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December Medium/Long Range Discussion


WxUSAF
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31 minutes ago, psuhoffman said:

 

I agree with Ji the easiest way is just get the northern stream out of the way.   The flow is pretty clogged up so it's not like that would be a quick progressive storm. Probably 10-20" of heavy wet snow along the max axis. 

Option 2 opens the door to insanity. A juiced up stalled bomb. Those 30"+ solutions in the gefs for instance. But it's more likely to fail. 

A 30" bomb in early Dec would be historic on many counts. But, I'm trying to understand options 1 and 2  option 1 brings the precip in from Ky and develops a secondary low off the coast, right?  And Option 2 is a phase of the N and S jet streams which would bring a bigger amount of snow up the coast, right?  Don't we do very well with a phase?  I'm trying to understand why that is a problematic solution.  Do we chance the D.C. Snow hole in that situation?  

Thank you all for insights.  While the roller coaster ride is fun, I wish it could be a little easier.  

 

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2 minutes ago, Bob Chill said:

10 run the coast and affect SNE. Most of our big hits are that scenario. Another 10 or so look like the FV3. The rest are whiffs and some fringe jobs. 

I’ll take that. Not sure about EPS in particular, but it seems like the northern edge is a brutal cutoff on most guidance. Distance between nada and WSW criteria could be less than 50 miles.

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Large contingent of members are NE of the mean track in a great spot for the DC/Balt region. Snowfall means are still not greatly reflecting this though probably because of the interaction between the 500's and the surface low. All I know is give me that inside track any day of the week and hope the 500's cooperate.

eps12zlowlocations.thumb.gif.fda5b13a5b20318d9796f5b0dd1d12c4.gif

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26 minutes ago, snowmagnet said:

A 30" bomb in early Dec would be historic on many counts. But, I'm trying to understand options 1 and 2  option 1 brings the precip in from Ky and develops a secondary low off the coast, right?  And Option 2 is a phase of the N and S jet streams which would bring a bigger amount of snow up the coast, right?  Don't we do very well with a phase?  I'm trying to understand why that is a problematic solution.  Do we chance the D.C. Snow hole in that situation?  

Thank you all for insights.  While the roller coaster ride is fun, I wish it could be a little easier.  

 

A phase is great if the timing and location is right. Otherwise, it can be a swing and a miss. A lot of our misses and Boston hits are late-phasers.

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There was some discussion earlier about the performance of the ICON, so I thought I'd fill in the gap between the EPS and NAM extrapolation with some data from last year.  The best site I've been able to find with ICON verification stats is this one.  It comes with the following disclaimer:

"These scores are provided by the WMO LC-DNV for testing and demonstration purposes only. They should only be used to give feedback to the WMO LC-DNV on the layout and functionality of these web pages."

so the numbers might not be reliable, but it matches up well with other sources I've seen.  Below are some scores from last winter for the 12z runs of models commonly mentioned here, except the NAVGEM (no scores available).  "NCEP" is the GFS, "MetOffice" is the UKMET, and "DWD" is the ICON.  All are three-month averages for January-March 2018 in North America and go out to 120 hours.

H5 anomaly correlation

ApSUzR9.png

Sea-level pressure anomaly correlation

vfYAyhz.png

850 temps

fQGuyLQ.png

Of course these are for last winter, and there's a lot of day-to-day variability hidden in these averages.  The ICON performed about as well as the (old) GFS, which I think is consistent with what we saw last winter in a number of events. 

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