VERY INTERESTING, BIG WINTER IMPLICATIONS...

Before I get to Wednesday's wet weather, here's something that really caught my eye and has the potential to get winter off to the fast start I anticipated. If you caught my winter outlook (which you can review by clicking the image below), I mentioned the potential for a sudden stratospheric warming event and how that opens the door to Arctic air intrusions. I anticipated this development later in November which due to the lag time time involved would potentially bring cold into play during December.

Well, to my surprise both the GFS and EURO show a healthy stratwarm developing and maturing by the end of October. If you are unaware, a sudden stratospheric warming occurs when the polar stratosphere warms and the winds that normally flow from west to east around the pole weaken dramatically and even reverse direction, which in turn causes a breakdown of the polar vortex. (5-30 miles above Earth's surface, very high). Stratospheric warmings can eventually cause the tropospheric jet stream to weaken and buckle, which allows cold air bottled up near the polar cap to escape and expand into the middle latitudes and the Midwest. Depending on variables the impacts vary.

Here's what a SSW looks like on the weather models by way of animation. I'll use the GEFS. Notice the blues and greens being replaced by the warmer reddish brown colors. This takes place during the period October 12-28th

This stagnant image shows on the 28th the warming reaching its peak. This is at 10mb, way up high where it's typically incredibly cold. In this case, it's still a bitter air mass but relative to normal its balmy.

So what does it mean? Around the peak of the event, the stratospheric Polar Vortex should weaken allowing a warming of the stratosphere. At this time the disruption of the vortex will cause high pressure to build and extend across the Arctic all the way from the stratosphere to the lower troposphere. The highest pressure should be centered on Greenland resulting in the negative phase of the Arctic and North Atlantic Oscillation. That in turn favors colder than normal weather from northern Europe back to the eastern half of the US. The process takes time to complete by I would think by early to mid-November the switch will flip. The new trend of the negative AO/NAO could last up to a month. That is why winter could get out of the gates fast this year.

This is a very early event, somewhat unprecedented if it unfolds as currently indicated on modeling. The impacts would not be as significant as if this was January but just the same should have wintry implications. Below is a view of what a negative A0/NAO typically looks like during winter.

The EURO weeklies control run does show both the AO and NAO in predominately negative phases from Halloween to the end of the forecast cycle November 25th.

The AO

The NAO

Just for kicks, the EURO weekly control shows this for snowfall through November 25th. Isn't the linkage interesting.

Well, I spent half the night on that so I don't have much time to devote to Wednesday and the forecast but it seems pretty straight forward. The big ticket item is the deep fall storm that rolls through the Plains into NW Minnesota the next 24 hours. You can watch it wind up and streak NE in the animation below.

The primary impacts in my area will be wind and rain with the bulk of the precipitation ending by early afternoon. There is likely to be a short afternoon lull and then with the passage of a cold front towards late afternoon or evening a renewed chance of showers and storms is possible. This second period should only see scattered activity (if any). However, if we get highs into the low to mid 70s there will be enough instability and shear for a strong storm or two. SPC currently only has my area in a marginal risk at this time.

As for rains, here's what the models are indicating.

The EURO

The 3k NAM

The GFS

Thursday will cool down with readings behind the cold front down in the mid to upper 60s.

That leads us to Friday and the GFS continues to paint a wet scenario while the EURO keeps everything well to the south. I much prefer the EURO solution and think most of the area will remain dry under a mix of sun and clouds. The one area the could see some showers and more clouds is the far SE. We'll deal with that little issue tomorrow.

The remainder of the weekend looks dry and more like October. Saturday should be the coolest day with highs low 60s while Sunday looks more in the range of the mid to upper 60s. Nightime lows will be a little frisky with readings around 40-45.

Well, time to call it a post. Have a happy hump day, keep that umbrella handy and hold on tight as winds will be whipping. Roll weather...TS