Category Archives: Historic Weather

Historical weather events and data

Remembering April 27th 2011

Today marks the 6 year anniversary of the historic super outbreak on April 27th 2011 . A day that forever changed thousands of people . A day when 218 tornadoes were recorded setting the record for most tornadoes in a single day . Deaths were reported in Mississippi, Alabama , Tennessee, Georgia and Virgina .  317 people were killed on April 27th 2011 making it the single deadliest tornado related day since 1925, 243 of those deaths occurred in Alabama alone . Destruction was spread far and wide and to this day the landscape across the southeast remains scarred from that day.

There were stories of heartache , stories of heroism and stories of complete strangers giving the clothes off their backs to people who lost everything . Communities pulled together in the days and weeks following the outbreak . Volunteers gathered by the thousands to help in the aftermath.

There were so many incredible survival stories across the southeast that day. Some families were completely  trapped after their house crumbled ontop of them. Survivors were being pulled from the rubble hours and hours after the storms passed . For me personally I remember grabbing my wife , a few sofa cushions , the dogs and running into the bathroom to cover take cover . We were lucky as the tornado passed a quarter mile south of our house but I will never forget the sounds from outside as we could hear the tornado and hear debris pelting our roof. We were very lucky , others were not.

April 27th 2011 is Day the Southeast will never forget . The experts say we won’t see another outbreak of that magnitude in our lifetime.  Regardless , its important to remember as we look back on this day that it does not take an EF4 or EF5 tornado to cause death and destruction. In the last 6 years society has become complacent to severe weather threats as they are sometimes described as ” not as bad as April 27th 2011″ . Please remember that all severe weather threats are dangerous. Don’t ignore a warning because it’s ” just a severe thunderstorm warning”  Severe thunderstorms kill people every single year . Don’t become complacent to a ” slight risk ” of a ” brief ” tornado as that brief tornado regardless of strength could end up being your April 27th 2011. Have a safety plan , PRACTICE your safety plan and make sure everyone in your household knows what to do and where to go.

We’ve learned a lot in the years since April 27th 2011. We’ve learned from tragedy, we’ve learned from mistakes and we’ve learned from each other.  It’s important that we keep learning from that day , it’s important that we keep moving forward and it’s extremely important that we always stop to reflect about the events of that day . Buts it’s just as important not to fear the next storm and to make sure your plan is in place in case one day you experience your own April 27th.


SE US daily winter temperature anomaly analysis by MJO phase: inside the left side of circle coldest

I got curious about the actual SE US tendencies associated with each MJO phase after seeing the charts showing temperature anomaly patterns for each phase. I knew the left phases tended to be cold and the right phases mild. But I wanted to know how cold and how mild. When I had some time and since I love analyzing wx stats, I decided that it would be interesting to see how Atlanta, which I figured could be used as a proxy for the SE US, was for each phase. So, I started off just looking outside the circle by phase. I did just January to be more efficient. I did this for 1975-2014 since this was done before January of 2015 was completed. 1975 was the first year that MJO day by data is available from this source:

As I was going along, I noticed a strong warm bias with these ~800 days. I noticed that phases 4 & 5 were quite warm as one would expect but what confused me was that the remaining phases were near normal with no phases averaging cold! That’s when I figured out that INSIDE the circle is where many of the cold days must be hiding.

So, that’s when I decided to analyze the ~430 inside the circle days. I discovered that inside is, indeed, where many of the coldest days were hiding! I then learned that inside the circle is also within the 8 phases (think 8 pie slices). So, when you see a map showing a cold SE phase 8, for example, the cold average is largely being carried by inside the circle phase 8 though just outside the circle in phase 8 was also cold.

By the way, every phase came in 3-6 F colder when inside vs outside and even phases 4-5 inside averaged near normal. The remaining 6 phases inside averaged colder than normal with inside 7 & 8 being the coldest.

The following diagram (ignore the 1978 reference) shows the Atlanta normalized average daily temperature anomaly for each phase, both inside and outside the circle (inside the circle phase 8 has an asterisk because it is the coldest at -6 F)(you may have to enlarge it to see it well):

Based on these findings, I drew an optimal path for the best chance for lengthy cold in at least January MJOwise (see diagram below). Optimally, start around the cool phase 6 within the circle and slowly circle around counterclockwise within the circle through the cold phases 7-8 and then through the still chilly phases 1-3 within the circle. This could easily take 2-3 weeks or so (the longer the better):


The following are many of the closest examples I could find to the optimal path….note that all of them resulted in anywhere from a 10 to 19 day period of solid cold domination:

1. 1/10-28/1977:

2. 1/6-15/1988:

3. 1/8-19/1994:

4. 1/4-14/1996:

5. 1/20-31/2000:

6. 1/13-27/2003:

7. 1/1-10/2014:

Neutral negative ENSO by far gives ATL best shot at major ZR

I thought this would be of extra interest for especially the SE US major CAD regions due to the current ENSO being neutral negative (NN). I counted a total of 36 Atlanta major ZR and/or IP on record. It is very impressive that half of these (18) were during NN ENSO, alone, when one considers that NN have occurred only about 1 every 5 years. I counted 28 NN’s. Of these 28, 16 (57%) had at least one major ZR and/or IP. In contrast regarding the other 109 winters, only 15 (14%) had at least one major ZR and/or IP. So, the % of NN winters with a major ZR and/or IP at Atlanta is a whopping four times as high as those for non-NN winters!


Dates of 18 ATL major ZR and/or IP during NN ENSO: