Absolute Vorticity

tron777 wrote: ↑Sat Feb 11, 2023 9:43 pm

Closet Meteorologist wrote: ↑Sat Feb 11, 2023 8:11 pm

tron777 wrote: ↑Sat Feb 11, 2023 8:03 pm

Can you translate this for us novices?

The tweet is talking about the Stratospheric Warming Event (SSW) event we've been discussing on here for the last few weeks. The Polar Vortex (PV) is weakening due to warming in the stratosphere in the Arctic region. If the winds reverse direction then the PV could split. There are different layers in the atmosphere if you remember that from high school earth science class. We need that warming to work down from the stratosphere into the troposphere for us to see impacts where we live at the surface. We won't know until early or mid March most likely if it has the desired effects for snow lovers. Blocking returns in March and a delayed spring would be likely. There are no guarantees of course. These SSW events don't always go our way so at this point, we are in watch and wait mode. I will say this... if the MJO also gets into the colder phases, which it is forecast to do after Pres. Day then we may have something to work with late in the winter season.

Bgoney wrote: ↑Sun Feb 12, 2023 9:09 am

tron777 wrote: ↑Sun Feb 12, 2023 9:05 am Good morning all and Happy Super Bowl Sunday! A gorgeous day to fire up the grill or have a party for the big game this evening! Go Eagles! (For obvious reasons)

So anyway, the forecast going forward is pretty straight forward. A weak system Tues night then all eyes are on Thursday. The SPC has expanded the severe threat area for Day 5 as you can see below.


day5prob.gif


The timing of the cold front will be critical to see how much heating we can get as well as CAPE. In the colder months you don't need as much CAPE as you would during the spring and especially the summer months. The dynamics are most certainly going to be there with some guidance showing 75 knot wind shear 200-300 J/kg of CAPE and decent 0-3KM helicity values of 400!

Going to be interesting to see what the NAM puts out once in range

Bgoney wrote: ↑Sun Feb 12, 2023 9:30 am Dont see any changes in the long range. Same pattern holds to the 24th, then it appears we at least see closer to normal temps going into the last 4 days of Feb. Thank goodness it appears the MJO will quickly move through 5/6, but we still see the lag effects from those phases .

tron777 wrote: ↑Sun Feb 12, 2023 12:15 pm GFS and CMC are definitely weaker / more east with the low track for Thurs. Will be interesting to see what the Euro does later. CMC also looks interesting by Day 10 for snow lovers.

tron777 wrote: ↑Mon Feb 13, 2023 4:49 pm New Euro Weeklies are out and they show mild weather thru the end of Feb and colder for the first 2 weeks in March. A -NAO and a +PNA actually develop. Now, due to the trends we have seen all winter, a +PNA is not likely to occur. However, the Scand. / Icelandic ridging, should it retrograde westward far enough into the NAO Domain then a -NAO would be very possible. We did have NAO blocking back in December with that frigid cold shot so we know blocking in that area can happen even if the +PNA doesn't. The -NAO would certainly help get the cold air more south and east especially with a broader PV over Hudson's Bay and the potential for the MJO to be in Phase 8 as well would also lend a helping hand. Again, low confidence and there is plenty of reason to be skeptical. However, at the same time, a nice gradient pattern is possible later this month and esp into March and if the baroclinic boundary is south of us, we can certainly cash in a time or two before spring. We've got to see some changes occur for sure or the pattern will be wet with a lot of severe wx should we continue down the current road we are on. See this coming Thursday as an example.

Bgoney wrote: ↑Mon Feb 13, 2023 5:22 pm

tron777 wrote: ↑Mon Feb 13, 2023 4:49 pm New Euro Weeklies are out and they show mild weather thru the end of Feb and colder for the first 2 weeks in March. A -NAO and a +PNA actually develop. Now, due to the trends we have seen all winter, a +PNA is not likely to occur. However, the Scand. / Icelandic ridging, should it retrograde westward far enough into the NAO Domain then a -NAO would be very possible. We did have NAO blocking back in December with that frigid cold shot so we know blocking in that area can happen even if the +PNA doesn't. The -NAO would certainly help get the cold air more south and east especially with a broader PV over Hudson's Bay and the potential for the MJO to be in Phase 8 as well would also lend a helping hand. Again, low confidence and there is plenty of reason to be skeptical. However, at the same time, a nice gradient pattern is possible later this month and esp into March and if the baroclinic boundary is south of us, we can certainly cash in a time or two before spring. We've got to see some changes occur for sure or the pattern will be wet with a lot of severe wx should we continue down the current road we are on. See this coming Thursday as an example.

That sums it up, but those are big changes that need to happen. I'm still hopeful the MJO is going to get through 7 and possibly enter 8. Just moving into 7 at moderate strength can help push the baroclinic zone a bit south , but I don't think it would be enough for us along the river, more a I 70 benefit and this would be the last few days of Feb. Possibly. If it can move Into 8 it should help with a better EPO and I think it would benefit all the OV with better chances at winter, especially with a shift in the low track

snowbo wrote: ↑Mon Feb 13, 2023 5:47 pm A little off topic. Just checked in to the Bay Mills casino overlooking Whitefish Bay on Lake Superior. Talked to the lady at registration and she said “the weather is supposed to get really bad! It’s supposed to get above freezing!” It’s all in your perspective!