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Author Topic: 3 Body Hail Spike  (Read 10508 times)

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Jeff Brislane

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3 Body Hail Spike
« on: 18 November 2006, 05:56:19 PM »
After looking over the images from Mt Stapylton radar from the supercell event on the 8th of november i'm thinking that the cell near springbrook which in my mind was the most impressive of the day shows a possible 3 body hail spike for 3 consecutive frames. These frames show a period of the cell when it was at it's most intense.
« Last Edit: 18 November 2006, 05:58:52 PM by Jeff Brislane »
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Offline Michael Bath

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Re: 3 Body Hail Spike
« Reply #1 on: 19 November 2006, 09:46:14 AM »
Hi Jeff - I have not heard that term before - can you please explain :)

MB

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Offline Geoff Thurtell

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Re: 3 Body Hail Spike
« Reply #2 on: 20 November 2006, 05:03:31 AM »
I'm with Michael on this one!
If it means that there are three intense precipitation cores, then the next storm to the north also exhibits the same characteristics.
Regards,
Geoff
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Offline David C

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Re: 3 Body Hail Spike
« Reply #3 on: 21 November 2006, 04:13:34 AM »
Good stuff Jeff. I had no idea what this was either, so resorted to google.

"The mid-level three body scatter spike (TBSS) Doppler
radar signature generally is a 10-30 km long region of arti-
fact echo aligned radially downrange from a highly reflec-
tive (>60 dBZ) echo core. Caused by non-Rayleigh radar
microwave scattering or Mie scattering (Zrnić 1987), the
TBSS (commonly called a hail spike) is widely used by op-
erational NWS forecasters as a sufficient but not neces-
sary indication of very large hail within a severe thunder-storm".



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Offline Geoff Thurtell

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Re: 3 Body Hail Spike
« Reply #4 on: 21 November 2006, 01:40:50 PM »
Thank you Jeff and David for adding to our education.  :)

It is definitely another feature to look for when observing radar.

Regards,

Geoff
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Offline Michael Bath

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Re: 3 Body Hail Spike
« Reply #5 on: 22 November 2006, 02:11:44 AM »
Sorry - but I still don't get it. Can someone please clarify or highlight on the radar image what it is?

MB

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Offline Jimmy Deguara

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Re: 3 Body Hail Spike
« Reply #6 on: 22 November 2006, 05:31:07 AM »
« Last Edit: 22 November 2006, 05:36:57 AM by Jimmy Deguara »
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Offline Dave Nelson

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Re: 3 Body Hail Spike
« Reply #7 on: 22 November 2006, 06:58:48 AM »
ok  good article   Jimmy,

   and from them one would deduce that the spike on the springbrook cell is the yellow appendage that is pointing
down towards  Murwillumbah, on the 3rd image,   I assume  :)

its the only signature I can make out that is roughly inline and on the opposite side of the cell from where'
the radar site is located

cheers
Dave N
« Last Edit: 22 November 2006, 07:05:15 AM by Dave Nelson »
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Offline David C

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Re: 3 Body Hail Spike
« Reply #8 on: 22 November 2006, 08:41:43 AM »
Quote from: Michael Bath on 22 November 2006, 02:11:44 AM
Sorry - but I still don't get it. Can someone please clarify or highlight on the radar image what it is?

MB



Hi Michael - quite evident in this NWS scan - bottom right image.


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Offline Jimmy Deguara

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Re: 3 Body Hail Spike
« Reply #9 on: 22 November 2006, 10:41:33 AM »
Hi Dave N,

You hit the nail on the head - spike away from the radar - good observation - particularly for insurance purposes:) It is something to watch - good catch Jeff.

Regards,

Jimmy Deguara
« Last Edit: 22 November 2006, 10:44:06 AM by Jimmy Deguara »
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Offline Dave Nelson

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Re: 3 Body Hail Spike
« Reply #10 on: 22 November 2006, 01:21:23 PM »
thanks Jimmy,
 
    that pdf file you put a link to was the clincher in being able to understand the process
TBSS  is a term I had not, and obviously a few others, hadnt heard of before.
Tis good to learn new things .... now only if we had a few more local storms to
practice on   hahaha ....    totally sux so far   


cheers
 Dave N
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Offline Jimmy Deguara

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Re: 3 Body Hail Spike
« Reply #11 on: 22 November 2006, 04:12:45 PM »
Hi,

I had heard of the term hail spike before but for some reason associated it with a vertical reflectivity feature. I guess the radar is a slice of a 3D range.

I'll see what Mal who is very keen on radar has to say about this.

Regards,

Jimmy Deguara
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Offline Michael Bath

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Re: 3 Body Hail Spike
« Reply #12 on: 23 November 2006, 02:53:05 AM »
Thanks for the links, I understand it now.   Though it is not very obvious on the Springbook cell images above, hence my slow take up on this.

regards, Michael


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Jeff Brislane

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Re: 3 Body Hail Spike
« Reply #13 on: 24 November 2006, 07:59:57 AM »
Sorry guys for explaining more. The spike I believe is most evident in the third image where it is the area of stronger reflectivity shaped like a point south of the main core with the tip over Murwillumba.
« Last Edit: 24 November 2006, 10:45:44 AM by Jimmy Deguara »
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Meso

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Re: 3 Body Hail Spike
« Reply #14 on: 24 November 2006, 04:30:30 PM »
G'day guys, interesting discussion.  There were some great storms around on that day.

Whilst hail flare echos (or TBSS) from an S-Band radar like Mt Stapleton would typically indicate hail >2cm, it's hard for me to see the spike in these images. Here's my reasoning...

As an example, take the bottom-right panel of the image that David posted earlier.  Note that the spike is very even and uniform along the beam propagation path. 

Now, look at some radials from the 3rd image:



There is a 'spike', but it's not consistent with the azimuth from the Mt Stapleton site.  I notice Les Lemon as a contributor to that PDF that Jimmy supplied the link for. Hold on to your hat Jimmy, but I could possibly have greater admiration for this guy than our mate Josh.   :)  In the 90's there was a lot of talk about hail spikes within the NWS/NOAA from Nexrad scans, and Les produced an interesting fact - the length of the flare is determined by the maximum slant range (shown as 'r') in the cone below:



This makes it easy to differentiate between hail flares and other artifacts (such as microwave interference) ; hail spikes will end after a certain distance, interference will not.

My 2c worth...

Mal
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