Tornado forecasting classes at ChaserCon 2012

As was announced on the ChaserCon 2012 website last month, I'll be teaching 2 tornado forecasting classes on Friday evening , Feb. 17 at ChaserCon in Denver.

The first class deals with Basics (surface maps, upper air maps, and computer model forecasts, from 7:00 pm to 8:45 pm), and the 2nd class is Advanced material (including skew Ts and hodographs, from 9:00 pm to 10:45 pm). Enrollment in advance is required (you also need to be registered for ChaserCon to attend), and each class is $15.00 individually, or $25.00 for both (CASH only at the door, NO CHECKS!).

We're getting close time-wise, and class enrollments are filling up, so send an e-mail to Roger Hill at rogerehill@earthlink.net or to me directly at davieswx@gmail.com to enroll. Please specify which class you will be attending (Basics, Advanced, or both)

Tim Vasquez from Norman OK has taught the forecasting classes in the past. Even though he's not teaching this year, he will have a vendor table at ChaserCon to sell his forecasting books and materials, which are excellent storm chasing resources. Tim also continues to do chase forecasting classes in Norman, another great way to learn about severe weather forecasting! So if you are going to ChaserCon, stop by his vendor table and check out his stuff! Or, check out his web site at www.weathergraphics.com

See you at ChaserCon!

Jon Davies - 2/2/12

First tornado deaths of 2012 in Birmingham AL area on 1/23/12

A large deadly tornado (at least EF3 intensity) struck the Birmingham AL area early this morning around 4 a.m. CST (1000 UTC, Monday 1/23/12), killing at least 2 people according to media information at early afternoon.

The weather environment was primed for generating significant tornadoes before sunrise on Monday in Alabama. A RUC analysis sounding at 1000 UTC (see above) at Birmingham while the tornado was moving through showed a massively large wind profile (hodograph) with nearly semi-circular curvature, ideal for generating low-level rotation in storms when notable instability is also present. In this case, there was around 700 m2/s2 of storm-relative helicity, with mixed-layer CAPE between 1000 and 1500 J/kg, putting the storm environment in a statistically dangerous area on an SRH-CAPE diagram (see red dot on scatterdiagram above) regarding support for strong or violent tornadoes. Compared to last Saturday's environment with severe storms in central Georgia (1/21/12, not shown) where representative SRH values were around 300 m2/s2 and CAPE was only 300-400 J/kg, this was a much more dangerous and life-threatening setting.

The overnight SPC mesoanalysis also suggested potential for significant tornadoes (see the 0900 UTC SPC graphics above), with large SRH-CAPE combinations indicated in the same area where storms were moving through. A strong negatively-tilted trough at 500 mb (roughly 18,000 ft MSL, see last chart above) prompted the deadly severe weather, pulling deep moisture into Alabama from the Gulf of Mexico, generating strong low and mid-level wind fields, and providing strong lift and forcing.

Given that it was still dark when the Birmingham area tornado moved through, the death toll could have been much larger. It surely helped that the storm potential was well-outlooked by SPC already on Sunday, and NWS warnings in the area were timely.

Jon Davies - 1/23/12

11 Jan 2012 "surprise" tornadoes in North Carolina

Yesterday's EF2 tornadoes in Rutherford and Burke counties of western North Carolina (see photos above) injured 10-15 people (one critically) and came as a bit of a surprise. This case is a good example of how difficult it is to forecast winter-time tornadoes. Instability (CAPE) is often small (around 500 J/kg or less), but wind shear and low-level storm-relative helicity (SRH) are often large (> 200-300 m2/s2); that makes it hard to assess when CAPE and SRH combinations are truly strong enough to support significant tornadoes. It's just as important to assess the strength and focus of the accompanying synoptic setting and how the CAPE/shear environment fits with that.

Wednesday's system (1/11/12) had been a mid-level cut-off low over Texas the previous day (1/10/12, see NAM 500 mb vorticity charts above), and was being pushed rapidly into the Carolinas by a larger wave at 500 mb digging into the Central Plains. Note that although Wednesday's upper system over the Southeast was no longer a closed low, it was now a tight and dynamic short wave with a strong vorticity max moving into the western Carolinas (red area and "X", see arrows), focusing upward forcing. This strong upper wave and vorticity max had also caught up to the associated surface front (blue curved line), addiing to the strong dynamic focus in the western Carolinas area. (The previous day, the same upper vorticity max located in Texas had lagged the surface front in Mississippi by some distance.)

