ILMRoss
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Everything posted by ILMRoss
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Tbh the big, smothering 1040 high is one of the most promising features of this setup thus far .
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Some thoughts; This is an uncommon, although not unheard of, setup that exists because of the thermal gradient. Check this out: There is a very intense thermal gradient here with a trough in the NE and a strong ridge poking in from Florida. The general mechanism for winter mischief is that any blip or impulse riding this gradient will be able to kick up precipitation from frontogenesis and general warm air advection (which sounds scary but in pure scientific terms is another way to produce lift. WAA = lift!) The high pressure also helps. I’m not really focusing on the potential coastal closer the euro has until a few more days pass. The issue here is the high 500mb heights; it may not be very cold throughout the entire atmosphere and *whatever* this is may evolve into a delicate mix forecast as cold air still has potential to undercut things at the surface. Synoptically, I think a similar event is 1/28/14 (which eventually brought a moderate snowfall along a wave riding a big thermal gradient) although not a perfect analog. It’s an imperfect setup but there’s a higher ceiling than most events due to the potential duration/moisture supply.
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The system on Thursday very much has legs. Let's be clear- Not a very high ceiling system! The best case scenario is probably a 1-3 inch event on the northern half of the state! But, beggars can't be choosers. The difference for the last few runs of the GFS is a much healthier merge between the two parent jet streaks on the shortwave. when it's exiting Texas.
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Thursday definitely has the potential to be a meat and potatoes, flat, light to moderate snow event. CMC solution is pretty tame and reasonable given the pattern. That other models don’t show a big snow i think is more indicative of how noisy/unpredictable to field of shortwaves is coming in after that. Short wave interaction is what could kill this opportunity and I think we’ll see inconsistency for one more run cycle or two before we know for certain this is worth keeping track of. The storm next weekend will be interesting, although unless something In the mid levels/high arrangement changes I don’t think the cold air will be robust enough for anything outside of a Acela corridor snow. Would love to be wrong though!
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I wouldn’t overlook the system coming next Thursday. The shortwave takes a nice track; it just gets sheared apart and just loses its integrity. Otherwise, it’s heading into a nice modeled air mass. If future runs begin to maintain the shortwave a bit further, Thursday gets more interesting.
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It wouldn’t take a lot of repositioning to make this shortwave on the euro a bigger deal. Perfect high. Something to keep track of.
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I would not write off some token flakes on Friday night, but those curling edges of the “front ends” are hard to predict 12 hours out, not just 5 days. Whatever falls would then have to be beefy enough to not evaporate in the residual dry air mass. So I wouldn’t put hard money on that. Next week looks cool, with ample opportunity if the structure of the pattern holds, but most veterans here know how quickly that can sour. Would not yet focus on any particular time period.
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Keep an eye on Tuesday. If the shortwave nudges a little deeper/stronger keeping with previous trends, I-40 corridor could be in for a quick treat.
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this snow threat is kind of cute but i'm mainly just POed that it's cutting the tail off of the fall golf season. courses will be brown and soggy by november
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Wow, the FV3 GFS has absolutely shown killer consistency, right to the end. If this storm follows it's script, what a coup! Nice to have a trustworthy (at times) tool in the the toolbox, or at least moreso than the current iteration of the GFS.
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From what I understand thunderstorms oriented perpendicular to the storm track essentially act as a firehouse of moisture into a system, whereas storms oriented parallel to the storm track can basically act to cut off the conveyor belt of moisture by disturbing the inflow into the storm.
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I like cranky, and I think he can have some moments of brilliance, but often I find his reasoning to be oversimplified... like right here. Gee, if it were as easy as looking at cirrus clouds, I'd be out of a job right now.
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RGEM has a sharper, more negatively tilted wave as early as 36 hours from now, which is causing the stronger solution. I don't know much about how the RGEM handles synoptics but I wouldn't attribute the run to mishandling of convection.
