THE TAMING OF THE SHREW...
The National Weather Service continues to survey and analyze Wednesday's tornado outbreak in Iowa. Preliminary research indicates there were 26 tornadoes across the state. This makes this the 3rd most tornadoes in a single day in Iowa since records began in 1980. The number of tornadoes could still increase as further data is analyzed in the coming days and weeks. At this point the NWS is working in coordination with emergency management while employing high resolution satellite imagery to help refine track details. Here are the storm reports from Wednesday's outbreak.
Notice the majority of the twisters developed in an east west fashion near or just south of HWY 20. In that area an outflow boundary (mini cold front) was laid out from thunderstorms earlier in the day. That backed the surface flow and generated the shear necessary for rotating storms known as supercells (the type that produce tornadoes). One tornado reached EF3 status, so far the others have been weaker on the order of EF1 or less. EF3 winds range from 136-165 mph while EF1 rankings require winds of 86-110. The NWS tweeted this image of the EF3, courtesy of Mike De Lange the photographer.
Ironically, several years ago my team and I at KGAN did a study to determine the location of Iowa's tornado alley. Our research indicated an enhanced risk of strong tornadoes centered around HWY 20 in most of eastern Iowa's bigger tornado outbreaks. That same general target area was again the focus of last weeks tornadoes. As our research indicated, the primary factor in the event was an outflow driven warm front that backed the surface flow creating the shear necessary for tornadoes. That's the classic recipe for a significant tornado event in my area. You can see my report by clicking on the graphic below.
Now it's fair to say we've tamed the shrew and the rest of the weekend is going to be delightful featuring a blocking pattern with little to no rain, and near to slightly above normal temperatures through next week. Here's the mean 500mb jet stream pattern the next 7 days.
Here's the 7 day average temperature departures.
No rain is expected this weekend. Over the next 7 days the EURO shows this for total precipitation.
As you can see, amounts over that period are 1/2 to 3/4 inch below what's typical.
Even going out 15 days the pattern looks rather quiet with the EURO projecting temperatures like this. Pretty typical mid summer readings. Warm but far from hot.
No sense beating a dead horse. For all intensive purposes the weather is going to be nice, especially this weekend. I guess well just have to enjoy it now that we've tamed the shrew! Roll weather...TS