The fixed-layer Sig Tor Parameter at 2100z (STP at 4 pm EST, see SPC mesoanalysis chart above) suggested a marginally favorable environment (> 1.0) for tornadoes over NW South Carolina inching into SW North Carolina, just ahead of the strong upper vorticity center seen earlier and the surface front, near the "triple point" where fronts met (see surface inset). These dynamic factors and environment provided enough focus for the south end cell of a broken arc of low-topped storms (see visible satellite image above) to become a damaging tornadic supercell as it moved into North Carolina.

A similar setting the day before over Mississippi, but with somewhat less focus and slightly less favorable STP values (not shown), did not generate any tornadoes, illustrating how subtle and difficult winter tornado settings with small CAPE can be to assess, in contrast to days like the Joplin tornado where CAPE exceeded 4000 J/kg. Again, an awareness of how synoptic features come together or focus into a particular area (e.g., strong short wave and vorticity max, frontal orientation relative to those features, along with prefrontal environment) is important. Typically, STP or EHI values slightly larger than 1.0 aren't impressive, but the surface and upper-air dynamic focus in this case suggested more attention.

A 2200 UTC RUC-estimated sounding at Shelby NC, about 20 minutes before the first tornado, is shown in the last graphic above. Notice that the CAPE was small (< 500 J/kg), but the SRH moderate to strong (260 m2/s2). With all the CAPE "compressed" below 400 mb (approximately 24,000 ft MSL), rapid supercell updraft accelerations may have been enhanced in low-levels, even though total CAPE was relatively small, helping with tilting and stretching of streamwise vorticity associated with SRH in the environment.

Jon Davies - 1/12/12

The 2011 tornado death toll - 2nd worst in U.S. history!

Here we are on the last day of 2011, and the U.S. tornado death toll for the year is at least 552, tied with 1936 as the 2nd deadliest U.S. tornado year! (The number of deaths may be even higher depending on how one categorizes them; the city of Joplin lists 161 tornado deaths for the May 22nd tornado instead of the National Weather Service "official" number of 158 deaths, probably due to how NWS categorizes some deaths as "direct" vs "indirect".)

I don't think most people who hear this in passing on TV comprehend how huge this is. In this day and age, that number is incredibly sobering! (See how dramatically 2011 stands out in the chart above among the last 50 years of U.S. tornado deaths.) Many of my colleagues, myself included, thought we would never see such huge death tolls again with the warning systems that are now in place in our country.

Given the violent tornadoes in 2011, without our warning systems, the death toll in 2011 would certainly have been worse. But I also think things could be better. The NWS assessment from Joplin earlier this year concluded there is considerable "desensitization" to warnings in our population from perceived overuse of sirens and warnings.

There obviously aren't easy answers. Some quick random thoughts with the new year upon us:

- Continued and ongoing public education is clearly needed about the importance of severe weather awareness and safety.

- Though not talked about much, siren policies across the country could be more standardized and less confusing... there are big inconsistencies regarding how sirens in different areas are used and activated. For example, some cities such as Joplin run them in shorter 3-minute bursts and then stop (as on the Joplin tornado day) which can be confusing to people in the most dangerous situations (when the sirens stop, is the danger past?), while other cities run them longer. And in many metro areas, sirens tend to be an all or none proposition until technology is installed to activate them only for localized areas directly threatened by an approaching tornado. Siren policies and equipment (as well as the NWS interface with those who activate them) appear to need closer examination and standardization between local governments so we don't inadvertantly train our citizens to ignore them due to a perceived "cry wolf" factor.

- If the NWS endorses use of "tornado emergency" statements to alert populated areas of imminent danger to life, then they can be more consistent in using them. If there was ever a situation that cried out for a tornado emergency statement conveying increased urgency, it was Joplin last May 22nd where 161 people died. But none was issued. By around 5:38 pm when the tornado was entering Joplin (about 20 minutes after a standard-worded "radar-indicated" tornado warning and 3 minute siren burst), there was enough information from radar and spotters to quickly issue a strongly-worded tornado emergency statement for local Joplin media, adding urgency and emphasis in a dangerous life-threatening situation. This would have been timely enough to possibly save some additional lives in spite of the hard-to-see and rapidly-developed violent tornado. The tornado warning was reissued at 5:48 pm with much stronger wording, but why wasn't an urgent tornado emergency statement issued 8 to 10 minutes earlier?

