One of the indicators that the summer has really arrived is the first issuance of a severe weather watch or warning. In fact, in my state, we’ve had tornadoes in every month except February, and have had severe weather (thunderstorms, not snowstorms) in every month. I can still remember one February afternoon when we had a really strong thunderstorm – I was in school and we were practising for an event that was coming up in the next couple of weeks. The next thing we know, there’s thunder and lightning outside. In the middle of February.
Anyway, when we get an alert for severe weather, it almost always starts with the issuance of a watch – either a Severe Thunderstorm Watch or a Tornado Watch, depending on the severity of the storms that are expected over the affected area. Generally, this will be for a large swath of land, covering hundreds or thousands of square miles – sometimes even including the better part of a state. Then, as the weather develops, warnings are issued for specific storms. In fact, as of October 1st, the National Weather Service is only issuing warnings for specific storms, instead of for whole counties. Typically, the warnings are issued for an area of about 100-200 square miles (I might be underestimating that, since a township is considered to be 36 square miles).
In this case, we’re afforded the opportunity to have (at least in my opinion) some of the best forecasting of severe weather in the world, despite the media going all out crazy when there’s a warning issued (if you read the HDTV forums for this area, you can read about people getting annoyed at stations for crunching the widescreen picture into a 4:3 picture to put the warnings on the screen – they do the same thing for the snow closings as well).
Now, let’s do a bit of compare and contrast. First off is a current radar image from the National Weather Service office in Shreveport, LA – the only office in the nation that has severe warnings out for their Forecast area. The yellow squares are the boundaries of the severe thunderstorm warning, issued for some parts of Texas.
Contrast that with this picture, from the Bureau of Meteorology in Australia, who have issued a severe thunderstorm warning for parts of Victoria. Again, the warned area is in yellow. Note that the warning covers about 2/3 of the state.
What is baffling to me is this sounds very much like a watch – because they issue these warnings for hours at a time, and for such a large area. Interestingly, they do have a page intended to guide you as to the conditions for a severe thunderstorm warning, but there isn’t much in the way of specifics. Also, they say that these warnings have very little lead time for their issue – To try and issue warnings with a greater lead-time would lead to a flood of false alarms, thus rendering the service ineffective.
Interestingly, if you look at the Melbourne Radar loop, you can see that communities that are part of this warning appear to not have received any rain at all, for example, Colac. Of course, that doesn’t mean that they haven’t gotten storms already or won’t get them in the near future, but to have them under a warning seems to, especially if they don’t get any storms, be counterproductive to their statement of avoiding false warnings.
Our warnings aren’t perfect either – we have quite a few tornado warnings that are issued for the possibility of a tornado – however, those are not over issued, so they are still taken very seriously; I’m surprised that those warnings aren’t a source of further controversy actually. I think part of that is that a tornado is one weather event you do not want to take a chance with – even a weak tornado has the ability to kill people, especially in a mobile home park.
If you are curious, the guidelines for issuing a severe thunderstorm warning are if a storm has a measured or estimated wind speed of 50 knots (58mph, 93km/h), or hail in excess of a certain diameter. It has nothing to do with a lot of lightning or heavy rain. There are a dedicated group of people who volunteer to watch for storms and report on their progress to back up data that is gathered on a radar image – they are the storm spotters and I know that I’ve listened to them many times when it’s been stormy out; in fact, if you read local storm reports during severe weather, you will see a lot of entries from amateurs – that means amateur radio operators who have gone and submitted a report via the radio which is relayed to the forecast office on a separate channel.
Aussies, I’d like your opinion – would you like to keep having warnings issued as they are now, for large swaths of states for long periods of time (like our watches), or separate the warnings into watches and warnings, with watches being the current warning product, and warnings being issued for specific areas of states?