LOOKING BACK: Days Before A Tornado Outbreak

Donavon_1W New Hartford_smaller May 25th, 2008 was the day a devastating tornado outbreak struck many parts of northeast Iowa. No part of Iowa was hit harder than Parkersburg.  The town of under 2,000 was in the path of a massive EF-5 tornado that struck the town at 5:00pm on that Sunday.  It was the start of a major tornado outbreak that spread across several counties and claimed the lives of 9 people.

With the weather currently as quiet as it is, I wanted to take some time to look back at not only the events of that day, but the details leading up to the tornado and the aftermath it left behind.

day2otlk_20080524_1730_prt Today I wanted to start by looking at the lead up to the historic storm.  Looking back at the forecasts issued by the Storm Prediction Center in Norman, OK, there was little to highlight.  A high end slight risk was issued two days ahead of the event.  A large area was highlighted over eastern Iowa, but the primary focus on the severe threat was emphasized over Wisconsin.

One main reason for this was the uncertainty.  Storm were expected to develop overnight across Iowa the night before and move northward, along with a warm front.  This all happened, but by daybreak on Sunday, there was little hope for severe weather.

mesonet_1700 That’s because the cloud cover left behind by the storms didn’t move out as fast as hoped.  And the warm front was pushing north at a faster rate than first thought.  That led the SPC to post the greatest risk for tornadoes in southern Minnesota.  That’s where the warm front was expected to be when storms began developing around mid afternoon.

At this point we believed there was little chance of a chase.  Nevertheless I packed up and prepared just in case while I took care of other things that day.  That turned out to be a good decision.  After meeting with a colleague, he urged me to head north as soon as possible.  He pointed to signs a secondary boundary was developing and slowly making its way north into northeast Iowa.

I began to make the preparations to chase and not a moment too soon.  Forecasters also took notice of this change and quickly increased the risk of tornadoes in northeast Iowa. 

ww0363_overview_wou As we made out way up Interstate 380 we heard the first tornado watch posted for that area.  The watch was issued at 3:30pm as a discrete line of showers and thunderstorms began developing in north central Iowa.  The watch was one of the rare tornado watches issued each year.  It’s called a PDS Tornado Watch.  PDS stands for Particularly Dangerous Situation.  Forecasters issue this type of watch when the danger of strong, destructive tornadoes is especially high.  And all signs were pointing to this being exactly the case.

This is the point where the storms really began to take shape and one unique cell took on a life of its own.  We’ll have more on that tomorrow as we continue our extended look at the tornado outbreak two years ago here on iowachase.com

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