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Big Snow threat, what will it do, part II


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I wasn't here for the last event to see how the GGEM and RGEM did, but in the borderline snows earlier in the year I thought it did better than most of the other models down here.  I'm surprised by all the GGEM hating. 

 

I don't think any solution is off the table especially those that involve even less snow.

 

The RGEM has been remarkable but thats inside 36 hours, the GGEM I thought has been bad beyond 48 and good inside 48...I've noticed the GGEM as I posted earlier overplays its hand given where most guidance is, if we're looking at a close in closed off system its west of everything, if we have a less phased system its always the most progressive.

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just found this...this is what it results in

obviously just one run and still far our, but it's picking up on the overrunning going too far N, and then the secondary is an inverted trof, while Emass smokes subsidence

the prior run had PVD with 8.6" and 10+ on cape so I take that with a huge grain of salt

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8 in mass stations other than MVY andACK which have 6

8 in northern ct, 6 southern

8 in southern nh including con

6 up to dryslot and most of the southern half of Maine.

 

hey Jerry - what do 1/2/4/6/8 mean. I just ran them for various locations. For Instance, I see ORH has a 6 for hr 72 and an 8 for hr 96. Thanks!

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hey Jerry - what do 1/2/4/6/8 mean. I just ran them for various locations. For Instance, I see ORH has a 6 for hr 72 and an 8 for hr 96. Thanks!

 

 

1 means 1-2" of snow in that 6 hour period

2 means 2-4"

4 means 4-6"

6 means 6-8"

8 means 8"+

 

 

so a 6 and an 8 in back to back 6 hour periods would theoretically mean 6-8" followed by 8"+....obviously a big snow total. I don't thjink I'd bite on that type of total at this point though.

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1 means 1-2" of snow in that 6 hour period

2 means 2-4"

4 means 4-6"

6 means 6-8"

8 means 8"+

 

 

so a 6 and an 8 in back to back 6 hour periods would theoretically mean 6-8" followed by 8"+....obviously a big snow total. I don't thjink I'd bite on that type of total at this point though.

 

Thanks Will - much appreciated.

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1 means 1-2" of snow in that 6 hour period

2 means 2-4"

4 means 4-6"

6 means 6-8"

8 means 8"+

 

 

so a 6 and an 8 in back to back 6 hour periods would theoretically mean 6-8" followed by 8"+....obviously a big snow total. I don't thjink I'd bite on that type of total at this point though.

How are those big snow numbers coming off the GFS which has like .75 LE at ORH?

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probability is a no fail way of forecasting

 

I think sometimes the public thinks we're afraid to fail. If that's the case then we're in the wrong business, because it's a given.

 

Probabilities are a way to convey uncertainty, and no forecast is certain. This event looks like a high probability for a widespread moderate event. There is a higher probability for more snow on the South Shore where there will be ocean enhancement.

 

I could say exact inches for all of SNE, but we already know somebody will get subsidence or a sucker hole dry slot screw job. You can't accurately predict those at this range, so probabilities are a better, more skillful way to depict it. I also don't think people understand that a range is a probability based forecast. Saying 8-12" for BOS is just as probabilistic as saying a 70% or greater chance of 8+, but saying 9" for BOS is deterministic. Really tough to show exact inches on a forecast map though because you'd never be able to see surrounding towns or what the gradient is between major towns/cities.

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How are those big snow numbers coming off the GFS which has like .75 LE at ORH?

 

 

It doesn't use just the model qpf. It uses other sets of parameters as well such as the BL flow, ML flow, temps, etc. It also has some "memory" of climo in there which will help it forecast based on past events with similar model parameters. It is one way that MOS can be useful...however you have to be careful as it can still be fooled at times. Particularly during marginal events.

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I think sometimes the public thinks we're afraid to fail. If that's the case then we're in the wrong business, because it's a given.

Probabilities are a way to convey uncertainty, and no forecast is certain. This event looks like a high probability for a widespread moderate event. There is a higher probability for more snow on the South Shore where there will be ocean enhancement.

I could say exact inches for all of SNE, but we already know somebody will get subsidence or a sucker hole dry slot screw job. You can't accurately predict those at this range, so probabilities are a better, more skillful way to depict it. I also don't think people understand that a range is a probability based forecast. Saying 8-12" for BOS is just as probabilistic as saying a 70% or greater chance of 8+, but saying 9" for BOS is deterministic. Really tough to show exact inches on a forecast map though because you'd never be able to see surrounding towns or what the gradient is between major towns/cities.

Good luck getting the GP to understand that. This certainly has been an entertaining read this morning, I don't know why folks want to separate threads, can you not scroll, skip and read? Geez
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