Weekend "Storm" Discussion Part III, 2/18-2/19

[MidlothianWX]

Look at your sim radar at 27. Your precip is about gone, and your ground temps are still above freezing.

if the nam is right, richmond itself has boundary layer issues ... no colder than 35 during heavy precip.

TEMPS

2 M (F) 51 44 37 41 36 35

850 MB © 4 2 0 -3 -5 -7

700 MB © -6 -6 -5 -4 -5 -8

500 MB © -18 -17 -16 -17 -20 -21

1000-500 THCK 548 545 545 543 540 536

MOISTURE

2 M DEW POINT (F) 36 32 27 30 32 30

850 MB DP©/RH -6/48 -6/56 -7/60 -4/89 -6/95 -9/85

700 MB DP©/RH -10/71 -12/65 -7/86 -4/99 -5/99 -8/96

500 MB DP©/RH -32/29 -20/80 -20/72 -30/31 -22/83 -23/84

PRCPABLE WTR (IN) 0.50 0.55 0.60 0.64 0.69 0.56

CONV PRECIP (IN) 0.00 0.00 0.00 0.00 0.00

TOTAL PRECIP (IN) 0.00 0.00 0.01 0.18 0.37

This is true. I love me some 850 maps but I knew from the beginning that BL issues would be present.

[WinterWxLuvr]

It may be a terrible model, but you gotta admit that outside of the convection blob rolling through Alabama and Georgia, due east at that, this thing looks pretty anemic to the north.

[Amped]

NAM changes it's mind and says that nyn stream troff that suddenly appeared in western PA out of nowhere on the 18z run isn't going to happen.

I feel a bit stupid for not noticing

[Sparky]

I feel for the forecasters during storms like this

Don't feel for DT. He is too full of himself.

[TalcottWx]

Caves to what? No model was this bad.

If you can't tell what models it caved to i dont know what to say

[Deck Pic]

I have actually seen it where it was wrong until the bitter end (i.e., even as the storm was ongoing it just had no clue what was going on). Groundshog day Feb 1 2011.

I dont take it seriously in the winter and never have......I am told it is a good model for severe, squall lines, etc....Maybe we should just table it in the winter....I'm not sure what value it has?....weather is complex...If it is only capable of handling easy systems, we probably shouldnt pay it much attention....no doubt this was a tough one for all the models though

[TalcottWx]

Don't feel for DT. He is too full of himself.

He really is. I dont know the details on why he left, but oh my god he is self obsessed. Can tell just by reading his final call discussion.

[SnowGoose69]

I have actually seen it where it was wrong until the bitter end (i.e., even as the storm was ongoing it just had no clue what was going on). Groundshog day Feb 1 2011.

One of the models was completely blowing the 1/26 storm last year up north as it was happening, it may have been the NAM as well.

[baroclinic_instability]

I dont take it seriously in the winter and never have......I am told it is a good model for severe, squall lines, etc....Maybe we should just table it in the winter....I'm not sure what value it has?....weather is complex...If it is only capable of handling easy systems, we probably shouldnt pay it much attention....no doubt this was a tough one for all the models though

It has winter utility, believe it or not. It has quite a bit of skill (for whatever reason) in situations where systems go negative tilt or feature very deep upper level PV's undergoing rapid cyclogenesis. Slow moving and deep systems are undoubtedly its forte. NAM also likes trop folds, and it has shown skill in rapidly bombing Miller B type Nor'easters with trop folds. What is worth mentioning here, however, is we are dealing with a "new" NAM since it was completely overhauled this fall.

[Deck Pic]

One of the models was completely blowing the 1/26 storm last year up north as it was happening, it may have been the NAM as well.

I understand NWS has budget constraints and limits on what they can do....I have no doubt it is full of talented mets and programmers....Maybe they can improve the model over the next few years...As far as I am concerned, the body of work is quite clear that this is not a model to be paid any credence in the winter....If mets and other forecasters utilize and rely on it for winter storms, it is not the fault of the NWS....it is the fault of the mets/forecasters....If it comes to fruition that this is a whiff up here and a bust in many other places, it isnt the Governments fault, and I hope people who used the NAM as guidance don't play the blame game....

[ORH_wxman]

I posted this about the NAM in the other banter thread:

Its a strange model but can be pretty good at times...but it needs a certain set of variables that aren't always apparent early on...usually I noticed in systems where hydrostatic approximation is not a good idea is where the NAM succeeds since it is not a hydrostatic model...it simulates the actual convection without hydrostatic assumption. It succeeded in beating the Euro in Jan 12 last year because of this...it also won in Dec 5, 2009 but that system it was less obvious. It wasn't as convective as 1/12/11.

