Highest recorded echo tops?

[JP Santiago]

I was watching the recent midwest storms over the last several days and noticed that the other night there were a few 55K echo top storms in western Kentucky. That got me thinking if there's any record of the highest echo tops observed? A friend told me that he'd seen some over 60K and another who is a cargo airline pilot recounted to me a storm over Texas last year where he was flying at FL310 and there was a good 50% more of the storm above his flight level as he deviated around the weather.

A cursory search of the Internet didn't find anything right off, but one weather site stated that the max height that can be reported is 70K.

 

[Kevin Scharfenberg]

Back in the days of the WSR-57 and WSR-74C there were often reports of echo tops above 70 kft with supercell storms on the plains (I remember many such reports from OKC, SEP, GCK, and LIC). I think most of those were radar artifiacts from sidelobe scatterering and/or partial beam filling in the vertical plane. The highest-altitude reflectivities I have seen with the WSR-88D that appear to be in the main lobe (30 dBZ or so) can be up to 55-60 kft in supercells. I'd imagine a good thunderstorm in the tropics where the EL tends to be higher could be a bit taller.

 

[Joe Zemek]

I remember a 70K indicated top on a storm near Amarillo in July about 3-4 years ago. For the record I was looking at Intellicast's Radar Summary (not sure how to judge their data quality). It would seem within reason given the latitude and tropopause height, summer CAPE values and the energy required to break the summer cap in that area.

 

[rdale]

Remember too that the ET product from NIDS is the highest 18dbZ echo, not the highest echo completely.

GRL2AE lets you modify that parameter to lower numbers (to get the true tops) or higher (if you want to quickly find the max 50dbZ height for example.)

 

[Tim Vasquez]

I used to think this was an interesting subject, but as Kevin pointed out, radar artifacts (and now radar design) is a big problem that corrupts the pool of trivia about echo tops.

The tallest storms I have seen have been in the deep tropics, where a high tropopause predominates. In the Philippines, 40 to 55K ft was a normal height for thunderstorms, which were rarely severe. That's where I observed the tallest height ever: 72,000 ft at Clark AB in March 1982 as measured by a FPS-77 (similar to WSR-74C). Since this was in low instability with little hail, sidelobe/3-body scattering was likely not a factor. Also the storm was close and the RHI elevation was high, so beam width error was minimized. So this was the highest credible height I can think of.

I saw a 72,000 ft RAREP reported in Charleston SC on a storm in August or September 1986. I give this measurement good credibility due to the nonsevere, summer environment and it being back in the days when radar operators actually had a RHI scope.

The 18 dBz algorithm that NEXRAD uses (that rdale points out) and the fact that NEXRAD does not do any elevation slices, relying on the preprogrammed scan strategies, IMHO, pretty much corrupts echo top trivia for the future. The ET products are a potshot. I'm more inclined to figure the stuff out on a SKEW-T, since "CINH density" is extremely high once you go above the tropopause, narrowing it to small ranges, so you can probably peg the overshoot heights pretty well.

Tim

 

[JP Santiago]

The 18 dBz algorithm that NEXRAD uses (that rdale points out) and the fact that NEXRAD does not do any elevation slices, relying on the preprogrammed scan strategies, IMHO, pretty much corrupts echo top trivia for the future. The ET products are a potshot. I'm more inclined to figure the stuff out on a SKEW-T, since "CINH density" is extremely high once you go above the tropopause, narrowing it to small ranges, so you can probably peg the overshoot heights pretty well.
[/b]

Thanks all for the information. From talking to friends who are pilots, I've heard that there's some discussion that the algorithm used by the radars needs to be modified to get a more accurate echo tops product as it has (obviously) significant implications for aviation- given that there's work to make more efficient use of airspace, particularly during the summer thunderstorm season when weather deviations are common, knowing the echo tops of a given storm more accurately might make some diversions unnecessary.

Would an improved echo tops product have implications for forecasting beyond what the aviation community's needs?

 

[rdale]

NWS/govt agencies already have access to a hi-resolution Echo Top product but it's not part of the NIDS feed. So FAA mets can utilize the same sort of display. I'm not sure I understand though why they need to know how high the 5 dbZ goes, it can't be terribly different from the 18dbZ region.

But go back to what Tim said - the radar only does slices, not true up&down scans. So you will NEVER know the true height of the storm, since you can't tell how much echo is in between the tilts (and that can be notable especially in some of the faster-scan VCP's.)