Sunday, July 25, 2010

Storm chase of July 17th, 2010

The morning of July 9th, 2010, I woke up, rubbed my eyes and walked out to my computer, much like I do every morning. I opened my usual links, which includes Facebook, our weather chat page, and the Storm Prediction Center's page. As I looked through the SPC's page, I noticed something that I hadn't seen in a while...a risk for severe weather in their 4-8 day outlook. My eyes got a little wider after seeing that, and I quickly went to take a look at the forecast models to see what they were talking about. The forecast for severe weather on July 14th looked really good. I started chatting with some of my buddies in the chat about that day and considered taking the day off of work so I could go and chase. I debated for a while about this, thinking that most of the severe weather has stayed well south and west of here and it was the middle of the week, so I wasn't sure if it would be worth it. Soon the afternoon forecast discussions started coming out and forecasters were talking about a potential outbreak of storms on that Wednesday. I couldn't resist, so I put in for time off of work on that Friday. Come Tuesday of the following week, I find out my request is denied. I'm bummed, my buddy that I was gonna pick up and go chasing with was bummed. Soon I see a moderate risk for severe on that day, in which case I am really really bummed, but for once Western Wisconsin was potentially the target area anyway. I wake up that Wednesday morning to the sound of my weather radio. Storms are already firing at 9am and Tornado Watches are being posted...at 9am?! I thought, hmmm this is way too early and not even the main cold front...this is probably not good for chances of severe weather later this afternoon. That was exactly what happened too. Cloud cover and morning rain really prevented the atmosphere from destabilizing a lot, so it did lower the risk somewhat of getting our "outbreak". Western WI did see some smaller tornadoes that day, however, and I did get to chase one of them with one of our reporters. We didn't see the tornado but did come across some of the damage that it had done. Overall it wasn't what it was hyped up to be, due to the morning clouds and rain. Damage was done, but that day could have been a ton worse if we would have had the sun baking us through the morning and early afternoon. It was later that day, however that I was brought to the attention, once again, of the Day 4-8 outlook, with Saturday, July 17th being highlighted over Minnesota and parts of Wisconsin. Again, I chatted with my buddies, and decided right there that we are going to chase on that Saturday. The storms seemed to have been going around most of us for too long, so it was time for us to go to them. Ok, the intro was a bit long, but I thought it would be fun to include all of that. Now, down to business....

The days leading up to Saturday, I looked over the models trying to figure out a good chase target. Initially I thought Southern Minnesota was, once again, going to get rocked, as they had been over the past month of so. So I thought we would be making a drive down the I-90 corridor into Minnesota. However with each passing day the better upper level dynamics seemed to shift further and further north, aiming more towards Central Minnesota as well as parts of Northern and Northwestern Minnesota. My initial chase target on Friday was Willmar,MN but I was concerned that would be too far north, and if storms began to fire in far southern Minnesota, we wouldn't be able to get to them, so I shifted my target a bit further south to Olivia, MN. Early Saturday morning, the SPC put out their risk maps and they seemed to highlight Northwestern Minnesota with the highest probability of tornadoes, but a pretty significant wind threat across the southern 2/3rds of Minnesota into Western Wisconsin. Even the hail threat was fairly high, and all the risks were high enough to warrant a Moderate Risk. Below are the risks from the SPC, top to bottom, Categorical Risk, Tornado Risk, Hail Risk, and Wind Risk.









After this outlook was issued, and looking at the latest models, I changed my decision back to Willmar, MN. It was centralized enough to where we could zip south if it was necessary. After talking with others in that chat room, they all agreed that would be good, and in fact Jon had mentioned that he had thought about that location a few days earlier as well. I also chatted with Steph about this location, as she is the smartest and most educated when it comes to weather forecasting, and she had thought even further NW of there may be even better, but I thought that if we get there early enough, we can zip north fast enough to catch whatever is going on up there. Jon and myself were to meet at Rick's place in St. Louis Park, then head west towards Willmar, with Alex and Schultzy meeting up then heading north to meet up with us in Willmar. Our scheduled meet time was 1pm in Willmar, with convection expected to really get going around 4pm. Traffic and construction in the Twin Cities was a bear, so it took me much longer than I thought it would to get to SLP, but eventually I made it, and we still met up in Willmar pretty close to that 1pm mark. On our drive, we could see clouds already billowing off to the north and west, with sunshine plenty of heating going on around us, so we knew that things were already starting to come together. We met at a hotel (or motel...whatever lol) in Willmar, where they were nice enough to let us borrow their Wi-Fi so we could plot out our first course of action. After our little meet and greet with Alex and Schultzy, it was time to check out radar and see where to go. There was already a nice cell north and west of us, to the northeast of Alexandria, MN. The cell was moving generally southeast, so we debated whether or not to go after it. We continued to watch it on radar while enjoying a lunch of sammiches (lol Rick), chips, and other goodies provided by our den momma Sandy. After a little while that cell began to intensify and take a sharper southeast route than before. We thought, do we go after it, or do we wait until the main show later in the afternoon started. After a little discussion we figured we would have time to get back to the west if we had to later in the day, but we were there to chase storms, so that's what we were gonna do. We packed up the cars, Rick, Jon, and myself in one, and Alex and Schultzy in the other, and we hit the road and took Highway 23 out of town towards Paynesville, MN. We traveled for a while, and as we got closer we noticed a nice inflow tail on the storm, which is seen below.



