Experimental Changes to NWS Warnings

[Robert Dewey]

Originally posted by nickgrillo
Rob, yep - sorry for not replying to you sooner. Will send you a PM a little later today, perhaps...

Exactly. I haven't heard a warning for <1 inch hail for at least several years now.

Here is a excellent example of what this new warning method could do:

...

That was just an example warning I written up. Doesn't everybody agree this type of warning could come in handy?

..Nick..

I agree Nick... Very high straight line winds (like the 120+ MPH with the May 31, 1998 derecho) can do damage similar to a weak to moderate tornado, and over a larger scale. Since so many warnings are issued for marginal criteria, the public probably treats a severe thunderstorm warning with 60MPH the same as a severe thunderstorm warning for 100+ MPH, when they should really be treating the latter like a tornado warning (and seeking shelter in a basement/etc.)...

 

[James McCormick]

.5 - .75 inch hail with any kind of wind is going to severely hurt crops, gardens, and will affect travel. I think these storms need to have advisories on them. I've seen a number of warnings that read 'hail to the size of nickels', which is .88 inches.

50 Kts is a good threshold to me. Any time trees start losing branches and rain or dust are being blown around creating a condition of near 0 visibility, the public needs to know about it, and often times convective winds aren't on a large enough scale to warrant a high wind warning. I have also noticed the public pays little attention to high wind warnings.

I do agree that storms with hailstones larger than 3" or so need to be differentiated or emphasized, and when storms are bringing 90-100 MPH winds, that they need to be addressed in clear and concise terms. During the bow echo event in southcentral Nebraska on May 29th, Hastings used the term 'hurricane force winds' frequently in their severe weather statements. But we have to make sure that we aren't issuing too many products for the general public. Enough people have a hard enough time understanding the difference between a watch and a warning. I would rather have people interpreting the severe weather statement, or having the TV meteorologist describe the specific report, which mentions the specific threat, than try to come up with a new warning system that seems likely to result in apathy towards storms that don't meet 'extremely dangerous' criteria.

Besides, we don't 'know' what a storm is doing until it hits something. We don't 'know' if a storm that is reporting .88 inch hail actually has 1.75 inch hail if nobody is in the hail core. And I'd rather have a warning that encompasses not only the present severe weather threat but the potential threat of the storm as well. I really don't like the idea of not only having to determine if a storm is producing .75 inch hail, but that all of the hail in the storm is less than a certain size as well.

There's enough stress in the warning decision making process as it is, and enough problems with radar algorithms as well. The only thing I can think of that I like is the 'Tornado Emergency' Statement, which I think needs to be reserved for metropolitan areas and tornadoes that have had major damage reports with them.

 

[George Tincher]

I still stand by my original statement that a severe storm is a severe storm and that we don't need seperate classes of warnings. You want to let the public know whether 50 knot or 100 knot winds are expected? Well, don't we already do that? I mean each severe thunderstorm warning I've read indicates the expected level of severity, ie winds of 60, 70, 80 or even 100 mph. Expected hail size is also mentioned when appropriate. So with this info being provided right along with the warning, I think most people can figure out the seriousness of the situation without having to change anything. Again, I am opposed to change just for the sake of change. IMHO, that's all this would be.

Also, in reference to hurricanes, that's not a fair comparison. With hurricanes, we often have days to prepare. With severe thunderstorms, we only have minutes. So the TWC mets, CNN mets and local tv mets don't have quite as much time to explain all of the categories to their audience as with hurricanes. Besides, even if no hurricane intensity category existed, as long as we have information on the wind speed, I doubt we'd suffer much as a result. I mean it's pretty obvious to your average person that a hurricane with 75 mph sustained winds is less a threat than one with 150 mph winds. Therefore having a category scale as a warning device isn't even necessary.

Again, as long as all relevent information is available within the warning (which it is already), I see no great need to start adding categories for warnings. It just further complicates things without giving us anything we don't already have. The public is familiar with current format. They are use to it. And I see no reason to start changing what we know works when the change provides us nothing we don't already possess. And I have yet to see an argument that would convince me otherwise.

Now, as far as releasing probabilistic warning information, I could see a great usefulness there. That would give us something in addition to what we already have. And it would be helpful, as it would show the exact areas within a county for example, that will experience the worst of the weather.....while at the same time allowing those not expected to get the severe weather to relax a bit. This would be much more useful than a blanket warning for an entire county when only a small portion of the county is really in danger. This I would support 100%.

-George

 

[Mike Johnston]

George, I believe this is the experimental purpose is of using irregular polygon shapes for the warning area. At our spotter training, the NWS showed us some slides of what the new warning areas will look like, and they seem to be very tailored to the predicted path of the storm - with some margin of safety for possible path changes downstream, kind of like a miniature version of the hurricane landfall probability graphs we see. Within this context, adding probabilities would probably be redundant. In other words, if you're in the box, take cover now.

 

[Dan Cook]

What are these polygons going to look like on the NWS graphical maps?

 

[George Tincher]

Originally posted by Mike Johnston
George, I believe this is the experimental purpose is of using irregular polygon shapes for the warning area. At our spotter training, the NWS showed us some slides of what the new warning areas will look like, and they seem to be very tailored to the predicted path of the storm - with some margin of safety for possible path changes downstream, kind of like a miniature version of the hurricane landfall probability graphs we see. Within this context, adding probabilities would probably be redundant. In other words, if you're in the box, take cover now.

