New wording in severe thunderstorm warning?

[Kevan Wagner]

Right now there is a thunderstorm warning for Palm Beach county.I just read in the follow up statement that said that weak rotation was spotted in the storm.In the last paragraph it say that thunderstorm lines can produce brief spin up tornado's and high wind damage. Is this something new being tried out in the national weather service?The thunderstorm is a squall line.I think that there shouldn't be a tornado warning for squall line tornado's but say in the warning that there may be brief spin up tornado's like today.You can't catch ever squall line tornado but there should be wording in a thunderstorm warning about spin up tornado's.Should this be the policy of the national weather service?

 

[rdale]

I'll try to take this apart piece by piece...

Is this something new being tried out in the national weather service?

No, it's not new. When there is rotation in a squall line, it sometimes can result in a tornado. Most are very weak and very short-lived, no worse than straight line winds, so you wouldn't issue a tornado warning. Unless you have a confirmed tornado that will last more than a few minutes.

I think that there shouldn't be a tornado warning for squall line tornado's but say in the warning that there may be brief spin up tornado's like today.

That's why the office did it like that.

Should this be the policy of the national weather service?

It is the policy - the NWS is the entity who issued the warning you are referring to.

(Side note: no apostrophe in "tornadoes")

 

[Kevan Wagner]

Thanks for answering my question.There looks to be a nasty squall line headed for West Palm beach Florida.I can see why they have that wording in there to warn about brief tornado's.I like the policy of saving tornado warnings for tornadoes on the ground in situation where you have a squall line.Trying to catch every tornado in a squall line isn't worth a tornado warning.I like the new policy.

 

[John Farley]

I would add, though, that it depends on the squall line. Sometimes they have embedded supercellular structures (often HP) that can produce stronger, longer-lasting tornadoes. Also sometimes even the mesovortices that occur with QLCS-type systems in squall lines can produce tornadoes as strong as EF-2. These can sometimes be quite dangerous - the husband of a woman I worked with was killed a decade or so ago when one of these hit a clothing store in Fairview Heights, IL. In situations like these, a tornado warning is entirely warranted. In other cases, where weak spinups are all that are likely and no persistent rotation is detected, the NWS may opt for a SVR warning with wording like what you mentioned, Kevan.