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Pattern Jammin' January

The GEFS continues to be much colder than the GFS overall. The GFS warm bias is ridiculous.

12Z Euro: Though mild day 10, the 12Z was much colder for the 10 days overall vs the 0Z. The 12Z FV3 is much milder than its prior 3 runs in the 11-15, but the FV3 is apparently at least as erratic as the unreliable GFS in the 11-15. So I’d toss.
 
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@Webberweather53 per Radiant met, you may already know this but the GEFS MJO forecast in phases 6-7 is so strong and much stronger than the EPS because it has a strong WWB whereas the EPS doesn’t.
 
RollTide18 said:
It’s probably a dumb question but how do models develop biases?
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Not a dumb question. They don't normally develop them but instead have them from the start and will keep them at least til the next version of the model. There are exceptions, however. Example: maybe a particular model stated running during La Nina and had, say, little temperature bias in the SE US. But then it was realized that during El Nino that a cold bias had become evident in the SE. So, sometimes it depends on the overall wx pattern such as associated with the various phases of ENSO.

Often these biases vary greatly depending on location. So, say there's a cold bias in the SE US but no bias in the Midwest. If you try to fix the cold SE bias, you could easily create one for the MW. No easy way to fix these in many cases.

Many times new versions are done to reduce biases. But even if not, as long as these biases are known and not too big and are rather predictable, adjustments can be made to output to keep the models quite useful. Why do they have biases? I've had the same thought before. I think because the programming going into them is so immense and the atmosphere is so complex and the Earth large that it is hard to not have some biases in some places. The hope is that these aren't too large. If you try to minimize the biases too much, you may sacrifice accuracy in other ways?
 
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Webberweather53 said:
I'm driving with a close friend of mine just after New Years from southeast Texas to Phoenix, AZ for this year's AMS Conference and we plan to do a lot of sight seeing along the way in the southern Rockies & four Corners regions.

I've never seen more than 18" of snow on the ground before and the Euro is throwing me a huge bone with a parade of storms to open up the New Year and feet of snow in the mountains of Arizona & New Mexico.

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My body is ready.
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Hey web, Flagstaff Arizona is where you want to be if there’s a system. They average over 100 inches of snow a year and usually get a number of 12-24 inch snows during the winter. My wife and I stayed there one night on our way to San Diego and there was a massive snow storm at the time. It snowed so heavily non stop from the time we got there until around 8am the next morning. Snow was up to the rooftops and is still to this day the most snowfall and heaviest snow I’ve seen in my life. Flagstaff is a nice little area to stay also plus the elevation is 7,000 feet in town.
 
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I think it is important for folks to realize that even if we get to a cold dominated pattern from mid Jan on, the transition (especially when MJO is in phase 6 but even afterward) could easily be back and forth cold and mild for short intervals. I think that's a major reason the current 2 week models look indecisive whereas in reality I think it is because you have cold coming in. mild replacing temporarily , cold again, etc. until the cold become more dominant. But remember that even in cold dominated, there are often some mild days interspersed as each Arctic high goes by in advance of the next one. The +PNA will often relax a little in between Arctic highs. Actually, that is better for winter storm potential.
 
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Yes, I think it is a bad model and I don't always follow it but the latest is fwiw either near or cooler than normal in the SE US every of the 5 day period after days 1-5 and it supposedly has a warm bias. Precip pattern looks ok, too.
 
GaWx said:
@Webberweather53 per Radiant met, you may already know this but the GEFS MJO forecast in phases 6-7 is so strong and much stronger than the EPS because it has a strong WWB whereas the EPS doesn’t.
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The reason the GFS has a stronger phase 6-7 MJO event isn't because it's showing a stronger WWB per say, the WWB is only really indicative of a bigger MJO event but it doesn't get to the heart of why the GFS has a bigger MJO event than the EPS. Convective parameterization schemes in the model & how it handles tropical-extratropical interactions, mountain torques, etc actually gets to the root of the discrepancy.
 
Possibly two hits before 200hrs. Happy hours indeed. That said you can see the west shift of the big ridge over the midwest happening 270hrs or so. Probably see the GFS trend toward its ensemble group.
 
Kylo said:
Most on the board will like this. Low heights off Newfoundland. PNA ridge nosing into HB.

We hug these runs.

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And to put it more simply, it is after a transition 1/1-2 absolutely nonstop very cold in the SE US 1/3-10 with then no end in sight. This is by a good margin the coldest run of any GEFS and probably also EPS yet. It has frigid written all over it. It even looks like it is establishing an -AO by the end of the run!
 
ATLwxfan said:
Atlanta will never get snow from a clipper.


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ATLwxfan said:
I guess that’s progress but ATL watching from the sidelines again.


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Pardon the Christmas evening intrusion, but ... (and this ain't Gainesville, GA) ... ;)

Now back to family ... and no snow ...
 
GaWx said:
And to put it more simply, it is after a transition 1/1-2 absolutely nonstop very cold in the SE US 1/3-10 with then no end in sight. This is by a good margin the coldest run of any GEFS and probably also EPS yet. It has frigid written all over it. It even looks like it is establishing an -AO by the end of the run!
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The cold on the EPS isnt just from a few freezing members either. Incredible agreement at 300 hours.
 
I think we’re trending towards a December 2017 redux on a smaller scale in the first week of January
 
Not bad at all. Positive PNA and -EPO bring in possibly frigid air. Keep the STJ alive and we could be looking at a winter storm for most of the South sometime within the next 2-3 weeks if we continue to see the Pattern like the GEFS is showing.
 

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The fact that half of the gefs ensembles show some snow accums for me already is an amazing signal itself, also looks like the gefs shows a weak -nao if I'm not mistaken and a beautiful +pna 240+
 
And to think 24hrs ago people were talking about wearing shorts and flip flops and summer temps. #SEWINTERS


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NoSnowATL said:
I’m not concerned, we will get one or two this year. Feels like a February type of year for a ATL.


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Sorry I realize I’m being a little MBY-ish but after being on the sidelines in December, just hoping to get in on the action. Though I realize our time is typically late winter.


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ATLwxfan said:
Sorry I realize I’m being a little MBY-ish but after being on the sidelines in December, just hoping to get in on the action. Though I realize our time is typically late winter.


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I feel your pain, MBY has been on the sidelines for a few years and SC as well.


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