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December Medium/Long Range Discussion


yoda
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1 minute ago, high risk said:

        In these events with very marginal temperatures, the Tropical Tidbits accumulated positive snow depth change are the best maps to examine.    They show what the model believes can actually accumulate on the ground.

I've always found those to be low, even in marginal situations, but they're going to be closer than those 10:1 wxbell maps!

Everyone has to keep normal Mid-Atlantic marginal event rules in mind here.  Elevation STRONGLY favored.  Rural N/W areas favored.  White rain likely for a time, even in places where accumulation happens.  That it might touch 60F Sunday doesn't matter much.  

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Just now, WxUSAF said:

I've always found those to be low, even in marginal situations, but they're going to be closer than those 10:1 wxbell maps!

Everyone has to keep normal Mid-Atlantic marginal event rules in mind here.  Elevation STRONGLY favored.  Rural N/W areas favored.  White rain likely for a time, even in places where accumulation happens.  That it might touch 60F Sunday doesn't matter much.  

Counterpoint...if we somehow don't get to 60 or even the mid 50s then it works out even better.

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3 minutes ago, WxUSAF said:

I've always found those to be low, even in marginal situations, but they're going to be closer than those 10:1 wxbell maps!

Everyone has to keep normal Mid-Atlantic marginal event rules in mind here.  Elevation STRONGLY favored.  Rural N/W areas favored.  White rain likely for a time, even in places where accumulation happens.  That it might touch 60F Sunday doesn't matter much.  

I agree completely.  Brunswick is NW rural.  I don’t see snow depth option for NAM on WB.  But I can post with other models if it gives a more accurate depiction if it is available.

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3 minutes ago, WxUSAF said:

I've always found those to be low, even in marginal situations, but they're going to be closer than those 10:1 wxbell maps!

Everyone has to keep normal Mid-Atlantic marginal event rules in mind here.  Elevation STRONGLY favored.  Rural N/W areas favored.  White rain likely for a time, even in places where accumulation happens.  That it might touch 60F Sunday doesn't matter much.  

          They do run tend to a bit low (especially when the ground is relatively "warm", but they're so much better than 10:1 maps in any event in marginal thermodynamic environment.

          I honestly don't blame WB or TT.    The problem is that NCEP doesn't generate true snow accumulation output for any models except RAP and HRRR, so it's up to the user to assign and apply an SLR.       This is going to be addressed going forward.

  

  

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11 minutes ago, WxUSAF said:

I'm pretty sure WxBell assumes 850mb temp below 0C = snow

In this very marginal situation, that's going to give a really bad impression.  

Happens every year though. People see snow maps and take them as gospel. 

9 minutes ago, Weather Will said:

I did.  I posted them as well.

you post every map there is available. 

9 minutes ago, leesburg 04 said:

Not here

you're at 0. congrats!

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5 minutes ago, high risk said:

        

          I honestly don't blame WB or TT.    The problem is that NCEP doesn't generate true snow accumulation output for any models except RAP and HRRR, so it's up to the user to assign and apply an SLR.       This is going to be addressed going forward.

  

  

Good to hear!  Are they going to output what SLR they're calculating as well as the accumulation?  That way we weenies will just adjust upward :)

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4 minutes ago, high risk said:

          They do run tend to a bit low (especially when the ground is relatively "warm", but they're so much better than 10:1 maps in any event in marginal thermodynamic environment.

          I honestly don't blame WB or TT.    The problem is that NCEP doesn't generate true snow accumulation output for any models except RAP and HRRR, so it's up to the user to assign and apply an SLR.       This is going to be addressed going forward.

  

  

Geoff, How does the Parallel GFS do compared to the current version.  I noticed the 00Z parallel from last night had much lower pressure over the Great Lakes than the 00Z operational so it forecast all rain across the area.  It was quite a bit farther west with the secondary.  Despite the overly rosey Eruo ensemble snow probabilities, the lows were all over the place,  lots of spread. 

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2 minutes ago, WxUSAF said:

Good to hear!  Are they going to output what SLR they're calculating as well as the accumulation?  That way we weenies will just adjust upward :)

         Honestly, those details haven't been sorted out yet.    It's not an output in the RAP/HRRR (which have actual snow accumulation as an output), although their SLR methodology is documented.       The plan is to carry over the RAP/HRRR products into the RRFS (replacing all of the regional models in 2023) and build it into the 2024 GFS/GEFS upgrade.

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6 minutes ago, usedtobe said:

Geoff, How does the Parallel GFS do compared to the current version.  I noticed the 00Z parallel from last night had much lower pressure over the Great Lakes than the 00Z operational so it forecast all rain across the area.  It was quite a bit farther west with the secondary.  Despite the overly rosey Eruo ensemble snow probabilities, the lows were all over the place,  lots of spread. 

Last I saw a few days ago, it performs worse than the Euro, current GFS, Ukie and CMC.  

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9 minutes ago, usedtobe said:

Geoff, How does the Parallel GFS do compared to the current version.  I noticed the 00Z parallel from last night had much lower pressure over the Great Lakes than the 00Z operational so it forecast all rain across the area.  It was quite a bit farther west with the secondary.  Despite the overly rosey Eruo ensemble snow probabilities, the lows were all over the place,  lots of spread. 

           The parallel GFS had statistically significant synoptic range improvement over the ops GFS in the medium range over the full course of the retrospective runs.     But that certainly doesn't preclude it doing worse on any single event.     I wish we were able to run it more than once per day right now.....

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13 minutes ago, high risk said:

           The parallel GFS had statistically significant synoptic range improvement over the ops GFS in the medium range over the full course of the retrospective runs.     But that certainly doesn't preclude it doing worse on any single event.     I wish we were able to run it more than once per day right now.....

That's what I thought I remembered from yesterday's Sterling winter weather workshop.

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