Storm chasers featured on The Weather Channel's web site

FWIW, I'm being featured currently on The Weather Channel's web site along with several other prominent storm chasers. See:

http://www.weather.com/tv/programs/Storm-Chasers.html

There's some photos, video, and miscellaneous information about me there. Thanks to Tony Grohovsky at TWC for setting this up.

Shawna and I just got back from the Denver Chaser Convention. It was great talking with so many chasers there, including Reed Timmer, Tim Samaras, Roger Hill, Mike Umscheid, Matt Crowther and Betsy Abrams, Jim Leonard, Tony Laubach, Brandon Ivey, Kory Hartman and Kenny Allen, and I could on and on. The presentations by experts such as Rich Thompson, Dr. Greg Forbes, Tim Marshall and others were excellent. And Shawna's talk about chaser preparedness and first response was very well received.

Here's a good recap of the convention at examiner.com:

http://www.examiner.com/x-219-Denver-Weather-Examiner~topic86015-weather-events

- Jon Davies 2/17/09

Deadly tornado after dark in south-central Oklahoma on 2/11/09

Sadly, 2009's first "tornado disaster" has come with a tornado after dark at Lone Grove (near Ardmore) in south central Oklahoma. With news reports of at least 8 dead, one has to wonder if darkness contributed to the death toll. In 2007, 2008, and now 2009, we continue to see damaging and deadly nighttime tornadoes in the Plains, something more commonly associated with the southeastern United States.

Above, two radar reflectivity images (see white arrows) show the deadly supercell at 0000 UTC, and again at 0135 UTC, just after the time the tornado was hitting Lone Grove. With a large line of storms to the west and north, this reaffirms that discrete supercells tend to produce the strongest tornadoes, removed from immediate interference by adjacent storms. As the line to the west overtook and engulfed the supercell after 0200 UTC, tornadoes ceased.

The environment was very primed for tornadoes after dark. Strong forcing was occuring with the upper system, seen in the 500 mb NAM/WRF forecast graphic above. The RUC model was forecasting strong combinations of CAPE and low-level shear (storm-relative helicity or SRH) well in advance of this event, seen in the first part of the forecast graphic above. The second half of the same graphic suggested a very moist, surface-based environment forecast in the same area, with large low-level CAPE.

A modified RUC analysis sounding at Ardmore (also seen above) as the tornadic cell was passing to the north and west, also suggests that an excellent setting for strong or violent tornadoes was present. Instability was large for after dark at this early time of year, with MLCAPE > 2500 J/kg, while 0-1 km SRH was also very large (> 500 m2/s2) for support of low-level rotation in storms. Deep layer shear was quite strong, approaching 60 kts to intensify updrafts, and low-level MLCAPE below 3 km (> 250 J/kg!) indicated a strongly surface-based setting with essentially no inhibition (MLCIN).

Excellent tornado warnings were issued for this storm by the National Weather Service. Better awareness and action by the public in response to such warnings and settings is what will save more lives with nighttime tornadoes.

My wife Shawna will be giving a talk at the Denver Chaser Convention this weekend (Feb 14-15) about how chasers can help with severe weather education, and be better prepared to assist in first response situations. This deadly early season Oklahoma event reminds me that it's an important talk.

- Jon Davies 2/11/09

Talks at Denver Storm Chaser Convention 2/14/09 and 2/15/09

I will be doing 2 talks at the Denver convention this year: "Thoughts and Research on Nighttime Tornadoes and Rain-wrapped Tornadoes", and "A Review of Some Recent Tornado Settings from a Chase Forecast Perspective". There will several excellent speakers, including Rich Thompson of SPC talking about tornado forecasting, Dr. Howie Bluestein on VORTEX-II, and also Dr. Steve Lyons and Dr. Greg Forbes from The Weather Channel.

In addition, my wife Shawna will be doing what I think is a very important and down-to-earth talk for chasers, "Beyond the Storm - Chasers Helping with Communities and First Response". See: http://chaserconvention.com.

I understand there may be live online streaming of convention talks this year. So I hope you can make it to Denver, or at least watch online.

