GFS moves storms up to Tuesday, ECMWF in another universe

The GFS continues to flip-flop on severe weather potential next week. This morning's and last night's run backed off a bit from yesterday afternoon's in terms of potential, but that's because it had the system speeding up. Today's midday run has it speeding up even more, with a surface low just shy of the tenth level of hell in terms of strength developing in the "sweet spot" to our north west. This forecast predicts what I'd call a rather robust tornado threat for the southern half of lower Michigan on Tuesday afternoon.

That supercell composite is yellow-to-orange with only a maximum level of 500j/kg of SBCAPE being forecast. That tells you something about the wind speeds being predicted.

I'm not going to lie - this 100kt upper level jet depicted scares the hell out of me. When that upper level jet points in a southwest/northeast direction and you see contours separating to the east and west like that, you have an indicating of rising air. The more perpendicular the 500mb jet is to your location, the more 'spin' storms will have. A 200-300mb jet core of 130kts is being forecast by this run. This picture alone indicates a tornado threat all the way from lower MI into Ontario...

...But let's throw in this one for shits and giggles. Take a look at that warm air coming up from the Gulf of Mexico and mixing violently into the air at the base of this negatively-tilted monster.

A very powerful cold front would be occluding a fairly strong warm front. This would lead to extraordinary forcing for ascent, meaning that even in weak instability, you'd likely have big thunderstorms

A couple of forecast soundings for southern lower MI. The first (above) is for around 5PM Tuesday. No quality analogs to any documented supercell thunderstorms, but a clear pronounced "TORNADO" threat (note, not "WEAK TORNADO"). 

The second is around 8PM a little further east. As can be seen, the same solid "TORNADO" threat is present. This sounding actually does have an analog weak-tornado producing supercell thunderstorm associated with it. 

Now, throw everything you see above out the window for the Euro model's forecast. The ECMWF is in a completely different dimension. Yesterday's run forecasts a backdoor cold front to descend from the north/northwest and pretty much destroy any chance of thunderstorms along with any chance of temperatures in the 70s:

A "back door" cold front is one that comes from a direction opposite typical weather patterns - usually from the north or northeast - and typically in the spring time. The ECMWF is forecasting such an event, caused by high pressure further north. This would choke any hot days/severe weather chances. The model also places the center of the much-weaker storm much further north and west, centered over Alberta/Saskatchewan. This would be way too far east to influence our weather yet. 

With the spread between the models being this large at this point, this is one of those situations where you can't count on anything. The GFS has definitely been consistent regarding this cyclone developing, and intensifying very, very quickly. If it's forecast verifies this could very well wind up being a bomb cyclone, which could do very nasty things in our neighborhood. The ECMWF has only had a couple runs that can even see this point, though, so it's important to give it some time to crunch numbers. As the week goes on, more samples will be collected and a more accurate forecast will be put together. My gut is pretty neutral. Storms from the northwest have intensified pretty good this year, but the GFS may be overblowing this one a bit. We could wind up with something forming, but not quite the bomb that the model is currently spitting out. I'll revisit this tomorrow and hopefully have more solid data to interpret.