Personal simulator vs NWS forecast

[brunota2003]

My parents live in central Kentucky, and just recently I happened to stumble across a personal model that can be designed for any site you wish, the guy designs the software to model your point as best as possible and I've heard quite a few good reviews about it (Wxsim for any curious people). Being the curious person I am, and wanting something to play with, I bought it with the data being set up for my parents' valley and figured this winter storm would be a good first test run for that particular location. It won't be perfect, nothing ever is, and I did not have any weather station data at the time for him to check out to see about any biases (I will in a few months though, got a wx station set up while home on leave). I just ran a forecast at 11 pm on the 28th. The forecast goes out until Sunday, so we'll see. I am mainly interested in the snow amounts at this time

NWS forecast (Last Update: 10:42 pm EST Jan 28, 2010):

Overnight: Mostly cloudy, with a low around 16. North northeast wind around 7 mph.

Friday: A 30 percent chance of snow, mainly after 5pm. Cloudy, with a high near 27. Northeast wind around 7 mph.

Friday Night: Snow, mainly after 9pm. Steady temperature around 24. East northeast wind between 7 and 10 mph. Chance of precipitation is 100%. New snow accumulation of 1 to 3 inches possible.

Saturday: Snow likely, mainly before 9am. Cloudy, with a high near 27. Northeast wind between 10 and 13 mph, with gusts as high as 18 mph. Chance of precipitation is 60%.

Saturday Night: A 10 percent chance of snow before 7pm. Partly cloudy, with a low around 8. North wind between 5 and 7 mph.

Sunday: Sunny, with a high near 28.

Sunday Night: Mostly clear, with a low around 13.

WXSim:

Tonight:
Fair to partly cloudy in the evening, becoming partly to mostly cloudy after midnight. Low 22. Wind north-northeast around 4 mph.

Friday:
Mostly cloudy to cloudy in the morning, becoming cloudy in the afternoon. A slight chance of snow in the afternoon. High 35. Wind northeast around 3 mph. Chance of precipitation less than 20 percent. Precipitation (liquid equivalent) mostly less than a tenth of an inch. Little or no snow accumulation expected.

Friday night:
Dense overcast. A chance of snow in the evening, then snow likely after midnight. Low 21. Wind chill down to 14. Wind east-northeast around 6 mph. Chance of precipitation 70 percent. Precipitation (liquid equivalent) mostly between a quarter and half an inch. Snow accumulation 3 to 5 inches.

Saturday:
Dense overcast in the morning, becoming cloudy in the afternoon. Patchy light fog in the morning. A chance of snow in the morning, then a slight chance of snow in the afternoon. High 28. Wind east-northeast around 6 mph. Chance of precipitation 30 percent. Precipitation (liquid equivalent) mostly less than a tenth of an inch. Little or no snow accumulation expected.

Saturday night:
Partly cloudy in the evening, becoming mostly clear after midnight. Patchy light fog after midnight. Low 6. Wind north-northeast around 4 mph.

Sunday:
Sunny. Patchy light fog in the morning. High 34. UV index up to 3. Wind west near calm in the morning, becoming 6 mph in the afternoon.

Sunday night:
Clear. Patchy light fog after midnight. Low 5. Wind west around 3 mph in the evening, becoming southwest after midnight.

[brunota2003]

Well, it seems there has been a change in forecast, up for the NWS and down for the simulator. The 12Z RAOBs have not come out yet, and am interested in how that will change the sim's forecast output. But, for grins and giggles, here is the NWS forecast (last updated at 5:05 am and valid starting at 8 am) and the sim run I just ran using 07 LST data and 00Z RAOBs.

NWS:

Today: A 30 percent chance of snow, mainly after 4pm. Cloudy, with a high near 27. Northeast wind around 6 mph.

Tonight: Snow, mainly after 9pm. The snow could be heavy at times. Steady temperature around 25. East northeast wind between 7 and 11 mph. Chance of precipitation is 100%. New snow accumulation of 1 to 2 inches possible.

Saturday: Snow likely, mainly before 11am. Cloudy, with a steady temperature around 24. Northeast wind between 8 and 11 mph, with gusts as high as 18 mph. Chance of precipitation is 70%. New snow accumulation of 1 to 2 inches possible.

