Jan 17-18th disco thread--1st big threat of the year

[MN Transplant]

[Ji]

this thread is pretty bad

 

does the 18z NAM carry more weight than the SREF? SREF will likely fold in the next run

[Ian]

does the 18z NAM carry more weight than the SREF? SREF will likely fold in the next run

SREF is supposedly the future of short range model forecasting.. tho im not sure it's there yet. if nothing else it's usually more steady in movement one way or another.

[NOVAForecaster]

I agree. We all know that the models except for the last  NAM (18Z, which we all know is the worst) and the Euro (which is not that good inside of 36 hours) are on board with the snow. Why are we throwing in the towel yet? I won't give up until we see another run or two of the NAM that is against the snow, and other models join in. I stick to my guns of 2-4 inches, and I will not flip-flop on the forecast more than Mitt Romney in election season.

So it's one 18z run(usually a ****ty run) of a ****ty model, and the European.....versus......everyone else? Yeah, not good enough reason to give up just yet.....lets see what the gfs says...

[wxmeddler]

The GFS is not 12km

My bad, I'm so used to using the 4km NAM-CONUS nest, that I thought for a moment it was 12 (Which is the NAM's normal horizontal res.)... Yes, your right the GFS's horizontal resolution is ~28km.

[BristowWx]

15z sref.jpg

Never saw this before so excuse the newbie question. Is the black the mean and the numbers on the left inches based on all the members?

[MN Transplant]

Playing around with the SREF plumes, if you remove the NMBs, which are all very agressive, and the two high outliers of the ARW/NMM, you still end up with a mean of 2" of snow at DCA.  It looks like only 3 members are shutouts.

[yoda]

Never saw this before so excuse the newbie question. Is the black the mean and the numbers on the left inches based on all the members?

yes and yes

[wxmeddler]

Never saw this before so excuse the newbie question. Is the black the mean and the numbers on the left inches based on all the members?

 

Yes, the mean is the black line and all the other lines are the 21 different members of the ensembles. The scale on the left is in inches of snow.

[AlexD]

I agree. We all know that the models except for the last NAM (18Z, which we all know is the worst) and the Euro (which is not that good inside of 36 hours) are on board with the snow. Why are we throwing in the towel yet? I won't give up until we see another run or two of the NAM that is against the snow, and other models join in. I stick to my guns of 2-4 inches, and I will not flip-flop on the forecast more than Mitt Romney in election season.

So it's one 18z run(usually a ****ty run) of a ****ty model, and the European.....versus......everyone else? Yeah, not good enough reason to give up just yet.....lets see what the gfs says...

thank you for being the voice of reason...... It's soo amusing to see the weenies ready to jump off a bridge, based on one model run....and they're been doing it for years...

[chris87]

SREF is supposedly the future of short range model forecasting.. tho im not sure it's there yet. if nothing else it's usually more steady in movement one way or another.

eventually some day we'll be able to run 1000s of simulations each day that better sampling the uncertainty of the system and provide statistically meaningful probabilities....unfortunately probably the more distant future...

[MN Transplant]

Never saw this before so excuse the newbie question. Is the black the mean and the numbers on the left inches based on all the members?

 

Yes.  It would indicate that the SREF mean of all of the members is a little over 4" at DCA.  You can play around with it here:  http://www.spc.noaa.gov/exper/sref/fplumes/

[SnowGoose69]

does the 18z NAM carry more weight than the SREF? SREF will likely fold in the next run

 

I've seen cases before where the 15 or 03Z SREFs have trended or are going heavily in one direction and then the 18 or 06Z NAM proceeds to go the opposite way...I'd say 90% of the time when that occurs the ensuing NAM run goes back the other way and caves and not the other way around...the reason being I think the 15Z SREFs may have 12Z RAOB data and the 18Z NAM as we know does not have the degree of data the 12Z runs do.

[nj2va]

Just so I'm tracking.  If the 18z NAM showed 0.7 QPF, we'd have the same people saying not to trust it, it's the NAM.  Now that it showed nothing at DC, we have the same people saying its right because we get nothing.  Got it.

[Swiscaster]

This is just like boxing day a few years ago, desperately hanging onto the SREFs even after all the real models clearly pulled the plug. Give up th ghost.

[Deck Pic]

Matts just doing a little chest thumping right now...no worries...if DC is getting snow tomorrow he will be a top 3 poster in the obs thread. It will be like the NAM never existed.

 

huh?..I am still leaning toward predicting snow....Do you like the possibility of 0.5 - 0.8" of QPF into DC metro tomorrow?..enjoy leaving the options open!

[MN Transplant]

Playing around with the SREF plumes, if you remove the NMBs, which are all very agressive, and the two high outliers of the ARW/NMM, you still end up with a mean of 2" of snow at DCA.  It looks like only 3 members are shutouts.

 

A visual on why I removed the NMB members.

 

[WxMan1]

Folks,

 

A few things I noticed while at work today, some of this you probably already know (knew):

 

1) The 12Z NAM was the most robust with the liquid equiv...0.50 to 0.75 through the DC metro region, though not all of it snow.

