The late May and early June portion of the 2009 severe weather season was characterized by split flow which forced the jet stream far to the north and left a series of cyclonic circulations wandering in the Gulf of Mexico. The former resulted in weak winds and shear across the region and the latter cut off the northward flow of moisture. Consequently there was little or no severe weather activity taking place during this period. Once again, my previously scheduled period for storm chasing fell during this period of poor atmospheric conditions. Fortunately, the pattern underwent a change back to a more normal configuration during the latter half of my vacation and I was able to see some interesting storms and to get some good photographs.

30 May 2009

ISS transiting the twilight sky in Arizona. Mammatus at sunset along I-25.

In preparation for this trip, I experimented with some night photography the previous evening and managed to get some interesting time exposure shots of the International Space Station (ISS) transiting the twilight sky over northern Arizona. Today was a travel day from Flagstaff, Arizona, to Denver, Colorado. I wasn't expecting much more than some "garden variety" storms and that's about all that we saw. Nonetheless, there were a few interesting moments. Early in the afternoon we watched large tumbleweed fall out of the sky and land on the road in front of us. Obviously, there must have been a dust devil nearby although I was unable to see it. Later in the day while driving through western New Mexico, we drove under some high-based, low-topped thunderstorms. We were surprised at how hard it rained and the raindrops were quite large and slightly slushy. To top it off, we watched a lightning bolt hit the top of a power pole just a few hundred meters up the road from us. Wow!

31 May 2009

Cumulus congestus along the DCVZ.

The abysmal flow pattern continues across much of the midwest with weak winds at most levels. Better flow exists much farther east (i.e., eastern Nebraska, western Iowa) but it is out of reach from my current location in Denver. Model data suggests a small region of moderate CAPE this afternoon in eastern Colorado but winds and shear in that region are very weak. Anything that develops will likely produce heavy rain and maybe some briefly severe-sized hail but rotating storms are unlikely. Need to make a decision on whether to go hiking today or drive east simply to photograph any convection -- however UNsevere it might be -- that might develop. Around mid-afternoon, strong convection developed across northern Colorado so I set out to intercept it. Before I got to that convection, new storms developed along a weak boundary—possibly outflow from the earlier storms. Nothing significant developed and these storms had heavy rain, very small hail, and infrequent lightning.

01 June 2009

Colorado wildflowers.

Models are showing only a small area of decent mid-level and upper-level winds across Texas—and the current model run appears to be a tad slower than the previous model run for ejecting the AZ/NM low eastward. Consequently, stronger winds could arrive too late. Farther north, wind profiles are not very good in CO/KS since this will be located on the north side of the slowly ejecting low. The options for marginal severe storms included eastern Colorado, the Texas panhandle (TXPH), the NE/KS border region, and probably a few others. None of these will produce anything very interesting so this will be a down day. Instead, we travelled to Boulder and we ran the Mesa Trail from Chautauqua to Bear Canyon for a round trip distance of about six miles. I remember this trail as being very rocky—and my memory was correct.

02 June 2009

Colorado sunset.

My original plan was to depart Denver early this morning with a target area in the northern TXPH. Although the forecast parameters have not changed significantly—it now appears it will be a moderate challenge just to get there. Widespread light to moderate rain has developed across much of Colorado including the highways I would need to travel. I must assume that reduced safe driving speeds in all of this rain will make it very difficult to get to my target area in a timely manner. My biggest concern, however, is that the cold air lying across southeastern Colorado will surge southward into the TXPH and push the target area farther southward and even more out of reach. We decided to call it a down day. Again. And the cold air did surge southward pushing the target area farther away.

03 June 2009

VORTEX2 vehicles. VORTEX2 vehicles.

Another day with meager instability and shear in the wake of the low and front that pushed through Colorado yesterday. Dewpoints are in the low to mid 40s but the KDNR sounding indicates this is fairly deep moisture so it might not mix out this afternoon. Surface data suggests that a DCVZ (Denver Convergence-Vorticity Zone) has set up with the circulation center east of Denver but west of Deer Trail and north of Elizabeth. Will meander east early this afternoon to take some photos of the DCVZ if it fires up. Even if it doesn't there is always the chance that the surface vorticity will be sufficient to generate some gyres along the convergence line and maybe even a few large dust devils. For tomorrow, conditions should improve across the High Plains. Finally!

