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Jan Medium/Long Range Disco: Winter is coming


stormtracker
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The 00Z trends on paper show a colder/more south solution for the weekend winter storm. But there's still plenty of time for more changes. Just using the GEFS for this exercise. Here is a Tomer Burg plot showing GEFS probabilities for 500mb troughs. It's a good thing to see a lack of even moderate probabilities (topping out around 20-30%) for toughing in Quebec, suggesting the higher probability for confluence there. However, note the primary shortwave trough in the Southern Plains. As was mentioned a couple times on the forum, part of this is less phasing/interaction with a northern stream shortwave. However, some of this signal could also be a signal flattening of the shortwave. Part is this is also growing dispersion in the GEFS (more ensembles showing more and more different potential amplitudes/positions of the trough drowning out the signal), but it likely includes some flatter solutions. We can get away with slightly less amplified features, particularly in an El Nino when the STJ is super charged and these southern stream disturbances are loaded with moisture. However, the need for strong upper level ascent out ahead of the trough is still important in generating both heavier snowfall rates and dynamic cooling.

In short, there are still signs where this trough could weaken, but there are enough solutions to suggest this system remains quite strong. It is simply too early to tell. But we could get by with still a meaningful and impactful event even with a weaker shortwave. A good example was February 26-28, 2003. Note on the reanalysis image for Feb 27 at 06Z-- the surface low along the Gulf Coast is weak, but there is an anchored high to the north and some tighter 1000-500mb thickness packing over VA. On the archived 500mb chart centered on 06Z Feb 28, 2003, the 500mb trough didn't exactly look that impressive. Still, they produced a swath of 4-8" (CIPS image), which given the snow drought we've experienced, just getting an event like that would be a start. Dulles managed 6.4" from this event, DCA 5.3", and BWI 4.5". We'll see how trends go in the coming days. Seems like a storm is coming. But to what extent is still up for debate.

500 troughs.gif

CIPS.PNG

2003022706.gif

500mb example.PNG

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3 hours ago, Ji said:

It's like how you drew it up

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Offshore 850 temps are much colder this run. Even with an E or ESE wind you're advecting -4 air. You won't have a lot of mixing concerns with that. 

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Good 'trends' on the 0z and now 6z guidance. Still a close call for I-95 and east, but now looking favorable for a mostly snow event just west of there. That surface HP over SE Canada is in a pretty good spot and stays locked in.

1704628800-7N139B33tLU.png

1704628800-fvN1KXTVXhA.png

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1 minute ago, CAPE said:

Good 'trends' on the 0z and now 6z guidance. Still a close call for I-95 and east, but now looking favorable for a mostly snow event just west of there. That surface HP is in a pretty good spot stays locked in.

1704628800-7N139B33tLU.png

1704628800-fvN1KXTVXhA.png

Any thoughts on what happens after this event as we approach mid month ? Happy New Year too ! 

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9 minutes ago, frd said:

Any thoughts on what happens after this event as we approach mid month ? Happy New Year too ! 

HNY!

I think it may be a struggle to get anything to track underneath for the mid month period with a trough centered more in the west/central US, but just beyond that things look much improved, especially if the EPS is more correct, with a west based -NAO, TPV pinned underneath, and lower h5 heights shifting out into the 50-50 region. Significant improvement on the Pacific side too.

1705276800-vmGGcJWwU1M.png
1705276800-1udMWspeCcs.png
 
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SIAP...This will be the first 'test' for the growing list of machine learning runs from the ECMWF suite. Verification has been pretty good, especially for some. Not going to get the specifics (i.e. ptype, snow totals, etc.), but at least we can see what the ML runs have in terms of the track into the medium range.

https://charts.ecmwf.int/?facets={"Product type"%3A["Experimental%3A Machine learning models"]}

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5 hours ago, Ji said:

Maybe we needed to have more faith in the mjo 2-3 phase. I mentioned out of stupid blind luck that models should trend colder based on our phase

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Your trend suspicion > PSUs trend suspicions. Who the hell had that on their NYD 2024 bingo card?

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What gorgeous runs. 2024 trying to start with a bang! These bigger storms are always sniffed out early and lead to long tracking nights. Going to be a grueling week. To see this trend our way for once is notable and I hope it does not trend back the opposite way.

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1 hour ago, WxMan1 said:

SIAP...This will be the first 'test' for the growing list of machine learning runs from the ECMWF suite. Verification has been pretty good, especially for some. Not going to get the specifics (i.e. ptype, snow totals, etc.), but at least we can see what the ML runs have in terms of the track into the medium range.

https://charts.ecmwf.int/?facets={"Product type"%3A["Experimental%3A Machine learning models"]}

I mentioned this yesterday...it looks like the 00Z ML suite also shifted significantly S/E with the low pressure compared to 12Z yesterday. Which tells me (from this extremely small sample size) most of the trend is a result of changes in the initial state, not biases in the ECMWF model physics. 

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