2) GFS was slightly drier (closer to 0.5 for DCA), though with the NAM, both NCEP runs were clearly wetter than the non-NCEP suite.

3) EC/UKMet/CMC at 12Z were all drier for the DC metro region, i.e. less than a quarter inch.

3) The 15Z SREF was consistent with the 09Z version, perhaps a smidge wetter for DC, though still more like in a 0.25 to .50 inch, or lighter than the 12Z NAM/GFS.

 

Now, this was most notable:

 

ALL the high-resolution runs at 12Z, which included the NCEP WRFs (ARW and NMM), NAM CONUS-nest, the NSSL WRF, SPC WRF, and the SSEO mean noted a much TIGHTER pcpn gradient on the northern side -- giving DCA more or less the shaft with a tenth of an inch or less of liquid equivalent pcpn -- while much higher QPF remained over central and srn VA.  What was alarming to me was that the NAM's own CONUS nest version (4km) was remarkably different from the parent 12km run with the moisture gradient on the northern side.  That's never a comforting sign.  It's almost as if the higher res runs were trying to resolve the strengthening deformation (frontogenesis) better, and in doing so, yielded a tighter moisture gradient N-S, thereby drying out the DC area.  Take it FWIW...though I'm hearing (though have not yet seen) the 18Z NAM went farther south with the more appreciable QPF.

 

Very, very high-bust potential forecast either way, because obviously not all the QPF farther south (into cen VA) would be all snow.  Still, that part of the world (EZF-RIC) would stand the best chance on getting in on the deformation axis steadier snows after 21Z or so, to a point where 35-36F can quickly cool to 32-33F.  Looks to me like the event late last year in which the RIC area got 4-6" or so, while little if any fell in the DC area.

[Deck Pic]

Just so I'm tracking.  If the 18z NAM showed 0.7 QPF, we'd have the same people saying not to trust it, it's the NAM.  Now that it showed nothing at DC, we have the same people saying its right because we get nothing.  Got it.

 

It has been explained ad infinitum in this thread that the NAM caved to the other southern guidance and did so in a run closer to the event...and it wasnt a slight adjustment...it was marked...you all enjoy...I am glad we werent sucked in for a week..I hope I am wrong and that the GFS comes in wet....imo there is no real reason not to go with a slightly wetter euro solution until we get more guidance tonight...so maybe .2" for DC..less as you go north and more south with a sharp gradient

[dtk]

I've seen cases before where the 15 or 03Z SREFs have trended or are going heavily in one direction and then the 18 or 06Z NAM proceeds to go the opposite way...I'd say 90% of the time when that occurs the ensuing NAM run goes back the other way and caves and not the other way around...the reason being I think the 15Z SREFs may have 12Z RAOB data and the 18Z NAM as we know does not have the degree of data the 12Z runs do.

Except it has more data as well as more recent data, most notably all of the obs we receive from aircraft (there are lots of flights during the day, so we have plenty of data).  The real problem with interpreting trends in the NAM and SREF is the use of partial cycling.

[Deck Pic]

Folks,

 

A few things I noticed while at work today, some of this you probably already know (knew):

 

1) The 12Z NAM was the most robust with the liquid equiv...0.50 to 0.75 through the DC metro region, though not all of it snow.

2) GFS was slightly drier (closer to 0.5 for DCA), though with the NAM, both NCEP runs were clearly wetter than the non-NCEP suite.

3) EC/UKMet/CMC at 12Z were all drier for the DC metro region, i.e. less than a quarter inch.

3) The 15Z SREF was consistent with the 09Z version, perhaps a smidge wetter for DC, though still more like in a 0.25 to .50 inch, or lighter than the 12Z NAM/GFS.

 

Now, this was most notable:

 

ALL the high-resolution runs at 12Z, which included the NCEP WRFs (ARW and NMM), NAM CONUS-nest, the NSSL WRF, SPC WRF, and the SSEO mean noted a much TIGHTER pcpn gradient on the northern side -- giving DCA more or less the shaft with a tenth of an inch or less of liquid equivalent pcpn -- while much higher QPF remained over central and srn VA.  What was alarming to me was that the NAM's own CONUS nest version (4km) was remarkably different from the parent 12km run with the moisture gradient on the northern side.  That's never a comforting sign.  It's almost as if the higher res runs were trying to resolve the strengthening deformation (frontogenesis) better, and in doing so, yielded a tighter moisture gradient N-S, thereby drying out the DC area.  Take it FWIW...though I'm hearing (though have not yet seen) the 18Z NAM went farther south with the more appreciable QPF.

 

Very, very high-bust potential forecast either way, because obviously not all the QPF farther south (into cen VA) would be all snow.  Still, that part of the world (EZF-RIC) would stand the best chance on getting in on the deformation axis steadier snows after 21Z or so, to a point where 35-36F can quickly cool to 32-33F.  Looks to me like the event late last year in which the RIC area got 4-6" or so, while little if any fell in the DC area.

 

 

Thanks for the info and great post and makes perfect sense...

[Scarlet Pimpernel]

Had to throw that stupid a$$ political comment in there, didn't you?

