ers-wxman1 Posted March 16, 2014 Share Posted March 16, 2014 Probably mainly unknown. I should mix in some praise too. You guys have one of the hardest CWAs to forecast for in the country and a huge population plus powerful eyes all around. I recognize there are many challenges and you all do about as well as can be reasonably expected in most cases. I hold NWS in very high regard on the whole. Glad you see that thanks. Our Cwa is 27,000 square miles. Back in my days as a Senior Forecaster at WFO ABQ, I had to deal with 90,000 sq miles with varied terrain. I would supervise shifts with TOR watches on the planes, Red Flag warnings and snow in the mountains. It was crazy! Link to comment Share on other sites More sharing options...
AlaskaETC Posted March 16, 2014 Share Posted March 16, 2014 Local forecasters are actually in lockstep with most other forecasts! Link to comment Share on other sites More sharing options...
yoda Posted March 16, 2014 Share Posted March 16, 2014 RGEM looks south from 18Z I hate collapses w/in 24 hrs from any model EDIT: not that it's a total collapse, but it's cutting back It is a lot south... 5mm on the 36 RGEM map for DCA Link to comment Share on other sites More sharing options...
Scarlet Pimpernel Posted March 16, 2014 Share Posted March 16, 2014 I've heard this before, but at some point I'll ask someone to explain this to me. Does this mean that if at some point the Euro gets to the resolution the NAM is currently at, it will be useless past 48 hours? I always thought the reason the NAM was pretty bad past 48 hours was because it's a regional model. Big difference is that the Euro is a global model, whereas the NAM is regional and relies upon boundary conditions fed in from a global (the GFS in that case). The Euro is actually quite high resolution, though offhand I cannot recall exactly what. GFS is currently...T574 for horizontal resolution I think? Which is ~25km. Link to comment Share on other sites More sharing options...
mitchnick Posted March 16, 2014 Share Posted March 16, 2014 RGEM is about .2" Link to comment Share on other sites More sharing options...
mitchnick Posted March 16, 2014 Share Posted March 16, 2014 It is a lot south yeah, and it was about this time frame that it came way south on 3/3 Link to comment Share on other sites More sharing options...
Scarlet Pimpernel Posted March 16, 2014 Share Posted March 16, 2014 It is a lot south... 5mm on the 36 RGEM map for DCA Ugh!! Hate to see that. Still so much uncertainty just when we thought we're getting near some kind of reasonable idea. Link to comment Share on other sites More sharing options...
yoda Posted March 16, 2014 Share Posted March 16, 2014 Well so far tonight on the 00z runs, we have NAM/4km NAM/SREFs which would say 3-5 DCA area... and RGEM just said lulz try for 1" Link to comment Share on other sites More sharing options...
high risk Posted March 16, 2014 Share Posted March 16, 2014 If it is a rainstorm, why is the NAM showing it on snowfall? The problem is that the NAM snow depth parameter that comes directly out of the model was never intended to be used for actual snow accumulation. It was meant as an accounting feature for the land-sfc model. If the precip falling is over 50% frozen, it gets tallied as all snow in the land-sfc model. So you can have 1" of liquid that is an almost equal mix of sleet and rain, and it will in effect tally 10" of snow. Some places plot and distribute this parameter as actual model snowfall, and that's not what it is. We at EMC are ultimately responsible for this, as the parameter is labeled as snow depth, and I can't blame customers for thinking it's really snowfall. The good news is that the upcoming NAM upgrade will treat this parameter in a more realistic way. It still really shouldn't be used to forecast accumulations, but it will be more reasonable, and we're headed towards eventually having it really represent accumulating snowfall. Link to comment Share on other sites More sharing options...
Ian Posted March 16, 2014 Share Posted March 16, 2014 RGEM is about .2"Don't worry the model is much better than it used to be. Link to comment Share on other sites More sharing options...
