While stationed in Duluth, there was a riptide related death on the lake side of Minnesota Point. It was August 17th, 2003. The lake was abnormally warm, partially due to the strong onshore winds holding the warmer water against the beach. So there was a lot swimmers out in the high waves. This unfortunately created a dangerous rip current situation, and a 21 year old died because of it. Junior Lessard, future Hobey Baker award winner, was also caught in the current. He was rescued by a surfer.
I was on the bay side of the point that day kayaking. I didn’t want anything to do with those big waves, and the bay had calm waters. I saw the helicopter hovering over the beach from afar, but didn’t connect that it had anything to do with riptides. I thought it was a boat related incident.
Two or three weeks later I snapped a few beach pictures in an attempt to help me understand riptides. No big winds that day, so the pictures aren’t particularly dramatic. This first picture shows the character of the beach. It isn’t straight. There are parts that stick out into the lake (I call them ridges) and the in-between areas that I call troughs.
The lake is shallower over the ridges compared to the troughs. So the waves shoal sooner when going over a ridge (example below).
So the water that flows over the ridge, drains into the adjacent troughs, and flows out back into the lake. This flow is the rip current. Each wave that comes in refills the trough to fuel the current. If you are caught in this current, you will be swept out into the lake with it. Now that you understand this, it makes perfect sense to swim sideways (parallel to the beach) when caught in a current. You swim sideways until you are even with a ridge, away from a trough… then you swim toward shore. The NWS published a page to better explain this.
Partly due to the bad batch of flooding in 2010 and 2011, MNDOT will be building a new bridge to go over flood waters. The picture below was taken when the river was near the record high. This is where the bridge will go.
Another computer, another node added to my Basement Super Computer Cluster. I am up to 3 computers in my weather model cluster. Added another 6 core Phenom II to the mess. This computer seems to be unstable, so I should be careful not to overhype this. Your cluster is only as good as your weakest computer. It has been up for 24 hours straight now, so hopes are higher.
What these 6 additional cores have afforded me is to convert my nearly continental US covering model run from 25 km to 20 km grid spacing. I then expanded my 4 km grid spaced “meso” run from covering just southern Minnesota, to nearly the 5 state area.
The other thing I tinkered with is the Turbulence maps. Some comrades over at Chicago are doing a study and they shipped over some preliminary results. They are comparing speed shear with pilot reported clear air turbulence. The results were quite promising, so I am going to see if I can use it operationally. The Turb 500 mb through the Turb 200 mb charts on the CONUS model run now show speed shear between 50 mb layers. These maps still highlight in thick red contours where the WRF thinks mod-sev Turb will be… so we have that for comparison. As far as the shading… blue = 25-35 kts shear (lgt-mod turb) | yellow = 35-50 kts shear (mod turb) | red = >50 kt shear (sev turb). It will be interesting to see how this verifies.