Saturday Night: A 10 percent chance of snow before 7pm. Cloudy during the early evening, then gradual clearing, with a low around 8. North northeast wind around 6 mph becoming calm.

Sunday: Sunny, with a high near 30. Calm wind becoming west southwest between 4 and 7 mph.

Sunday Night: Mostly clear, with a low around 13.

Monday: Mostly sunny, with a high near 36.

Monday Night: A 20 percent chance of snow. Mostly cloudy, with a low around 23.

Note the NWS is calling for 2 to 4 inches of snow. Wxsim is now only calling for around 2 inches, whereas before it was 3 to 5 inches. Another side note, the NWS is calling for 1 to 2 inches tonight, with 1 to 2 inches tomorrow during the day...where the sim is calling for all accumulating snow to fall tonight.

Wxsim (ran at 7:45, using 07 METAR and 00Z RAOB, along with the other stuff it uses):

Today: Cloudy. High 29. Wind northeast around 7 mph.

Tonight: Dense overcast. Snow likely. Low 22. Wind chill down to 11. Wind northeast around 10 mph. Chance of precipitation 70 percent. Precipitation (liquid equivalent) mostly around a quarter of an inch. Snow accumulation around 2 inches.

Saturday: Dense overcast in the morning, becoming mostly cloudy in the afternoon. A slight chance of snow. High 31. Wind northeast around 10 mph. Chance of precipitation 20 percent. Precipitation (liquid equivalent) mostly less than a tenth of an inch. No snow accumulation expected.

Saturday night: Partly cloudy. Patchy light fog after midnight. Low 10. Wind north-northeast around 5 mph in the evening, becoming 2 mph after midnight.

Sunday: Sunny. Patchy light fog in the morning. High 35. UV index up to 2. Wind west-northwest around 2 mph in the morning, becoming 6 mph in the afternoon.

Sunday night: Clear. Patchy light fog after midnight. Low 5. Wind west-southwest around 3 mph.

Monday: Sunny in the morning, becoming partly to mostly sunny in the afternoon. High 40. UV index up to 2. Wind south near calm.

Monday night: Fair in the evening, becoming fair to partly cloudy after midnight. Low 16. Wind south near calm in the evening, becoming southwest after midnight.

And indeed, there is a Winter Weather Advisory posted for the county my parents are in:

341 AM EST FRI JAN 29 2010

...WINTER WEATHER ADVISORY IN EFFECT FROM 7 PM THIS EVENING TO
7 PM EST SATURDAY...

THE NATIONAL WEATHER SERVICE IN JACKSON HAS ISSUED A WINTER
WEATHER ADVISORY FOR SNOW...WHICH IS IN EFFECT FROM 7 PM THIS
EVENING TO 7 PM EST SATURDAY. THE WINTER STORM WATCH IS NO LONGER
IN EFFECT.

* SNOW IS EXPECTED TO START FALLING BY THIS EVENING AND TO CONTINUE
UNTIL SATURDAY EVENING.

* SNOWFALL ACCUMULATIONS OF 2 TO 4 INCHES ARE EXPECTED BY SATURDAY
EVENING.

* SNOWFALL IS EXPECTED TO ACCUMULATE ENOUGH TO CAUSE HAZARDOUS ROAD
CONDITIONS ACROSS EASTERN KENTUCKY...ESPECIALLY OVERNIGHT INTO
SATURDAY MORNING.

* CHANGES IN THE EVENTUAL TRACK OF THIS WINTER STORM WILL AFFECT
EXPECTED SNOWFALL AMOUNTS. STAY TUNED TO FUTURE FORECASTS FOR
POSSIBLE CHANGES TO THE SNOWFALL FORECAST.

[srainhoutx]

Very cool brunota2003! Will be interesting to see how this verifies. Thanks for your service! Are you on leave?

[brunota2003]

I was earlier this month, but not anymore. The model I found prior to going home on leave (the gentleman that creates it is actually a high school teacher, and I thought it would be cool to have him set one up for my parents' place, since I noticed they usually ran below the forecast guidance from the NWS, one night they were forecasting a low of 12 degrees and we bottomed out at 5.8!). My internet here is a little faster than the dial up they have (though overall it is pretty similar) and figured during my off time I could play around with the model and see how close it comes to what they actually get. I wish I could get the data from my weather station, but with them having dial up, I couldn't hook it up to my weather underground account . I did rerun the model around 8:15 am after downloading the 08 EST METAR and the 12Z RAOBs.

