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Arctic April

This run shouldn't be interpreted as legitimate, but it's definitely a good example how you get triple phasers (like the Mar 1993 superstorm for ex). Southern stream wave gets out in front of the main long wave axis, causing the whole trough to rapidly tilt negatively & make the most of barotropic energy conversions that allow the trough to lean against the mean westerly shear and convert the background momentum into eddies.

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If the euro ran further, If I was a betting man, I would bet that trough in the NE would get out in time and that southern stream wave would phase with that trough digging around the northern US (ND/SD) cuasing us to get in the warm sector and yet another severe event, that’s a active pattern, for severe and big weather changes (cold/warm) 2F6732D1-6444-4FAC-AEF8-219BDB6F7FE2.png
 
Webberweather53 said:
This run shouldn't be interpreted as legitimate, but it's definitely a good example how you get triple phasers (like the Mar 1993 superstorm for ex). Southern stream wave gets out in front of the main long wave axis, causing the whole trough to rapidly tilt negatively & make the most of barotropic energy conversions that allow the trough to lean against the mean westerly shear and convert the background momentum into eddies.

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Holy shart batman
 
Webberweather53 said:
Hey, I got another one for your weather model archive @Ollie Williams


Just your casual 966 over Michigan

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Webberweather53 said:
This run shouldn't be interpreted as legitimate, but it's definitely a good example how you get triple phasers (like the Mar 1993 superstorm for ex). Southern stream wave gets out in front of the main long wave axis, causing the whole trough to rapidly tilt negatively & make the most of barotropic energy conversions that allow the trough to lean against the mean westerly shear and convert the background momentum into eddies.

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Myfrotho704_ said:
still EPS is slower with that shortwave, still trending more favorable for severe
(My bad for the blurry GIF I just found a random website to make a gif) View attachment 38493
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This is the site I typically use: https://gifmaker.me/

Indeed, feels like we're beating a dead horse but here we are again with a strengthening southeast ridge on the models. It's just like winter, except we don't have to worry about cold rain.

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I just had a very nice and fairly strong thunderstorm roll through. In 15min got 0.24" of rain, tiny hail, gusty winds, and lots of thunder and lightning (mainly cloud to cloud). Sun is back out now
 
Hate to admit it, but the 12z EPS definitely supports the LR op Euro in a very general sense. Minute details make all the difference between several sheared waves moving along the gradient, one monster cyclone, or something in between.

ecmwf_z500a_us_9.png

ecmwf-ens_z500a_us_9.png
 
Webberweather53 said:
Hate to admit it, but the 12z EPS definitely supports the LR op Euro in a very general sense. Minute details make all the difference between several sheared waves moving along the gradient, one monster cyclone, or something in between.

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Yep, this look is more similar to what we saw in the winter, -EPO, but a -PNA coupled with it, with breathing room for the SER, I wanna bet by tommorow afternoon, that trough will be in the western US E14D9504-0320-4778-AB9D-A22C8D8B63DA.gif
 
It would also make sense for the SER to expand given the fact that many ensembles create a mean that dampen and “expand” that trough in a way to make it look larger, add the fact that wavelengths are shorter, welp bring the SER on, lol
 
Myfrotho704_ said:
It would also make sense for the SER to expand given the fact that many ensembles create a mean that dampen and “expand” that trough in a way to make it look larger, add the fact that wavelengths are shorter, welp bring the SER on, lol
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Yeah, basically what we're seeing in that instance is the entire wave train just amplifies as we get closer to verification over the Pacific & North America, which shortens the wavelengths and causes the SE ridge. The stronger than forecast Pacific-W Hem tropical forcing (mainly in the form of Kelvin waves) is one likely reason for the stronger SE ridge, and I suspect the really warm SSTs plus lack of upper air data are other reasons for the recent volatility.
 
Next week's threat of severe weather in the southern US & unusually strong subtropical jet are closely tied to a slow moving Convectively Coupled Kelvin Wave in the Pacific (blue shading). The enhanced tropical convection associated with the favorable convective envelope of the Kelvin Wave causes increased potential vorticity redistribution as well as poleward potential vorticity advection (basically this just means that convective heating causes upper level heights to rise (creating ridge anomalies) due to thermal expansion from the heating (PV redistribution), and these ridge anomalies propagate poleward (poleward PV advection)).
Ultimately, the increased upper level height anomalies and divergence creates more poleward angular momentum which gets dumped into the subtropical jet, locally accelerating the jet stream. This argument is also consistent w/ thermal wind balance where horizontal temperature & pressure gradients (baroclinicity) are related to the strength of the jet. Thus, you'll often see the subtropical jet becoming stronger over longitudes of active tropical convection, this is a classic case of that.

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