Bob Chill Posted March 16, 2014 Share Posted March 16, 2014 I've heard this before, but at some point I'll ask someone to explain this to me. Does this mean that if at some point the Euro gets to the resolution the NAM is currently at, it will be useless past 48 hours? I always thought the reason the NAM was pretty bad past 48 hours was because it's a regional model. No, euro will always improve. Resolution is relative to the job the model is meant to do. Globals are amazing for what they do. They smooth things out because they aren't designed to forecast a zip code. It's that same smoothing that makes things like precip edges not being modeled at accurately as short range guidance Each piece of guidance has strengths and weaknesses. All short range stuff goes haywire late but is really good closer in. We've seen the rap being crazy at hr18. It would be fun to see a rap solution out to 84 hours. It would show snow in July. But the rap/hrrr are deadly accurate close in their range Link to comment Share on other sites More sharing options...
Scarlet Pimpernel Posted March 16, 2014 Share Posted March 16, 2014 Well so far tonight on the 00z runs, we have NAM/4km NAM/SREFs which would say 3-5 DCA area... and RGEM just said lulz try for 1" Guess we'll see what the GGEM says, and the GFS. I'm not going to stay up for the Euro. Was really hoping the 00Z NAM was stabilizing things somewhat, and we'd come away reasonably pleased with the 00Z suite. We still could, but that exclamation point by the RGEM sucks. Link to comment Share on other sites More sharing options...
Bob Chill Posted March 16, 2014 Share Posted March 16, 2014 Don't worry the model is much better than it used to be. I'm worried Link to comment Share on other sites More sharing options...
hosj III Posted March 16, 2014 Share Posted March 16, 2014 Don't worry the model is much better than it used to be. It was the last to go south on 3/3. Link to comment Share on other sites More sharing options...
nj2va Posted March 16, 2014 Share Posted March 16, 2014 It is a lot south... 5mm on the 36 RGEM map for DCA Wow, that's about a 1/3 of what it was at 18z. RGEM nailed 3/3 so it may be onto something. Link to comment Share on other sites More sharing options...
hosj III Posted March 16, 2014 Share Posted March 16, 2014 Wow, that's about a 1/3 of what it was at 18z. RGEM nailed 3/3 so it may be onto something. Uhh... It was the last to go south. NAM was the first. Link to comment Share on other sites More sharing options...
mitchnick Posted March 16, 2014 Share Posted March 16, 2014 It was the last to go south on 3/3. nope http://www.americanwx.com/bb/index.php/topic/43069-march-2-3-disco-part-iii/?p=2850526 Link to comment Share on other sites More sharing options...
chris87 Posted March 16, 2014 Share Posted March 16, 2014 The reason I don't look at the nam past 48 hours is because of its high resolution. Tiny errors with initial conditions become grand canyon sized errors down the line. It should stop at 48-54 like the rgem. Nam is a good tool for certain things. And a monster ull at the end of its run with zero support is nothing more than a massively magnified error. I know most know this but it's always worth repeating It has much less to do with resolution and more to do with it being a regional model that relies on having boundary conditions provided during integration which leads to a new set of issues that global spectral models don't have to deal with. Link to comment Share on other sites More sharing options...
mitchnick Posted March 16, 2014 Share Posted March 16, 2014 It has much less to do with resolution and more to do with it being a regional model that relies on having boundary conditions provided during integration which leads to a new set of issues that global spectral models don't have to deal with. yep, a boy in a bubble and the bubble has a hole Link to comment Share on other sites More sharing options...
high risk Posted March 16, 2014 Share Posted March 16, 2014 It has much less to do with resolution and more to do with it being a regional model that relies on having boundary conditions provided during integration which leads to a new set of issues that global spectral models don't have to deal with. and it's using 6-hr old boundary conditions (i.e. those from the previous GFS cycle) which makes it even tougher. Link to comment Share on other sites More sharing options...
Huffwx Posted March 16, 2014 Share Posted March 16, 2014 Well, I like the RGEM I know this form will B & M if you don't get snow up there, but we could use a nice event down here. Like Hi Res NAM and RGEM bullzeye this far out. Interesting is that if you look at soundings, at KLYH wet bulbs are already below freezing at 7am. (hope that is correct) I'm planning ratios at 7-1 once snow is falling. I figured between .5 and .8 falls as snow, so that gives me 3.5 to 5.6 Link to comment Share on other sites More sharing options...