Here is what the new text forecast came out with (note it is now saying 2 to 3 inches tonight):

Today:
Cloudy. High 28. Wind northeast around 3 mph in the morning, becoming 7 mph in the afternoon.

Tonight:
Dense overcast. A chance of snow in the evening, then snow likely after midnight. Low 21. Wind chill down to 10. Wind northeast around 11 mph. Chance of precipitation 70 percent. Precipitation (liquid equivalent) mostly around a quarter of an inch. Snow accumulation 2 to 3 inches.

Saturday:
Dense overcast in the morning, becoming cloudy in the afternoon. A chance of snow in the morning, then a slight chance of snow in the afternoon. High 28. Wind northeast around 11 mph. Chance of precipitation 50 percent. Precipitation (liquid equivalent) mostly less than a tenth of an inch. Snow accumulation about a quarter inch.

Saturday night:
Mostly cloudy in the evening, becoming partly cloudy after midnight. Low 12. Wind northeast around 6 mph in the evening, becoming 3 mph after midnight.

Sunday:
Sunny. Patchy light fog in the morning. High 34. UV index up to 2. Wind west-southwest around 2 mph in the morning, becoming 5 mph in the afternoon.

Sunday night:
Clear in the evening, becoming mostly clear after midnight. Low 7. Wind west-southwest around 3 mph.

Monday:
Sunny in the morning, becoming partly to mostly sunny in the afternoon. High 38. UV index up to 2. Wind south-southeast near calm.

Monday night:
Mostly clear in the evening, becoming clear after midnight. Patchy light fog after midnight. Low 10. Wind south-southeast near calm.

The model is designed pretty much around temperatures (he has a degree in physics, if I remember right) and wanted an accurate model in temperatures, but it also gives output on the precip and such (and from what I've read from a few people, it is fairly accurate in both areas). Since I don't have access to the actual highs/lows at the house (besides bugging my mom for them everyday, which I don't want to do), I'll just save the forecasts here and there and look to see how close they were once I get home. I'll have to call home tonight to see what it is doing there and then again tomorrow evening to see how much snow they actually got (and will probably ask for the high/low). NWS says 2 to 4 inches, that run there says 2 to 3 inches now, so.

[shibumi]

Just a note after reading this thread.....

I doubt that what you bought can be called a model...it is a software program that uses some type of blend of the existing model data to generate a forecast.....

Nothing wrong with that of course...just a matter of terms...

To put it simply, even if an individual might be able to create a weather model (like the GFS), there would be no way to input all the data that would be necessary for it to run...the program would have to get the data from somewhere else...and I imagine it would take a hell of a lot of time on a single computer to generate the results....

How are the inputs set up? It is obvious what data it use? Is there any description of where the data comes from?

Locally one of the TV stations has such a program called VIPER.....he always calls it a model, but it is not..it is a software program that pulls data from existing models...basically interprets the results differently from any individual model we have access to the results from.

That is what the NWS does itself and you can see it reflected in their discussions when they give a weighted average from certain models when making their forecast....

It will be interesting to see over time how the program does for you.....you might want to take certain time segments to test it....like look at the short term forecasts and results, say 24-48 hours out.....you could make a spreadsheet for comparisons...

[brunota2003]

Yes, it is a software program and not a true "model" in the sense you would think of with the GFS. It uses GFS model and advection data, along with RAOBs (nearest 3 sites), METER data, GFS/NAM MOS data, FSU Buoy data, NAM FOUS, and it can even import data from a personal weather station to use. The thing that sets it apart though is it is for a specific point on the earth, with terrain for that area input into the software coding and use of historic data from the NCDC for points nearby, along with any weather station history you may have for him to look at. I'll change the title to simulator, before people start thinking I have a super computer in my basement or hidden somewhere in Iraq since I am running the program on a Windows Vista.