We got about a mile from Paynesville when Jon thought we should pull over and take a look at the structure of the cell, as it was evident that this thing was looking like a very classic supercell. We pulled off onto County Highway 6 and looked towards the north as the cell was going by. This cell looked amazing. It overall just had a nice structure to it, big tops on it topping 50,000 feet according to radar, and was estimated at putting out hail over 2 inches in diameter. In fact in the clouds, you could see a turquoise blueish/green coloring, which is a pretty good sign that there is some decent hail falling below it. We later found out that hail over 4 inches in diameter (softball size) had fallen. Below is a photo of that cell, showing the overall structure of it, as well as a potential wall cloud near the left of the rain shield. Also below is a radar image of the moment that picture was taken, including hail size estimates and cloud top estimates.









After getting several photos there, we decided to stay on this cell to see what else it may produce. We continued southeast on Highway 55 out of Paynesville till we got to the intersection of where Highway 55 and Highway 4 split off. Again, we got out of the car and watched as a pretty wicked looking wall cloud passed by to our east. Radar showed some pretty good rotation going on in the cell, and we could see it as it went by. Below is the picture taken of this cloud, the radar image, as well as the Storm Relative Velocity, which helps to determine if there is rotation in the cell. The brighter greens and pinks notched up next to each other is a sign of strong rotation within the cell.







We then proceeded east on Highway 55 into the town of Eden Valley. Once we got into the edge of town, we again stopped to get out and watch as the clouds rotated overhead, with the stronger rotation passing to our east. Below, once again, is the radar image, SRV image, and a photo taken at that time frame.







After leaving there, we continued east, and wound our way south and east in an effort to keep up with the cell. However due to the roads only going north to south or east to west, bit became difficult to keep up. Several tornado reports were beginning to come in, however we did not spot any of these tornadoes. We did come across a few areas where tree tops were snapped off and twisted, possibly from a funnel that passed overhead and dropped to the top of the trees. We also saw lots of leaf and tree debris on the road, likely from the large hail that fell there earlier. Since we couldn't catch up with that cell, we decided to just pull off the road and get some pictures as it moved away.



While trying to figure out our next course of action, we noticed on the radar that the main show was just moving into Western Minnesota. We first began heading back towards Willmar when we noticed an awesome looking cell off to the northwest of St. Cloud. We decided, instead, to go after that one. As we passed northeast through St. Cloud, the cell was showing signs of bowing. It had a tornado warning on it for quite some time, with a few reports of some possible brief tornado touchdowns. We decided to stop once we got closer to try to get pictures, as this cell was showing an awesome shelf structure to it. We got out and quickly snapped a few pictures as the cell got closer, then moved further up the road to set up to get wind measurements as it passed by. We had a nice look at an open field, and could see the rain get blown across the field as the wind gusts approached. The anemometer on the car gave us a wind gust around 50mph, which wasn't too bad, however much weaker than a previous report of over 80mph on that same cell. Below you can see some lowering that has happening under that tornado warned cell.



We continued northeast on Highway 23 until we got into Milaca. There, the rain was so heavy that the water was starting to pond on the roads. We decided to pull off into a parking lot and maybe wait it out. However looking at radar, it didn't look like it was gonna let up anytime soon. After a few minutes, we again hit the road, this time to head towards St. Francis, as some strong cells were moving towards that area, causing some wind damage in its path, downing trees and powerlines, and knocking out power through the far northern parts of the Twin Cities metro. We eventually caught the back edge of the cell near Princeton and began seeing some sunlight peak through, creating a pretty cool looking double rainbow. It was near there that Alex and Schultzy decided to begin their long drive back to Southern Minnesota. All in all, it was a pretty fun day, as we got plenty of pictures, and no one was physically hurt by these storms. I'm really looking forward to our next chase day.