Severe weather warning almanac?

April 13, 2009 4:24 PM

Weather almanac filter: The recent string of severe weather in my area has led me to wonder - is the occurrence of National Weather Service warnings (ie. severe thunderstorm, tornado warning) actually increasing or does it just seem that way? Specifically, does anyone know if this type of information is tabulated anywhere, such as the annual/monthly number of warnings by parish (or county). Is there somewhere I could look up how many times a warning was issued in my area for 2008? I would think this data would be available somewhere, but my google-fu is failing me.
posted by tryniti to science & nature (6 comments total)

I don't think so, its probably a combination of confirmation bias and better reporting and forecasting.
posted by Mach5 at 4:26 PM on April 13

Yeah, those hundred-year floods have always happened every year. Nothing to worry about.

Slightly hyperbolic, but... ?
posted by Aquaman at 4:38 PM on April 13

I don't know if there is any increase or not, but I can say that imaging and forecasting has gotten better. There was a small tornado in the area, and I was able to watch it bop along on the NWS radar website. That sort of detail was unimaginable just a few years ago.

And with every weather event, they are better able to have a picture of what the conditions for trouble are. So there may well be more false alarms- not because of over-cautiousness, but because we can now see things that we couldn't previously see.
posted by gjc at 5:51 PM on April 13

I get a lot of NWS warnings now about fire danger, wind and fog. I think they're just being overcautious. My feeling -- unsubstantiated of course -- is that there are exactly the same number of severe weather events now that there were back in 1809. We just have better data and a 24-hour news cycle.
posted by drinkcoffee at 6:20 PM on April 13

Events, not so much, but tornado warnings? Yes. Now that radar is better at showing storms that "can" produce tornadoes, there are more preemptive warnings than there were 20 years ago.
posted by wierdo at 7:26 PM on April 13

Finding severe weather that actually occurred is fairly easy. They have listings at the National Climatic Data Center that you can search by county and date. The number of warnings that the NWS issues, on the other hand, doesn't seem to be as easily available. I think the information might be available under NCDC's Service Records Retention System, but that function is offline at the moment. Your best bet might be to contact your local NWS office and ask.

Drinkcoffee is probably right that there isn't more severe weather now than there was in the 1800's. Data has been pretty consistent showing a rise over the last 50 years in the number of weak tornadoes reported, while the number of strong/violent has stayed pretty steady. Most experts agree this is due to more chasers out looking for the tornadoes, where as previously the weak ones would have went unnoticed. General population growth also contributes to more reports.

As for increasing warnings, yes, some of that has to do with more sophisticated detection systems that can see the mesos that may or may not produce tornadoes. The NWS is aware of the "crying wolf" problem and has been trying to find ways to bring false alarms down. But as someone who's been on the radar desk, all I can say is that none of us wants to be the one sitting there while a tornado rips through a town unwarned. So many of us err on the side of caution.
posted by weathergal at 3:39 AM on April 15