weatherwiz Posted February 28, 2016 Author Share Posted February 28, 2016 Where do you look at nROT? Link to comment Share on other sites More sharing options...
OceanStWx Posted February 28, 2016 Share Posted February 28, 2016 I went back and looked at OKX the night of the storms and nROT was sky high on that line in CT thanks to the shear induced signal you described. Thankfully cooler heads prevailed on Long Island and they didn't issue a bogus warning. That's why it's not a fail safe product. You still have to know what you're looking at, and you'll pretty much know it when you see it if you have enough radar experience. Those shear signatures just look different than a rotation one, and they are pretty easy to confirm with velocity. So really my tornado display on GR is a four panel with reflectivity, SRM, CC, and NROT. Link to comment Share on other sites More sharing options...
OceanStWx Posted February 28, 2016 Share Posted February 28, 2016 Where do you look at nROT? It's a Gibson Ridge thing. Not available anywhere else, since he developed it. Link to comment Share on other sites More sharing options...
weatherwiz Posted February 28, 2016 Author Share Posted February 28, 2016 It's a Gibson Ridge thing. Not available anywhere else, since he developed it. It is on GR lvl 2 analyst? Link to comment Share on other sites More sharing options...
CoastalWx Posted February 28, 2016 Share Posted February 28, 2016 Cool. Thanks for the explanation. I guess Ryan answered my question. I was wondering if it would help reduce false alarms, but you need to know what you are looking at by comparing other products too. Link to comment Share on other sites More sharing options...
OceanStWx Posted February 28, 2016 Share Posted February 28, 2016 It is on GR lvl 2 analyst? Yes. Link to comment Share on other sites More sharing options...
OceanStWx Posted February 28, 2016 Share Posted February 28, 2016 Cool. Thanks for the explanation. I guess Ryan answered my question. I was wondering if it would help reduce false alarms, but you need to know what you are looking at by comparing other products too. Yeah, we don't have a magic way to avoid the high FAR of TORs yet. As an example of NROT, here's Springfield presented with minor commentary. NROT over 1.5, and over 100 knots on that couplet just after it emerged from the BOX purple haze. DOPPLER RADAR INDICATED WEAK ROTATION WITHIN THIS STORM. WHILE NOT IMMEDIATELY LIKELY...A TORNADO MAY DEVELOP. REMAIN CALM...BUT TAKE COVER NOW. GO TO AN INTERIOR ROOM ON THE LOWEST FLOOR OF A STURDY BUILDING. AVOID WINDOWS. Link to comment Share on other sites More sharing options...
OceanStWx Posted February 28, 2016 Share Posted February 28, 2016 What a storm. When the debris ball spiked at Monson, the NROT was 2.27. Huge for this area. I had totally forgotten how the debris ball had a TBSS attached to it as if it was hail too. Link to comment Share on other sites More sharing options...
weatherwiz Posted February 28, 2016 Author Share Posted February 28, 2016 Yes. Oh crap I have that. I'll have to find some literature and read up more on it Link to comment Share on other sites More sharing options...
OceanStWx Posted February 28, 2016 Share Posted February 28, 2016 What's interesting in the Springfield case is the original TOR near Belchertown had an 0.5 NROT of under 0.70 (it was over 1 at 0.9 degrees but 0.5 degrees is already 6000 feet AGL out there). Springfield was immediately well over 1.00 NROT once the velocity image was not affected by purple haze. Link to comment Share on other sites More sharing options...
weatherwiz Posted February 28, 2016 Author Share Posted February 28, 2016 How do you tell how far AGL the tilt is? Link to comment Share on other sites More sharing options...
OceanStWx Posted February 28, 2016 Share Posted February 28, 2016 How do you tell how far AGL the tilt is? Actually I misspoke, AWIPS does AGL, but I believe GR is above radar level. If you hover the cursor over the spot in question you'll see a height readout on the bottom of the application. Link to comment Share on other sites More sharing options...
OceanStWx Posted February 28, 2016 Share Posted February 28, 2016 Checking back on the ENX radar, and NROT hit 0.80 as soon as the couplet formed (around 4:02 PM) and provided about 15 minutes lead time on the tornado touchdown. Of course it was also over 1 on the Belchertown TOR, so sometimes you have to take the good with the bad. I would rather have the TOR out on an NROT of 1 than not, so you just accept that some warnings will false alarm. Link to comment Share on other sites More sharing options...
weatherwiz Posted February 28, 2016 Author Share Posted February 28, 2016 Actually I misspoke, AWIPS does AGL, but I believe GR is above radar level. If you hover the cursor over the spot in question you'll see a height readout on the bottom of the application. Oh sweet thanks. I think I know what you're talking about. I just never knew what that number meant Link to comment Share on other sites More sharing options...
CT Rain Posted February 28, 2016 Share Posted February 28, 2016 That's why it's not a fail safe product. You still have to know what you're looking at, and you'll pretty much know it when you see it if you have enough radar experience. Those shear signatures just look different than a rotation one, and they are pretty easy to confirm with velocity. So really my tornado display on GR is a four panel with reflectivity, SRM, CC, and NROT. Yup. The only other issue I could see with people relying too heavily on nROT is that really small (spatially) mesocyclones with a tiny but strong couplet frequently look pretty meh on nROT. Especially for a QLCS or a mini supercell when you may only have a few inbound/outbound pixels in the couplet it can be not so hot. I find myself using regular BV more than SRM a lot in severe situations and using nROT as the 4th panel as a check to make sure I'm not missing anything. Link to comment Share on other sites More sharing options...
CT Rain Posted February 28, 2016 Share Posted February 28, 2016 Checking back on the ENX radar, and NROT hit 0.80 as soon as the couplet formed (around 4:02 PM) and provided about 15 minutes lead time on the tornado touchdown. Of course it was also over 1 on the Belchertown TOR, so sometimes you have to take the good with the bad. I would rather have the TOR out on an NROT of 1 than not, so you just accept that some warnings will false alarm. It's not like the setup was ripe for tornadoes or anything Link to comment Share on other sites More sharing options...
OceanStWx Posted February 28, 2016 Share Posted February 28, 2016 Yup. The only other issue I could see with people relying too heavily on nROT is that really small (spatially) mesocyclones with a tiny but strong couplet frequently look pretty meh on nROT. Especially for a QLCS or a mini supercell when you may only have a few inbound/outbound pixels in the couplet it can be not so hot. I find myself using regular BV more than SRM a lot in severe situations and using nROT as the 4th panel as a check to make sure I'm not missing anything. It's easier when you have 3 screen of AWIPS to work with. Link to comment Share on other sites More sharing options...
CT Rain Posted February 28, 2016 Share Posted February 28, 2016 It's easier when you have 3 screen of AWIPS to work with. lol that does help - I'm at 2 and a laptop at work at least! Link to comment Share on other sites More sharing options...
OceanStWx Posted February 28, 2016 Share Posted February 28, 2016 lol that does help - I'm at 2 and a laptop at work at least! Severe wx ops is pretty much two AWIPS terminals devoted to radar, one to things like satellite and mesoanalysis. Then the PC is one screen with GR2Analyst and the other on webpage like SPC, etc. Link to comment Share on other sites More sharing options...
CoastalWx Posted February 28, 2016 Share Posted February 28, 2016 I gotta get GR. Link to comment Share on other sites More sharing options...
OceanStWx Posted February 28, 2016 Share Posted February 28, 2016 I gotta get GR. Pretty much worth every penny I've ever spent on it. Apps like RadarScope are awesome, but sometimes 4 elevation angles just isn't enough. Link to comment Share on other sites More sharing options...
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