[shibumi]

Yes, it is a software program and not a true "model" in the sense you would think of with the GFS. It uses GFS model and advection data, along with RAOBs (nearest 3 sites), METER data, GFS/NAM MOS data, FSU Buoy data, NAM FOUS, and it can even import data from a personal weather station to use. The thing that sets it apart though is it is for a specific point on the earth, with terrain for that area input into the software coding and use of historic data from the NCDC for points nearby, along with any weather station history you may have for him to look at. I'll change the title to simulator, before people start thinking I have a super computer in my basement or hidden somewhere in Iraq since I am running the program on a Windows Vista.

That is interesting!

If you end up with some comparison graphs and such, please post so we can see them!

[brunota2003]

I will. I have saved some of the forecasts here and there and will compare them to what my weather station at the house actually recorded, once we go home from deployment and I can visit my parents again. I am also interested in how it would run if I strictly used the data from my station, though I know it would be no where near as accurate (if it would be at all).

Here is an accuracy test done by the guy that designs the models:
http://www.wxsim.com/accu.htm

Here is info on the customization that goes into the program:
http://www.wxsim.com/custom.htm

And here is some history behind the program and some technical information:
http://www.wxsim.com/tech.htm

[brunota2003]

I did an evening run, running the simulator a little after 9 pm, once I was sure I could access the 00Z RAOBs and the 9 pm METARs. Seems both the NWS and the sim bumped up snowfall totals (NWS updated at 8:50 pm), so will post the evening forecasts for both. NWS is now saying 2 to 6 inches (4 to 6 according to the newly issued WSW) and the sim is saying 2 to 4 inches.

NWS:

Tonight: Snow. Low around 18. Northeast wind around 9 mph. Chance of precipitation is 100%. Total nighttime snow accumulation of 1 to 3 inches possible.

Saturday: Snow, mainly before 2pm. High near 25. Northeast wind between 6 and 10 mph, with gusts as high as 18 mph. Chance of precipitation is 90%. New snow accumulation of 1 to 3 inches possible.

Saturday Night: A 10 percent chance of snow before 7pm. Cloudy, then gradually becoming partly cloudy, with a low around 9. Light northeast wind.

Sunday: Sunny, with a high near 31. Calm wind becoming west southwest between 4 and 7 mph.

Sunday Night: Mostly clear, with a low around 14. Light west southwest wind.

Monday: Mostly sunny, with a high near 36.

Monday Night: Mostly cloudy, with a low around 22.

Wxsim:

Tonight: Dense overcast. Patchy light fog in the evening. A slight chance of snow in the evening, then a chance of snow after midnight. Low 14, but temperatures rising after midnight. Wind chill down to 4. Wind east-northeast around 7 mph in the evening, becoming 12 mph after midnight. Chance of precipitation 60 percent. Precipitation (liquid equivalent) mostly around a tenth of an inch. Snow accumulation 1 to 2 inches.

Saturday: Dense overcast. A chance of snow in the morning, then a slight chance of snow in the afternoon. High 25. Wind east-northeast around 12 mph. Chance of precipitation 60 percent. Precipitation (liquid equivalent) mostly less than a quarter of an inch. Snow accumulation 1 to 2 inches.

Saturday night: Mostly cloudy in the evening, becoming mostly clear after midnight. Patchy light fog after midnight. A slight chance of snow. Low 5. Wind north-northeast around 6 mph in the evening, becoming 2 mph after midnight. Chance of precipitation less than 20 percent. Precipitation (liquid equivalent) mostly less than a tenth of an inch. No snow accumulation expected.

Sunday: Sunny. Patchy light fog in the morning. High 35. UV index up to 3. Wind west-southwest near calm in the morning, becoming 6 mph in the afternoon.

Sunday night: Clear. Low 4. Wind west-southwest around 3 mph.

Monday: Mostly sunny in the morning, becoming partly cloudy in the afternoon. High 40. UV index up to 3. Wind south-southeast near calm.

Monday night: Partly cloudy in the evening, becoming partly to mostly cloudy after midnight. Low 14. Wind south-southwest near calm.

[brunota2003]

Well, my parents said they got about 5 to 6 inches of snowfall total. Win for the NWS this time around in terms of snow totals. Though most of that fell Friday night, so the very first run (predicting 3 to 5 inches Friday Night) was pretty accurate. Mom also said they dropped down to 4 degrees this morning (Sat night), the NWS was calling for 8 and Wxsim 6 degrees on the very first run...and the very last set I posted the NWS said 9 and Wxsim said 5.