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Post by ndolan387 on Dec 13, 2019 18:17:29 GMT -6
The 18z GFS soundings show some dry air in the dendrite growth zone (DGZ). I know it's still far out...tomorrow's 12z runs will be more telling as the system will be in N CA and further west on land. It looks like this event will have most of its ice nucleation formation just below the DGZ at around 600mb. Using the top down approach, there looks to be a moderate warm wedge from 700mb down to 850mb. Then, refreezing taking place (3* C colder) from 850m down to 950mb. Then some warming near the surface. Overall at 00z Sun, the column looks fully below 0* C so most likely snow. Though, I have my doubts...bc that sounding to me says sleet. It's possible that we may not get good dendrite growth. As well, we are going to have some trouble with freezing rain IMO after midnight into very early. Mon once the warm wedge from 700mb to 850mb gets more intense and ice crystals melt more (column gets above 0* C). And the cold air from the surface isn't at least 3* C colder so freezing rain forms instead of sleet/snow at the surface. Overall, I think at least a 3 hr window of potentially intense WAA snow is becoming likely to start at 2-3pm on Sun. Most of all WAA events start a couple hours earlier. I think Chris's forecast looks good. Although once again, I am wondering if sleet will cut into our totals.
Moving on deformation snows look possible later Mon which would easily get us into the 1-3" range. But we know that isn't a given until are 24 hrs out up to the time it's snowing (when wave 2 rolls through).
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Post by ndolan387 on Dec 10, 2019 11:09:39 GMT -6
12z ggem is nice. It’s a weaker version of the gfs, with a moderate impact event. Yeah the GEM looks beautiful. Weaker, but better quality for STL. Not too bad for you in Chicago either.
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Post by ndolan387 on Dec 10, 2019 10:18:14 GMT -6
12z gfs has the storm. Quick hit of WAA snow and ice before the main show shifts into northern Missouri and Illinois. Smorgasbord of precip types that the GFS is giving out for STL. Let's see what the GEM/Euro have for lunch today.
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Post by ndolan387 on Dec 9, 2019 12:35:28 GMT -6
The HRRR is picking up on some surfaced base CAPE for that band!
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Post by ndolan387 on Dec 6, 2019 18:19:15 GMT -6
Happy Birthday Snowman99! I hope the atmosphere can make the next snow storm a Union jackpot and not a Union hole haha.
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Post by ndolan387 on Dec 6, 2019 12:57:17 GMT -6
The data assimilation monitoring page is here. www.nco.ncep.noaa.gov/idsb/nwprod/realtime/The 12Z cycle incorporated 36,689,170 pieces of information. The 18Z cycle incorporated 38,006,003 pieces of information. Quality is probably more important than quantity though. The 6/18 cycles are still missing the crucial RAOBs of course. This is partially offset by aircraft soundings which are said to be at least as accurate as RAOBs, but the data is constrained by the limited altitude of commercial aircraft. Its probably worth mentioning that the 6/18 cycles build upon the 6 hour forecast from the 0/12 cycles so if you improve the quality of the on-hour initialization it should have a positive impact on the off-hour initialization as well. Unless something has changed recently I believe RAOBs are still essential for improving model skill past day 5 likely owing to the direct sampling of the stratosphere. I was actually just looking at model skill scores this morning. It seems as though the FV3 may have closed the gap between 6/18 and 0/12 even more. Though the gap was already small enough that it likely had little if any statistical significance. The differences were still only in the thousandths of a decimal place even on D8 forecasts at 500mb. Objective verification scores can be found here. www.emc.ncep.noaa.gov/gmb/STATS_vsdb/Thanks for all the info. I'm impressed by the amount of detail you know!
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Post by ndolan387 on Dec 6, 2019 12:55:16 GMT -6
Watching the models too closely is like watching the stock market too closely. Both will leave you confused haha. The 18z GFS run went back to showing a little snow for Tuesday. Sometimes it's best to just sit back and not get caught up in the model madness haha (unless you like it). Do you guys know if the 06/18z runs still have less data than 00/12z runs? I’ve heard that’s just a rumor and the verification scores of the off hour runs are just as high as the 00z/12z runs. This makes sense. Good to know, thanks!
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Post by ndolan387 on Dec 5, 2019 16:50:23 GMT -6
Watching the models too closely is like watching the stock market too closely. Both will leave you confused haha. The 18z GFS run went back to showing a little snow for Tuesday. Sometimes it's best to just sit back and not get caught up in the model madness haha (unless you like it). Do you guys know if the 06/18z runs still have less data than 00/12z runs?