Yes, that would be pretty much the same thing, as obviously the closer to the center of the projected path you go, the greater the expected danger of experiencing the most severe of the weather. IMHO, this change would be good.

 

[Mike Johnston]

Well, good question and unfortunately I didn't think to ask her. Since it is experimental for just a handful of offices this year, I'm not sure at what NWS map levels (ie. national, regional, local etc.) the shapes will be displayed. The NWS person did tell me that communications to the public will still be made with reference to county/city locations for clear understanding. However, localities with siren systems will evidently activate sirens only in the actual area warning.

 

[Andy Wehrle]

Originally posted by Mike Johnston
However, localities with siren systems will evidently activate sirens only in the actual area warning.

It's about time. When I'm at home the sirens go off every time there's a tornado warning for Dane County. I'll bet a lot of people have started ignoring them. Anyone know if MKX and GRB are among the offices doing this?

 

[rdale]

The polygons have been used for a while, it's just now that some offices are using them for verification too. Programs like GRLevel3 plot them instead of the county line.

- Rob

 

[Robert Dewey]

Originally posted by rdale
The polygons have been used for a while, it's just now that some offices are using them for verification too. Programs like GRLevel3 plot them instead of the county line.

- Rob

Yes... They have been doing this for quite some time... The very first time I seen a polygon warning was with the Swift WX software, version 1.

Rob, do you know if GEMPAK is able to plot polygon shaped warnings?

 

[David Schuttler]

Sounds alot like what our local tv stations already do and use.

Around here I believe most people get their info from the tv and that stations met anyway. Which they use thier own radar to pinpoint a storm and it's track.

 

[Ben Cotton]

Originally posted by Alex Lamers
The best idea I've heard thus far on this thread (sorry I forgot the name so I can't give kudos) is to have some sort of a Thunderstorm Advisory for hail between 0.50 inches and 1.00 inches (upping svr hail crit to an inch like the original post said) and winds from 40-60 mph. These may not cause extensive damage but they can still create some problems. This way information would get broadcast a lot easier than if they just issue a NOW. I think that some offices down south issue significant weather advisories for strong thunderstorms already. Why not make it an official advisory nationwide?

The Special Weather Statement (SPS) can be used in cases like these. On May 30, several tornadoes hit the Louisville area in the early/mid-afternoon. Later that evening, LMK issued an SPS for an approaching squall line (while it was still well west of the CWA) in order to alert the public to another round of potentially dangerous weather. Used judiciously, the SPS can accomplish just what you've said without having to add a new product.

Such information could be useful, in particular to boaters or marine interests.

Methinks you shouldn't be out on a boat during a storm of any severity. That having been said, a NOW or SPS broadcasted on the AHR would still convey the same information.


Ben

 

[Scott Olson]

I tend to think that having various types of thunderstorm warnings wouldn't prove much more helpful for the public. More people would probably tend to ignore the lowest of the severe warnings. However, I think having a single established criteria that is more in tune of what is widely considered severe will help prevent un-necessary severe warnings for storms that just don't warrant it. I have long believed that a specific or special warning be made for bow echo events as I have seen the devastation caused by straight line winds.

 

[Jeff Wear]

I'm not sure if I like the idea of raising the minimum severe criteria....I'll agree that hail under 1" usually isn't much of a problem (especially if falling sporadically and/or winds are light) - but I do have some minor dings on my vehicle though from hail in the 0.75 to 0.88 inch range. That makes me wonder....wouldn't a vehicle be more likely to sustain damage from hail while moving than it would if it were parked?

Another concern I'd have would be the increase in the number of 1 inch hail reports if the minimum criteria was raised to that level....I'd like to see the NWS attack the problem of all the estimated reports and start putting more emphasis on measured reports and reporting storms that actually cause property or tree damage before raising the criteria. Perhaps there could be a 25% penalty put on all estimated reports? Or even totally reject estimated reports altogether unless some more specific information comes along with the report (like did it dent cars, break windows, or snap tree limbs?)

 

[Ben Cotton]

Originally posted by Jeff Wear
That makes me wonder....wouldn't a vehicle be more likely to sustain damage from hail while moving than it would if it were parked?

I would think so. Anything that increases the change in momentum of the hailstone (whether it be an increase in speed of the hail itself or of the object it strikes) will produce a greater net change in momentum and thus greater damage. Now, if you're in your car, and the hail is coming down at an angle such that you're driving away from the hail....

Another concern I'd have would be the increase in the number of 1 inch hail reports if the minimum criteria was raised to that level....I'd like to see the NWS attack the problem of all the estimated reports and start putting more emphasis on measured reports and reporting storms that actually cause property or tree damage before raising the criteria. Perhaps there could be a 25% penalty put on all estimated reports? Or even totally reject estimated reports altogether unless some more specific information comes along with the report (like did it dent cars, break windows, or snap tree limbs?)

This is the larger problem, I think, but the less easily resolved. Hail sizes are easy to overestimate, especially when you're excited. I carry a ruler with me when I chase, but that doesn't mean I always remember to use it. At the risk of offending some of the NWS-types on this board, I think the NWS is equally responsible. The warning mets are under pressure to issue quality warnings. A warning isn't very high quality if it doesn't verify. In the past two summers volunteering at a WFO, I've worked several severe weather cases. Part of my duties during these events were calling local police dispatchers to get reports. When marble-sized hail was reported, the MIC told me to ask if it was penny-sized (and thus severe), since marble is somewhat ambiguous. This may not occur at every office, or for every event, but certainly there's plenty of responsibility to go around.


Ben