okie333 Posted October 13, 2011 Share Posted October 13, 2011 Sorry if there's something wrong with making a topic here, but I thought I'd mention something I just now discovered. I have been looking at snow depth maps from TwisterData and InstantWeatherMaps for a while, and I noticed that the TD maps were always higher, usually by a factor of about 2. Now I just figured out why. TWISTERDATA DOES NOT USE SNOW DEPTH TO MAKE THEIR SNOW DEPTH MAPS!!! From the maps I have posted below, you can see that TwisterData takes the Snow Depth Water Equivalent and multiplies by 10. While this is passable for snowfall amounts, for snow depth it is abysmal, usually way too high; as compaction usually reduces the ratio to 1:6 or lower. It would be wise to solely use InstantWeatherMaps.com for snow depth maps unless and until TD corrects this error; I have verified their accuracy with the original GRIB files, not to mention, they have snow depth in the native 0.205-degree GFS grid for short range and the native 0.625-degree GFS grid for long range and are the only site that does so to my knowledge... plus the maps are out MUCH faster than TD. InstantWeatherMaps snow depth: TwisterData snow depth: Heh, there's a difference... Now compare the TwisterData map to this one... imagine multiplying the bottom map's values by 10: InstantWeatherMaps snow depth water equivalent: Perfect match, minus the resolution differences and the "jaggies" that the TD analysis program adds to the map Link to comment Share on other sites More sharing options...
Chicago Storm Posted October 13, 2011 Share Posted October 13, 2011 lol we get it. Link to comment Share on other sites More sharing options...
okie333 Posted October 13, 2011 Author Share Posted October 13, 2011 lol we get it. Sorry, I was just pointing out something... people have been posting these maps (I mean the TwisterData maps... IWXM is great for the GFS) without even knowing that they are wrong... many fantasy posts so far this season have been fueled by incorrect (or rather, exaggerated) information. Sadly InstantWeatherMaps does not have the NAM up yet, but for now you can use the NAM Graphics page... it has lots of latency though. Or you can divide the TwisterData maps by 2, but that will only produce a rough estimate. Link to comment Share on other sites More sharing options...
PhineasC Posted October 13, 2011 Share Posted October 13, 2011 Snow maps are always wrong. Only weenies look at them. Link to comment Share on other sites More sharing options...
ORH_wxman Posted October 13, 2011 Share Posted October 13, 2011 I'm not sure people generally use the models for snow depth data in the future. Most just look at the snow maps for total snowfall rather than depth...and even that is obviously quite dubious given the model's accuracy. But you are correct that twister obviously over estimates future depth. Link to comment Share on other sites More sharing options...
JoMo Posted October 13, 2011 Share Posted October 13, 2011 I love snow maps, even if they don't come true. The more the better. Link to comment Share on other sites More sharing options...
phlwx Posted October 13, 2011 Share Posted October 13, 2011 I'm not sure people generally use the models for snow depth data in the future. Most just look at the snow maps for total snowfall rather than depth...and even that is obviously quite dubious given the model's accuracy. This. Other than some 14 year old weenie who wants to know snow depth because it may increase the slim odds of school being canceled I'm not sure many really give a damn about snow depth. Link to comment Share on other sites More sharing options...
tamarack Posted October 13, 2011 Share Posted October 13, 2011 This. Other than some 14 year old weenie who wants to know snow depth because it may increase the slim odds of school being canceled I'm not sure many really give a damn about snow depth. Hoping this was intended as hyperbole, as lots of folks over 14 are quite interested, or why northern states have extensive snow-sampling regimes for hydro supply and flood threat evaluation (among other things.) Plus snowmobilers, x-c skiers, wildlife biologists, and so forth. Link to comment Share on other sites More sharing options...
icebreaker5221 Posted October 13, 2011 Share Posted October 13, 2011 Nice find Okie. While I agree that no one should use forecast snow depth maps to create a snowfall forecast, they can be a quick and dirty way to estimate where it's going to snow and roughly how much, and determine an approximate rain/snow line when you don't have time to look at forecast soundings, PBL temps, etc. Link to comment Share on other sites More sharing options...
phlwx Posted October 13, 2011 Share Posted October 13, 2011 Hoping this was intended as hyperbole, as lots of folks over 14 are quite interested, or why northern states have extensive snow-sampling regimes for hydro supply and flood threat evaluation (among other things.) Plus snowmobilers, x-c skiers, wildlife biologists, and so forth. Most who fall into those categories don't look at model maps for snow depth (unless it's a skier wondering what the depth is going to be on Day 10 from when s/he looked at the map if they were planning a trip) considering there are better sources of information for that information, especially on the hydro side. They would probably sample NHORSC data for real time info first and foremost (how much water is in that snowpack, for starters). Link to comment Share on other sites More sharing options...
okie333 Posted October 15, 2011 Author Share Posted October 15, 2011 Today's map Snowy for Halloween! Did you even read the thread? 0_o Link to comment Share on other sites More sharing options...
BethesdaWX Posted October 15, 2011 Share Posted October 15, 2011 Did you even read the thread? 0_o zooom Link to comment Share on other sites More sharing options...
wxmeddler Posted October 15, 2011 Share Posted October 15, 2011 Did you even read the thread? 0_o No, I only read and post maps that have the highest totals /:weenie: Link to comment Share on other sites More sharing options...
OKpowdah Posted October 16, 2011 Share Posted October 16, 2011 No one cares. No one actually uses those maps for anything. Link to comment Share on other sites More sharing options...
okie333 Posted October 20, 2011 Author Share Posted October 20, 2011 No one cares. No one actually uses those maps for anything. Yes they do... I see them posted here and on Accuweather Forums all the time. Link to comment Share on other sites More sharing options...
JoMo Posted October 20, 2011 Share Posted October 20, 2011 No one cares. No one actually uses those maps for anything. I do, it shows where the model is pinpointing the possibility of snow, plus it's fun to see the outrageous totals. Link to comment Share on other sites More sharing options...
okie333 Posted November 8, 2011 Author Share Posted November 8, 2011 EDIT: Please delete this post... it appears RaleighWX's maps are fine, aside from being a bit jagged. I could have sworn they had the TwisterData problem during the October snowstorm though... Link to comment Share on other sites More sharing options...
Wow Posted November 8, 2011 Share Posted November 8, 2011 EDIT: Please delete this post... it appears RaleighWX's maps are fine, aside from being a bit jagged. I could have sworn they had the TwisterData problem during the October snowstorm though... I remember last winter him saying that he had corrected his snow depth maps. I believe they used to have that problem. Link to comment Share on other sites More sharing options...
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