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Post by ndolan387 on Dec 4, 2019 21:07:39 GMT -6
!AccuNotWx!Pro has a relative vorticity mean product on the EPS. Good to know! Thanks...you are very knowledgeable with the weather. It's fun to always see your upcoming pattern viewpoints (ideas).
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Post by ndolan387 on Dec 4, 2019 21:06:21 GMT -6
I understand, true! But does the GEFS provide the 500mb maximum vorticity? The more I think about, I guess it would be overkill to have. I can't find it. But, I haven’t looked that hard for it haha! Ok, I'm going to geek out for just a moment... Vorticity on a 500mb chart is usually either absolute vorticity or sometimes just relative vorticity. And, you of course already know that absolute vorticity is the sum of planetary vorticity, curvature vorticity, and shear vorticity (note relative vorticity is just the sum of the latter two). Now I'm not aware of any site that computes the ensemble mean absolute or relative vorticity but I do know of one site that produces charts showing the probability of trough axis location based on the magnitude of curvature vorticity of all members; though I'm not really sure what thresholds are used. The caveat is that shear vorticity isn't accounted for and that's probably ok because the product is really meant to be used as a medium/long range diagnostic of the synoptic pattern of which curvature is perhaps more important. So the product can't really be used as a true representation of the "mean max vorticity". And besides the washing out of features when averaging several members several days out probably wouldn't make that anymore useful than what this product already does. Another thing to consider is that "probability" in an ensemble suite can be taken too literally. This issue is that ensembles tend to be under-dispersive and don't necessarily represent the true spread of possible outcomes. Anyway, here's the link... www.atmos.albany.edu/student/tburg/analysis/loop.phpSelect GEFS, then Probability tab, then Features -> Trough Probability. Thanks for your insight! It's very detailed. We care about where the maximum absolute vorticity is being advected. Where it's being advected is important and has a correlation to exciting weather at the surface.
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Post by ndolan387 on Dec 4, 2019 14:38:17 GMT -6
Anybody on here like fruitcake? To all who don't like fruitcake! The 12z Euro run was like eating fruitcake instead of pumpkin pie for us snow enthusiasts haha.
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Post by ndolan387 on Dec 4, 2019 11:43:23 GMT -6
exercise in futility to try and iron out GYB features this far out... we're only within the territory of a decent synoptic setup. I understand, true! But does the GEFS provide the 500mb maximum vorticity? The more I think about, I guess it would be overkill to have. I can't find it. But, I haven’t looked that hard for it haha!
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Post by ndolan387 on Dec 4, 2019 11:41:53 GMT -6
For late next Mon into Tues: The GEFS 850mb mean low is SW of the 12z GFS model run, but not by much. Maybe 30ish miles. That doesn't look that bad of a placement for the 850mb low. Someone correct me because I'm still iffy on this. In addition, regarding the deformation bands, we don't look to be in the prime zone: 150ish miles from the 500 vorticity maximum, but are close for the 12z GFS. Does one of the model platforms for the GEFS provide a mean of the 500 vorticity maximum? On Tropical Tibits, it doesn't. I know it's 6 days out haha, but I was wondering if any of you knew. Chris has brought attention to this GYB rule. I was looking at individual members and they looked closer the 12z ggem. I agree the general ingredients look good, but the cake being spit out is carrot instead of double chocolate I see what your saying. I'll take carrot cake at this stage of December and double chocolate around Christmas haha! I like the analogy.
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Post by ndolan387 on Dec 4, 2019 11:25:20 GMT -6
GEM is close... similar pattern, but a bit more sheared out. Gfs ensembles are no bueno for Monday-Tuesday For late next Mon into Tues: The GEFS 850mb mean low is SW of the 12z GFS model run, but not by much. Maybe 30ish miles. That doesn't look that bad of a placement for the 850mb low. Someone correct me because I'm still iffy on this. In addition, regarding the deformation bands, we don't look to be in the prime zone: 150ish miles from the 500 vorticity maximum, but are close for the 12z GFS. Does one of the model platforms for the GEFS provide a mean of the 500 vorticity maximum? On Tropical Tibits, it doesn't. I know it's 6 days out haha, but I was wondering if any of you knew. Chris has brought attention to this GYB rule.
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Post by ndolan387 on Dec 4, 2019 10:18:07 GMT -6
That’s a kaboom for Chicago. Hopefully we can get the models to trend towards a solution similar to this 850mb low looks to be near/just south of Ste. Genevieve on that run which is decent.
