Jan 23/24 Major Coastal Storm Discussion

[IsentropicLift]

The initial overrunning makes it to about I-80 in NJ.

[NycStormChaser]

Yeah this is nothing like the Euro. If the Euro hadn't made such a big shift I would have just considered this noise.

What do you mean?

[IsentropicLift]

You can see the differences in the mid-level jet. The strongest 700mb winds are over Central and Southern NJ as opposed to Central and Northern NJ.

[Allsnow]

CCB crush job 18z Saturday

[Drz1111]

You can see the differences in the mid-level jet. The strongest 700mb winds are over Central and Southern NJ as opposed to Central and Northern NJ.

Come on man.  You're looking for signal in 50mi changes from run to run.  That's just model noise (as amply evidenced by ensemble forecasting).  This is the same run, in substance.

[Superstorm93]

Now I have issues with the precipitation on the GFS 

 

With this kind of RH field you would not see the QPF so closely packed into the surface low like the model is showing. There would be an extension to the N and W as the cyclone matures. 

 

Doesn't add up

 

[stlirish]

What do you mean?

He means these differences in the GFS are minor enough from the 12Z run that if he had never seen the EURO at 12Z, he would see these minor subtleties in GFS as just "noise" ...I think that's what he means

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[UlsterCountySnowZ]

Now I have issues with the precipitation on the GFS

With this kind of RH field you would not see the QPF so closely packed into the surface low like the model is showing. There would be an extension to the N and W as the cyclone matures.

Doesn't add up

This is a good catch... The northern extension as well as the western extent should be more expansive than what's being shown

[IsentropicLift]

At least the mid-level centers are tracking more Northeasterly so the CCB is able to come NNE. Very little falls North of SWF.

[Superstorm93]

Ton of convective garbage dragging away the surface low and really robbing the coast of precip

 

I vehemently believe that you would see more in the way of a precip shield with that kind of H5/H7 setup 

 

[IsentropicLift]

Come on man.  You're looking for signal in 50mi changes from run to run.  That's just model noise (as amply evidenced by ensemble forecasting).  This is the same run, in substance.

How is this the same run? Virtually nothing falls North of I-84.

[UlsterCountySnowZ]

18z looks very similar to its 06z run... Not much north of 84

[SnoSki14]

Significant data comes in for the next two model suites. That data made all the difference last year and even for our hurricane threat this summer.

[snowman19]

How is this the same run? Virtually nothing falls North of I-84.

The closed 500mb low is like 100 miles south of 12z now. It's trending towards the Euro

[Drz1111]

How is this the same run? Virtually nothing falls North of I-84.

"virtually" is doing a lot of work in that sentence.  Again, don't exaggerate what it shows.  Just say what it shows.  Which is a 50mi shift south.  Add it to the blended, weighted mean.  Time and again, that's been shown to be the best way to forecast.  You don't need to editorialize, especially when it adds no value.

[IsentropicLift]

12z 

 

 

vs 18z at the same time

 

 

Now ask yourself this, if you lived in the LHV would you consider these runs the same?

[Zelocita Weather]

Great looking run for the vast majority of the Metro.

[N. OF PIKE]

If you look at the Mid level low orientation and location it is considerably south at 18z Sat and 0z Sunday on this run compared with 12z

[Blizzardo]

12z

vs 18z at the same time

Now ask yourself this, if you lived in the LHV would you consider these runs the same?

Absolutely not. That is a clear 50-60 mile south shift.

[Superstorm93]

Not a terrible run. 

 

I just really, really need to see that H5 low gain latitude after closing off otherwise we will all be smoking cirrus. The 18z GFS did wink at the ECMWF a bit by moving east for a frame or two after H5 closed, but that could be nothing. We'll have to see what the GEFS and subsequent runs do. 

 

[Drz1111]

12z 

 

 

vs 18z at the same time

 

 

Now ask yourself this, if you lived in the LHV would you consider these runs the same?

 

That's not the question.  The question is whether or not the forecasts are within the de facto margin of error (wrong term for a model output, but conceptually the same thing).  After either run, the forecast for the LHV is the same thing - you're on the northern edge of the big precip, it's basically a 50/50 shot.  That one run prints out X QPF and the other prints out 3X doesn't change that - the depiction (sharp northern cutoff, cutoff somewhere north of NYC and south of ALB) is fundamentally the same. 

[IsentropicLift]

New 18z run

 

 

Vs old 12z run

 

[IsentropicLift]

That's not the question.  The question is whether or not the forecasts are within the de facto margin of error (wrong term for a model output, but conceptually the same thing).  After either run, the forecast for the LHV is the same thing - you're on the northern edge of the big precip, it's basically a 50/50 shot.  That one run prints out X QPF and the other prints out 3X doesn't change that - the depiction (sharp northern cutoff, cutoff somewhere north of NYC and south of ALB) is fundamentally the same. 

I hope you realize that one more shift like that at 00z and you would be close to the Euro solution.

[snywx]

Great looking run for the vast majority of the Metro.

Def not as impressive for northern sections.. Then again im not expecting much. 

[IsentropicLift]

When you see this type of cutoff on the Northern edge it definitely raises a few flags. The good news is we still have a long way to go with this one. I really thought given the agreement we had yesterday that this one was pretty close to a certainty but once again I have been humbled.

 

[IsentropicLift]

Def not as impressive for northern sections.. Then again im not expecting much. 

I know the GFS technically would still be a few inches for your area but I feel like I've read this book before and it doesn't end well.

[Zynlamar]

I hope you realize that one more shift like that at 00z and you would be close to the Euro solution.

One can easily say a shift by the euro can lead to a solution closer to the GFS.  Bottom line is.  The models don't make the weather.  Lets see how this plays out and enjoy tracking something as we all deserve that :-)

[e46and2]

if you're on the jersey shore or long island, the whole setup is very promising and we have some margin of error to still get a 6+ storm.  I can see emotions running high for everyone north of the metro...in the best ones this is how it usually breaks down.  more often than not moisture makes it a little further inland/north than the final solutions would show, especially with unusually warm ocean temps.

[Drz1111]

I hope you realize that one more shift like that at 00z and you would be close to the Euro solution.

 

Exactly, but that's trend forecasting, which has never been shown to have any skill.  There's no evidence that the model going 50mi south at 6Z increases the odds of it going an additional 50mi south at 12Z, other than the fact that models get more accurate the closer you get to the event (though that's not that big of an effect over a 6 hour interval at this range).

 

Put differently, it's almost as likely that the 12Z run would shift back north.

 

This run didn't change the blended mean.  It's a classic example of a hold-serve.

[Superstorm93]

If the 00z models trend further south then I'd say parts of the LHV and NW NJ should really start to temper any expectations...

 

Not having the Euro on my side always scares me. Then again, we had the whole debacle with Juno...but I digress.