Weather Wednesday

We have all seen them, those slowly scrawling texts across our TV’s:

“The National Weather Service in (insert your City) has issued a (insert warning) for (insert county) until….”

Then when said thunderstorm or whatever passes through, you shrug your shoulders and wonder what all the worry was for.

What this has created is a false sense of security, people do not take National Weather Service warnings seriously and the results can be tragic.  What I hope to do here is to give you an idea of why the National Weather Service issues the warnings they do.

Flash Flood:  A Flash Flood warning means that the NWS radar has estimated that a significant amount of rain (or combination rain/snow melt) has fallen over a very short period of time, obviously if you don’t live in a flood prone area, you might not notice much (other than it is wet), but if you do live in a flood zone, then water may be rising fast, sometimes a several foot rise can occur in only a few minutes.  Also keep in mind that it is not necessary for it to be raining at your location to have a flash flood.  Flash flooding usually only lasts a couple of hours an is sometimes listed as an “Urban and Small Stream Advisory”.  The urban is for clogged storm drains and parking lots, which tend to collect water fast.

Flood Warning:  A flood warning is generally issued when flooding is expected to be a long duration event and is more widespread.  Main stem rivers may be involved, flooding is generally widespread, but may or may not be severe.  Water rises tend to be much slower than in flash flood situations and are thus more predictable.  Often a Flood watch is issued a day before the rain starts to alert people to the potential of flooding.

Severe Thunderstom Warning:  A Severe Thunderstorm Warning is issued when meteorologist, using sophisticated radar (or so they would like to think) has a thunderstorm that is producing winds of 55 mph or greater or 3/4″ inch hail or greater.  In Canada, heavy rain is also a criteria for a Severe Thunderstorm Warning.  A thunderstorm only has to exhibit these criteria once, in which case a warning is issued.  Sometimes one gust is all a storm has got, I have seen situations where the storm has dissipated prior to the Warning reaching the TV.

While many Severe Thunderstorm Warning barely if ever verify, you never know which ones will, which ones won’t.  Thus you should treat each warning seriously, that means moving to a sturdy shelter when these warnings go off and making sure your pets and children are accounted for.

Most Severe Thunderstorm warnings come after a Severe Thunderstorm Watch has been issued.  Watches are issued by the Storms Prediction Center  in Norman, Oklahoma, while warnings are issued by the individual National Weather Service offices.  However you do not need a Severe Thunderstorm Watch to have a warning.

Tornado Warning:  A Tornado Warning is issued, when either a) NWS Radar had indicated a tornado or at least, very strong rotation in the storm or b) a confirmed funnel cloud or c) a Tornado on the ground.  Like Severe Thunderstorm Warnings the vast majority never come true, but with a Tornado Warning, even if you don’t get a Tornado (and that is a good thing) you are likely to experience Severe Thunderstorm conditions with high straight-lined winds, hail and lots and lots of lightning.  If a Tornado Warning is issued for your area, you should head to your basement (if you feel awkward fold some laundry or something), if you don’t have a basement the lowest interior room of your house.  You should abandon cars and mobile homes if a tornado is spotted.  If caught in the open, lay flat in a ditch.  Its not so much the wind that will harm you, but the debris within the cloud.

There are of course other types of weather warnings, related to Winter Storms, Hurricanes and other events, but those will be discussed at a later time. 

Please take these weather warnings seriously, even though most to not do catastrophic damage, there is always that chance that the next time that warning scrolls across your screen it will.

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