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My guess is that the suppression trend is partly tied to this: the trend is for the ULL to "landfall" into Baja California as a more and more positively tilted wave. This positive tilt has ramifications downstream for its orientation, how amp the wave gets, and where some temperature profiles set up because a more negative tilt can raise heights downstream.
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Something I’d watch out for in this next suite is cyclogenesis along the Atlantic- so far not a single global has represented this well to my eye. The mesoscale models look more believable. Here’s what I mean: Cyclogenesis is favored to occur in areas where there’s already a distinct low level vorticity axis (think: frontal boundary! “Low level vorticity axis” sounds like an intimidating weather term but it’s really just represents a wind shift!) In CAD regimes, there’s always a super distinct axis just off the coast between the CAD Airmass and the coastal front. Thus, as that area has some lift imparted on it, you’d expect pressures to drop and cyclogenesis to initiate. The globals don’t show this. Here’s the GFS: it has not signature along the Gulf Stream at all... and I’m not sure I buy that. Here is the nam in comparison at the same time: In the nam, there’s a much more distinct signature of this taking affect, and this represents what “supposed” to occur in this scenario. I think this is helping toss everything more northward in the NAM. Now, obviously, meteorology doesn’t always bend towards what’s “supposed” to happen, as any seasoned weather enthusiast knows. That being said, I wouldn’t be surprised to see a “CAM vs Global” battle emerge today as more CAMs get in range. Lastly- CAM = convection allowing model- think NAM, RGEM, HRRR, etc. They don’t have to parametize convection with their higher resolution. .
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All I’m going to say is, Fish loves ensembles, and Fish loves certainty, and the ironclad nature of 1 inch + totals on the ensembles have probably weighed on that team.
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CAD actually warms the other side of the Apps. We’re all familiar with how cold, dense air “piles up” on our side, creating CAD. However, on the Tennessee side, there’s all of the sudden much less air making it over the mountain, which lowers air pressure (why you see an inverted trough here) and ultimately warms the area.
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I spoke a little too soon, next frame the r/s line makes a bit of a comeback, almost back to the previous run
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Solid 40 mile shift N with r/s line, weaker high here.
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18z FV3 already looking like a pure weenie run
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Wouldn't be surprised if there's a diminished gradient because more members are throwing some of that front end thump further east. that initial finger of precip extending ahead of the storm can be a doozy. I would still expect the main rain/sleet line to developed somewhere along RDU/CLT during warmest portion of storm
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Really I wouldn't even focus on p-types much right now at all, not until the NAM-3km and RGEM has taken a couple of cracks at this storm. Until then, a rough guideline would be to take the modeled 850 0C line and imagine another line 50-75 miles north of that... there's your sleet zone between those lines. We're still talking NC snow, lol.
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FV3 is fine, the low is going to gravitate towards the Huntsville/Knoxville area a little before the transfer because of the CAD forming lower pressures on the OTHER side of the Apps... One more thing to think about is the overall pressure field remains similar, but that little "L" icon is going to shift. It's there because Levi's or whoever's code puts that L at every local minimum... and in a transfer like this, that could be a lot of areas! Run to run, the "L" could jump by hundreds of miles, but in the grand scheme of things, it's probably not a big shift. It's a psychological thing! Be careful!
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FV3 looked fine to me, a touch slower but overall maintained the same general r/s line.
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GFS is wild. Check this out. I got two trend gifs. First one is the 500 vort over Texas: So, there's some variation, and these differences are important! But for the most part, it's just noise, and the front end outcome hasn't changed much with this system. Now fast forward 24 hours later: There are worlds of differences here- vort maxes aren't just in different states, they're in different regions- Especially on the last 3 runs. This has a lot implications for how our trough is oriented, where the best lift is, where the SLP ends up, and consequently, where the high gets pushed. Don't really know what's going on upstream for the GFS to cause these differences. I also don't know if other models have this, it's just the first thing that caught my mind on the GFS. Any of these solutions are still probably plausible but it's definitely weighing on my mind that the GFS has no idea what's going on once this shortwave gets into the SE.