04 June 2009

Twin funnel clouds near Elbert, Colorado.. Rainbow in eastern Colorado. Sunset in the Pawnee Grasslands. Photographing the photographer.

Shear has increased substantially across the region and is now sufficient for supercells. The remaining problem—and it's a big one—is the lack of moisture. Dewpoints are only in the upper 40s to lower 50s today and surface trajectories will not improve this very much. Rainfall in the past few days may add a bit through evapotranspiration (ET) but it won't be much. On the other hand, moisture extends through a reasonably deep layer so mixing might not be much of a problem. RUC and NAM are quite different with the depiction of CAPE this afternoon. NAM has the more realistic, albeit somewhat low, values of around 500–750 J/kg. The RUC has very high values exceeding 2500 J/kg. In reality, I expect we will see something closer to 1000 J/kg, locally as high as 1500. The NAM develops southerly surface winds while the RUC has southeasterly surface winds this afternoon. Consequently, the RUC has better 0–6 km shear although both the RUC and NAM have more than sufficient shear for supercells. Cool temperatures over the eastern plains will limit the eastward extent of convection today. Expect storms will develop over the higher terrain of the foothills and the Palmer Lake Divide then move ESE. Eastward of about a FTM–LIC line, expect that storms will diminish as the boundary layer becomes too stable. So it comes down to the moisture and how well these storms that initiate over the higher terrain can utilize it before they diminish in intensity over the lower terrain of eastern Colorado. We plan on caravanning with Matt Crowther and Scott Bell later today. We met up with Matt and Scott near Watkins and watched convection slowly develop before heading south across the Palmer Divide to intercept the storms. For a brief time, the convection looked impressive but as it moved to the east and into the more stable air it quickly diminished—as we had forecasted. So we waited near Kiowa. New convection developed to our WSW and we drove southward toward Elbert. A short distance south of Elbert we stopped and observed multiple funnels from the storm to our west. As the rain began to fall on us, we moved farther to the south where we ran into Jon Finch. This storm also dissipated as it moved off the higher terrain. We drove east along US24 towards Limon to try and intercept additional storms but these, too, were quickly diminishing in intensity as they moved eastward. We did manage to get a great rainbow for all of our efforts! About this time, we ran into the Original Twister Sisters (OTS), John Moore, and Patrick Kerrin. Throwing in the towel, we drove to Fort Morgan. Along the way, we heard warnings for storms along the Cheyenne Ridge so we moved north to intercept those at sunset. These storms showed lots of laminar structure and there was plenty of CG lightning so there were many photo opportunities. We stayed in Fort Morgan for the night. The Pub and Grill serves excellent pizza.

05 June 2009

Gas pump depot, Pine Bluff, Wyoming. Goshen County, Wyoming, tornado. Photographing the photographers (Blanchard, Hodanish, Crowther, Bell). Goshen County, Wyoming, supercell and tornado. Goshen County, Wyoming, tornado. Supercell at sunset, Nebraska. Supercell at sunset, Nebraska.

We are again chasing with Matt and Scott. Target for today is the 3-corners region of WY/NE/CO and northward. We arrived at Pine Bluff, Wyoming, early in the afternoon and stopped to look at data and to wait for convection to develop on the higher terrain of the mountains in eastern Wyoming. There is a service depot for old gasoline pumps in Pine Bluff and the collection is worthy of a photograph or two. Steve Hodanish joined us in Pine Bluff. As convection developed we moved north from Pine Bluff on WY215. After passing through Albin, we continued a few miles more on Albin-LaGrange Road while observing a new storm to our WNW. Other storms farther north were moving NE and were likely putting down cold outflow. It was our hope that this new storm would roll more to the E or ESE along this boundary. And, more or less, that is what happened. We found a great vantage point with off the road parking and a clear view to the west and began photographing and videoing the storm at least 15–20 minutes before the tornado developed. Consequently, we have some excellent documentation of the structural evolution prior to tornadogenesis. Eventually we had to abandon our location because rain from the forward flank and lightning were getting too close. We dropped south a few miles and found some more off road parking and once again set up to photograph and videotape. We saw the tornado emerge from its rain-wrapped phase and then enter the long-lived rope phase from this location. This was a Top–5 tornado and supercell event for me because of: Correctly identifying the target area and arriving with plenty of time to observe before the tornado developed. Excellent viewing location with unobstructed views, great foreground, and excellent scenery. Watching the evolution of the storm from pre-tornadic through its demise. Duration of tornado. Fabulous structure—and changing structure—of the tornado. Excellent photography with 28mm wide angle and 80-200 mm zoom, plus time-lapse video with a 28mm wide angle lens. After the demise of this long-lived tornado, we began to move eastward for any new development that might occur. We saw a brief, weak funnel but no additional tornadoes. As the day came to an end and the boundary layer began to cool, the low levels of the storm became more laminar and we took advantage of the excellent late-afternoon lighting to photograph this amazing storm. Late in the day, I had a chance to chat with Erik Rasmussen, FC for VORTEX2, and let him know of the photographs and video we captured in the event they might be useful in the VORTEX2 analysis of this storm.

