Mid FEB through March Threats/Snow Storms

[Scarlet Pimpernel]

So everyone's hopeful with the GFS north shift. I'm not very. Still dealing with the same features or lack thereof.

 

Well, sure we're hopeful by what it showed.  But I'm very nervous that a lot of ensembles, in particular the 12Z Euro ensembles, had a lot of whiffs or near whiffs to the south (at least from what I read earlier).  Even the 18Z GEFS were south of the ops.  It gives one pause, but at the same time seeing the high res ops show what it did just now is encouraging.  I still think we see a plethora of solutions in the ops over the next day, and a lot of people are going to be up and down in how they feel.  That could make for a lot of tension, I fear.

[BaltimoreWxGuy]

So everyone's hopeful with the GFS north shift. I'm not very. Still dealing with the same features or lack thereof.

Seems to me it comes down to the Baja low and if that gets absorbed into the diving vort..of course the entire northern stream plays a role too...I know you dont like it, and there are reasons not to, however I think its the best bet so far this winter even though that may not sound like much

[ers-wxman1]

The runs between yesterday and today are the goal posts at this point. Anywhere between a glancing shot at a few inches to a miss out to sea. Still a rather wide uncertainty. Certainly can change but would have to see a shift in the overall pattern to allow for more significant snows. Without a blocking high this thing will do the speed limit up and out.

[nj2va]

The runs between yesterday and today are the goal posts at this point. Anywhere between a glancing shot at a few inches to a miss out to sea. Still a rather wide uncertainty. Certainly can change but would have to see a shift in the overall pattern to allow for more significant snows. Without a blocking high this thing will do the speed limit up and out.

 

If you think the goal posts have been set, I'd say for DC, it's between a miss out to sea and 5 or 6".  I think our high end is better than "a glancing shot at a few inches" - I know it's parsing details that aren't worked out but if we're talking goal posts...

[nj2va]

Pulling out all the stops here - 18z NAVGEM is ~0.40" for DC.  

[Heisy]

18z gfs was phasing the baja energy at 84 hours. That's the real key to getting a stronger storm. It can still make it up this way without but if the phase happens and things are more juiced across texas/gulf coast, it can only help our chances. I'm focusing on that. 

 

FWIW- the 18z nam was not even close. It was cutoff and spinning over baja 12z gfs @ hr 90 has it open but still hanging back over the gulf of CA. 18z gfs @ hr 84 had the energy over n central mexico. This is a very important feature to keep an eye on. 

 

Phasing still doesn't guaranty anything of course. But it can really help. The large difference in precip expanse and strength in TX/gulf coast with the 18z vs 12z was because of this. Were getting to the range now where this piece of the puzzle will be resolved one way or the other. The 0z runs tomorrow should mostly agree on what happens in that dept. 

 

FWIW, the 18z DGEX is actually pretty close to a nice hit. 

 

For those unaware the DGEX is just an extension of the 84 hr NAM using GFS parameters ( I believe)...but regardless good post Bob

[ers-wxman1]

If you think the goal posts have been set, I'd say for DC, it's between a miss out to sea and 5 or 6". I think our high end is better than "a glancing shot at a few inches" - I know it's parsing details that aren't worked out but if we're talking goal posts...

I can see that. 5-6" would be a max case scenario at this point. Min case is out to sea.

[Heisy]

Not like anyone cares, but here is my current thoughts on this event...

 

I feel like we're stuck in the middle of two scenarios, with the 18z GFS possibly being the 3rd

 

SCENARIO 1) The trough stays positively tilted, with the good thermal gradient the Southeast gets a nice event with good overrunning, but the shortwave doesn't get neg tilted in time and the low kind of scoots out to sea. This is the scenario being portrayed by the EURO/GGEM etc. 

 

 

SCENARIO 2)  The trough goes negative in time, but with no HP to the north temps could be an issue. I know temps/mixing are the last thing on anyone's mind. BUT HEAR ME OUT...If you took the 18z GFS 500mb map and sharpened it up more (which is def. possible), there is no high pressure to our N, and the one to our W is not in an ideal spot. The closest HP is actually to the E. If you looked closely there are some decent SE Winds that get very close to DC on the 18z run. 