 

No more so than having one contained in one's avatar picture!    Actually, I thought it was pretty funny...would have been equally funny if someone said "...model changes quicker than Bill Clinton can swap interns" or something like that.

 

Now, back to the weather...

[SnowGoose69]

The old ETA matches the Euro pretty closely although its latest run did go north a bit.

[dtk]

The old ETA matches the Euro pretty closely although its latest run did go north a bit.

Who runs the old ETA?

[Deck Pic]

My point was that you can't just say it had no support. I have no hand in this fight I've always been out of it but I'm not sure what your crusade is about. If u adjust the nam for its known bias of overdoing precip it actually matched up well with the gfs sref and rgem. The ggem And unmet were with the euro. I think it's unfair to imply anyone was basing their forecast on the nam alone. The nam had plenty of support just not from the euro. You seem to have gone full tilt today.

 

in 6 hours the NAM swung from the wettest most robust solution to the driest and biggest whiff....my crusade is the NAM sucks...it has been my crusade for years and I am validated more often than not....

[aldie 22]

huh?..I am still leaning toward predicting snow....Do you like the possibility of 0.5 - 0.8" of QPF into DC metro tomorrow?..enjoy leaving the options open!

No...im not in the predicting business..i do get the sense you like being right though and i definitely know you love snow

[SnowGoose69]

Who runs the old ETA?

 

If you go to the PSU Ewall and click the DGEX links and then go up top to where it says 00/06/12/18 UTC and click there it takes you to a page where you can view the regional breakdowns for the NAM/GFS/ARW and the "NMM" which is the old ETA.

[usedtobe]

Folks,

 

A few things I noticed while at work today, some of this you probably already know (knew):

 

1) The 12Z NAM was the most robust with the liquid equiv...0.50 to 0.75 through the DC metro region, though not all of it snow.

2) GFS was slightly drier (closer to 0.5 for DCA), though with the NAM, both NCEP runs were clearly wetter than the non-NCEP suite.

3) EC/UKMet/CMC at 12Z were all drier for the DC metro region, i.e. less than a quarter inch.

3) The 15Z SREF was consistent with the 09Z version, perhaps a smidge wetter for DC, though still more like in a 0.25 to .50 inch, or lighter than the 12Z NAM/GFS.

 

Now, this was most notable:

 

ALL the high-resolution runs at 12Z, which included the NCEP WRFs (ARW and NMM), NAM CONUS-nest, the NSSL WRF, SPC WRF, and the SSEO mean noted a much TIGHTER pcpn gradient on the northern side -- giving DCA more or less the shaft with a tenth of an inch or less of liquid equivalent pcpn -- while much higher QPF remained over central and srn VA.  What was alarming to me was that the NAM's own CONUS nest version (4km) was remarkably different from the parent 12km run with the moisture gradient on the northern side.  That's never a comforting sign.  It's almost as if the higher res runs were trying to resolve the strengthening deformation (frontogenesis) better, and in doing so, yielded a tighter moisture gradient N-S, thereby drying out the DC area.  Take it FWIW...though I'm hearing (though have not yet seen) the 18Z NAM went farther south with the more appreciable QPF.

 

Very, very high-bust potential forecast either way, because obviously not all the QPF farther south (into cen VA) would be all snow.  Still, that part of the world (EZF-RIC) would stand the best chance on getting in on the deformation axis steadier snows after 21Z or so, to a point where 35-36F can quickly cool to 32-33F.  Looks to me like the event late last year in which the RIC area got 4-6" or so, while little if any fell in the DC area.

 

Good post.  I pretty much agree.  I'm not sure I trust the SREF with a system having such a tight gradient. 

[bjohnson102184]

in 6 hours the NAM swung from the wettest most robust solution to the driest and biggest whiff....my crusade is the NAM sucks...it has been my crusade for years and I am validated more often than not....

 

Its one run......and it hasnt happened yet

[wxmeddler]

...

ALL the high-resolution runs at 12Z, which included the NCEP WRFs (ARW and NMM), NAM CONUS-nest, the NSSL WRF, SPC WRF, and the SSEO mean noted a much TIGHTER pcpn gradient on the northern side -- giving DCA more or less the shaft with a tenth of an inch or less of liquid equivalent pcpn -- while much higher QPF remained over central and srn VA.  What was alarming to me was that the NAM's own CONUS nest version (4km) was remarkably different from the parent 12km run with the moisture gradient on the northern side.  That's never a comforting sign.  It's almost as if the higher res runs were trying to resolve the strengthening deformation (frontogenesis) better, and in doing so, yielded a tighter moisture gradient N-S, thereby drying out the DC area.  Take it FWIW...though I'm hearing (though have not yet seen) the 18Z NAM went farther south with the more appreciable QPF.

 

Completely agreed, and it's what I was trying to get at earlier. It's that the global models are going to make the gradient more diffuse than it will actually be. These convergence zone cut-off are notorious for having grass to 4" within 10 miles and the GFS and other global models and to some extent the Op. NCEP 12km NAM can't handle that kind of gradient. This is what also concerns me also about the SREF, which has a 16km horizontal grid resolution.