XM/Wx-Worx "Tops" feature to predict initiation?

Dec 11, 2003
Denton, Texas
I've heard from several people that Jeff Piotrowski gave a short talk in Denver on using the Wx-Worx tops feature to help locate cb that were advanced enough to look like developing storms, but which had not yet generated enough (or any) precip that returned signal on reflectivity.

I was wondering if anybody could post a few words about what he said or your own personal experiences with this as another means to use XM in the field. Thanks!


PS: Wasn't sure if this belonged in Weather & Chasing or Gear, so put it where I thought more might see it.

Last year in nebrasks on 5-24 we used the Tops feature to help us catch the Thayer county supecell.

The sky was somewhat overcast and very hazy so you couldnt see towers going up more than 10 miles away. we showed towers going up 25 miles SW of us using the tops feature when radar showed nothing. we knew anything going up would explode quickly so we jumped on it. We arrived right as it dropped the first tornado of the day. Most chasers missed the first 2 or 3 tornadoes from this cell since it went up so fast and they reacted to it after it was on radar or warned on. it went from just being a spec on tops to a tornado in about 30 minutes.

if we hadnt used the Tops feature we would have missed a big part of the show even being that close. Until they add hi-res satelite I will continue to use the tops feature. Also it should be noted tht since radar updates only every 6 minutes the tops may how something exploding faster than the radar will. especially in explosive environments like may 24th. Also it should help alot with LP storms since they dont always produce correct reflectivity but if its 50,000 ft high it will show up like a beacon on tops.

just one example of how we used it last year. hopes this helps.
Yes, I have used the tops feature many times before too. The tops feature has been extremely helpful on a few chases. I would say the majority of the time, new convection will almost always show up on tops before actual reflectivity. XM/Wx Worx is very expensive, it was invaluble last year and im sure will be this year as well however.
I used it quite a bit last year to anticipate initiation. You could typiically see towers going up on Tops about 30 minutes before it would show up on radar. I found it to be very reliable in finding areas of convergence. On some of the days you could see towers go up and get knocked over repeatedly before one managed to break through the cap. I personally think it is the most valuable product on the XM system.
I think I sent you a PM about this after you posted about having gotten XM.
Ok, I am unfamiliar with the product suite from wxworks, but is the "tops" product the same as the NIDS storm top product? If so, then composite reflectivity or VIL would be as valuable or more so. The base scan reflectivtivity will not show precip until well after the tower reaches the tropopause on most high CAPE days - but there is precipitation in the cloud higher up - which the higher elevation scans will see. In fact, the echo tops product (if this is the same thing you are talking about) is created by identifying the highest height of I believe the 35 dBZ echo. Since composite reflectivity and VIL are both vertically composited - they can show echoes well before the base scan picks up on them.

Here is a good reference:


My guess is that possibly composite reflectivity is not available in WxWorx? Clearly using CR would be a quicker method of determining precip aloft that echo tops.