The Giant 1969 Memorial Day Weekend Storm

Until yesterday if you asked me about the year 1969 the only things that would probably come into my head were Hurricane Camille, the moon landing, and Woodstock. Am I missing anything else?

Well it turns out I am! Yesterday I was going back through some of my geeky weather archive sites to figure out how often New London County has received significant (>2″) hail. As it turns out there have been only 2 cases of significant hail in New London County since 1955 – one in 1969 and another in 1995 during the super hail storm. The 1969 report from May 29th (the day before Memorial Day) is of baseball size hail in Groton. You don’t see that everyday! Here’s how Storm Data described the 1969 thunderstorm in Connecticut.

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The reports from Rhode Island and Massachusetts are equally as impressive.

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Radish size hail in Pawtucket – I love it! The storms obviously were quite intense given the dramatic descriptions in Storm Data. The weather pattern that day was favorable for severe thunderstorms – and one of those rare days where southeastern Connecticut was in the running for a violent evening storm.

Windsor Locks reported a sustained wind of 37 mph from the northeast during the storm with about 0.50″ of rain. Little rain fell in New Haven or Bridgeport – it would appear the storm missed them to the east.

In some of the cooperative weather reports from the Memorial Day morning you can get a general idea of where the storm(s) tracked.

  • “Trees and limbs” down in Brooklyn with a power outage and 0.56″ of rain
  • 0.23″ rain and thunder reported at the Cockaponset Ranger Station
  • 0.44″ of a “hard rain” along with thunder and hail in Colchester
  • 0.86″ of rain with thunder and hail in Groton
  • 0.86″ of rain at Pachaug State Forest

The morning weather balloon launch from JFK Airport in Queens showed very steep mid level lapse rates. The 500-700mb lapse rate was an impressive 7.9 C/KM! The weather map for 5/29/1969 showed a deep closed low over the Canadian Maritimes with a fast northwesterly flow through the mid troposphere. The JFK weather balloon data shows a northerly wind at 700mb of 46 knots.

comphour.71.234.167.147.246.8.14.7

There was also a fairly impressive backdoor cold front bisecting New England. While winds were generally out of the west and northwest in Connecticut during the day the winds were due east at Logan. The high temperature at Logan was only 72F while it was 86F at Worcester and 92F in New Haven, Bridgeport, and Bradley. Eastern New England can really suck in the spring!

The air was also quite sticky over Connecticut. By mid afternoon Bridgeport had a dew point of 68F with 92F on the thermometer. The combination of the moist and hot boundary layer and steep mid level lapse rates likely set up a very unstable atmosphere over western New England. While this is only conjecture (since I don’t have the data) one can envision severe storm initiation near the backdoor front as a shortwave raced south on the strong northwesterly flow aloft to get things going. The strong mid level flow also cranked up fairly impressive deep layer shear – a requisite for organized severe convection.

comphour.71.234.167.147.246.8.15.19

As it turns out this kind of setup is not unusual for severe weather in Connecticut. We’ve seen cases before where an elevated mixed layer (characterized by steep >8.0 C/KM lapse rates) have advected eastward along the US/Canadian border and have helped spawn severe weather in New England with deep northerly/northwesterly flow.

The 1995 hail storm comes to mind as one example of this. The storm occurred near a backdoor cold front. This storm was able to drop base ball size hail (for 20 minutes!!!!) in Deep River. The northerly/offshore flow can help keep the shoreline unstable and hold the marine influence at bay. You can see a similar setup here with a deep low over the Canadian Maritimes and northwest flow across New England.

comphour.71.234.167.147.246.8.16.35

It also is somewhat similar to the May 26, 2010 overnight severe weather event that managed to drop hail to ping pong ball size in Bridgeport in the middle of the night.

The offshore wind component is necessary for big severe storms in southeastern Connecticut. This is especially true around Memorial Day when water temperatures are still quite chilly.

I love looking back through old weather data to learn about storms I have never heard of and also how meteorologists and others described the weather back then. The “radish” size hail description in Pawtucket, RI was a new one for me. I may have to snag that one for myself next time we’re doing storm coverage. A Twitter follower wrote this to me last night after I tweeted about the radish size hail report. He nailed it – and made me laugh too.

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One other interesting note from the May 1969 storm data report that caught my eye. On May 3rd around 3:30 Grosvenordale had one freaky storm…

Screen shot 2013-09-04 at 11.03.46 AMI’ll take their word for it.

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2 thoughts on “The Giant 1969 Memorial Day Weekend Storm

  1. Can’t recall off the top of my head if CT saw anything, but there was an event…in June or July of 1992 which produced some big hail storms, including in Springfield, MA. Think it was golf ball (may have been larger) that hit downtown and did quite a bit of damage.

  2. I greatly appreciated your assessment of this event. May I ask how you obtained weather map for 5/29/1969? I have only been able to find the Daily Synoptic Weather Maps (Northern Hemisphere) from the NOAA Central Library. Years ago I was able to compose CLIMVIS Temp-Rain-Sun-Wind Daily Vector Graph Samples from NOAA but that service has disappeared. E-mail me and I can send samples of the latter. Maybe that service is still around somewhere. Thanks

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