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Warm. Dry. Sunny. Repeat. That’s pretty much the forecast for the next three days! Mostly sunny skies will allow us to warm to near 80 today and into the low to mid 80s over the weekend. Clear skies at night will allow temps to drop to near 60. Humidity will be increasing each day, so you’ll likely feel that change, especially by Sunday. The next chance of rain comes Monday, as we heat up to a muggy 85 degrees. An isolated shr or storm is possible by the afternoon/evening. Those rain chances tick up to about 40% or so by Tuesday and Wednesday, again, mainly afternoon and evening heat-of-the-day type stuff.


That picture is one of the few taken of the worst tornado to ever strike New England. The one-mile wide twister hit Worcester, Massachusetts on June 9, 1953. It took the lives of 90 people as it tracked for 46 miles. The tornado bent steel towers that were built to withstand winds of up to 375 mph! The storm dropped debris on Boston and then out into the Atlantic Ocean.  1953 was the third deadliest year for tornadoes in the US, with 519 lives lost. This is in spite of the fact that tornado counts were below average that year. Of the 519 killed, two-thirds of those were lost in only three tornadoes (Flint, MI, Waco, TX, and Worcester, MA).  This emphasizes the point that we try to make with hurricane season. You don’t have to have an active year to have a bad year. It only takes one storm.

Incidentally, 1953 caused the Storm Prediction Center (SPC) to reorganize. The Flint and Waco tornadoes had been forecast, but the Worcester was a complete surprise (it was 1953, after all). At that time, the SPC consisted of young men who had gained their meteorological training while serving in the military during WWII.  Many of them had less than 10 years experience.  One of the men was Joseph Galway, the inventor of the “lifted index” that we use today as a severe wx parameter. The birth of convective outlooks came out of all this, a product that many of us everyday. The size of severe wx watches was also reduced and is comparable to what we use today.

The reorganizing of the SPC must have worked because we hadn’t seen a tornado with such death tolls until 2011, with the super outbreak in the South and then again with Joplin.

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Tornadoes associated with the cold core low in North Dakota on June 8, 2017

Last night, I shared the video of the tornado in North Dakota. As you may have noticed, there was no precipitation surrounding the tornado. We often see supercell tornadoes that are either wrapped in rain, or on the brink of becoming wrapped in rain. The supercells in the southern US tend to form in much more humid environments. These humid environments are made possible due to the close proximity of the Gulf of Mexico. As one gets farther away from the moisture source, there’s less moisture to work with. There are “hiccups” to this idea, in that areas with lots of agriculture (ie. Corn fields of Indiana) have noticeable jumps in humidity due to evapotranspiration of the crops (moisture evaporating from the crops).
The main culprit for yesterday’s tornadoes was what we refer to as a cold core low. This is basically a cold pocket of air spinning in the atmosphere. It is not based on the surface of the earth, like a hurricane’s low pressure center, but it is based much higher up within the atmosphere. This spinning pocket of cold air is rather common across the Plains, especially during the spring months. Now, if you can get a lot of sunshine underneath these lows, that sunshine will warm the earth’s surface. Since we’re getting a higher sun angle every day that we closer to the first day of summer, it can really warm the ground up this time of year! That warm air underneath that pocket of cold air above can create the perfect environment for clouds to develop, as that warm air rises into the cold air and cools and condenses. The winds with these cold core lows increases pretty dramatically with height, so that adds a component of shear. In other words, the faster winds aloft allow the updraft to tilt, which allows it to gain/maintain strength without being choked out by the nearby downdraft.
With winds increasing with height (speed shear) and instability (sun heating the ground), the ingredients were in place for thunderstorms. An area of surface low pressure then formed just southwest of where the tornadoes were reported. This development produced a frontal boundary across eastern North Dakota and provided directional shear for the winds. Speed shear is when winds increase with height, directional shear is when winds change direction with height. We now have southeast winds at the surface, increasing and becoming southwesterly aloft, which is the perfect wind combination for rotating supercells. The only thing left to talk about is surface moisture and that’s what leads us to the next point: why is there no precipitation around the tornado?
Interestingly, a cold front had made its way across the Dakota’s earlier in the afternoon. That front robbed the atmosphere of some of its moisture. However, dewpoints were still able to climb to around 60, which was just enough moisture to create thunderstorms. That’s enough to create the rotating thunderstorm, but not enough to produce a lot of precipitation. We call these ‘low precipitation supercells’ and they’re actually rather common across the northern Plains. Remember the guy mowing his yard during that very visible tornado in Canada a week or so ago? Same situation! There’s enough moisture to create a storm, but too little moisture for the storm to produce heavy precipitation. In the southern Plains we may see dewpoints in the 70s with supercells, which is more than enough moisture to not only create storms, but create storms that produce copious amounts of moisture that can wrap around the rotating supercell and hide the tornado.
If the sun hadn’t come out and heated everything up so much, there wouldn’t have been enough instability to create thunderstorms. Plus, without that warming the surface low that formed wouldn’t have been as strong, and the wind fields would have been weaker. It really all boils down to that sunshine and that cold pocket of air that we call a cold core low.
The tornado has been rated an EF-0 by the NWS. Cold core lows often produce weak tornadoes, and that certainly seems to be the case here.
I hope this helps you understand how the tornado originated and why we were able to see it! If you have any questions at all, please don’t hesitate to let me know!
For more radar, satellite, storm environment, etc information, go to…
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A shower or two to dodge today, beautiful weather for Friday and the weekend!