- Jon Davies 1/30/09

EF-1 tornado in Alabama on 1/10/09: a subtle small CAPE setting

A weak tornado occurred shortly after 2300 UTC (5 pm CST) on Saturday, Jan. 10, about 30 miles north of Mobile in southwest Alabama. It wasn't very impressive (1-2 mile path, EF-1 winds around 100 mph), and thankfully no one was hurt, but it did do some damage (see NWS photos above, also click here). Given the subtle setting, it was kind of interesting from an environment standpoint.

Radar reflectivity at 2304 UTC from Mobile above shows the tornadic cell, and NWS Mobile did a good job with tornado warnings that were issued across southern Washington county for more than 45 minutes before the tornado struck the town of McIntosh.

The RUC analysis profile above for Mobile (MOB) at 2300 UTC is somewhat unusual, with small total CAPE (only around 400 J/kg!), and most of the CAPE below 600 mb, very low to the ground. Settings like this can enhance stretching near the ground, and with decent SRH (> 200 m2/s2 in the lowest 1 km), they can occasionally support tornadoes, even with small total CAPE.

The SPC graphics above show a large positive tilt 500 mb trough was heading southeastward, with a cold front (not shown) ahead over central Tennessee into central Mississippi. The Alabama tornadic cell occurred well in advance of this front in a moisture axis of 60s F dew points. In the parameter graphics, the SPC total MLCAPE field over southwest Alabama wasn't impressive (> 250 J/kg), but low-level CAPE was large (near 100 J/kg below 3 km) along with low-level SRH (200-300 m2/s2) overlapping the southwest Alabama moisture axis. These ingredients, combined with the low-to-the-ground vertical CAPE distribution in the RUC analysis above, were just enough to help generate a tornado with the cell north of Mobile.

This case is a reminder that storm environments with CAPE "squeezed" low to the ground certainly aren't limited to cold-core events (for example, see here).

- Jon Davies 1/12/09

Damaging thunderstorm winds in south Kansas City on 12/27/08

It's unusual to get severe thunderstorms in the Kansas City (KC) area around Christmas, but it sure did happen yesterday morning (Saturday 12/27). The setting involved a very strong upper trough that brought unseasonably warm air northward ahead of it (record temps in the 60s F in KC on Friday), and an early morning bow echo type thunderstorm feature that interacted with a quasi-stationary outflow boundary in the south KC area.

The first graphic above shows the deep mid-level trough around midnight going into early morning on 12/27, along with SPC storm reports, and a WRF forecast of low-level CAPE suggesting an unstable surface-based environment extending northward into the KC area overnight. The 2nd graphic is a radar reflectivity image showing an ENE-WSW outflow boundary in place across the south KC metro area at 4:00 am, the result of thunderstorms that had moved across to the north of KC in the 2-3 hours prior. The bow echo thunderstorm feature is also visible approaching KC from the SW. Surface temperatures south of the ENE-WSW boundary were in the low-mid 60s F, while north of this same boundary, temperatures were at least 10-15 F colder as a result of storm outflow.

The 3rd graphic is a RUC analysis profile estimating the environment just south of the ENE-WSW boundary at Olathe KS (OJC) about 40 minutes before the damaging winds hit Johnson County (the SW side of the KC metro area). Although there was not a lot of CAPE (maybe about 200 J/kg), the profile was fairly surface-based with a deep low-level moist layer and around 50 J/kg of CAPE below 3 km. Also notice how strong the southerly low-level winds were at only 2000 ft above the surface (roughly 900 mb), with sustained speeds to 50 kts (nearly 60 mph)! It wouldn't take much storm downdraft to move these winds downward to the surface, particularly in a surface-based setting like that just south of the ENE-WSW boundary. In contrast, the 4th graphic above is a RUC profile at KC International Airport (MCI), roughly 20-25 miles north of the same boundary. Notice that with colder temps north of the boundary, this profile is "elevated", with no CAPE at all from lifted parcels in the lowest 100 mb. Even though the strongest part of the radar bow echo went across northward near the airport, the damaging winds were limited to the area along and just south of the ENE-WSW boundary. That's probably because that's where the warm surface-based environment was, where it was relatively easy to move strong winds downward from not far aloft, whereas farther north the cold near-surface setting probably kept damaging downdrafts from reaching the ground.

