Southwest Illinois had a pretty neat little mesoscale feature pass through this morning - a wake low. Right before 3am we had a significant pressure drop of about 7mb over the course of 15 minutes with 5mb falling in 1 minute (which is highlighted in the graph below from my weather station). That was quickly followed by strong wind gusts - I peaked at 36mph here at the house but I've seen reports of 60mph just across the river in Missouri.

So what is a wake low and what caused it to happen? A wake low is an area of lower pressure that we typically see on the backside of a squall line or in stratiform rain (much like we got this morning as you can see in the radar screenshot below). It appears as though the rain-cooled air built up a small region of higher pressure (several millibars higher than the surrounding air) as it moved through the area creating a strong pressure gradient over a short distance. Since nature is always working to be in equilibrium, that sharp of a pressure gradient is unsustainable. Eventually, this pressure bubble 'burst' in and when it did, it sent out a rush of strong winds that prompted numerous damage and high wind reports across the St. Louis metro and southwestern IL. 

If you have any questions, inquiries or suggestions, feel free to shoot us a message! We'll be happy to help. - Billy​

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As of 5:30 p.m. we are still waiting the arrival of the CME (Coronal Mass Ejection) with currently no indications of its arrival. This isn’t surprising. Forecast guidance from the Space Weather Prediction Center were indicating a glancing blow as a best-case scenario with the bulk of the CME missing earth. So, we’re either looking at a complete miss or the CME has yet to arrive.

I have been monitoring the data streams all day today anticipating its arrival. As it stands, there has been no increase in low-energy protons which often occurs as a CME approaches. It’s a helpful tool to use as an indicator that an impact is imminent. There has also been no uptick in solar wind speed, solar wind density, or the interplanetary magnetic field – all of which are used to monitor space weather conditions.

So, as I was eluded to with yesterday’s post, I think the odds of Illinois (and even southern Wisconsin for those of you wanting to skip town and head north a bit), seeing the aurora are close to zero especially now that we have a blanket of clouds moving in from the west and southwest (seen below).
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As always, if you have any questions, shoot us a message and we’ll be happy to answer.

Yesterday morning the sun decided it wanted to wake up from a deep slumber when it launched a CME (coronal mass ejection) towards earth. This CME was associated with a C4 solar flare which typically isn’t even newsworthy. However, we’ve been deep in a solar minimum for quite some time now as the sun begins its transition towards Solar Cycle 25 so anything like this gets our attention. Especially for those of us who are aurora-starved and just looking for an excuse to get out and photograph the night sky.
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So, what are my thoughts on Illinois seeing the northern lights this weekend? Well, they probably aren’t what you all were hoping. A lot of things are going to be working against us here. First of all, a C4 flare and CME is nothing to write home about. As stated above, this generally isn’t newsworthy. After reviewing model data (below) of the CME, it looks as though the CME will arrive sometime during the day on Saturday. My initial guess tells me sometime between 8am and 6pm. Clearly, the latter would be much better for us here in Illinois since that is closer to sunset. CMEs are notoriously difficult to model, though, so that time window should be taken lightly. I will have to monitor space weather data from the DSCOVR satellite to determine when the CME arrives. 

Secondly, there is the possibility of cloud cover for parts of the state. Given it is still a couple days out and there are  chances of rain showers across portions of the state, I’ll hold off on issuing a cloud forecast until we get closer to the event and I can analyze satellite data to make a call. Nowcasting is very important when it comes to space weather.

Finally, we have to overcome the moon phase. We just had a full moon so the moon is still almost completely full in the night’s sky and unfortunately it will be rising close to 10:30 on Saturday night. While it isn’t impossible to see the aurora with a full moon, it does make it much more difficult. Especially down here in the middle latitudes where our aurora are often more faint and subdued in terms of color than those magical photos you often see from Norway, Iceland, Churchill or Alaska.
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So what can we actually expect? Personally, I don’t expect much. I think the G2 warning is likely overdone and I don’t think anyone in Illinois will be able to see the aurora with their naked eye due to the inhibiting factors listed above. That being said, the aurora tends to produce very well around the equinoxes due to a process called the Russel-McPherron Effect. While it is not well understood, the magnetic field lines that connect the sun and earth tend to align around the equinoxes. Because of this, even weak disturbances in space weather conditions can spark auroras. I believe that was taken into consideration when the SWPC made their G2 forecast. With that being said, I think we would need a stronger solar storm generated by a more potent CME– ideally G3 to G5 – with a new moon and the arrival of the CME timed where the peak of the storm is occurring around midnight in order to provide us with maximum darkness in order to see the northern lights in Illinois with our naked eyes. Oh, we also need the weather on earth to cooperate too and you would need to find a location away from city lights – sorry, Chicago. 

Assuming everything comes together, i.e. we get clear skies, the CME happens to arrive around 5pm or so and it peaks shortly after sunset, I will be monitoring conditions and post any updates as to whether the aurora can be seen on camera (possible) or if I think the aurora will be visible with the naked eye (unlikely).
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For those of you who want to risk it and test your luck regardless and want some viewing advice, it’s really pretty simple. Go out and find yourself a good, unobstructed view of the northern horizon. The aurora (if seen on camera or with the naked eye) will likely be low on the horizon. I also want to make sure to note that if you are lucky enough to see the northern lights with your naked eye, don’t be surprised if what you see is a dull gray or diffuse color rather than the rich, vibrant colors you often see in photos. This is because a camera can see a lot more than our eyes can. The photo I took below was when the aurora was clearly visible over Lake Superior but I saw no color. What I saw was a waving curtain rippling across the sky in a gray/dull white color. However, my camera picked up all the color you see here in the image. Hunting for the northern lights is a fickle hobby. If you like sitting and waiting this might be the thing for you! It’s worth it. But that’s about it for viewing tips. As I said, it’s really pretty easy. Just keep your fingers crossed for a substorm (a short-lived intensification in the aurora, to keep it basic) and you might get lucky! 

If anyone has any questions on camera settings, shoot us a message and I’ll be happy to answer them. I’ve photographed the aurora several times from my home down near St. Louis so it is possible to do. I’ve also seen them with my naked eye on the shores of Lake Superior and they are absolutely mesmerizing. It’s something I hope each and every one of you get to see at some point in your lives. 

​- Billy

(6:00PM - 3/9/19) It's that time of year again...Time to push the clocks forward 1 hour at 2AM tonight. Losing an hour of sleep tonight and having to get used to the time change can be hard for some, but the good news is that it will once again be staying light out later in the evening beginning tomorrow. It's also another sign spring in around the corner!

JP

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