 

SCENARIO 3) The trough goes negative in time, but doesn't get overly sharp. Strong enough to get the low close to us. This is basically a carbon copy of the 18z GFS scenario.

 

------

 

Baja Low: This plays a significant role. If this phases in it adds "energy" to the base of the trough, slowing it down, and giving it time to come up the coast. Like I said, I have trouble explaining my points sometimes using meteorology terms, but I hope you get what I mean...lol. The 18z GFS phased this in, and you saw the results.

 

Lead Wave: As expected at this range, the models are having trouble dealing with this lead wave. Basically as modeled this lead wave is a shortwave that scoots ahead on the northern jet. Precipitation breaks out since we have a really good temp gradient. Over the last 14 years of model watching I've observed that sometimes at this lead time models over-do this lead wave and eventually just focus on one low. Now, what this lead wave can do, whether it is weak or not, is it sets up the baroclinic zone. The 18z GFS had the baroclinic zone farther N than the 12z...here is an image showing the two. Note how much farther N the 18z GFS is with the precip which is the baroclinic zone. 

 

12z GFS:

 

18z GFS:

 

 

 

200-300mb Winds: This is important of course, the 18z GFS pointed the jet more N than the 12z run, obviously helps on bringing the low NW

 

 

What this event has going for it is a great antecedent airmass, nice PNA, and a weakened SE ridge. We need the trough to be sharp enough to bring the low up the coast, but not too strong as to bring the low too close to us. 

 

I don't have a meteorology degree, and probably never will, but Iv'e been looking at models my entire life. I sometimes have trouble explaining what I see because I guess I kind of learned meteorology/modelology in an abnormal manner. Kind of self-taught.

 

After this event I imagine we'll see some below normal temps for a bit. There is no sign of a NAO , but the PNA doesn't want to die. There should be more threats down the line, but they will all be marginal since we can't get a block. 

[ers-wxman1]

Not like anyone cares, but here is my current thoughts on this event...

I feel like we're stuck in the middle of two scenarios, with the 18z GFS possibly being the 3rd

SCENARIO 1) The trough stays positively tilted, with the good thermal gradient the Southeast gets a nice event with good overrunning, but the shortwave doesn't get neg tilted in time and the low kind of scoots out to sea. This is the scenario being portrayed by the EURO/GGEM etc.

SCENARIO 2) The trough goes negative in time, but with no HP to the north temps could be an issue. I know temps/mixing are the last thing on anyone's mind. BUT HEAR ME OUT...If you took the 18z GFS 500mb map and sharpened it up more (which is def. possible), there is no high pressure to our N, and the one to our W is not in an ideal spot. The closest HP is actually to the E. If you looked closely there are some decent SE Winds that get very close to DC on the 18z run.

SCENARIO 3) The trough goes negative in time, but doesn't get overly sharp. Strong enough to get the low close to us. This is basically a carbon copy of the 18z GFS scenario.

------

Baja Low: This plays a significant role. If this phases in it adds "energy" to the base of the trough, slowing it down, and giving it time to come up the coast. Like I said, I have trouble explaining my points sometimes using meteorology terms, but I hope you get what I mean...lol. The 18z GFS phased this in, and you saw the results.

Lead Wave: As expected at this range, the models are having trouble dealing with this lead wave. Basically as modeled this lead wave is a shortwave that scoots ahead on the northern jet. Precipitation breaks out since we have a really good temp gradient. Over the last 14 years of model watching I've observed that sometimes at this lead time models over-do this lead wave and eventually just focus on one low. Now, what this lead wave can do, whether it is weak or not, is it sets up the baroclinic zone. The 18z GFS had the baroclinic zone farther N than the 12z...here is an image showing the two. Note how much farther N the 18z GFS is with the precip which is the baroclinic zone.

12z GFS:

18z GFS:

200-300mb Winds: This is important of course, the 18z GFS pointed the jet more N than the 12z run, obviously helps on bringing the low NW

What this event has going for it is a great antecedent airmass, nice PNA, and a weakened SE ridge. We need the trough to be sharp enough to bring the low up the coast, but not too strong as to bring the low too close to us.

