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cae

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  1. The models came into agreement around 6 days out for January 2016. There was a strong signal on the ensembles, but this is what it looked like 7 days out:
  2. https://www.esrl.noaa.gov/psd/data/composites/day/
  3. Moving this conversation to the new thread... Looks about right. Here's a composite of the good years you listed. And here's a composite of the bad ones. And here's the GEFS from March 4th to 9th this year.
  4. February Banter Thread

    Still has some leftover snow from a snowman this evening. 72 degree snowball fights are fun.
  5. February Mid/Long Range Discussion 2

    I did put it together, thanks. It probably looks like more work than it was. I just pulled data from here and put it into Excel. http://w2.weather.gov/climate/local_data.php?wfo=lwx
  6. February Mid/Long Range Discussion 2

    With the discussion recently about temps and March snow, I was curious as to what the historical relationship is. The below plot shows Jan-Feb-March temps vs. snowfall for Baltimore for all years since 1884. The vertical lines show the average temps for each month over all years. (In case you're curious, the month with 50" was February 2010.) The first thing that comes to mind is that there's clearly a relationship between temps and snow. In March months when we had above-average temps, Baltimore got an average of 1.9" of snow. When we had below-average temps, Baltimore got an average of 6.2". We've never had snow in a March with average temps above 50, and we've always had snow in years when average March temps were below 39.8 (4 degrees below the long-term average). But there's also a lot of spread. 1942 stands out as a month in which the temps were more than 3 degrees above average but we still got 22" of snow. The other thing I noticed is that given a February and March with the same average monthly temperature, we'll probably get more snow in March. It's better to be in the upper 30s in March than in February. Of course usual caveats apply. This is all broad brush analysis, and the particulars of every year are different.
  7. February Banter Thread

    I agree. It seems like there have been more personal attacks this year. I wonder if it's been exacerbated by the number of people who seem to "like" them. At times this forum reads like a bunch of schoolkids cheering on bullies in a playground. Everyone on this forum has made bad posts, myself included. And everyone has their own personal issues they are dealing with. We're all here because we love weather, an odd sickness that apparently cuts across all types. Some might not be as mentally sharp as others, some might be struggling with issues in their personal lives, and some are still kids. In the quiet periods between storms, I think this forum works best when people feel like they can come here to learn something, and I wonder how many potential posters are scared off by watching other posters get torn down. If we're in storm mode, then by all means let the mods clear out the bad posts. But over the years I've learned that insulting bad posters doesn't make them better. Teaching them does.
  8. February Mid/Long Range Discussion 2

    Subtropics, the reasons people disagree with this post are: 1) The upcoming torch over the next week or so will be gone by March. 2) You're right that surfaces, asphalt roads in particular, will be warmer in March in the daytime due to sun angle. But in a strong storm the solar radiation will be partially blocked by the clouds, and snow will come down at rates that are fast enough to overcome the remaining solar heating. Once the first layer of snow accumulates on the surface, about 80% of the solar radiation will be reflected by the snow, limiting further warming of the ground.
  9. PD3.5 Lite Obs and Nowcasting

    ICON did pretty well too. Picked up the storm about as soon as it was in range and never lost it.
  10. Post-event model discussion

    A few thoughts on model performance for 02/17/18: 1. Kuchera ratios generally performed better than snow depth, especially for the Euro. The above Euro snow depth plots look horrible, but the Kuchera ratio plots were much closer to reality. For comparison, here's the Kuchera ratio plot for the Euro's last run before the storm. 2. Generally I don't put much weight in ops beyond 5 days, but the long-range performances of the Euro, GGEM, and ICON were impressive. The Euro picked up on the snow threat as soon as it entered its 240-hour window. It kept it for five runs, then lost it for four runs, then picked it up again 120 hours out and never lost it. The GGEM picked up on the storm 156 hours out and never lost it, and the ICON picked up on the storm at least 156 hours out and never lost it. I can't find images back that far, but I think the ICON got the storm as soon as it was within its 180-hour range. The GFS kept the storm suppressed for too long, first finding it 114 hours out and then losing it before finding it for good 102 hours out. I want to point out that this does not mean the GFS did poorly. It's not normal for ops to lock on to storms 6 1/2 days out. But someone who was focused on the Euro and GFS ops might have missed what the GGEM, ICON, and many ensemble members were indicating nearly a week in advance. It's hard to know which model is going to have the right idea far in advance. For the Super Bowl ice storm, it was the GFS. (If I find time I'll try to add that one to this thread.) 3. The Euro seemed to do a good job with qpf, and so did the ICON. The ICON calculates its own snow ratios, which paint a more impressive picture than the snow depth maps shown above. It consistently called for a widespread 1-3", with some relatively minor run-to-run fluctuations, and that's eactly what we got. The details of who got what were less consistent. 4. The RGEM ensemble did a nice job of picking up on the jackpot zone in central MD early.
  11. PD3.5 Lite Obs and Nowcasting

    The ICON stuck with the basic idea of a widespread 1-3" all week, with relatively minor fluctuations. Looks like it was right. I like that the ICON calculates its own ratios, taking some of the guesswork out of figuring out whether we should use Kuchera, snow depth, etc.
  12. PD3.5 Lite Obs and Nowcasting

    Model comparison is up. I'll add verification data when it becomes available. https://www.americanwx.com/bb/topic/50849-post-event-model-discussion/?do=findComment&comment=4829155
  13. Post-event model discussion

    February 17, 2018. Below is the stage IV precipitation analysis (verification data) for the event. The color scale is the same as used for the model runs. Below are the 00z and 12z model runs up to the event. The Euro is top left, GFS is top right, GGEM is bottom left, and ICON is bottom right. This gif starts 12 hours before the last run. Only the last two runs are shown because there was rain on the two days leading up to the event, and weather.us doesn't have a way to distinguish between the precip totals. To get a better sense on how the models did in predicting snow, I plot the snow depth maps below. Snow depth is not a great metric because 1) Every model seems to calculate "snow depth" differently. (The Euro appears to use a more generous algorithm than the other models.) 2) There is something wrong with the snow depth maps for the GGEM on weather.us. It appears to ignore all depths below 2", which makes it look like the GGEM predicted no snow in areas where it predicted low snow depths. Unfortunately, it's the only metric of snowfall available for all four models on weather.us. The Euro is top left, GFS is top right, GGEM is bottom left, and ICON is bottom right. This gif starts 216 hours before the last run. For comparison with teh above plots, here are the reported snowfall totals from LWX.
  14. PD3.5 Lite Obs and Nowcasting

    About 2 1/4" here, but most surfaces have 0.25" - 0.5" less because accumulations started later. There was a lot of compaction. In the last 2-3 hours of the storm, cleared areas gained about an inch, but areas with existing snow cover only gained about 1/2". I suspect if I'd been clearing and measuring repeatedly, the total would probably be closer to 3".
  15. PD3.5 Lite Obs and Nowcasting

    RGEM says you guys are next.
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