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December 27/28 Storm Threat


Baroclinic Zone

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I agree fully. To be honest, I don't look at those AO/NAO forecasts from CPC all that much....I'm a visual person, so I tend to gravitate to looking at the H5 pattern on all three ensembles. I get all I need from that. However, if they wanted a more accurate depiction, I think your method would certainly help in calculating a more true AO.

Awesome. So now that you have no time at all, you want to make this new data set with me? haha..

Another quick and dirty way to take a look at the NH annular mode ... just a time-latitude section

1000mb height anomaly:

post-128-0-57226100-1356107996_thumb.gif

500mb height anomaly:

post-128-0-13604700-1356108005_thumb.gif

Supports a "negative AO" around the end of November into the start of December, but certainly not the last 10 days.

My brotha' from another motha' always comes through with the goods. Thanks man. The CPC method is flawed.

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Guys, when you have 850 mb temps below freezing and want to look to other layers to see if it would be too warm to support snow actually reaching the sfc what is the best to use? Do you just have to look at the thicknesses in the other layers of the atmosphere or am I making it too simple?

925mb

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925mb

http://vortex.plymouth.edu/

has nice graphs (soundings) for stations that show the temperature throughout the column 200mb to surface

if there is any hint of warming aloft you may wanna look at these because if 850 and 925 are cold, there can be a sneaky warm layer between 750-825 mb that turns you over to sleet. these skew diagrams are soundings can be found there.

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Guys, when you have 850 mb temps below freezing and want to look to other layers to see if it would be too warm to support snow actually reaching the sfc what is the best to use? Do you just have to look at the thicknesses in the other layers of the atmosphere or am I making it too simple?

Thickness of the 1000-850 mb layer is usually good enough to use. Generally below 130 dm is cold enough for snow.

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http://vortex.plymouth.edu/

has nice graphs (soundings) for stations that show the temperature throughout the column 200mb to surface

if there is any hint of warming aloft you may wanna look at these because if 850 and 925 are cold, there can be a sneaky warm layer between 750-825 mb that turns you over to sleet. these skew diagrams are soundings can be found there.

Good link, I can't see those other layers on SV, Thanks

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Just a word of warning: if the GFS is correct with how features are handled in Canada, there will be some short-term tendencies as we approach storm date.

1. The low in Canada not lifting out, will decrease the CAD/High presence and open the door for coastal areas to warm up.

2. The h5 trough going negatively tilted early then opening up will mean dynamics will weaken somewhat, as it climbs northward, across the interior areas along the deformation zone.

3. The storm will probably trend faster as it gets "sling-shotted" to the northeast ahead of this low in Canada.

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Just a word of warning: if the GFS is correct with how features are handled in Canada, there will be some short-term tendencies as we approach storm date.

1. The low in Canada not lifting out, will decrease the CAD/High presence and open the door for coastal areas to warm up.

2. The h5 trough going negatively tilted early then opening up will mean dynamics will weaken somewhat, as it climbs northward, across the interior areas along the deformation zone.

3. The storm will probably trend faster as it gets "sling-shotted" to the northeast ahead of this low in Canada.

IOW.....its either rain, or a castrated wave :lol:

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Some cutters, some whiffs, so lets look at the mean which looks like a Jan 1996 repeat.

The spread tool and just plain simple statistics (how many out of 20) should obviously be used. Since it is a probabilistic tool, you cannot make a deterministic conclusion from it as metfan did. This is a perfect example of using tools such as these incorrectly.

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The spread tool and just plain simple statistics (how many out of 20) should obviously be used. Since it is a probabilistic tool, you cannot make a deterministic conclusion from it as metfan did. This is a perfect example of using tools such as these incorrectly.

Yeah, the spread graphics are very useful in almost any situation tracking winter storms. The spaghetti plots aren't terrible either as you can see where the members are compared to the OP. But if we use the individual members...we get this. Seems like many are more amplified than the OP, only one in agreement, and a few are pretty flat.

f120.gif

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Yeah, the spread graphics are very useful in almost any situation tracking winter storms. The spaghetti plots aren't terrible either as you can see where the members are compared to the OP. But if we use the individual members...we get this. Seems like many are more amplified than the OP, only one in agreement, and a few are pretty flat.

f120.gif

lol gotta love P007 versus P010

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Yeah, the spread graphics are very useful in almost any situation tracking winter storms. The spaghetti plots aren't terrible either as you can see where the members are compared to the OP. But if we use the individual members...we get this. Seems like many are more amplified than the OP, only one in agreement, and a few are pretty flat.

f120.gif

To me that's an encouraging graphic. Tells us the GFS had a real struggle with initial conditions.

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