The last graphic above is both reflectivity and velocity showing the strongest winds coming into the south KC area around 4:40 am, reaching measured speeds around 80 mph. This was south of the strongest radar echo, but along the advancing outflow southeast of the bow echo feature. Again, that's where the warm surface-based setting was (south of the ENE-WSW boundary), better for allowing damaging winds to reach the surface.

What a weird week in the KC area... sub-zero (F) temperatures early on (Sun-Mon), then temps recovering to record high levels on Friday with thunderstorms, and back to ice and snow during the day on Saturday. On Friday evening, Shawna and I found ourselves driving in a heavy thunderstorm in north KC with sharp CG lighting, then getting up to ice covered trees on Saturday morning while more storms raged to our southeast. If you live in the Plains, just wait a few minutes... the weather will probably change :-).

- Jon Davies 12/28/08

Twin Horseshoe Vortices! (6-17-08 in Nebraska)

Looking back at some photos my wife Shawna took on 6-17-08 while we were in northwest Nebraska waiting for storms to develop, I ran into these shots above that we had forgotten about. We've both seen plenty of "horseshoe vortices", but never a twin pair like this, south of Alliance. Shawna has a good eye for picking them out (I would have missed these).

There are probably several ways such vortices can form, but the most common idea is shown in the black and white explanation figure above. As a cumulus updraft builds, it may encounter rapid and strong vertical wind shear (differing wind speeds and/or directions within a short distance of height). This may cause the updraft to develop horizontal spin that, when stretched further by the small updraft, spins faster and is deformed into a "horseshoe" shape. Condensation within the cloud allows us to visually see the vortex. As dry air mixes into the cloud, it evaporates, except for the spinning horseshoe vortex, which resists dry air entrainment for a little while longer. In reality, horseshoe vortex formation is complex (otherwise they would happen all the time), but the diagram above summarizes some basics.

An estimated wind profile for Alliance is also shown above. Note the rapid and sharp wind shift from southeast to northwest at about 3000 ft above ground. This may help explain the horizontal spin that developed and stretched into "horseshoe" shapes with condensation as these cumulus updrafts on 6-17-08 encountered this sudden wind shear with height.

I don't think I've ever seen a photo of twin horseshoe vortices before. Thanks, Shawna, for catching these!

- Jon Davies 11/23/08

Southwest Kansas cold core setup on 11/10/08 - Mike Umscheid photographs large tornado

Lead forecaster at NWS DDC and storm chaser/photographer extraordinaire Mike Umscheid documented a rare Kansas November wedge tornado, in the far southwest corner of the sunflower state yesterday. Wow! Go to: http://www.underthemeso.com/blog/ to see and read more.

The setting was a cold core setup (read paper here), with a 500 mb low attempting to cut-off over eastern Colorado within a strong upper wave lifting northeast (see SPC graphics above). An area of CAPE was over southwest Kansas, just east of the surface low where boundaries intersected (a fairly classic localized setup, see surface map above). The cell Mike chased looked to be pretty close to this key boundary intersection (see radar above), with sunny skies to the south on satellite (not shown), generating a good surface heat axis pointing into the area.

The RUC analysis sounding in the Johnson/Ulysses KS area at 21 UTC (see above), about 20-25 minutes before the tornado, showed good CAPE for a cold core setup (near 700 J/kg), all bunched below roughly 400 mb for a classic small supercell profile. With plenty of really cold air aloft (-10 C at 700 mb!), dew points in the 40s F and temps in the 50s F were all that was needed. Amazing!

A potential cold core setup in South Dakota last week (11/5/08) didn't pan out for tornadoes, as there appeared to be way too many low clouds for needed surface heating and instability near the boundary intersection with that system, unlike the one in southwest Kansas yesterday.

Excellent job, Mike!

- Jon Davies 11/11/08