Rare Tornado Event Part One: Role of the National Weather Service

Although official spring has not started (March 20th will be the first day of spring in 2017), hasn’t it felt as if mother nature is determined to make it feel like spring?  Perhaps you noticed the first taste of spring when a record breaking stretch of warm temperatures were felt across northern Illinois?  Or maybe it seemed more spring like across the Midwest when thunderstorms, instead of snow, occurred?  No matter what your idea of spring is,  one of the more dangerous types of weather that typically develops during late spring/early summer, occurred on February 28th, when a rare tornado outbreak hit the Mid-Mississippi Valley and the Lower Great Lakes region.

National Weather Service Warnings

Meteorologists in National Weather Service offices in Chicago and central Illinois were intensely watching the radar on the afternoon of February 28th, looking for telltale signs to pull the trigger on severe thunderstorm and tornado warnings.  This may seem like a difficult task to do, and it is.  While I was employed by the National Weather Service, I often was in the same position – monitoring radar to determine when and where to issue a convective warning.  It takes a lot of training, meteorological knowledge, and feedback from reliable folks in the path of these storms to determine where to issue a warning, how long the warning needs to go, and what type of warning (severe thunderstorm, tornado, and flash flood).  So how does the National Weather Service do it?

National Weather Service Hazardous Weather Staffing 


Meteorologists hard at work in the National Weather Service.  Photo: National Weather Service

When severe weather strikes, the affected office evokes its severe weather staffing plan.  Although National Weather Service offices across the country handle differencing types of hazardous weather, there is one common goal: to protect the life and property of the public.  So that means they are working hard to make sure you will be protected from dangerous weather, like tornadoes and flash flooding.  They do not only work this hard when convective weather strikes an area.  Blizzards and wild fire outbreaks are two other examples when staffing and the workload increase.  The difference is issuing a warning has be done in a very short period of time, as severe thunderstorms, tornadoes, and flash floods can quickly develop and intensify.  Given the recent tornado outbreak that hit the Mid-Mississippi Valley and Midwest, we’ll take a look at the difference between a weather watch and a weather warning.

Hazardous weather watches

Usually when an event like this one that just occurred, meteorologists are fully aware that the possibility exists for these types of storms.  For days they have been monitoring complex computer models that display a wide variety of weather elements while also analyzing the atmosphere near the surface to thousands of miles above. Often times, the Storm Prediction Center located in Norman, Oklahoma, will issue a severe thunderstorm or tornado watch for an area.  Watches cover tens of thousands of square miles and typically last 4-6 hours long.  When a watch is issued for your area, that means conditions are favorable for that particular weather element to occur in or near the watch area.  Basically this means you need to keep an eye to the sky and be prepared to take shelter when threatening weather hits.

Hazardous weather warnings 

Meteorologists in the individual National Weather Service offices closely monitor radar, satellite, and other weather data when hazardous convective weather is possible,  much more often then when no precipitation is occurring.  When meteorologists feel hazardous convective weather is imminent, has been detected on radar, or received word that a severe thunderstorm, tornado, or flash flooding is occurring, they will issue the appropriate warning.  So warnings are much more dire than a watch and basically when there is a warning issued for your area, you need to take cover immediately!  Warnings are much smaller in size and typically cover portions counties the storms will move across.  Warnings also do not last nearly as long, usually 45-60 minutes in length.  So remember when a watch is issued for your area, be ready to take shelter and when a warning is issued, take cover immediately.

February 28, 2017

Meteorologists in northern and central Illinois were extremely busy February 28th as a significant severe weather event unfolded across the Midwest.  In Part Two of this series, we will analyze what happened on this day.




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