Day 8 - Dirt Roads, Streets and Traps

11 June 2010

Today we started well positioned for a local chase. (Yes, we've said that before, but this really was a bit more local...we've only clocked up 400 miles or so!)The Storm Prediction Centre was, once again, issuing an outlook that looked good for North East Colorado. We were on the far east of the state, and the action was likely to kick off via lift from the foothills of the rockies. As per, this is where I do the education section!When there's enough energy in the air (temperature and moisture) storms can just kick off from the suns heating during the day. But normally there is some catalyst to fire the storms. This is any factor that adds more lift to the air, to kick start the convection that big storms need. And, indeed, small storms...This catalyst for lift can be a large number of factors, but two really common ones are "frontal lift" and "orographic lift". Frontal lift is what we saw more of yesterday, where a cold air mass pushes into a warmer one (a cold front) which forces the warmer air up. Orographic is where the air moves over higher ground, forcing it upwards. Once the air is forced up high enough, by one means or another, then this can get all that energy to a firing point, and up go the clouds.Today it was more about the orographic lift. Wind was pushing air into the foot hills in the east, while the air moved in from the west. So the foothills would probably be the source of the storms. Most chasers decided to head to the southern end of the probable storm area. We opted for a bit further north.As the storms started firing we continued west. They were rising off the foothills, as expected, and developing into a few supercells. This was quite early in the day, around 2pm. We were near them and there were a few to choose from, it was going to be a good chase...We locked into a cell moving east from Denver, while most chasers were down in Limon, further south on a bigger cell than our chosen one. Both storms showed signs of rotation and looked in good shape to create tornadoes. We got to Fort Morgan and could see the monster quite clearly, and at this stage, quite well defined with relatively little interference from general cloud cover. It already looked good, so we set out to intercept. We were to the cell's north, and it was moving east. Some quick calculations and route planning; and we decided we could get below it on a road south before it caught us. Benefits of June storms - they move slower! We drove south into that now familiar mid afternoon night time that the storms create. Our route took us onto farm roads - proper 4x4 territory, particularly when there's rain and hail involved to mash up the tracks. Our first stop had us about a mile south east of the storm that was moving west. It was a stunner...which appeared to have a tornado from it! (Actually this is just a particular scenario that sometimes gets misreported as tornadoes...)

SPC Day 1 Weather Outlook as at 06:00UTC (01:00 Central Time the night before)

SPC 01:00UTC day 1 forecast for Fri June 2010

SPC Day 1 Weather Reports for the day.

SPC storm reports for Fri June 2010

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