I hope some lessons from last year's tornado disasters (unprecedented for our modern technological age) result in growth and learning for all of us, as well as better tools and preparedness in 2012.

Jon Davies - 12/31/11

Don Harman

Some extremely sad news today... Long-time Kansas City meteorologist and weathercaster Don Harman died yesterday. He worked at WDAF-TV since 1999, and was very popular on their morning show.

Don had an awesome sense of humor, both on-air and off. He was always enthusiastic about weather, very knowledgeable, and a great communicator. My wife Shawna and I always enjoyed watching him on TV, as well as seeing him at AMS meetings, and have fond memories of the time a few years ago when he interviewed us about our kids book on storm chasing. He was a friend, and we are quite taken aback today at his passing.

With all the posts and discussion Shawna has been monitoring today on Facebook, it is clear that Don was an important part of KC area mornings for many many people, and will be missed beyond words. No one can replace him.

Our hearts and thoughts go out to Don's family and little girl, as well as the staff at WDAF. I can't imagine what they are feeling right now. This is a huge loss...

- Jon Davies 11-30-11

Some further comments about SRH & CAPE in tornado nowcasting

I've gotten some private responses and discussion about my post last week regarding the Joplin tornado and the use of SRH (storm-relative helicity) and CAPE combinations to assess "more dangerous' tornado enivronments.

Here's excerpts from one response by John Farley, an experienced storm chaser in the western IL/eastern MO area:
"...one problem with what [Jon] is suggesting regarding enhanced warning wording in situations with unusually favorable environments for strong tornadoes might have the unintended effect of contributing to the false alarm problem. I am referring... ...to situations with unusually favorable parameters and tornadic radar signatures, but no "ground truth" confirmation of actual tornadoes at the time the warning is issued... ...On the same day [as Joplin]... ...I was chasing east of Hermann, MO, (west of STL) where the SRH was 300 and the CAPE was 3000. I observed three supercells between around 4 and 7 p.m. that day, two of which were TOR-warned... ...The storm in that area on Jon's 5 p.m. image is the second of the three I observed... I observed strong rotation in this storm, but neither it nor any of the three supercells I observed ever produced a tornado..."

John makes an excellent point. It is a gross-oversimplification to use only the 2 parameters I've discussed so far (SRH and CAPE) for assessing supercell tornado environments. There are most certainly other important ingredients and issues to look at. The situation John has outlined also is a reminder that the decision to use enhanced wording or a "stronger warning" is not simple.

Let's look again at May 22nd, this time at the area where the storms John observed occurred. The 1st graphic above (from my previous post, but with arrows indicating the storm area west of St. Louis) confirms that CAPE and SRH were also large over eastern Missouri at late afternoon on the Joplin day, and would fall well above the red curve on my scatterdiagram (not shown). The 2nd graphic above (also repeated from my previous post) also shows the CAPE and SRH axes on May 22nd from a wider view, as well as EHI (energy-helicity index, combining the two parameters into a single dimensionless number), with the eastern MO storm area indicated by small black arrows. All this information suggests that potentially deadly supercell tornadoes were also possible in eastern Missouri, with large CAPE/SRH/EHI indicated here. But as John noted, tornadoes did not occur, even though storms were rotating.

A closer look at both graphics also shows that the storm area west of St. Louis, unlike the Joplin storm, was on the eastern side of the instability axis moving _away_ from the largest helicity and largest CAPE, and moving _toward_ an area of increasing MLCIN (light blue; SBCIN was even larger near St. Louis, not shown), suggesting some increasing low-level stability as storms moved toward the Mississippi River. Strong tornadoes can certainly occur on the east side of an instability axis, but are almost always near a warm front or within an area of warm advection in low-levels (increasing warmth and moisture) where SRH grows _larger_ as one moves east or northeast into or across the warm advection area. Notice that this was _not_ the case on March 22 in eastern MO, where SRH was trending downward some in value toward the St. Louis area.