I don't have a meteorology degree, and probably never will, but Iv'e been looking at models my entire life. I sometimes have trouble explaining what I see because I guess I kind of learned meteorology/modelology in an abnormal manner. Kind of self-taught.

After this event I imagine we'll see some below normal temps for a bit. There is no sign of a NAO , but the PNA doesn't want to die. There should be more threats down the line, but they will all be marginal since we can't get a block.

Good write up

[MacintoshPro]

I would take the GEFS in a heartbeat if this map is right.

[Ian]

It does feel weenie to always just go with the north trend but it does play out so often it's hard to ignore, esp without blocking.  For some reason I feel the minor or OTS solutions are still the most likely as of now though. Perhaps it's just trying to be anti weenie though.  I'm like 55/45 on that scenario.. a gradual north shift would not be surprising based on history at all of course.

[yoda]

I probably am wrong, but it looks like 21z SREFs at 87 are leaning towards the 18z GFS on the h5 chart?

 

Yes, grasping for good news to start the night

[mitchnick]

It does feel weenie to always just go with the north trend but it does play out so often it's hard to ignore, esp without blocking.  For some reason I feel the minor or OTS solutions are still the most likely as of now though. Perhaps it's just trying to be anti weenie though.  I'm like 55/45 on that scenario.. a gradual north shift would not be surprising based on history at all of course.

the problem is that the models, all of them as a whole, overestimate blocking in SE Canada or underestimate ridge off the SE Atlantic coast >48 hours out

that's not meteorology, it's modelology, but in this day and age when every met and weenie relies so heavily on models, modelology is, imho, just as important as meteorology knowledge

so when considering the odds in any particular storm at this range the models will do as I have suggested above, you will be more successful at 3 day+ forecasts by assuming the northward trend every time since I'd bet a storm that trends south or stays exactly as modeled 3+ days out well <1 out 10 times

[Ian]

the problem is that the models, all of them as a whole, overestimate blocking in SE Canada or underestimate ridge off the SE Atlantic coast >48 hours out

that's not meteorology, it's modelology, but in this day and age when every met and weenie relies so heavily on models, modelology is, imho, just as important as meteorology knowledge

so when considering the odds in any particular storm at this range the models will do as I have suggested above, you will be more successful at 3 day+ forecasts by assuming the northward trend every time since I'd bet a storm that trends south or stays exactly as modeled 3+ days out well <1 out 10 times

I think you're more right than not. I also think people forget the storms that shear apart or slide to the south innocuously. There was one like 10 days ago we had a thread for and it didn't even precipitate at all (err, maybe there were some flurries with the front).

[cae]

I wonder if this is going to turn out to be like the Feb 2nd event, where the models were close to the final solution about 5 days out, then moved south before coming back north again.

[mitchnick]

I wonder if this is going to turn out to be like the Feb 2nd event, where the models were close to the final solution about 5 days out, then moved south before coming back north again.

there's plenty of time to move every which way and back twice

[Leaking Gut]

when looking at 500MB vort, what do the 12's represent, energy?

[Bob Chill]

Good post Hberg. I think the least likely scenario right now is all rain or nothing at all. Big qpf event is quite unlikely as well. Beyond that will take the weekend to really pin down.

The exact placement and progression of the important features should come into focus soon enough. Until then we are simply in a range of possibilities as you laid out. Sure would like to see some agreement with the 18z's handling of the Baja energy and subsequent juicier storm in the deep south. Or at least movement in that direction.

[mitchnick]

even at 39 hrs., if the NAM is close to being right with the strength and location of tomorrow's system, it is going to cause some serious ripples in the atmosphere, the consequences of which to the storm next week will not be quickly known I'm bettin'

http://mag.ncep.noaa.gov/Image.php?fhr=039ℑ=data%2Fnam%2F00%2Fnam_namer_039_500_vort_ht.gif&model=nam&area=namer&param=500_vort_ht&group=Model+Guidance&preselected_formatted_cycle_date=20150214+00+UTC&imageSize=M&ps=model

[84 Hour NAM]

NAM looks like it wants to phase the baja low

[cae]

Big qpf event is quite unlikely as well.