06 June 2009

LP supercell #2, Nebraska. LP supercell #2, Nebraska. LP supercell #2, Nebraska. LP supercell #3, Nebraska.

Forecast: Currently in Ogallala, Nebraska, (along with many other chasers) and we think the best chances for supercells—and possibly tornadoes—may be right where we are at this time. Both the RUC and NAM show southwest to west surface winds pushing across Wyoming and far western Nebraska this afternoon with southeasterly flow along the frontal zone. Best convergence, CAPE, least CIN, and most favorable hodographs all are located in this general region. Susan and I—along with Matt Crowther and Scott Bell—had "patrol duty" along I-80 as we drove west to Sydney then back east to Ogallala all the while trying to decide if we should plunge northward into the cooler air or wait for the dry line storms from northeast Colorado to move towards us. By taking so long to make a firm decision, a decision was made for us and we awaited the Colorado storms. The first LP supercell approached us as we were north of OGA and it became a photogenic storm, albeit high based. We stayed ahead of this storm to Sutherland then let it go and turned back west for the next storm. We dropped south at OGA and intercepted the second LP supercell storm as it became more sculpted with modest rotation, a wall cloud, and a bit too much CG lightning near us. Dropping farther south to Grant, then east to Madrid, we were able to enjoy the amazing structure on this storm in the twilight. At this time, Matt and Scott bade us farewell and continued east to North Platte while Susan and I turned back west to return to Ogallala. The third and final LP supercell was quickly approaching Grant and we had to duck south to avoid any hail it might have. This was the most amazing of the three supercells of the evening with classic bell-shaped base feeding into a corkscrew updraft, all lit up by nearly continuous lightning. Fantastic!

07 June 2009

Colorado wildflowers. Colorado wildflowers. Colorado sunset.

Strong subtropical jet bringing SW flow aloft continues but there is also a digging polar jet moving across the intermountain west today. In between the "LF quads" of these two jets lies northeast and east-central Colorado. Moist and cool air has pushed southwestward to near the Front Range of northern Colorado and this should suffice to generate enough instability for higher terrain storms to initiate this afternoon. Farther east, the best combination of modest CAPE, 0–6 km shear, and jet level winds looks to be in northeast and east-central Colorado. Because of a requirement to be back in Flagstaff late tomorrow, my choices are limited and this looks like a reasonable option for another day of modest supercells. We left Ogallala, Nebraska, in drizzle and cool temperatures and finally broke out of the overcast near Brush, Colorado. A weak storm was located south of Fort Morgan and more active convection was over the Front Range. After taking a lunch break, we learned that funnels and tornadoes had been reported in the Denver area. Because that was still too far away we targeted the storm south of Fort Morgan. After observing for awhile it became clear that these updrafts were not going to do much this early in the day and more time was needed to heat the convective boundary layer. However, the Front Range convection was surging eastward and would eventually overrun these storms. We took a position on a hill near Last Chance and watched the leading edge of the outflow—which had been recently TOR warned. Nothing of significance was visible and the surface outflow had surged far ahead of the updrafts so there was little chance of a tornado in this area. We picked up the pace towards Limon to get south of the south end of the outflow and convective line in case there was large hail embedded in it. Once we got past this, we stopped and watched the leading edge of the outflow rapidly surge southeastward and away from us. Once it became clear that we were done chasing for the day, we resumed our drive home to Flagstaff. We stopped in the Comanche National Grasslands for a while and shot photos of the wildflowers.