It tends to do terrible in systems with a lot of moving pieces far from the center of circulation IMHO. I don't have any stats to prove this, but just anecdotel when thinking about storms it has succeeded in versus its larger failures.

[Deck Pic]

It has winter utility, believe it or not. It has quite a bit of skill (for whatever reason) in situations where systems go negative tilt or feature very deep upper level PV's undergoing rapid cyclogenesis. Slow moving and deep systems are undoubtedly its forte. NAM also likes trop folds, and it has shown skill in rapidly bombing Miller B type Nor'easters with trop folds. What is worth mentioning here, however, is we are dealing with a "new" NAM since it was completely overhauled this fall.

sure...but I dont sense that the meteorological community at large understands its fortes and biases so to the extent it is put forth as guidance for east coast winter storms....>I think there is a shared responsibility between the forecasting community and the government....Forecasters need to understand the best way to utilize the guidance that is out there and the government has a responsibilty to put out a product that doesn't perform so poorly on the most important aspects....track, QPF, upper level temps, surface temps

[Absolute Humidity]

One of the models was completely blowing the 1/26 storm last year up north as it was happening, it may have been the NAM as well.

It was the NAM, had a 1.25" blob over DC at 24h and barely anything for NJ NYC.

[Coach McGuirk]

NAM looks good for me.

[baroclinic_instability]

I understand NWS has budget constraints and limits on what they can do....I have no doubt it is full of talented mets and programmers....Maybe they can improve the model over the next few years...As far as I am concerned, the body of work is quite clear that this is not a model to be paid any credence in the winter....If mets and other forecasters utilize and rely on it for winter storms, it is not the fault of the NWS....it is the fault of the mets/forecasters....If it comes to fruition that this is a whiff up here and a bust in many other places, it isnt the Governments fault, and I hope people who used the NAM as guidance don't play the blame game....

Yeah I agree, nobody should blame a model for their own forecast. The potential for this to occur has been on the table since the inception of this storm when we knew it would be severely positive tilt. Elongated warm fronts and a very moist GOM will wreak havoc on the guidance should MCS's develop...which is currently occuring. Unfortunately it is difficult to use probability snow total maps with the public...but when you have the potential for massive shifts in snow totals where the synoptic development itself is dependent upon convective activity, that is the solid way to go.

[Ji]

NAM looks good for me.

ya its not going to stick...your in Va beach and the air mass sucks

[Midlo Snow Maker]

damn just catching up looks like a huge whiff for dc, man what a south trend, still looks like southside va into ric get the biggest storm of the year

[baroclinic_instability]

sure...but I dont sense that the meteorological community at large understands its fortes and biases so to the extent it is put forth as guidance for east coast winter storms....>I think there is a shared responsibility between the forecasting community and the government....Forecasters need to understand the best way to utilize the guidance that is out there and the government has a responsibilty to put out a product that doesn't perform so poorly on the most important aspects....track, QPF, upper level temps, surface temps

Trust me I am not defending it at all. Personally I would love to see more "forecasting" these days, but there certainly has been a reliance on models by many forecasters these days. Little effort is put into diagnosing the synoptic/dynamic environment anymore, and too much reliance is put into QPF and the final model output. This is a problem everywhere in forecasting.

[clskinsfan]

NAM looks good for me.

Yeah. If you like rain.

[baroclinic_instability]

I posted this about the NAM in the other banter thread:

Its a strange model but can be pretty good at times...but it needs a certain set of variables that aren't always apparent early on...usually I noticed in systems where hydrostatic approximation is not a good idea is where the NAM succeeds since it is not a hydrostatic model...it simulates the actual convection without hydrostatic assumption. It succeeded in beating the Euro in Jan 12 last year because of this...it also won in Dec 5, 2009 but that system it was less obvious. It wasn't as convective as 1/12/11.

It tends to do terrible in systems with a lot of moving pieces far from the center of circulation IMHO. I don't have any stats to prove this, but just anecdotel when thinking about storms it has succeeded in versus its larger failures.

Full agreement. IMO the NAM is in a "tough" spot since it is non-hydrostatic at 12 km grid. Subgrid scale paramaterizations in a non-hydrostatic model can wreak havoc in certain situations. It is also those traits that make it so useful with deep PV's over moist and intense baroclinic zones. Slow moving single part systems are its forte.

