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Key to christmas storm making a comeback


HKY_WX

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Many people are talking about the subtropical vort being the main culprit of this system evolving more favorably today. But it is not. If you look at the animation below, you can see a comparison from 18z yesterday to 12z today. Notice how the southern vortex is basically unchanged, in size and location. The main player now is the northern stream. It has trended remarkably different in just 3 runs. As we were discussing last night, we need the northern jet to come in behind and re-energize the southern surface low, ie "phase". If you look back at any great phased system, that is what results. Over the last two days, we've been seeing the northern stream too fast and suppressive, shearing out the southern vortex.. The models could bounce around, but if we want to go back to the euro from a few days ago, we need to keep seeing this particular trend continue.

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Many people are talking about the subtropical vort being the main culprit of this system evolving more favorably today. But it is not. If you look at the animation below, you can see a comparison from 18z yesterday to 12z today. Notice how the southern vortex is basically unchanged, in size and location. The main player now is the northern stream. It has trended remarkably different in just 3 runs. As we were discussing last night, we need the northern jet to come in behind and re-energize the southern surface low, ie "phase". If you look back at any great phased system, that is what results. Over the last two days, we've been seeing the northern stream to fast and suppressive, shearing out the southern surface low. The models could bounce around, but if we want to trend back to the euro from a few days ago, we need to keep seeing the trend continue.

thats a goood move!!! maybe i could get my 6-8 inches like they said at first. hmmm looks plausible if it keeps trending.

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thats a goood move!!! maybe i could get my 6-8 inches like they said at first. hmmm looks plausible if it keeps trending.

not sure if the gfs is right, but it is interesting how this move happened at 12z. usually big jumps at 00z and 12z are due to data ingestion. considering the northern s/w is entering the US soon, could be legit'.

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Great analysis as always Brandon...I know it's an overused cliche, but tonight's 0z's are HUGE. Wouldn't shock me if this ends up being nowcasting storm for some areas with the NWS playing catch-up the whole time.

thanks dan, i think this has been the most difficult storm to anticipate, that i can remember in several years.

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whats interesting in your post is that the 'players' are sort of lining up like you and the other great forecasters have been discussing, and what it would take to actually get a decent snowstorm. sort of odd to see the obs and that it may be occurring, and the models are missing it (i hope)

should be an interesting night, and hopefully not a complete dream crusher at 00z

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The models continue to be playing catch up with this wave. WV loop shows it in eastern Montana diving towards NW Nebraska. The RUC continues to trend west with this each consecutive run and you can it see on WV loop (dry slot over eastern MT/northwest SD) still west of the latest RUC run (00z below),

Time Sensitive

sat_wv_us_loop.gif

ruc_500_001s.gif

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This is away form the Thread so, how do you feel about our lee side? Now after the NAM?

Looks wetter but will it produce into WNC or the foothills?

The upper levels look great to me for most of nc. The question remains how does this keep trending? Anytime you see the 500mb low cutoff over the midwest like it does on the nam at 36, with the vorticity advection going up the coastal plain, you can usually sit the coastal low on the coastline or just offshore. GFS should be very interesting.

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The upper levels look great to me for most of nc. The question remains how does this keep trending? Anytime you see the 500mb low cutoff over the midwest like it does on the nam at 36, with the vorticity advection going up the coastal plain, you can usually sit the coastal low on the coastline or just offshore. GFS should be very interesting.

indeed. upper air suggests a ride up or just off the coast. NAM is actually west of the 18z GFS, but the NAM has a scattering of vorticities at the head of the ULL influencing the position, trajectory and intensity of the SLP, which is why the GFS has the ULL a little more cut off than the NAM. If the GFS has the trough position of the NAM this could be a coast hugger

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indeed. upper air suggests a ride up or just off the coast. NAM is actually west of the 18z GFS, but the NAM has a scattering of vorticities at the head of the ULL influencing the position, trajectory and intensity of the SLP, which is why the GFS has the ULL a little more cut off than the NAM. If the GFS has the trough position of the NAM this could be a coast hugger

agreed. checkout latest ruc. vort over texas is still cutoff at 5 hours.

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The upper levels look great to me for most of nc. The question remains how does this keep trending? Anytime you see the 500mb low cutoff over the midwest like it does on the nam at 36, with the vorticity advection going up the coastal plain, you can usually sit the coastal low on the coastline or just offshore. GFS should be very interesting.

best baroclinicity should be just a bit offshore given very cool SST's at shore.

One of the things I saw with the GFS/NAM at 00z is there's quite a comma head developing at 700mb of deeper RH's, and deep 850mb moisture as well in the 36-48 hour range. I wonder if two things are being subtlely missed on the wraparound. it is overplaying downslope with this setup and thusly underplaying dynamics here on a mesoscale sense.

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