Weather History: May 31, 2017

May 31, 2017 - Written by: Brandon Molyneaux

Let's briefly discuss a bit of weather history. A lot of people know this day to be the day a devastating tornado hit the town of El Reno. However, there were two other significant weather events that occurred. Two of these events take place in Pennsylvania, and one takes place in Oklahoma. All of these events had devastating effects on their communities.

Tornado outbreak in Pennsylvania, Ohio, and New York - May 31, 1985

Kicking off this article, we begin with the tornado outbreak that occurred in Pennsylvania, Ohio, and New York. Over 40 tornadoes occurred, which caused over $600 million in property damage. Over 80 lives were taken across Ohio and Pennsylvania, and over 1,000 people were injured.

This day produced tornadoes with intensities ranging from F-0 to F-5. The longest tornado that lasted was an hour and 25 minutes, which trekked right through Moshannon State Forest, PA. This tornado ended up being rated F-4.

For severe weather, you need 4 ingredients: lift, instability, shear, and moisture. Above is a surface analysis at 23z (7PM EDT) that day. It shows western Pennsylvania in the warm sector ahead of the cold front, which brought the severe weather. Temperatures were in the lower 70's with the dewpoint temperatures not too far behind. With dewpoints close to the temperature and a cold front pushing through, half of the ingredients needed were checked off. KPIT (Pittsburgh, PA) at 00z (8PM EDT) sounding showed 2800 J/kg CAPE, which was another ingredient: instability. Lots of low level shear was also present, which allowed for storms to rotate as the front was passing through. Winds were out of the southeast at 5 knots, and just above their heads at 900mb, winds were out of the southwest at 15 knots.

A lesson that was learned after this event was that "under the proper atmosphere conditions, major tornadoes can occur irrespective of the location or terrain" (per NWS State College)

Source: National Weather Service State College, PA

Johnstown, PA Flooding - May 31, 1889

Staying in the same state but jumping back nearly 100 years, flooding occurred in 1889 in Johnstown, PA. Heavy rainfall occurred before the event. The South Fork Dam failed mid-afternoon, and the water fell downstream for 14 miles, before getting to Johnstown, PA. The National Weather Service Mid Atlantic River Forecast Center (NWS MARFC) sent out a tweet the morning this article was created, explaining the event in a series of 4 photos.

El Reno, OK Tornado - May 31, 2013

One of the most well known tornadoes occurred on this day 4 years ago. This tornado holds the record for the widest tornado, sitting at a massive 2.6 miles. It spared the city of El Reno by staying to the south, but still took lives. A few of those lives lost were Carl Young, Tim, and Paul Samaras. The trio were conducting research on the TWISTEX project. The project's goal was to study the lifecycle of tornadoes - from tornadogenesis to dissipation.

A quasi-stationary was draped from NW to SE Oklahoma the morning of. A dryline was advancing eastwards, and ahead of the dryline was clear skies. This put cities such as Moore and Oklahoma City "under the gun". As mentioned before in the Pennsylvania tornadoes section, you need 4 key ingredients for severe weather. All ingredients were present at this time. By mid to late afternoon, storms began erupting near the dryline/frontal boundary. Once these storms fired, they began rotating as they moved into a more favorable environment.

At 6:03PM CDT, the tornado touched down. With multiple chasers chasing this tornado, there is what feels like an endless supply of videos and personal accounts. A few chasers were caught in the path of this tornado as it grew. One of these chasers, who unfortunately got caught, was Richard Henderson. He took a photo of the tornado and sent it to a friend before they got on the phone with one another, as Richard was chasing.


  1. National Weather Service Norman, OK
  2. Washington Post - Capital Weather Gang
  3. NewsOK