The EF Scale is put into effect today

[Jim Tang]

http://www.spc.noaa.gov/faq/tornado/ef-scale.html

Note that I believe that they've been rating tornadoes similarly to what they will rate from now on. The poorly constructed home can now only receive an F3 rating at the highest, whereas in the past, a poorly constructed home blown away deserved an F4. (Thus the controversy in 2006 regarding F3 vs. F4.) Thus, it shouldn't be too much of a change, I think.

Anybody want guess when and where is the first tornado to be rated using this new scale?

 

[Aric Cylkowski]

Considering Florida has a 5% risk for tornadoes today, I'm going to read the tea leaves and suggest today in Citrus County, Florida.

 

[rdale]

"The poorly constructed home can now only receive an F3 rating at the highest"

Remember to put the "E" in front of it...

 

[Greg Stumpf]

in the past, a poorly constructed home blown away deserved an F4.

Incorrect - many destroyed poorly constructed homes in the past were rated below F4, including some that I've rated. A classic example is the home in La Plata MD that incorrectly was originally rated F5, downgraded at least two notches (and may have deserved more).

As Tim Marshall always reiterates - compare to the surrounding damage. And always approach the "destroyed home" with skepticism before jumping the F5 (or EF5) gun.

 

[Shane Adams]

It's going to be weird going from someone who was pretty good at accessing damage in the past to being someone who doesn't have a clue how to rate tornado damage anymore.

 

[Greg Stumpf]

It's going to be weird going from someone who didn't have a clue at accessing damage in the past for DIs other than those described by Fujita, to being someone who will be pretty good at rating tornado damage for these new DIs.

Actually, I've already used the EF scale on surveys (e.g., El Reno OK 24 Apr 06), so it isn't really "weird" to me (plus, I'm a contributor to the WDTB EF-Scale training course). I'm only trying to get folks to think of the positives coming with the new EF scale. A lot of the guesswork in rating non-traditional DIs is going to be removed using the EF scale, and the scale can be expanded to include new DIs, and amended to change the wind speed estimates for existing DODs based on new scientific information.

 

[Gene Moore]

Incorrect - many destroyed poorly constructed homes in the past were rated below F4, including some that I've rated. A classic example is the some in La Plata MD that incorrectly was originally rated F5, downgraded at least two notches (and may have deserved more).

As Tim Marshall always reiterates - compare to the surrounding damage. And always approach the "destroyed home" with skepticism before jumping the F5 (or EF5) gun.

[FONT=&quot]I suggest that the implementation of this scale would be a great time to inform the public of a long-standing misunderstanding about the F-scale. I think in the beginning Fujita made the F-scale to illustrate to the public what damage could be done by strong tornadoes. Since then the ratings have become more of an instrument to help engineers and meteorologists, not potential victims in the path of an oncoming tornado.

Most people in tornado prone areas accept the fact that (so called) mobile homes, now referred to as manufactured homes and modular homes cannot withstand a tornado, even a weak one. Unfortunately, meteorologists over the years have emphasized that any well-built house can probably withstand all but the strongest tornadoes. For instance, "get out of your car, get inside a well built structure and take shelter." I've heard warnings like this many many times over the years. The public has it in their head that they have a chance of survival if they are not hit by an F-5, because only F-5's clear the house to the foundation. Actually, there was a time in my earlier years as a meteorologist that I thought this. How is someone to know their new $260,000 home is not well built? Will everyone check the rafters for hurricane clips, see if the first and second floors are "tied together" and the garage door has proper supports.....I say no, not a chance. Most homes bought are "spec homes," already constructed and sold by large contractors. People go on appearance (it's a strong brick home honey) not by what is behind the sheet-rock.

It should be made clear that people taking shelter anywhere in a home that their house can be blown away, that it may be cleaned to the foundation by an F-3 tornado, or perhaps even weaker! In the past we were taught F-4/5 tornadoes are less than 5 percent of the total number of tornadoes, some figures show 2 percent. Thus, people are willing to gamble that their home won't be hit by that worst case 2 percent. As we drop the strength to F-3 or F-2 for extreme damage to a badly constructed home that drastically changes the percentages that their home could be blown away by what was previously thought to be a weaker tornado.

Gene Moore
[/FONT]

 

[David Dildine]

Incorrect - many destroyed poorly constructed homes in the past were rated below F4, including some that I've rated. A classic example is the some in La Plata MD that incorrectly was originally rated F5, downgraded at least two notches (and may have deserved more).

