Thursday, June 19, 2014

Large Tornadoes, Heavy Rain, and Nebraska Twin Tornado Update

The severe weather on Monday from Nebraska eastward to southern Wisconsin was far from the last of it this week. The day after one of the "twin tornadoes" in northeast Nebraska leveled the town of Pilger, another supercell Tuesday evening spawned at least two huge tornadoes. These were unusual in several respects. They were both "wedge" tornadoes - menacing looking storms that were perhaps a half mile wide at times. The most unusual aspect was that a second large tornado (there probably were several tornadoes generated by this cell over its four hour lifetime) was on the ground almost spinning in place for well over an hour. It first set down north of Laurel, NE in Cedar County, and moved very slowly to the southeast. Here are few radar images of the storm when this tornado was on the ground.

The base reflectivity image at 10:07 p.m. CDT (left) from the Sioux Falls, SD radar. The hook echo pattern is evident on the west side of the cell. The right image is the storm relative velocity display at 10:02 p.m. A circulation is located where the red/yellow and green/blue colors are adjacent to each other.

This is a wider view of the radar at 10:19 p.m. The hook echo is clearly evident on this image. The red box is the tornado watch that was in effect.

Storm relative velocity image at 10:51 p.m. CDT. The circulation is still evident but is weaker. The violet polygon is a tornado warning and the green polygon is a flash flood warning.

Tornado on the ground near Coleridge, NE.
Photo: Matthew Higgins via Twitter

The National Weather Service in Omaha is still in the process of completing a survey of this storm and noted that several tornado tracks were found. The good news, if you can call it that, is this storm stalled over a sparsely populated area or otherwise damage could have been much worse.  It will take a few days to determine the tracks, times, and number of tornadoes that occurred.Here is a preliminary assessment they released today.

For more information and future updates, see the Coleridge Area June 17 tornado page on the NWS Omaha/Valley, NE web site.

The NWS Weather Prediction Center put together this excellent video which shows the development of the storms on satellite, overlaying the surface weather and radar images.

Earlier in the afternoon another large tornado touched down in southeastern Montana in Carter County near the South Dakota border. This had the distinction of being the first ever EF-3 tornado in southern Montana.  What caught my eye about this storm was this spectacular wide shot by Roger Hill, a professional photographer. The tornado can be seen just to the right of the bright area on the left side of the storm.

Carter County, MT tornado on June 17. 
Photo by Roger Hill via Facebook
More information on this storm can be seen at the NWS Billings, MT web site.

On Wednesday there were additional tornadoes in South Dakota, and damaging winds from a complex of storms from southern Wisconsin to western Pennsylvania.  However, heavy rain was a major occurrence from southeastern South Dakota on Tuesday to Minnesota, Wisconsin, and northern Illinois on Wednesday and Wednesday night.  On Monday the slow-moving storms in northeast Nebraska and southeastern South Dakota produced torrential rain. Canton, SD measured 8.43 inches of rain as of 6:00 a.m. CDT Tuesday, and many more locations in southeastern South Dakota measured from 3 to more than 5 inches of rain.  24-hour rainfall amounts in southern Minnesota topped 3 inches in many areas, and totals for the past four days have exceed 6 inches in some locations. Minneapolis set a new calendar record for rainfall for any day in the month of June today (June 19) with 3.95 inches of rain as of 1:30 p.m. There was more rain after that time.

24-hour rain fall for June 18 (L) and June 19 (R) ending at 7:00 a.m. CDT
Finally, the NWS released an update on the "twin tornadoes" in northeastern Nebraska on Monday. There were five tornadoes in northeastern Nebraska.  Four tornadoes, including the one that hit Pilger, NE were rated EF-4, and the remaining tornado was rated an EF-0. A summary of these tornadoes can be seen at the NWS Omaha/Valley web site.

No comments:

Post a Comment