jiharris0220
Member
The 1991 Andover outbreak had a semi discrete storm mode with storms tightly spaced. Obviously though the cells had no problem producing multiple violent tornadoes.
-
Welcome to TalkWeather! We see you lurking around TalkWeather! Take the extra step and join us today to view attachments, see less ads and maybe even join the discussion. CLICK TO JOIN TALKWEATHER -
April 2024 Weather Video of the Month Post your nominations now!
Severe Weather Threat - May 6, 2024
- Thread starter KevinH
- Start date
Shakespeare 2016
Member
Are temps in the 80s more favorable for violent tornadoes than temps in the 70s?
Right. Especially in these cases where dewpoints are near and into the lower 70s and RH below the cloud base is running pretty high, causing RFDs to tend to be warmer and not able to efficiently cold pool on the rear flank or the forward flank, you can have even full-blown EF5s with relatively close storm spacing. It doesn't require cleanly spaced supercells with nothing around one for 50+ miles for a long-lived EF3-EF5 tornado to be able to happen.
Shakespeare 2016
Member
I have mostly seen dewpoints reaching the upper 60s throughout the area for the most high risk. How does upper 60s dewpoints any different than low 70s dewpoints. Like for instance 77.0°F/72.0°F VS 74.0°F/69.0°F.
jiharris0220
Member
Joplin and the 2011 El Reno tornado are both examples of ef-5 tornadoes occurring while being fully embedded in the forward flank of other cells.
As we've previously discussed, it's not just about the surface temperature or dewpoint at face value. Instability is about how temperature and dewpoint change vertically with height. That's not an opinion on the matter. That's how basic thermodynamics work as fact with no room for debate or negotiation or disagreement. VERY generically speaking, the warmer the surface temperature, the more room there is for moisture content in the low-levels, and the better chance you have of having higher instability. However, the warmer you get, the higher your dewpoints have to be as well or you will start having higher LCLs and higher cloud bases, which are more favorable for colder RFDs, which lowers the strong/violent tornado threat. Once you start getting temperatures into the lower 80s or higher, you really need those dewpoints to be 65+ (and really, 67+ is better) in order to not have LCLs that are high enough to lower the strong/violent tornado threat. Once you start getting on up into the mid 80s and higher, dewpoints into the 70s start becoming more of a flat out necessity.
Deeply, desperately, from the pit of my soul, I need you to finally understand the concept we've already repeatedly discussed that surface temperature and dewpoint alone are not instability. It's how those two parameters change with height that makes up the instability profile. That's not debatable. It's scientific fact.
I'll simply put it this way. As long as the mid/upper levels are sufficiently cold and dry enough, a supercell would rather have a surface ob of 68/67 than 86/64 if it wants to have a higher chance of producing an intense tornado.
And to add to that, you can take that 68/67 surface ob and put it under 500mb temperatures that are -16 deg C and colder, and you can have the potential to end up with 2000+ SBCAPE given other favorable things in the vertical profile. You can also take that 86/64 and put it under mid-level temperatures that are noticeably warmer, and end up with very little CAPE. It's the vertical distribution of these ingredients that controls instability.
I'm not trying to be rude. You're a stand-up dude! I'm always happy to help out and explain things as I am able. I wouldn't be so aggressive here if it wasn't for the last time we had this same conversation back on the Omaha day (but it was violent tornadoes being possible with temps in the 60s then), when you asked me similar questions, instead of trying to understand my answers explaining things, you were too busy trying to argue about it, all the while being proven wrong in real-time.
Shakespeare 2016
Member
I must just second guess myself as I tended to have gotten obsessed with temperatures and dewpoints needed for violent tornadoes considering everything else is in place. Joplin is a very good example as the temperature that day reached 84.0°F and the dewpoint reached 72.0°F. However as the tornado was occurring the temperature was like 68.0°F/69.0°F and the dewpoint was like 65.0°F/66.0°F. Maybe it just boggles my mind on how it works the way it does.
The HRRR certainly has its faults, and sometimes it falls completely on its face altogether. However, it is firmly locked on this high-end violent solution now run after run after run after run after run after run. In 13 years of dealing with the HRRR now, back to the days when it was still experimental, it has usually only done that when it has sniffed out the real deal for whatever it is trying to show.
- Thread starter
- #312
KevinH
Member
- Thread starter
- #313
KevinH
Member
Given the high POTENTIAL of today’s event, what are everyone’s thoughts on the Outbreak Intensity Scale by Thomas P. Grazulis? I don’t think I have seen the OIS mentioned before in this forum.
From Wikipedia:
For the OIS, only significant tornadoes, those rated F2 to F5 on the Fujita scale and those rated EF2 to EF5 on the Enhanced Fujita scale are used for the score of the outbreak. F2/EF2 tornadoes are given 2 points, F3/EF3 tornadoes are given 5 points, F4/EF4 tornadoes are given 10 points, and F5/EF5 tornadoes are given 15 points.
From Wikipedia:
For the OIS, only significant tornadoes, those rated F2 to F5 on the Fujita scale and those rated EF2 to EF5 on the Enhanced Fujita scale are used for the score of the outbreak. F2/EF2 tornadoes are given 2 points, F3/EF3 tornadoes are given 5 points, F4/EF4 tornadoes are given 10 points, and F5/EF5 tornadoes are given 15 points.
| Type of outbreak | Weak | Minor | Significant | Major | Devastating | Historic | Super |
|---|---|---|---|---|---|---|---|
| Number of points | 2–6 | 7–10 | 11–29 | 30–79 | 80–119 | 120-249 | 250+ |
warneagle
Member
Do you know how to read a skew-T diagram? That might help you visualize how instability/CAPE works in relation to surface temperature.
SmokeEater
Member
Tornado driven high risk coming next outlook, will include most of OK, including OKC.
Where are you seeing this?
Norman WFO posted it in NWSChat a little bit ago that SPC is drawing it up for the forthcoming outlook.
Keldeo
Member
. Jon Slater a KFOR met saying SPC going High risk
Be safe everybody, I should be getting off work to watch some of this later. Hopefully some of the threat fizzles out.
cincywx
Member
Past 12 hours have shown a pretty consistent signal for a dangerous afternoon and evening. At this point, I've run out of words to describe the forecasted environment and I just hope that it underperforms significantly.
