. Despite the duration and alignment here, this is a nice combo of factors from N VA into S-C PA, including DC. You can see 650mb frontogen in the light brown/orange contours.

post-176-0-31207300-1386614250_thumb.jpg

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Zoomed in at 12z tomorrow on GFS. Despite the duration and alignment here, this is a nice combo of factors from N VA into S-C PA, including DC. You can see 650mb frontogen in the light brown/orange contours.

Trouble with the frontogenesis idea is that those regions of frontogenesis are sloped and using a plane view of them can give different answers if you use different  pressure levels.  For example,  today you get west of the city with the 650 level and over the city with 750.  I've never had much success guessing where one might set up.  Usually, it's a little north of where the raw guidance would put it but at least once last year, I think it wasn't.  If i had to guess, I'd place it north and west based on climo but I could see it forming anywhere.  The zone of good F  forcing will be different on the Euro versus the NAM or GFS. 

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are people really taking weatherbell snow maps verbatim?...what ratios do their maps use?....do they take into account the whole thermal profile?

No....my point was that I thought any snow map based on the euro description was gonna show NW high and dry...was surprised to see its qpf distribution was all

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are people really taking weatherbell snow maps verbatim?...what ratios do their maps use?....do they take into account the whole thermal profile?

 

I think we had tried to get to the bottom of this a couple of days ago -- the raw ECMWF output has a categorical yes/no for a series of p-types -- if for a given timestep, if snow=yes, he's sums up the liquid equivalent and applies a 10:1 ratio -- this causes some issues because just because the categorical p-type is snow at say 18z doesn't mean that it was snow for the entire 6-hour time step for the output -- that's simply how to end up getting more snow even if the thermal profiles don't support it -- it's either sloppiness on Maue's part or he's limited by temporal sampling of the ECMWF output, which in that case renders most ECMWF snow maps worthless when you have thermal profiles that may not support snow over the entire 6-hour binning of QPF.

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Trouble with the frontogenesis idea is that those regions of frontogenesis are sloped and using a plane view of them can give different answers if you use different  pressure levels.  For example,  today you get west of the city with the 650 level and over the city with 750.  I've never had much success guessing where one might set up.  Usually, it's a little north of where the raw guidance would put it but at least once last year, I think it wasn't.  If i had to guess, I'd place it north and west based on climo but I could see it forming anywhere.  The zone of good F  forcing will be different on the Euro versus the NAM or GFS. 

 

Yes, the entire process is 3d/sloped which means 1 layer puts subsidence around it at a certain height etc.

 

I am in agreement here that the NW areas see the better snow band, despite the QPF.

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You can easily see where the best banding will set up on the euro snow map. Just in case you cant see it, I made it easier

 

attachicon.gifeurosnow.JPG

Violently agree.  Although I won't be around to see it :(

 

are people really taking weatherbell snow maps verbatim?...what ratios do their maps use?....do they take into account the whole thermal profile?

I still wouldn't take it verbatim, but in this type of scenario, they should do quite a bit better than they would in something like yesterday. 

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