[usedtobe]

I think there are times when you can use the nam so I'm not as negative as some. When all the models have a similar surface and qpf it will have the better temp field on average as it is better with damming events. It also sometimes does a better job with the mesoscale banding and CSI when the system is well behaved.. No model is good with lots of moving parts and the nam is then is usually worse than the GFS and Euro.

[Deck Pic]

Now that we are done bashing the NAM it may be too far south.....doesn't matter much for me but for the places still in the game for good snow, I'd use the GFS tonight as my primary forecasting tool and hope the Euro generally agrees with it...still high bust potential but that is going to be the best forecast.....using those 2 models the best one knows how....The NAM has to be disregarded on this one....

[Coach McGuirk]

ya its not going to stick...your in Va beach and the air mass sucks

I don't live in Virginia Beach.

[clskinsfan]

I don't live in Virginia Beach.

Yeah. You live in Yorktown and have the same boundary temp issues on the NAM.

[ORH_wxman]

Now that we are done bashing the NAM it may be too far south.....doesn't matter much for me but for the places still in the game for good snow, I'd use the GFS tonight as my primary forecasting tool and hope the Euro generally agrees with it...still high bust potential but that is going to be the best forecast.....using those 2 models the best one knows how....The NAM has to be disregarded on this one....

I would agree its probably too far south...for the same reasons I spoke of above. Its non-hydrostatic so it can have a lot of problems when there is a lot of convection far from the center and then convection near the center too at the same time...it will have trouble resolving the larger scale synoptic lift I think...but it obviously could be onto something since its always the first model out with the new 00z data.

But I usually just hold it off to the side if it shows a different solution on a new raob primary run and wait for the others to chime in. This was never an obvious system until later in the game where the NAM would be poor...early on it looked a bit more tighter wrapped and it kept trending more strung out with its dynamics and convection, so I think that is where the NAM got in trouble really bad.

For those who aren't familiar, "hydrostatic" means an assumed balance in the atmosphere between the pressure gradient and gravity, but when steep convection is evident then this balance can be out of whack a bit...but overall its a good assumption and that is what most global models use...but models like the NAM and most (if not all?) SREFS are non-hydrostatic and actually will go into hydrostatic imbalance if the convection simulates it on their model (which does happen in real life for brief times)....but it can often cause problems in modeling if the convection is off a bit...esp synoptically when the convection is far off from the center. I'm no expert on this, but this is what I have read in the past and seen it play out in actual systems as mentioned above. I could be in slight error in my explanation but I think I managed to cover the basics of it. Anyone who knows more can correct me.

[Coach McGuirk]

Yeah. You live in Yorktown and have the same boundary temp issues on the NAM.

Yeah, If you've seen my posts I've expressed the boundary layer problems for the Hampton Roads.

[clskinsfan]

NWS is starting to cancel some WWA's for the northern counties.

[mitchnick]

RGEM is further south too

EZF on north, fuggetaboutit, and probably a bit south of that (per RGEM)

[Midlo Snow Maker]

Yeah, If you've seen my posts I've expressed the boundary layer problems for the Hampton Roads.

atleast you get some QPF and have a chance i guess better than others

[Amped]

I would agree its probably too far south...for the same reasons I spoke of above. Its non-hydrostatic so it can have a lot of problems when there is a lot of convection far from the center and then convection near the center too at the same time...it will have trouble resolving the larger scale synoptic lift I think...but it obviously could be onto something since its always the first model out with the new 00z data.

But I usually just hold it off to the side if it shows a different solution on a new raob primary run and wait for the others to chime in. This was never an obvious system until later in the game where the NAM would be poor...early on it looked a bit more tighter wrapped and it kept trending more strung out with its dynamics and convection, so I think that is where the NAM got in trouble really bad.

For those who aren't familiar, "hydrostatic" means an assumed balance in the atmosphere between the pressure gradient and gravity, but when steep convection is evident then this balance can be out of whack a bit...but overall its a good assumption and that is what most global models use...but models like the NAM and most (if not all?) SREFS are non-hydrostatic and actually will go into hydrostatic imbalance if the convection simulates it on their model (which does happen in real life for brief times)....but it can often cause problems in modeling if the convection is off a bit...esp synoptically when the convection is far off from the center. I'm no expert on this, but this is what I have read in the past and seen it play out in actual systems as mentioned above. I could be in slight error in my explanation but I think I managed to cover the basics of it. Anyone who knows more can correct me.

Certainly a lot of convection far from the center. The Srefs and ETA all come way south also. Thanks for the insight. Amazing how this winter is finding ways to suck that are too complex for most of us to understand.