To look further at warm advection, the 3rd graphic above is again the Joplin day at 5 pm CDT (22 UTC), while the 4th graphic is 2 days later on 5/24/11 at 5 pm CDT for comparison; both EHI and temperature advection at 850 mb from the SPC mesoanalysis are shown in these 2 graphics, along with surface and radar features. Notice on both graphics, strong warm advection (indicated in pinks and reds) was co-located with the instability/EHI axes where violent tornadoes occurred in southwest MO (the 22nd) and central OK (the 24th), respectively. Also notice that on 5/22/11, the warm advection area was well removed to the southwest from the St. Louis area. In my database work, I've found that the stronger tornadoes are usually associated within or immediately to the south of strong warm advection areas, where lifting and SRH tend to be larger because of the associated atmospheric processes, along with increasing CAPE.

Certainly, the positioning of the storm John was following, on the eastern side of the instability axis and away from the strong warm advection, would not preclude tornadoes from occurring, and a responsible meteorologist should clearly warn on a storm in that environment (as was done) _if_ significant rotation was indicated by radar and/or spotters. But the surface pattern on the 22nd, showing a surface low back in southeast Kansas with increasing SRH and convergence along with enhanced warm advection and energy focus in southwest MO, might suggest that the better potential for strong tornadoes would be there. Adding to this the maximized combinations of SRH and CAPE, southwest MO would be a "red flag" area for possible stronger wording in tornado warnings at late afternoon, while this would appear less true for eastern MO, given the location relative to the instability axis, warm advection, and surface/low-level pattern focus farther southwest.

Again, to be clear in my recent posts, I'm not suggesting that we are able to forecast tornado intensity. And I'm not suggesting that enhanced wording in warnings be used every time SRH and CAPE appear to be in the "more dangerous" part of the scatterdiagram. But I am suggesting that we can detect and see at least some settings where stronger tornadoes are _more likely_. That involves knowledge of surface patterns where winds are backing and the atmosphere is focusing, where warm advection is occurring, thus increasing SRH and CAPE, along with other ingredients. That's a lot different than just looking at points on a diagram; it involves some understanding of important processes in severe weather production and a sense of atmospheric trends and evolution over an area being monitored. On the Joplin day, getting away from the SRH/CAPE points on a scatterdiagram, the atmosphere's _focus_ at late afternoon using surface and other basic weather products appeared rather impressive over southwest MO; look at the strong warm advection east of the surface low in the 3rd graphic above, and the "bulging" EHI pattern back to the northwest east of the surface low. The increasing SRH and CAPE values in this area just "sealed the deal", environment-wise.

Chuck Doswell has written extensively about the danger of using "magic" numbers and indices in weather forecasting. Isolated numbers, indices, and points on diagrams have _no place_ in forecasting without basic knowledge and thoughtful consideration of other issues, such as the surface pattern focus and evolution, along with other ingredients. I apologize if I gave any impression otherwise, when I was oversimplfying using the SRH and CAPE diagram to make a point in limited space. I'll write more about this in future posts.

Thanks, John, for sharing the situation above along with your thoughts and discussion.

- Jon Davies 10-1-11

An additional look at the Joplin tornado, after the assessment report

The NWS assessment report for the Joplin tornado came out last week (see here and here), 4 months after this horribly tragic event. I was glad to see that the authors of the report picked up on the public perception of high false alarms, and their tendency to ignore warnings and sirens because of an optimistic bias and the perception that "they happen all the time" in southwest Missouri. I was also glad to see some discussion in the report about the possibility of different tiers of warnings, and even different siren tones or patterns to get people's attention in situations that are truly more deadly. These are some things I touched on (particularly a two-tiered warning system) in a discussion I posted at the very tail end of July.

Given the broad environment area of sizable low-level shear and large CAPE present at late afternoon over southwest Missouri on May 22, when significant storm rotation was detected on radar in that environment, particularly moving toward a populated area like Joplin, that would have been a good situation for the use of enhanced wording or even a "higher tier" of warning. And, even though the tornado developed very fast on the southwest edge of Joplin 17 minutes after a tornado warning with standard wording had been issued, it seems possible that if more urgent action had been performed rapidly around 5:40 pm when the first tornado reports were coming in (e.g., a "tornado emergency" statement or reissuing of the tornado warning with more urgent wording prompting continuous sounding of sirens at that point), some additional lives might have been saved.

