September 30 Severe Weather

Yesterday saw the state under a tornado watch with several storms capable of producing a tornado at one time or another during the evening hours. Areas of northwest Iowa and then southern & eastern Iowa were the hardest hit with damaging winds and hail, as well as at least two tornadoes that traveled through Marion, Jasper and Poweshiek counties in Iowa. We'll start with those two tornadoes as the surveys have already been completed and they have been rated with an EF1 and EF2. To read the entire report on those two tornadoes and their track statistics, view the Des Moines NWS webpage. Arial photos of those tornadoes, their path and the damage that ensued can be found via the Iowa Environmental Mesonet courtesy of IowaHelicopters. Those storms continued on into eastern Iowa where they became mainly wind producers during the early nighttime hours.

Other storms erupted in eastern SD/NE and moved into the state expanding with time during the evening hours. Several tornado warnings were issued with such rapid low level rotation that was present with the storms, however as of now there are no official reports of tornadoes in the northwest Iowa area. For the most part the reports in the first couple hours of storm evolution were large hail, including one report from 3 miles east of Cushing where 2 inch diameter hail fell. After 6 PM when the storms became mainly linear there were reports of winds along the storms path, although several tornado warnings were issued for the storms as they went through areas of Sac, Pocahontas, Palo Alto and Kossuth counties. Wind reports came out of Alta, near Oyens and my report from just south of Emmetsburg. Yes, I ended up punching through the line as it went through Palo Alto county during the late evening hours in my route back to Ames. I was met by some blinding rains and some wind that decided to blow all of it nearly horizontal to the south of Emmetsburg.

All of these storms were caused by a fairly potent system, although not nearly as strong as it could have been. A low pressure system was moving into the state from Nebraska at the surface, where it was slowly beginning to dissipate. The pressure falls were not great enough to keep it sustained, thus as it entered the state it was weakening in nature. Nonetheless the strong rotation near the low was enough to warrant several of those warnings yesterday. The lack of instability due to moisture and sunshine also hampered the severe weather threat... Overall the day turned out to be not as potent as it has potential for, leaving several severe weather enthusiasts disappointed. It did however produce tornadoes that unfortunately caused damage to a few homes and farmsteads. Another severe weather event is possible tomorrow, more details on that will be available in the morning.