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Dec 29-Jan 2 potential storm event


Brian D
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12 minutes ago, StormChaser4Life said:

Long range nam so take it with a grain of salt but it's way south with the 500mb low. Has sfc low at 84hrs just off shore from Houston. Crazy

If we still had the DGEX it might have had the low in Cancun

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Just now, RCNYILWX said:

For those keeping score of the 00z cycle, the RGEM came in way south with wave 1.

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Indeed.

Regarding wave 1, the Canadian has been insistent on a somewhat respectable corridor of ice running through here or nearby.  It's interesting because southerly/southeasterly flow is not really favorable to be locking in freezing rain for a long time, especially without a prime antecedent airmass.  I guess something this has going for it despite the S/SE flow is that warm layer aloft is not extremely warm this far north and the surface low is still relatively weak and organizing as it's passing through.

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Indeed.
Regarding wave 1, the Canadian has been insistent on a somewhat respectable corridor of ice running through here or nearby.  It's interesting because southerly/southeasterly flow is not really favorable to be locking in freezing rain for a long time, especially without a prime antecedent airmass.  I guess something this has going for it despite the S/SE flow is that warm layer aloft is not extremely warm this far north and the surface low is still relatively weak and organizing as it's passing through.
Also coming off the very dry surface high, the dew points start quite low and southeast surface wind through 06z or 09z is pulling from dew points still in the upper teens to lower 20s over central Indiana.

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1 hour ago, Kaner88 said:

If we still had the DGEX it might have had the low in Cancun

Good ol' DGEX. I miss that whack model. I can tell that this 2nd wave is going to be held back from fully taking off because of the confluence downstream. 0z gfs definitely se more with sfc low. It did close off a 500mb contour and even has some residual energy after Fri. I wish gem had more model support but it seems to be a stand alone on 1st wave being that south.

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Good ol' DGEX. I miss that whack model. I can tell that this 2nd wave is going to be held back from fully taking off because of the confluence downstream. 0z gfs definitely se more with sfc low. It did close off a 500mb contour and even has some residual energy after Fri. I wish gem had more model support but it seems to be a stand alone on 1st wave being that south.

The GFS has been bumping south each run, and the UKMET was in similar range of the GEM.


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For wave 1, thinking that I could manage about 1" before changing to mix and then rain to wash away whatever snow falls.  Not supremely confident in that amount yet though.

For the New Years part, I am very confident in it not being 100% plain rain.  Even the least wintry scenario should at least start as a period of ice, but a snowier possibility is still on the table.

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1 hour ago, StormChaser4Life said:

Long range nam so take it with a grain of salt but it's way south with the 500mb low. Has sfc low at 84hrs just off shore from Houston. Crazy

 

1 hour ago, Kaner88 said:

If we still had the DGEX it might have had the low in Cancun

Would definitely love to see the next few frames on the DGEX right now, for personal reasons. :weenie:

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21 minutes ago, hawkeye_wx said:

The Canadian has shifted well southeast with the Friday system and falls apart when it crosses the Ohio river.

We needed the threat of the storm fading to add some drama.

The ICON is on other end of the spectrum, pretty far north (I look at it now that we're within 5 days :P)

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Yeah, as a couple other models fade back southeast, the UK keeps inching nw.

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All about how quickly the southern wave gets sheared out. Even on a stronger/NW solution like the UKMET, the wave opens up but is able to lift much farther north with incoming northern stream energy much slower. GEM is much stronger and faster and therefore farther southeast earlier with the northern stream energy, which shreds wave 2 in the confluence.

 

So many pieces coming into play for wave 2 that won't be sampled fully until mid week and it's already a faster flow pattern that gives the models fits, so expect the operational runs to have large variance and large spread in the ensembles until more than satellite data from the key features can get inputted into the model initialization.

 

 

 

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The GEMs especially but also the UKMET have been consistently farther south with wave 1, and we've seen a several run south bump from the other guidance since. Question is do we see the southward adjustments continue once the first wave is fully sampled?

In making a hypothetical forecast blend at this point, I think I'd give a nod to the consistency of the GEMs and UKMET and weight them more than the Euro, GFS, NAM. Will be interesting to see trends with the 12z guidance when the wave is fully sampled.

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What is wrong with these models? 

I'll take a stab at this. It would be cool to get a take from an actual modeler on the frustration we all share in the apparent degradation of short-medium range forecasts, especially in the winter.

 

My perception since I've worked at NWS Chicago in 2010 is that the operational model forecasts haven't improved much if at all for our region. Meanwhile, I know that the modelling is so much more advanced now than it was then. I think there are a few feasible culprits to lack of good model consensus at fairly short lead times and changes in the forecast in short lead times.

 

1) Fast flow patterns have seemed to the rule in recent winters. Have seen it speculated on other forums/subforums that the fast flow may be linked to CC. Whatever the case may be, it makes logical sense that faster flow is tougher for even our advanced NWP of today to accurately handle key features that can often start as lower amplitude earlier in the forecast process. As we know, any errors at initialization get amplified the later into the forecast.

 

2) Lack of more recon sounding data over the all important Pacific basin. I don't know the full story behind data inputs that are no longer there, but it seems clear that satellite (despite the recent advances satellite data) and sparse aircraft soundings out over the open Pacific are insufficient to bridge the gap until RAOB sampling.

 

3) Doubled edged sword to ever higher resolution: Can very small scale features picked up by higher resolution modelling systems cause errors to increase quicker than more smoothed out data of the past?

 

Further discussion on this can probably be sent to banter, but I'm curious if anyone else has any other ideas on this.

 

 

 

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