Severe Weather: Watches and Warnings

Severe weather, the type that can cause property damage and loss of life, can take a variety of forms depending on season and location. But during spring and summer in the northeastern United States, it usually takes the shape of an intense thunderstorm. In addition to thunder and lightning, these storms produce strong winds, heavy rain, hail, and the possibility of a downburst or tornado. Therefore, it is important to understand the difference between the various alerts issued by the National Weather Service. They include advisories, watches, and warnings.

  • Advisory: Issued when significant, but not necessarily hazardous, weather conditions are likely to occur. Residents should exercise caution.
  • Watch: Issued when dangerous weather conditions are possible over the next several hours.  They generally cover a large geographic area.  Residents should be prepared to take action.
  • Warning: Issued when dangerous weather is imminent or already occurring.  They cover a smaller, more specific geographic area.  Residents should take action immediately.

Stay safe!

How Does Hail Get to be the Size of a Grapefruit?

Spring is considered severe weather season in the Central US and on Tuesday the power of Mother Nature was on full display across the region. More than 300 severe storm reports were counted and the vast majority included very large hail.

In Kansas and Nebraska, hailstones the size of a grapefruit were reported. Those are balls of ice measuring about four inches in diameter. According to the NWS, once a thunderstorm produces hail with a one inch diameter or more it is considered severe. So, how does hail get that big?

The answer to that question lies with the speed of a storm’s updraft. Basically, the stronger the updraft, the longer the ice remains suspended in the cloud where it can grow larger. Below is a chart that shows approximately how strong an updraft has to be to support different sizes of hail.

The largest hailstone ever recorded fell in Vivian, South Dakota on July 23, 2010 and measured eight inches in diameter – about the size of a volleyball. To support a hailstone that size, the updraft likely exceeded 150mph.

Credit: NWS

Credit: NWS

Deadly Tornado Devastates Towns in Northern Illinois

tornado outbreak barreled across the mid-west on Thursday night. The strongest of these twisters caused widespread destruction, two deaths, and at least twenty injuries in the neighboring towns of Fairdale and Rochelle in northern Illinois.

The National Weather Service has given the deadly tornado a preliminary rating of EF-4, the second highest ranking on the Enhanced Fujita Scale. Measuring a half-mile wide with winds near 200mph, the wedge shaped twister is reported to have traveled nearly thirty miles on the ground.

Local officials in Fairdale say the storm affected every home in the community with eighteen swept completely off their foundations. The tornado also destroyed many trees and power lines across the area and even toppled a tractor-trailer on Interstate-39.

Tornadoes of this intensity are not that common in northern Illinois. The NWS says Thursday’s storm was the strongest tornado on record (since 1950) for the two counties where Fairdale and Rochelle are located – DeKalb County and Ogle County, respectively.

Year to date, tornado season – which typically begins to ramp up in March – has been fairly quiet. But, as this latest storm shows, it only takes one tornado to devastate a community.

Tornado Damage.  Image Credit: Rockford Fire Dept.

Tornado Damage. Image Credit: Rockford Fire Dept.

Twin Tornadoes Tear Through Nebraska

Barreling across northeastern Nebraska on Monday, a pair of twin tornadoes leveled the small farming town of Pilger, NE. The so-called “sisters” claimed the lives of two people and injured numerous others.

The two wedge tornadoes were reported to have been on the ground for nearly an hour and traveled along parallel pathways getting as close as one mile apart. With winds ranging between 166 and 200 mph, the National Weather Service has rated both twisters EF-4. That is the second highest ranking on the Enhanced Fujita Scale.

Massive twin tornadoes are rare events. Experts say, if one thunderstorm spawns two separate twisters simultaneously, one usually dissipates or is overtaken by the other. The size, strength, and longevity of Monday’s tornadoes were extremely unusual.

With warm, moist air lingering over the region, violent weather returned to Nebraska on Tuesday. A multi-vortex tornado was spotted in Coleridge, NE, but that storm has not yet been rated. More severe weather, including possible tornadoes, is expected in the area again on Wednesday.

Rare twin tornadoes tear across Nebraska. Image Credit: KEYC

Rare twin tornadoes tear across Nebraska. Image Credit: KEYC

Multi-Day Tornado Outbreak

After getting off to a slow start, the severe weather season has kicked into overdrive. A multi-day tornado outbreak has been wreaking havoc across the southern and central United States since Sunday. Widespread destruction, power outages, and a mounting death toll have been reported across several states. Some of the hardest hit areas include Arkansas, Mississippi, and Alabama.

According to local authorities, the twister that hit Vilonia and Mayflower, Arkansas on Sunday night was on the ground for 29.2 miles and claimed the lives of at least 16 people. With winds in excess of 136 mph, the NWS has assigned it a preliminary rating of EF-3. On Monday, the same deadly storm system moved into Mississippi and Alabama and generated even more tornadoes. Local officials there say hundreds of homes were destroyed and at least a dozen people were killed. The strongest storm in this outbreak so far was an EF-4 (preliminary rating) that touched down in Louisville, Mississippi. With winds ranging between 166 and 200 mph, it was also the strongest tornado to form in the U.S. to date this year.

Tornadoes are par for the course in this part of the country in spring, but the longevity of this outbreak is unusual. With warm, moist air moving up from the Gulf of Mexico and feeding into a very slow moving low-pressure system, the threat of severe weather continues to linger.

Tornado ravaged Vilonia, Arkansas.  Image Credit: EpochTimes/AP

Tornado ravaged Vilonia, Arkansas.  Image Credit: EpochTimes/AP