Scarlet Pimpernel Posted March 16, 2014 Share Posted March 16, 2014 It has much less to do with resolution and more to do with it being a regional model that relies on having boundary conditions provided during integration which leads to a new set of issues that global spectral models don't have to deal with. I cannot recall exactly how the boundary conditions are applied, so will ask here. My understanding (such as it is) is that the NAM for, say, the 00Z cycle uses the 6-h forecast from the 18Z GFS as boundary conditions. But I cannot remember offhand if BCs are applied throughout the entire NAM run, or only at the start? Link to comment Share on other sites More sharing options...
Ian Posted March 16, 2014 Share Posted March 16, 2014 I'm worriedFunny today I noticed all sorta of ads for Canada on the metro https://twitter.com/islivingston/status/444922953986478080 Link to comment Share on other sites More sharing options...
Yeoman Posted March 16, 2014 Share Posted March 16, 2014 Steve Rudin ABC7 @SteveRudinABC7 3m 2" to 4" for the #District - higher amounts south. Keep in mind models don't account for snow that will melt on contact at the start. What's Al Roker's take? Link to comment Share on other sites More sharing options...
Scarlet Pimpernel Posted March 16, 2014 Share Posted March 16, 2014 Funny today I noticed all sorta of ads for Canada on the metro https://twitter.com/islivingston/status/444922953986478080 I saw that too...yeah kinda funny! Link to comment Share on other sites More sharing options...
chris87 Posted March 16, 2014 Share Posted March 16, 2014 No, euro will always improve. Resolution is relative to the job the model is meant to do. Globals are amazing for what they do. They smooth things out because they aren't designed to forecast a zip code. It's that same smoothing that makes things like precip edges not being modeled at accurately as short range guidance Each piece of guidance has strengths and weaknesses. All short range stuff goes haywire late but is really good closer in. We've seen the rap being crazy at hr18. It would be fun to see a rap solution out to 84 hours. It would show snow in July. But the rap/hrrr are deadly accurate close in their range Small but important correction the ecmwf is now T1279 which is around 16 km so not much different than the NAM so don't give too much thought to resolution differences when the important distinction is between regional and global modeling Link to comment Share on other sites More sharing options...
chris87 Posted March 16, 2014 Share Posted March 16, 2014 I cannot recall exactly how the boundary conditions are applied, so will ask here. My understanding (such as it is) is that the NAM for, say, the 00Z cycle uses the 6-h forecast from the 18Z GFS as boundary conditions. But I cannot remember offhand if BCs are applied throughout the entire NAM run, or only at the start? I'm not sure of the operational specifics but boundary conditions are needed for the entire simulation in regional models. Link to comment Share on other sites More sharing options...
Bob Chill Posted March 16, 2014 Share Posted March 16, 2014 It has much less to do with resolution and more to do with it being a regional model that relies on having boundary conditions provided during integration which leads to a new set of issues that global spectral models don't have to deal with. Thanks Chris. You know a lot more about this stuff than me. In my simpleton view I've always thought that the same things that make the nam do well with fine details early in the run make it become really inaccurate later on. Is this a fair assessment for a hobbyist? Link to comment Share on other sites More sharing options...
Scarlet Pimpernel Posted March 16, 2014 Share Posted March 16, 2014 I'm not sure of the operational specifics but boundary conditions are needed for the entire simulation in regional models. Ahhh, OK...thanks. So then it's using the GFS forecasts (from 6 hours prior) throughout integration. Guess that makes sense, you can't just "drop" the BCs after the initialization, have to keep them going throughout. Link to comment Share on other sites More sharing options...
high risk Posted March 16, 2014 Share Posted March 16, 2014 Ahhh, OK...thanks. So then it's using the GFS forecasts (from 6 hours prior) throughout integration. Guess that makes sense, you can't just "drop" the BCs after the initialization, have to keep them going throughout. yes, that's basically it in a nutshell. But the key is that, because we are running the NAM before the GFS, the 6-hr old GFS has to supply the boundary conditions. In a perfect world, the GFS would run first, and then the NAM would use it for boundaries. Link to comment Share on other sites More sharing options...
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