WSET.com - ABC13SPC Gets It Done by Sean Sublette

In the wake of last Saturday's severe weather outbreak, I wanted to publicly acknowledge and commend the work of the meteorologists at SPC in Norman, Oklahoma.

SPC (Storm Prediction Center) is a special office of the National Weather Service dedicated to the forecasting of severe local storms. They issue all of the Tornado Watches and Severe Thunderstorm Watches you see. The Warnings that follow those Watches come from the local NWS offices (ours is in Blacksburg).

Several times every day, SPC issues a Convective Outlook. This is usually the first step before a Watch is ever issued. These outlooks entail three primary levels of severe weather risk.

The problem is that the levels of risk mean one thing to a meteorologist, but another to the general public. Their official definitions in italics:

A Slight Risk implies that well-organized severe thunderstorms are expected but in relatively small numbers/coverage, or a small chance of a more significant severe event. Not all severe storm events will be covered with a Slight Risk, especially during the summer when short-lived, "pulse-type" severe storms are relatively common during the afternoon.

So it is important to remember, that Slight Risk does not mean the threat is to be ignored. Slight risk is still substantially higher than zero risk. It means a small number of severe storms are expected in the area of interest.

A Moderate Risk implies a greater concentration of severe thunderstorms (or tornadoes), and in most situations, greater magnitude of severe weather and greater forecaster confidence compared to a Slight Risk. A Moderate Risk is usually reserved for days with substantial severe storm coverage, or an enhanced chance for a significant severe storm outbreak. Typical Moderate Risk days include multiple tornadic supercell thunderstorms with very large hail, or intense squall lines with widespread damaging winds.

A High Risk implies that a major severe weather outbreak is expected, with a large coverage of severe weather and the likelihood of extreme events (i.e., violent tornadoes or very damaging convective wind events). The High Risk category is reserved for the most extreme events with the least forecast uncertainty, and is only used a few times nationally each year.

Once the Saturday morning data were analyzed, A Tornado Watch (See Figure 1) was issued for eastern North Carolina at noon Saturday, and the area was placed in High Risk at 1pm (See Figure 2,).

The first tornado occurred in North Carolina at 1:41pm. The infamous Raleigh tornado entered Wake County, NC at 3:30pm (Raleigh is in the center of Wake County). Figure 3 shows the verified tornado paths in North Carolina that day.

Unfortunately, this also illustrates a more daunting problem of how to get this information out quickly to the public. It would seem easier with television, radio, internet, and mobile devices all available.

But sometimes, there can be too many conflicting messages. How many times have you heard people discussing the weather starting with the phrase, "They're saying it's gonna _______." Or "I heard it's gonna _______."

I still remember one of my college instructors emphasizing to us as freshman meteorology students that the best forecast in the world is useless if no one hears it or understands it. This is where we need to go from here.

Without question, the storms caught some people off guard. And I imagine that to some extent, that will always be the case. But to be clear, it is absolutely false to state that meteorologists did not foresee strong tornadoes developing on Saturday afternoon.

SPC did its job.