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Post by ndolan387 on Dec 3, 2019 10:23:09 GMT -6
850mb low is close to our wheel house (SE MO, border with IL, KY, just north of Memphis, TN) for next Mon late into Tues on the 12z GFS run! The 06z GFS was further north with the 850mb low and had it passing almost directly over us, but spitted out more digital snow haha. Interesting trends, this one will be fun to watch like worldseries said.
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Post by ndolan387 on Dec 1, 2019 21:08:33 GMT -6
Looks like a lobe of more concentrated sn sh might ride down the river and affect st louis and points east in a couple hours. Maybe even a light coating in spots. Yeah that band moving slightly NW to the SE parallel to the Mississippi looks likely to bring a dusting across metro especially on elevated surfaces! Edit: starting to loose steam, still will see more dendrites.
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Post by ndolan387 on Dec 1, 2019 14:55:38 GMT -6
I second your thought unclesam. Steep lapse rates, strong backside cyclonic flow, some lift, just enough moisture, and cold 850mb temps made/make for some pretty mood snow today as we ring in Dec and the last month of 2019!
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Post by ndolan387 on Nov 30, 2019 21:50:59 GMT -6
The WAA wasn't as strong as predicted. The fog played a role in us not seeing the 60s! Important to note regarding bigger low pressure systems this upcoming winter if there's a trend.
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Post by ndolan387 on Nov 24, 2019 21:30:55 GMT -6
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Post by ndolan387 on Nov 23, 2019 9:51:08 GMT -6
We got some little pockets of snow/sleet/rain coming through the metro. I'll take it before the pattern reestablishes itself after Turkey Day!
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Post by ndolan387 on Nov 20, 2019 8:36:44 GMT -6
00z gfs obliterates Nebraska next Tuesday and Wednesday. That storm is mean The storm gets so wrapped up it actually becomes warmer on the northern side and colder on the southern side This just shows you how wild the wx pattern is next week...at this point what we know now like others have said is that some areas in the middle part of the country will experience a potential blizzard, heavy rain (severe thunderstorms), and or high winds haha. At this point if you are traveling next Tues/Wed, I would pay attention because there could be bad delays and slow ETAs!
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Post by ndolan387 on Nov 15, 2019 22:16:21 GMT -6
GFS is cutter city. Enough to pull in some CAPE and shear. Now that's what we are used to. We know that storm track all too well haha.
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Post by ndolan387 on Nov 14, 2019 11:44:48 GMT -6
impressive to see snowpack still popping up on visible satellite. Snowcover is hanging tough here. Even with temps a few degrees above freezing Take Kansas City, MO for example. The solar elevation angle is a little over 14* less on November 14th than March 14th @ 11:45-50am. Therefore, although daylight is around the same for these dates, the solar elevation angle is less for these dates across the Midwest so this may be playing a role in slowing down the melting of our snow. Take 2:30pm CST (Nov) or 3:30pm DST (Mar) time (peak heating hours), the solar elevation angle is around 8* greater on Mar 14 than Nov 14. www.esrl.noaa.gov/gmd/grad/solcalc/azel.html
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Post by ndolan387 on Nov 13, 2019 10:06:36 GMT -6
All, don't forget to update your snowfall totals so far this season in your status 😉
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Post by ndolan387 on Nov 13, 2019 9:58:32 GMT -6
So how does Thanksgiving look? Still to early? Trending toward a zonal pattern right now...15 days out tho haha
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Post by ndolan387 on Nov 12, 2019 21:49:12 GMT -6
1911-12 snowiest winter ever- 67.6”- corrected last post Wow that's a lot of snow
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Post by ndolan387 on Nov 11, 2019 18:57:36 GMT -6
2” here in Wildwood just south of Wildwood Horse Creek Rd.
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Post by ndolan387 on Nov 11, 2019 14:56:59 GMT -6
Back to a good moderate clip in Alton...M1.7" on an elevated surface in the shade. You should still be getting a good snowfall rate!
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Post by ndolan387 on Nov 11, 2019 14:53:06 GMT -6
Was pouring in downtown Clayton! Anxious to see how the snow east of Jefferson City acts in the metro. Snowstorm920 has a great point...it's much easier than this morning for it to add up with temps in the mid 20s. Right now up through sunset, the sun angle is decreasing as well. It's more like a fluffy snow now. I expect the evening commute to be more than interesting with potentially some problems.
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