Confidence is really high that we are in store for a beautiful weekend. First though, we may have to dodge a shower or two today, as we have a weak disturbance that will be passing through this afternoon. It certainly  won’t produce anything heavy. Tonight we clear out again and it is going to be a bit chilly, with lows dipping into the upper 40s. Friday, Saturday, and Sunday look spectacular! Highs on Friday will approach 80, the lower 80s for Saturday, and mid 80s for Sunday. Humidity will tick up each day, so be aware of that. Lows each night will be in the 50s. The newest data has Monday mostly dry, with shrs and t-storm chances holding off until Tuesday. Regardless, next week is still looking hot and humid. I’ll update the rain chances that will go with that heat and humidity tomorrow.

Late last evening a post was made on social media of a tornado in North Dakota. I shared it with our weatherTAP social media and people are going crazy over it! Check it out below if you haven’t already. You’ll notice that there seems to be no precipitation with the storm. We call these low precipitation supercells, as opposed to high precipitation supercells that we often have in the South. When you get as far away from the Gulf of Mexico as North Dakota is, you have much more limited moisture for storms to work with. This tends to lead to much better visibility of tornadoes and overall storm structure. I’ve attached the video below, for your viewing pleasure! :)


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Beautiful spring weather, followed by hot and humid weather

You can’t order better weather than what we’ll have today! Highs will top out in the lower 70s, with mostly clear skies. Tomorrow will be much of the same, but with a few more puffy cumulus clouds around. We might even squeeze out a shower, especially east of Highway 127. Highs will once again be in the lower 70s, after a crisp morning low in the lower 50s. On Friday, we start the warm-up. Highs will approach 80 by Friday afternoon, lower 80s by Saturday afternoon, and mid 80s by Sunday. Lows each night will be in the lower 60s. Along with the high temps, the humidity will begin increasing too. By Sunday you’ll really notice a difference. Looking ahead to the start of next week, the forecast looks hot and humid with isolated to scattered t-storms.

You may have noticed the beautiful sunset yesterday evening? I was lucky enough to be able to snap a picture of it and then share it with WATE news ch. 6 in Knoxville. They ended up sharing it on the news last night! It was cool to hear my name on the air again. I was a ch. 6 weather watcher for several years when I was in high school.  With some clouds around Thursday, keep your eyes open for another beautiful sunset!