Are small violent tornadoes very noticeable on radar

[STurner]

I am just wondering if small violent tornadoes are just as noticeable on radar as large violent tornadoes. For example like the OKC tornado from 5-3-99 and the Greensburg tornado from 5-4-07 were definitely classic supercells on radar. But if a small tornado around 100yds or so wide was going to do EF5 level damage to a community would you be able to tell it just as much as the ones described above. Also what I mean by noticeable is for certain you will know something bad is going to happen just as much as the other two described above. There are probably other things to consider such as the tornado being rain-wrapped etc. But lets say storm chasers and spotters have directly identified this tornado with their own eyes just like the OKC and Greensburg tornado.

 

[Jeremy Den Hartog]

In general, a tornado that is going to cause EF5 damage is going to be noticeable on radar - especially with todays technology. That being said, I don't know of any narrow tornadoes of 100 yards wide (or similar width) doing EF5 damage. Typically EF5 tornadoes are multiple vortex tornadoes that last for extended periods of time and travel fairly lengthy distances. They require very strong rotation which makes them easier to detect on radar. However, 'strong' tornadoes can go undetected if they are rain wrapped or if they occur at night time. Also, some tornadoes do not have any associated mesocyclone with them, but these tornadoes are typically weaker. Also, I should mention that narrow tornadoes can still cause significant damage but because they are narrow they obviously aren't as devastating to a community as say a 'stove pipe' tornado would be just because the shear size of the tornado. I hope this helps answer your question. I should mention, I'm not trying to pretend to be an expert (as I'm not) - just trying to help .

On a side note, many of the residents of Greensburg reportedly thought they were hit by 2 tornadoes. However, it was determined that this was likely because of the shear size of the tornado. In other words, people were hit by the 'front' of the tornado, then there was a lull (like an eye of a hurricane) and then hit by the 'back' of the tornado...

 

[mikegeukes]

Remember, WSR-88D radars do not detect (actual) tornadoes.

 

[Mikey Gribble]

Radar is picking up on rotation above what you think of as the "tornado" usually. How low to the ground the radar can scan is determined by the tilt of the dish, the distance to the storm and the terrain in between. The radar can't see the actual tornado so they are looking for strong gate to gate shear at whatever level they can scan at. If this rotation tightens or builds down (or does other things I don't understand) then they'll issue a tornado warning, but they have no idea if a tornado is on the ground or not without spotter reports. I know very little about radar and the equations/algorithms that are used to qualify a TVS (tornado vortex signature) and I know very little about interpretting velocity data, so I'm the wrong guy to be asking on this.

BTW there isn't an accurate correlation between size and strength of tornadoes.

 

[craig buchanan]

The curve of the Earth is a big factor in determining if you will even see any vortex signatures at all. I live 40 miles from the closest radar site, so there is a chance that even relatively strong tornado's could be happening here and no radar can see it. Add to it the size you are talking about, and at my distance each pixel on the radar screen is probably going to be bigger than that...

Maybe we will get some stimulus money to put more radars in and fill in those holes... Yeah Right

 

[Scott Lincoln]

Remember, WSR-88D radars do not detect (actual) tornadoes.

In 99.9% of cases, yes, but there are a handful of cases where the WSR-88D is likely detecting the tornadic circulation itself, by both BV and SW. The Moore, OK, 1999 case and the Greensburg, KS, case come to mind.

 

[Greg Stumpf]

In 99.9% of cases, yes, but there are a handful of cases where the WSR-88D is likely detecting the tornadic circulation itself, by both BV and SW. The Moore, OK, 1999 case ... come(s) to mind.

Not exactly. From: http://wdtb.noaa.gov/modules/sls00/M3RADAR.pdf

The difficulty in relating close-range gate-to-gate WSR-88D velocity differences to the tornado is worthy of further discussion. The lack of the traditional TVS gate-to-gate relationship was present for both KTLX and KCRI. The noisy character of the TDWR data in the vicinity of the tornado prevented comparison with that radar. One of the possible reasons for the lack of a meaningful gate-to-gate signature is that, at close range, the large diameter of the tornado might produce a signature spread across several azimuths. To check this possibility and to better define the velocity field in and around the tornado, DOW data were examined. Comparison of DOW data with KTLX and KCRI data for two times (Fig. 3) indicates that the tornado diameter is smaller than the WSR-88D Delta-V signature. This is true even when taking into account the possibility that sampling of the tornado vortex along its centerline could produce a signature spread across three azimuths instead to two. Other sampling issues exist. One is that radar returns used to measure velocity are power weighted. If the large amounts of debris present with the tornado are being centrifuged to locations outside of the radius of maximum tornado wind and are traveling at slower speeds, echo from the highest-wind area may be too weak to be properly detected. Note that the DOW data, particularly at 0013, indicate that there are is a well defined signature (velocity peaks) larger than the tornado...the tornado cyclone. Thus, the WSR-88D returns may be more related to the tornado cyclone and less related to the tornado itself. If this is correct, tornado cyclone strength must be closely related to tornado strength to produce the good correlations between radar-detected TVSs and tornadoes.