 

I wouldn't be confident even saying that.  I guess it depends on what you mean by "big".  Someone could get more than 1.5" qpf out of this event.  The 18z GFS puts that axis through NC, but 4 days is plenty of time for it to shift. 

[winterymix]

even at 39 hrs., if the NAM is close to being right with the strength and location of tomorrow's system, it is going to cause some serious ripples in the atmosphere, the consequences of which to the storm next week will not be quickly known I'm bettin'

http://mag.ncep.noaa.gov/Image.php?fhr=039ℑ=data%2Fnam%2F00%2Fnam_namer_039_500_vort_ht.gif&model=nam&area=namer&param=500_vort_ht&group=Model+Guidance&preselected_formatted_cycle_date=20150214+00+UTC&imageSize=M&ps=model

That's a red hot squealer.

[usedtobe]

Nam does look like it will get things up to us and it does pick up the baja low and more importantly seem to really want to dig the northern stream southward to help back our flow.   Has me interested enough to stay up for the GFS. 

[lsukev]

NAM looks like it wants to phase the baja low

Definitely looks better than 18z.

[Bob Chill]

I wouldn't be confident even saying that. I guess it depends on what you mean by "big". Someone could get more than 1.5" qpf out of this event. The 18z GFS puts that axis through NC, but 4 days is plenty of time for it to shift.

I'd be surprised if our area gets 1". Storm is going to move fast. I suppose some sort of elongated shield well in front of the low is possible but getting more than 1" of qpf with no block and barely a sub 1k low isn't common

[mitchnick]

0Z NAM 84 hrs

http://mag.ncep.noaa.gov/Image.php?image=data%2Fnam%2F00%2Fnam_namer_084_500_vort_ht.gif&model=nam&area=namer&storm=&cycle=00&param=500_vort_ht&fhr=084&group=Model+Guidance&imageSize=M&ps=model&use_mins=no&preselected_formatted_cycle_date=20150214+00+UTC&scrollx=0&scrolly=0

18Z GFS 90

http://mag.ncep.noaa.gov/Image.php?image=data%2Fgfs%2F18%2Fgfs_namer_090_500_vort_ht.gif&model=gfs&area=namer&storm=&cycle=18&param=500_vort_ht&fhr=090&group=Model+Guidance&imageSize=M&ps=model&use_mins=no&preselected_formatted_cycle_date=20150213+18+UTC&scrollx=0&scrolly=0

[Bob Chill]

0Z NAM 84 hrs

http://mag.ncep.noaa.gov/Image.php?image=data%2Fnam%2F00%2Fnam_namer_084_500_vort_ht.gif&model=nam&area=namer&storm=&cycle=00&param=500_vort_ht&fhr=084&group=Model+Guidance&imageSize=M&ps=model&use_mins=no&preselected_formatted_cycle_date=20150214+00+UTC&scrollx=0&scrolly=0

18Z GFS 90

http://mag.ncep.noaa.gov/Image.php?image=data%2Fgfs%2F18%2Fgfs_namer_090_500_vort_ht.gif&model=gfs&area=namer&storm=&cycle=18&param=500_vort_ht&fhr=090&group=Model+Guidance&imageSize=M&ps=model&use_mins=no&preselected_formatted_cycle_date=20150213+18+UTC&scrollx=0&scrolly=0

LOL- I was just going to post the exact same thing. Baja energy in n central mexico getting sucked right in. This is a good sign.

[usedtobe]

I think you're more right than not. I also think people forget the storms that shear apart or slide to the south innocuously. There was one like 10 days ago we had a thread for and it didn't even precipitate at all (err, maybe there were some flurries with the front).

I think that's true and most people do forget the sheared out messes.   I suspect that the north trend works better with a positive NAO than with a strongly negative one. 

[Heisy]

FWIW NAM is beautiful @ 84 hours

[MacintoshPro]

FWIW NAM is beautiful @ 84 hours

 

 

Looks South to me.