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March 5 Snow Thread-Model Discussion ONLY

stormtracker

By stormtracker,
in Mid Atlantic

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Scarlet Pimpernel

Scarlet Pimpernel

Posted
Posted

When don't they? In all seriousness, that choice does seem to verify most of the time.

 

True.  But here, at least in terms of precip, it seems like a blend of one of the wetter models (Euro) with just about the driest one (GFS) for this event.  Kind of odd.  However, that said, the discussion mentions that both the Euro and GFS are stronger with the digging shortwave trough (compared to the NAM).  Maybe that's what they're referring to more than the QPF amounts.

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Ian

Ian

Posted
Posted

The high resolution maps i just saw are kind of in between those 2... weird

This is for after 12z

Westminster .65

MRB .55

JYO .7

IAD .8

DCA .8

BWI .75

 

We are splitting hairs here though it was a GREAT run

DCA is prob like .75+.. rounding. Close enough. 

 

Zgx1jz1.png

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Bari

Bari

Posted
Posted

So what does this mean? It's a different event. We will soon see anyway.

True, and it's always important to keep that in mind, I'm just voicing caution with the larger qpf outputs with the European. If we were burned as bad as ny was we might be being more carefulwith qpf assessment.

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clueless

clueless

Posted
Posted

True, and it's always important to keep that in mind, I'm just voicing caution with the larger qpf outputs with the European. If we were burned as bad as ny was we might be being more carefulwith qpf assessment.

4-8 is fair region wide. We have been burned before so if DC gets 5 and I get 4 we are still within range. Plus the NY debacle was at peak climo. After all is said and done we finished the winter pretty well.

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Ian

Ian

Posted
Posted

True, and it's always important to keep that in mind, I'm just voicing caution with the larger qpf outputs with the European. If we were burned as bad as ny was we might be being more carefulwith qpf assessment.

Silly comparison anyway. Euro was on its own there unless you count one run of the GGEM.
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WxMan1

WxMan1

Posted
Posted

True. But here, at least in terms of precip, it seems like a blend of one of the wetter models (Euro) with just about the driest one (GFS) for this event. Kind of odd. However, that said, the discussion mentions that both the Euro and GFS are stronger with the digging shortwave trough (compared to the NAM). Maybe that's what they're referring to more than the QPF amounts.

This. If I can put my work hat on for a second...the PMDHMD is really geared for diagnosing the mass field differences, i.e. timing and amplification of upper level features (troughs, ridges, jet streaks, etc.) as well as the reflection at the surface (timing of fronts, etc.).

There are instances where from a mass field perspective, a cluster of models will agree, yet not with the QPF. That's where our QPF (and WWD) discussions come into play. As someone already noted, while the GFS and EC may differ in QPF, the timing and amplitude of the pattern may blend fairly well, which would impact fropas, wind shifts, temp trends, and other non-QPF parameters that some (like the aviation users and mariners) find critical to operations.

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Bari

Bari

Posted
Posted

4-8 is fair region wide. We have been burned before so if DC gets 5 and I get 4 we are still within range. Plus the NY debacle was at peak climo. After all is said and done we finished the winter pretty well.

I agree,

but I will mention that 4-8 inches is quite a range, it's the difference between the gfs or the euro verifying

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WxMan1

WxMan1

Posted
Posted

I agree,

but I will mention that 4-8 inches is quite a range, it's the difference between the gfs or the euro verifying

4-8" is he best "cover your @ss" range we have, if I can be blunt, and I can since I've used that range before in previous forecasts. You won't get a broader range of impact within one forecast -- as we know 4" is a far cry from 8". Back in the '80s, the old WBC forecast office would use this range quite a bit initially prior to the big NorEasters, then trend up with 6-10 and 8-12 with time. Jan 22 and 25 1987 were examples of this. So was the system prior to Thanksgiving 1989.

6-10" and 8-12" are also 4" ranges, but obviously the difference from min to max in terms of impact lessens.

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cae

cae

Posted
Posted

Looks more like ~9" with 10:1 ratios. Still I'd be thrilled with it.

 

I think 4-8" is a good call, with GFS as a low end and EURO as a high end.

 

I agree that's a good call.  Here are my estimates for qpf that falls as snow for the 12z runs imby.

 

NAM          0.67"

HR NAM    0.5"

RGEM       0.55"

HR RGEM 0.51"

GGEM       0.71"

GFS          0.35"

UKMET     0.79"

Euro          0.7"

 

Average:  0.6"

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Bari

Bari

Posted
Posted

Silly comparison anyway. Euro was on its own there unless you count one run of the GGEM.

I was looking at it more of it more statistically, looking at verification for the euro's larger outputs hasn't been as good as some of the other models performances whith larger qpf events, with raises a red flag in my books. Where's it's right or wrong, I'm just trying to see where there might be issues when we have slightly different solutions.