As Tim Marshall always reiterates - compare to the surrounding damage. And always approach the "destroyed home" with skepticism before jumping the F5 (or EF5) gun.

La Plata was an F4, and nothing short of it. Having been there at the time, I would have probably considered it an F5 at first glance as well. So my question is this: if a tornado with 300 mph winds hits nothing but a mobile home park, is it still an F3 even though debris was lofted a mile downwind? Even though poorly constructed homes are demolished easily, the degree of decimation might still be good evidence.

 

[Karen Politte]

La Plata was an F4, and nothing short of it. Having been there at the time, I would have probably considered it an F5 at first glance as well. So my question is this: if a tornado with 300 mph winds hits nothing but a mobile home park, is it still an F3 even though debris was lofted a mile downwind? Even though poorly constructed homes are demolished easily, the degree of decimation might still be good evidence.

At your first glance at the tornado or the damage?

W/r/t rating tornadoes that strike mobile homes/poorly built structures; sometimes you can't GET an F-rating higher than F3 or so. It's like you can only squeeze so much juice out of an orange. Sometimes, the structure being damaged would be blown away at F3......therefore there is no hope of getting anything above this rating from it. In this case - I think it's always wise to remember what Tim Marshall always preaches. Look for what's still there - not what's been blown away. If you have a poorly built, unanchored home that has been blown off it's foundation, and yet there is a small sapling two feet away that is still standing/still has small twigs on it, or a mailbox on a post that's still by the side of the road......F2 by default would probably be the max. one could assign.

To get back to my point - it's possible for a tornado that possesses winds well below F5 criteria to cause damage that APPEARS LIKE F5 to a poorly built structure.

KL

 

[rdale]

La Plata was an F4, and nothing short of it. Having been there at the time, I would have probably considered it an F5 at first glance as well.

Not to sway the discussion - maybe a new thread required - but had the F5 never been mentioned, La Plata would have likely been only an F3 per the response team...

 

[Greg Stumpf]

La Plata was an F4, and nothing short of it.

Not F4 at the home I was referring to...the infamous "slider" home that was originally rated F5, and that Tim Marshall felt deserved no higher than an F2, perhaps even F1, but he was under pressure not to downgrade it that low.

There was F4 damage in the downtown area to one or two buildings.

 

[Jeff Snyder]

So my question is this: if a tornado with 300 mph winds hits nothing but a mobile home park, is it still an F3 even though debris was lofted a mile downwind? Even though poorly constructed homes are demolished easily, the degree of decimation might still be good evidence.

Well, that's always been one of the shortfalls damage scales (like the F and EF scales). We've seen this many times when strong tornadoes stay in fields and fail to hit anything substantial (the Throckmorton, TX, tornado of 2002 comes to mind). Interestingly, in the EF-Scale Report, there is a line that says that radar data from mobile radar CAN be used to supplement the damage assessment. So, if the DOWs, UMass mobile radars, or SMART-Rs get near-ground velocity data, that data may be used to supplement the rating. When things are completely destroyed, all that can be reasonable ascertained is that the winds were AT LEAST some threshold necessary to completely destroy those things. I would think that once something is destroyed, the "distance thrown" would be very much a function tornado size and residence time over said structure.

If nothing else, the EF-scale contains guidance for rating damage to hardwood and softwood trees, which should help when no structures are hit (DI 27 and 28). In fact, the top DoD for "Hardwood Trees" is in the EF-3 range... So, technically, a tornado could be rated EF3 even if it doesn't hit anything but trees. You certainly wouldn't not see this with the old F-scale.

 

[rdale]

Speaking of the old F-scale, I was at a talk with Kaz Fujita (his son) about the EF scale yesterday and he had some remarkable unpublished manuscripts from the early days and there are MANY surprising tidbits in there. I'll try to get permission to put the powerpoint up.

 

[Aric Cylkowski]

Rdale, were you also at the Enhanced Fujita Scale Conference yesterday at Central Michigan University? If so, I'm surprised we hadn't run into each other during one of the breaks.

 

[Andy Wehrle]

I haven't seen this noted, and I'm surprised it hasn't been (I apologize if it has been and I just didn't see it)...

With the implementation of the EF-scale, Bridge Creek/Moore, OK 5/3/1999 is officially the last F5 in history.