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Weekend Storm Discussion 2/18-2/19


stormtracker

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Man oh man oh man. I can't believe we have in a matter of 24 hours gone from suppressed, to fringe light snow, to 992 MB Bomb and rain - and our 50/50 is getting weaker and weaker every run. I liked this better when it was suppressed, although I guess some wind and heavy rain from a 992 mb chesapeake bay storm might be somewhat interesting.

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There will be no one left in this subforum to enjoy that if this run plays out as depicted.

It's probably a mistake to attach high expectations for a cold snowy outcome at this point, given the preceding pattern winter-to-date, and lack of run to run stability in the best global models. 4-5 day out simulations are just that, and are bested viewed with a sense of detachment, even this evening's euro

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FWIW, here is the 00z GGEM solution tonight (to compare it to the GFS Solution)

108 -- SE AL/SW GA border at 1003mb

120 -- off HSE by about 50-100 miles at 999mb

132 -- wait for color

144 -- not out yet

There is a 50/50 low at 120 and a 1029 H in W Quebec as well at 120

Northern edge of the precip shield is over RIC at 108 - this one should be coming further up the coast than 12z.

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FWIW, here is the 00z GGEM solution tonight (to compare it to the GFS Solution)

108 -- SE AL/SW GA border at 1003mb

120 -- off HSE by about 50-100 miles at 999mb

132 -- wait for color

144 -- not out yet

There is a 50/50 low at 120 and a 1029 H in W Quebec as well at 120

no matter how many times you post it, it will never be worth anything

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If you run a loop at 500mb for the N PAC on the new 00z GFS, you'll see why the MJO is our friend. The propensity for a NE PAC ridge and NW PAC trough will allow waves to cut more southward than eastward across the western CONUS, allowing room for this potential phase in the eastern 2/3s.

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If you run a loop at 500mb for the N PAC on the new 00z GFS, you'll see why the MJO is our friend. The propensity for a NE PAC ridge and NW PAC trough will allow waves to cut more southward than eastward across the western CONUS, allowing room for this potential phase in the eastern 2/3s.

Now lets just hope it phases with the correct spoke of energy around the 50/50 otherwise its rain or OTS ;)

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Now lets just hope it phases with the correct spoke of energy around the 50/50 otherwise its rain or OTS ;)

The bigger players can only take you so far sometimes, true...

The other complicating issue is something that hasn't been talked about which is the wave dropping in from the NW Territories / Yukon. If this trends faster, it will help to compress the flow even more in Canada (buckling already from 50-50). It is not a big deal but it is something that may cause further alterations.

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I'm not surprised by the extreme run to run discontinuity from the GFS. The biggest player finally is coming on the table. The big feature in question? Its a arctic shortwave that is breaking apart over Alaska. I want to highlight how difficult it is going to be to resolve this small feature. But it also means some very interesting things, including a legitimate chance we could see a tripple phaser. In the following images I am going to compare the 18z run with the 00z run and show how small changes in the initialization have caused major changes in the storm evolution.

ezmss5.gif

So where are the changes coming from at the initialization. Well first we can tell the pacific ridge slightly less amplified than the 18z run. This does little to change the position of the primary shortwave, but two most northernmost shortwaves, both are shifted slightly south. This is going to make all the difference as we advance forward in time.

2qsc7rb.gif

Fast forward to +24 hours (00z Feb 16th)... The Pacific ridge is now a bit more amplified than before, but look how its evolved the two most northernmost shortwaves. The arctic shortwave is actually slower and slightly less amplified than before, while the shortwave located over western Canada has actually sped up slightly. The primary shortwave over the Western US is in nearly the same place at the same intensity, so its likely not a huge source of why we saw a large change between 18z and 00z.

flggav.jpg

Now we are +48 hours (00z Feb 17th)... The first obvious thing to not is how quickly the northernmost shortwave has really sped up... to the point that its now further east than the 18z run. This is the missing piece that allows the shortwave over Canada to dig down more as both of these pieces of shortwave energy interact. Meanwhile the southernmost shortwave now over the southwest has moved slightly further east of the 18z run, but the change is negligible compared to the other two shortwave features.

21lsewn.jpg

Finally at +72 hours (00z Feb 18th)... Major changes are now taking shape. The two northernmost shortwaves are now starting to phase together, but the southern stream shortwave is not far behind. All of the features at 72 hours are much closer together than 18z, and its off to the races beyond that. However, its important to note how important that northernmost shortwave is to getting all the pieces to fall into place. Any slight changes like we saw between the 18z and the 00z cycle are going to completely change the outcome.

So the 00z solution was an interesting phase between the polar and subtropical shortwave, but if the phase occurs earlier between the subtropical/polar shortwave as the arctic interaction occurs, this solution could get very interesting in a hurry. As is, the solution is rather extreme, but plausible given how sensitive these shortwave features are as the subtropical ridge over the northwest pacific amplifies.

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