Chase Report: July 20, 2009
|
||||||||||||||||
 SPC Day 1 Outlook |
 SPC Tornado Probability |
 SPC Hail Probability |
 SPC Wind Probability |
I had just finished watching the Rockies game and was preparing to crash out for the night when a few storms started to go up in the foothills south of Ft. Collins. The storms were moving south/southeast and looked to head into the northwestern suburbs of Denver, so I thought I would head out to shoot lightning.
 10:09pm – Reflectivity |
 10:09pm – Velocity |
 10:09pm – Storm Relative Velocity |
I grabbed some gear and half-assed made my way down I-25 to I-76 as the storms EXPLODED over Arvada. A tornado warning went up on this storm and I quickly turned my attention from lightning to a very serious storm chase.
 10:14pm – Reflectivity |
 10:14pm – Velocity |
 10:14pm – Storm Relative Velocity |
As I neared Wadsworth and I-70 (about 10:15pm), I observed power flashes to my west in what looked to be an area south of I-70 near Kipling. Above the flashes, I noted a narrow funnel cloud.
 10:18pm – Reflectivity |
 10:18pm – Velocity |
 10:18pm – Storm Relative Velocity |
A weak couplet showing up west of Wheat Ridge near Kipling between I-70 and Colfax about the time the most intense damage was occuring in Wheat Ridge.
TORNADO! I quickly began wondering if I was watching the beginning of something very serious as I went for my phone to make the report. About the same time, the RFD/straight line winds slammed the interstate. Traffic came to a stop as construction cones were blown across the interstate. It was several minutes before the visibility cleared up enough to crawl forward, still with howling northerly winds.
 10:23pm – Reflectivity |
 10:23pm – Velocity |
 10:23pm – Storm Relative Velocity |
RELATED INFORMATION
I eventually made it to Kipling and I-70, getting off to see power knocked out. I went south on Kipling and arrived on the scene about the same time as emergency crews. The storm was still tornado warned as another tornado report came in fromt Englewood. Unfortunately its forward speed quickly took it out of play, not to mention the damage I was coming across on Kipling.
I started documenting the damage, first noting the flooding in the area around down trees.
Flood video starting as I got moving again on I-70. Footage shot near Kipling and 44th Ave.
As I got further into the damaged areas, I started observing severe damage to trees and vehicles, including a large tree that destroyed a house along 44th. 44th Avenue was closed to thru traffic due to the significant damage, but I was let through via 43rd Avenue which turned into Moore Street that dumped me off in the heaviest damaged areas on 44th.
I filmed up and down 44th Ave, focusing mostly on a house that was destroyed by a large tree that crashed through during the storm.
Storm damage was extensive up and down 44th between Kipling and Tabor Street where I was blocked from proceeding west due to numerous down trees.
Storm damage across Wheat Ridge and Lakewood shot overnight. Power outages and hail fog made it very hazardous to get around.
It was approaching 2:30am and I was running low on batteries, so I had to run back home to grab more gear, then returned to the area, documenting damage from 44th Ave and Kipling in Wheat Ridge to Mississippi and Wadsworth in Lakewood. I filmed most of the morning, waiting for the sun to come up so I could start with photos and get a better picture of the damage.
When daylight broke, the hail fog was creating an eerie picture across most of the damage areas. Power was restored in most places by this time with a few exceptions.
Damage video from the morning after when the sun came up.
I shot over 200 photos after the sun came up, click the thumbnails for caption and larger image. 80 of the over 200 photos are in the table below.
 |
 |
 |
 |
 |
 |
 |
 |
 |
 |
 |
 |
 |
 |
 |
 |
 |
 |
 |
 |
 |
 |
 |
 |
 |
 |
 |
 |
 |
 |
 |
 |
 |
 |
 |
 |
 |
 |
 |
 |
 |
 |
 |
 |
 |
 |
 |
 |
 |
 |
 |
 |
 |
 |
 |
 |
 |
 |
 |
 |
 |
|
 |
 |
 |
 |
 |
 |
 |
 |
 |
 |
 |
 |
 |
 |
 |
 |
 |
 |
The storm was the top story of the local news stations and also made the national news. Below are two clips of my footage used on KMGH 7News in Denver and Good Morning America.
On-air clips from KMGH 7News the morning of July 21.
On air clip from ABC’s Good Morning America airing on July 21.
MY CONCLUSION
As this storm marched south/southeast, two more tornado reports came in from Englewood and Castle Rock. Including my report (which went in late and didn’t make the reports), a total of 3 came in from this storm. Radar signatures showed a weak couplet on the leading edge of this storm as it moved over western Denver and the storm stayed tornado warned from Arvada all the way through Castle Rock.
Unfortunately, the Denver/Boulder NWS did not do a damage survey and wrote this storm off as purely a straight line event. The summary that was issued a couple days after the event said that no rotation was indicated by radar and a max measured wind gust was 61mph. The lack of a damage survey and their lazy 50-words-or-less summary is sadly the “official” report that this storm will go down as. Their report of no rotation in the radar is contridictory to the KFTG velocity scans that clearly showed a weak couplet as well as the “radar-indicated” tornado warnings that went off prior to the first tornado reports.
Given my extensive look at the damage, I believe it was highly likely a series of weak tornadoes spun up along the leading edge of this storm, touching down in Wheat Ridge, Englewood, and possibly Castle Rock. The straight line winds, likely in excess of 90mph, came through and likely destroyed any tornatic evidence that may have been left behind. I believe the power flash and funnel I saw was in the area of 44th and Oak St just south of I-70 where I observed an area of more concentrated severe damage (including street signs bent completely to the ground). This was likely a brief tornado that may have remained on the ground from roughly 44th and Oak to around 35th and Kipling.
I believe the tornado likely lifted, possibly touching down again to correspond with reports out of Englewood and Castle Rock. I did not survey those areas, nor have I seen and conclusive damage photos/videos to verify these reports. However, given the nature of the storm and the longevity of the velocity couplet, I would not rule out the possibility of multiple brief weak tornado touchdowns.
The damage pattern was all in a south/southeast direction indicating the event was primarily a straight line wind event combined with the excessive amount of rain and hail up to golfball size. However, my observation of the funnel/power flashes along with some of the isolated areas of concentrated damage lead me to count this as a tornatic event. But given the extreme intensity of the straight line winds, I believe the tornado damage was “swept under the rug” and thus left the only tornado evidence to radar signatures and the spotter reports.
|
|||||||||||||||||||||
[...] Tony Laubach’s [...]