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NYC CWA January 26-27 OBS and Discussion Thread


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Srefs are from 4:00pm and have no 0z data in them.

Thanks for saying this. I was about to but don't like always being a downer. The idea that the SREFs almost always lead the NAM (in terms of trending) is a myth IMO. I've always observed the NAM to lead the subsequent SREF run.

I do agree that the full ensemble mean is more important that an individual NAM run.

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Thanks for saying this. I was about to but don't like always being a downer. The idea that the SREFs almost always lead the NAM (in terms of trending) is a myth IMO. I've always observed the NAM to lead the subsequent SREF run.

I do agree that the full ensemble mean is more important that an individual NAM run.

Fair point, but the 18z NAM was drier than the 21z SREFs which ticked NW and wetter as well as more amplified by 4hpa at the surface..so something has to give

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Never said it wasn't a good model. It has its moments though. All Im saying is that it can be VERY volatile with QPF from even 6-12 hours out. Watch the 6z NAM at 6hours and compare it to the 00z run at 12 hours....Trust me

It most likely Is wrong here..but, I think the model is very useful in spotting trends within 48 hours of an event....even the heavy banding as we get closer . While it is off many times, I've seen it come ridiculously close in predicting where the heaviest banding will set up, though not necessarily where the heaviest qpf will always show up

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The 0z NAM is very similar to its 18z run in every respect except QPF. But even in this respect the idea is the same. It's just a little drier in the mid-atlantic and more pronounced with the relative minimum near SENY and WCT. If this run is wildly incorrect, that would implicate at least the previous run if not the past few.

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"Feedback error" is code for "that's ugly, I don't like it."

It is not just JB, other meteorologists are saying similar. I am not naming names but either way I will not just discount what professionals are saying because the NAM came in drier more than 24 hours away from the main event and because the NAM has been good in this range every now and then in winters past.

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The 0z NAM is very similar to its 18z run in every respect except QPF. But even in this respect the idea is the same. It's just a little drier in the mid-atlantic and more pronounced with the relative minimum near SENY and WCT. If this run is wildly incorrect, that would implicate at least the previous run if not the past few.

This is just plain wrong. The surface low is def. placed to the s and e and misplaced at that. Between 12 and 15 hours the NAM send the surface low chasing a qpf bomb into the atlantic which is classic convective feedback and then tries to correct itself but its too late. All the best moisture is gone and its too late.

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It is not just JB, other meteorologists are saying similar. I am not naming names but either way I will not just discount what professionals are saying because the NAM came in drier more than 24 hours away from the main event.

A lot of mets are throwing this run out.

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"Feedback error" is code for "that's ugly, I don't like it."

really? two days before the boxind day storm upton had an in depth discussion I believe by our very own BillG talking about convective feedback on the euro. Every model is subject to it. Its real and the nam does it more than any other model.

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This is just plain wrong. The surface low is def. placed to the s and e and misplaced at that. Between 12 and 15 hours the NAM send the surface low chasing a qpf bomb into the atlantic which is classic convective feedback and then tries to correct itself but its too late. All the best moisture is gone and its too late.

Whenever you see some random QPF bomb out in the Atlantic and some spurious low develop there that robs from everything else, you know convective feedback has to be an issue. The NAM did this with the 12/26 storm as well as the 12/19 storm last year that developed from the Gulf. Each one of those, the NAM had weird runs like this that cut back way too much on the northern extent of the storm.

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It is not just JB, other meteorologists are saying similar. I am not naming names but either way I will not just discount what professionals are saying because the NAM came in drier more than 24 hours away from the main event.

I've seen this kind of thing written about various model runs literally dozens of times, usually when there is an outlier solution or a sudden model change. And I have never observed a correlation between error identification and the relative likelihood of the solution verifying. Sometimes the supposed erroneous solution has the right idea, and sometimes it doesn't. And just in my opinion, meteorologists are not good at distinguishing these two cases. I think you would have to be well versed in numerical modeling to correctly spot an error that adversely impacted the result.

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