While of course I'm hoing for the best outcome for the dca, I'm just trying to be as objective as possible if I like it or not

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Roger Smith

Roger Smith

Posted
Posted

I could imagine this going into the 10-15 inch total range in parts of noVA, MD and se PA, DE and s NJ, tapering off south of DCA to about 5-10 in central VA and 3-7 for RIC after some heavy sleet. The main energy center is back around s/c AR at this point and snow has broken out along the frontal boundary mainly between 540 and 552 dm thicknesses. There appears to be abundant moisture in the approaching system and no particular reason for it to diminish over time. Certainly 8-12 is very easy to see, but I will go with these numbers for your amusement:

 

BWI and IAD both around 12.5

DCA around 7.5

PHL and MDT around 10.5

SBY around 6.0

RIC around 4.0

CHO around 6.5

 

some spotter reports north of I-95 and in ne WV, noVA could reach 18-22 inches.

 

This should change the old seasonal contest a bit. Party on.

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clueless

clueless

Posted
Posted

I was looking at it more of it more statistically, looking at verification for the euro's larger outputs hasn't been as good as some of the other models performances whith larger qpf events, with raises a red flag in my books. Where's it's right or wrong, I'm just trying to see where there might be issues when we have slightly different solutions.

While of course I'm hoing for the best outcome for the dca, I'm just trying to be as objective as possible if I like it or not

I think the point is that every event is discreet. Getting into model comparisons is not helpful Blending forecasts based upon model biases AND performance is a sober methodology. Eliinwood put out a forecast with a 4-8 range down here. Maybe you should engage him on this.

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paulythegun

paulythegun

Posted
Posted

Yeah, there hasn't been any real shift in the primary components from what I can see, just a tightening of the secondary precip gradient as the boundary slides south ahead of the slightly delayed 2nd impulse.

I can already foresee the panic early Thursday morning when we're in a lull between waves and those N/W have racked up 3-4" while DC is just changing over. Then the 2nd impulse rolls through and it's the westerners that are shafted.

Generally I think people are going to be yelling at OPM about closing when the roads are wet and it's sleeting or snowing lightly at 8am in DC. But I think it's almost a no-brainer decision to make at 4am with the heavy rates LIKELY later and POSSIBLE during the end of morning rush hour (particularly in the NW side of the beltway). Also factor in the potential for snow covered roads with continued light snow during the afternoon rush, and I don't see how they make any other decision than closure. 

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Bari

Bari

Posted
Posted

4-8" is he best "cover your @ss" range we have, if I can be blunt, and I can since I've used that range before in previous forecasts. You won't get a broader range of impact within one forecast -- as we know 4" is a far cry from 8". Back in the '80s, the old WBC forecast office would use this range quite a bit initially prior to the big NorEasters, then trend up with 6-10 and 8-12 with time. Jan 22 and 25 1987 were examples of this. So was the system prior to Thanksgiving 1989.

6-10" and 8-12" are also 4" ranges, but obviously the difference from min to max in terms of impact lessens.

True true, and it does concert your butt with mesoscale dynamics and can easily modify your qpf on a local scale.

I'll have to keep this in mind for future forecast, especially with this degree almost complete.

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SNO

SNO

Posted
Posted

I could imagine this going into the 10-15 inch total range in parts of noVA, MD and se PA, DE and s NJ, tapering off south of DCA to about 5-10 in central VA and 3-7 for RIC after some heavy sleet. The main energy center is back around s/c AR at this point and snow has broken out along the frontal boundary mainly between 540 and 552 dm thicknesses. There appears to be abundant moisture in the approaching system and no particular reason for it to diminish over time. Certainly 8-12 is very easy to see, but I will go with these numbers for your amusement:

 

BWI and IAD both around 12.5

DCA around 7.5

PHL and MDT around 10.5

SBY around 6.0

RIC around 4.0

CHO around 6.5

 

some spotter reports north of I-95 and in ne WV, noVA could reach 18-22 inches.

 

This should change the old seasonal contest a bit. Party on.

I hope you verify :snowing:

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ravensrule

ravensrule

Posted
Posted

I could imagine this going into the 10-15 inch total range in parts of noVA, MD and se PA, DE and s NJ, tapering off south of DCA to about 5-10 in central VA and 3-7 for RIC after some heavy sleet. The main energy center is back around s/c AR at this point and snow has broken out along the frontal boundary mainly between 540 and 552 dm thicknesses. There appears to be abundant moisture in the approaching system and no particular reason for it to diminish over time. Certainly 8-12 is very easy to see, but I will go with these numbers for your amusement:

 

BWI and IAD both around 12.5

DCA around 7.5

PHL and MDT around 10.5

SBY around 6.0

RIC around 4.0

CHO around 6.5

 

some spotter reports north of I-95 and in ne WV, noVA could reach 18-22 inches.

 

This should change the old seasonal contest a bit. Party on.

Thanks for the ballsy call Roger. Good luck.

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clueless

clueless

Posted
Posted

True true, and it does concert your butt with mesoscale dynamics and can easily modify your qpf on a local scale.

I'll have to keep this in mind for future forecast, especially with this degree almost complete.

Good luck with the degree. I'm interested as well in what model may have a better take on QPF...as NAM is rolling.

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