With the Joplin report now out, this is a good time and context to go back and look at the Joplin setting using SPC mesoanalysis graphics, which are generally good estimates of parameter patterns and ingredients useful in various types of weather forecasting. The first graphic above shows MLCAPE (mean-layer CAPE) and 0-1 km SRH (storm-relative helicity) graphics at 20 UTC (3 pm CDT) on 5/22/11 after the first storm had developed in southeast Kansas near Parsons (black arrow). Notice that while MLCAPE was quite large (> 4000 J/kg), 0-1 km SRH appeared rather unimpressive at this point (around 100 m2/s2). The 2nd graphic above shows the same paramaters, but 2 hours later at 22 UTC (5 pm CDT) about 30 minutes before the Joplin tornado. Notice that MLCAPE was still very large, but 0-1 km SRH had _increased dramatically_ ahead of the supercell complex approaching Joplin (black arrow), more than _doubling in value_ to greater than 250 m2/s2!

Looking at a SRH/CAPE scatterdiagram (3rd graphic above), notice how this low-level shear increase moved the SRH/CAPE data point from below the red curve upward to _well above_ it. This trend was very important, probably helped by a surface low forming over southeast KS (4th graphic). This should have been noted by any mesoscale analyst working as support to radar/warning meteorologists in the southwest MO/northwest AR/northeast OK area that afternoon. Even though no tornadoes had occurred yet in the s.e. KS/s.w. MO area, such an increase would be a red flag for considering the use of enhanced wording in warnings (or a higher tier of warning, if such a system were implemented) based on any significant rotations detected on radar in such an environment, particularly if a very populated area (such as Joplin) were threatened.

Let's contrast the Joplin setting with a situation that occurred at midday in Kansas City on 5/25/11, 3 days later. The last graphic above shows CAPE (11 pm CDT) and SRH (noon CDT), similar to the earlier graphics, though SBCAPE (surface-based CAPE) is used due to the "cold-core" nature (500 mb closed low nearby) of the setting where SB lifted parcels are typically more representative of true instability. Note that SRH was quite meager (around 50 m2/s2), and CAPE was less than 1500 J/kg in the immediate Kansas City area (left black arrows in last graphic above), with the resulting position on the same SRH/CAPE diagram above far to the lower left _well below_ the red curve. Although it is quite possible to get small short-lived tornadoes in such settings, strong "cold core" tornadoes are almost always linked to settings with much larger SRH. Indeed, there were 2 or 3 reports of brief weak tornadoes from south to north across the KC metro area, but certainly no significant damage. Compared to Joplin, the threat over the Kansas City area was small in this situation. But tornado warnings with wording not much different than the intial Joplin warning 3 days earlier prompted several people in KC to call my wife Shawna and me in panic to ask what was going on, given that Joplin had occurred only a few days earlier. We told people to take cover and precautions, but that the risk was only a small fraction of what it had been for Joplin. This is an example of a situation where 2 tiers of warnings (and possibly different siren modes) might be useful in conveying the relative threat to the public.

Admittedly, the Kansas City situation on 5/25/11 was complicated by the rapid increase in parameter values and support for tornadoes some 70 to 80 miles east-southeast of Kansas City, where a significant EF2 tornado hit Sedalia just after noon. With SRH in the 150-200 m2/s2 range and SBCAPE near 2500 J/kg in the Sedalia area and southeastward (see right black arrows on last graphic above), the SRH/CAPE potential was very close to the red curve on the SRH/CAPE diagram above, signaling a much greater tornado threat there. So the May 25th situation was not a simple one to assess. But use of the tools above were definitely helpful in indicating the increased tornado threat and tornado risk as one moved well east and southeast of Kansas City.

To be clear, I do understand and know that there are many, many tornado warning situations where it is essentially impossible to distinguish between warning and not warning using radar in combination with environment conditions... in those cases the environments are simply too "borderline" to make such calls given the knowledge and observing situations we have. BUT, there are also situations where tornado environment parameters are clearly impressive as thunderstorms form, suggesting increased risk of death and injury over larger areas. Those are the times when we need to do everything we can to convey the true risk to the public.

I do also know that many people still don't seem to know the difference between a watch and a warning (maybe the term "alarm" instead of "warning", avoiding the "waa.." word sound confusion between the two words, would be better?). So I often get arguments that much of our populace is too "dumbed down" to deal with a 2-tier warning system. But is that really a reason to continue status quo in our current system when today's technology and knowledge can offer more information in many warning situations? That is something to think about.

- Jon Davies 9/26/11