Super Outbreak 5 years later: My story and the meteorology (Part 2 – the outbreak begins)

Good afternoon.

Yesterday, I began a series on what would end up being the biggest tornado outbreak ever recorded and one of the most devastating outbreaks in US (and world) history. It was also an outbreak with major personal connections, as will be explained later. Yesterday 5 years ago, more than 3 days from the peak of the event, we knew that significant severe weather was likely in the week ahead (including on the 27th) but had little idea yet that it would be what it turned out to be.

This second part focuses on the events – both meteorological and personal – of Monday, April 25, 2011, largely considered the first day of the outbreak. It was a very impressive severe weather day in itself, and also held many other clues to what lied ahead.

On another note, although far from the Northeast, there is likely to be a significant severe weather outbreak in the central Plains tomorrow, particularly in Nebraska, central and eastern Kansas and northeastern Oklahoma. Those with interests in those regions should be taking preparations now since some of the tornadoes may be strong and long lived. The SPC has already issued a moderate risk for tomorrow (although the models suggest the threat may expand farther north and east).

sfcplot_sm_20110425

Surface weather map on the morning of April 25, 2011 (Weather Prediction Center/NOAA). Several squall lines from overnight activity are present, as is a well-defined frontal boundary with two closed lows forming. They would represent the initial activity.

April 25: A very active day with mixed signals

Monday, April 25, 2011 was the day after Easter and largely considered the “beginning” of the outbreak, as severe weather activity was virtually continuous for the next 72+ hours starting that afternoon until late Thursday afternoon. A 1000 mb closed low had developed over Texas along with a dry line which would prove to be the trigger for “Round 1” that afternoon. It is important to remember that this outbreak had many rounds to it. Models had agreed by now that the frontal boundary was going nowhere fast, even as the blocking ridges to the north and east were expected to slowly move away. In addition, they knew the low pressure area – and a secondary one farther north – were going to amplify. In other words, the situation was much more ominous than it was 24 hours ago.

Responding to the model consensus, not only was a moderate risk (with a significant tornado threat) maintained for the current day, but it was also issued for Tuesday (Day 2) AND for Wednesday (Day 3)Little mention was made for Thursday (Day 4) since timing issues were still in play, with a school of thought suggesting the storms would move offshore before daytime heating could kick back in. For all three days, mentions of strong/significant and long track tornadoes were included. In addition, most of the inland Northeast and Mid-Atlantic were placed in slight risk areas for both Tuesday and Wednesday as well, with enhanced risk areas not far to the south/west.

Introducing a moderate risk 48 hours out is quite rare, and quite risky too since so many parameters have to come together with at least four full (00Z and 12Z) model runs and four partial (06Z and 18Z) runs lying in between. It doesn’t take much for a severe weather day to turn out quiet. However, there was a sense that a high-end event was increasingly possible, so the decision to pull the trigger early gave valuable heads up. Such was especially true given that two days of significant severe weather preceded the main event.

110425_rpts

April 25, 2011 storm reports (SPC/NOAA).

In the end, there were numerous destructive tornadoes on April 25 from Round 1 of the outbreak, which resulted in five tornado-related fatalities (plus at least ten flood-related fatalities) and dozens of injuries. The first tornado touched down at approximately 9:00 am local time, although most of them were from mid-afternoon to mid-evening. In total 42 tornadoes were confirmed by midnight that night, primarily in Texas, Louisiana and Arkansas before the southern activity weakened. In addition, late that evening through the next morning, tornadoes – some strong – also occurred in the middle Mississippi Valley (more on that story tomorrow as the strongest were after midnight). The strongest tornadoes were rated EF-3 that day. Most of the tornado fatalities came from Vilonia, AR, where a mobile home park was hit hard by a strong tornado (although would be hit even harder by an even stronger tornado 3 years and 2 days later). It would be a significant tornado outbreak day in its own right, but what lied ahead grabbed our attention even more.

Decisions, decisions…

While all that was going on, I was less than 48 hours from the long-advertised vacation to Florida. The moderate risks really grabbed my attention, as did the risk extending northward right into the path. I also knew the models showed severe weather right up into the initial path, as well as all alternate routes. Timing started to be the key question mark, but I started to realize Wednesday – and possibly Thursday – would be rough. Flash flooding was another consideration that had to be played, since at home 5 to 10 inches of rain was expected. Also I was getting concerned about having to travel through areas that would potentially be devastated later if the most impressive model runs verified, as I would pass through them Thursday or Friday.

The moderate risk for Wednesday eliminated the possibility – which my parents suggested – of leaving a day early, as it would place me in the bullseye Wednesday night facing nocturnal tornadoes. I started to look into alternative possibilities, perhaps slowing down the trip or shifting it eastward, while still ensuring we reached Cape Canaveral by Saturday evening. It takes 3 full days to drive there and they are long days in that timetable – exhaustion sets in, and leaving Thursday would seriously jeopardize my parents making their cruise. No matter what, we had to leave Wednesday in spite of the severe weather. So I decided to up my phone plan and purchase a weather radio, since I figured they would likely be necessary as even the inland Northeast and eastern Midwest were facing a potential severe weather threat. Alternate routes and hotel plans began to be considered, since I knew challenges lied ahead.

However, given the fact we were still 48 hours away from the event, and the northern extent was still unknown plus the downstream conditions were also still an issue to be solved, it was agreed to let the current plans hold for one more forecast run. The 0600Z and 1730Z Day 2 forecasts, as well as the upcoming Day 3 forecast, would play greater roles. It was like…stay tuned, but things are happening.

Conclusion

What would turn out to be a historic and life-defining week for me was still beginning to unfold on April 25. Confidence was increasing in a multi-day tornado outbreak at least matching, possibly exceeding, April 14-16. The first day of the outbreak did not disappoint, producing many tornadoes in the southern Plains and Ozarks. What lied ahead looked nasty and potentially devastating as well. But there were still questions to be answered. Tomorrow, I will post what Tuesday brought.

Forecaster Craig Ceecee

Remainder of the series:

Part 1 (Sunday, April 24) – Introduction and strong warnings

Part 3 (Tuesday, April 26) – More tornadoes setting the stage

Part 4 (Wednesday, April 27) – The day everything changed forever

Part 5 (Thursday, April 28) – The last vestiges and initial aftermath

Part 6 (Friday, April 29) – Conclusion, lessons learned and the future

One comment

Leave a Reply