5/27/09: The Pattern and More

I learned a valuable lesson the last few days of my trip (I am sitting here at DIA waiting for my plane as I type this). I realize that most severe storm researchers here are looking ahead to a possible pattern shift, and what's happened in Colorado the last few days may not seem important.

But that Commerce City storm three days ago, and the storm southwest of Limon were eye openers for me. Those were not "landspout" storms (in the sense of a non-supercell thunderstorm just spinning up vorticity of the boundary layer). These were storms that formed initially in an environment that should not have supported supercells in the sense of the deep layer shear. Yes, yes, we are all used to pontificating about storm motions off the hodgraph and how you can get supercells in otherwise unfavorable environments. We all use the term "mesoscale accidents" to refer to storms that become supercellular out here without the obvious shear signatures in the morning's hodographs and wind profiles.

But even though I know that, and all severe storms researchers know that, I doubt anyone chasing Colorado those the Denver Convergence and Vorticity Zone (DCVZ) days over the weekend were thinking "...oh, I really think some mesoscale accidents will happen and, forget single cells spinning up a spout, we are really going to see some good structure..." Maybe someone did. I didn't. All that I know who were out here were looking for landspouts, no more, no less.

Frankly, those two days felt like "chase" days to me in the traditional sense. Thom and Scott and I were chasing supercells, with the updrafts in the correct locations with respect to the forward flank, with RFDs, etc. You know what, those two days allow me to leave the Plains feeling as if this trip was somewhat successful. Scott and I may write up something on the DIA storm on 24 May because of this.

But there's something odd about this pattern that we are in. Perhaps it relates to global warming, perhaps not.

I think the consensus from the linked ocean-atmosphere models used to project climate trends into the late 21st century show that most of the "warming" will take place in the upper middle and polar latitudes. If that's the case, the meridional temperature gradient will decrease a bit at the same time that the mean temperatures of the whole shabang go up.

Decreasing the pole-equator temperature gradient USUALLY means higher wave numbers (more long wave meanders). This suggests that whatever controls external to the atmosphere are at play (say SST patterns) might act to anchor these meanders. Suppose one "anchor" was a trough on the West Coast....that had a response a ridge over the Plains downstream. Then we'd have a season or a period like the one we've just experienced.

Suppose another time the anchor was in a different location, so that a mean trough sets up over the Rockies. That's what I meant really. I am not trying to relate mean temperatures to lapse rates or anything like that.

All other things being equal, the latter would result in a "synoptically-evident" pattern for severe weather in the Plains. And that could go on for weeks, or even months.

As far as lapse rates go, if the heating is equally distributed through the troposphere's depth, then the environmental lapse rate won't change much. However, the higher mixing ratios mean that when storms do go they would go with more CAPE. Hence, maybe not more storms, but storms, when they occur, that would be more violent. Who knows about how the lapse rates will really be affected, though.

There is much to ponder here for severe storms meteorologists and climate change atmospheric scientists.

05/25/09: Carlsbad and Exit

Last night Scott and I witnessed the bat flight from Carlsbad Caverns. Because of the dry conditions locally the usual number of bats had not been making this flight; there were not enough insects for them to forage. The previous night the rangers told us only 10 bats had come out. The usual size for the colony is 400,000 bats. When Thom and my nephew Bruce and I saw this event in the early 2000s, it was an awesome vortex of black rushing out of the natural opening of the cave.

Well, fortunately, last night a respectable bat flight did occur. Though smaller in size than I remember it, the flight still probably had 100,000 bats or so exiting over 15 minutes.

Today, we are leaving early to descent into the caverns for the two to three hour walk (goes about three miles). This will be my sixth time through, and I have yet to tire of this spectacular descent into a wonderland of colors, shapes, and spaces.

5/25/09: On to se New Mexico

Our initial plan is to hope that the dry line does not set up too far east today. But, even if it is in southeastern New Mexico, where the shear environment appears somewhat favorable for a rotating storm or two, the moisture return from the Gulf is still meager. There is still a disjoint between where the greatest buoyancy is and the best shear. This has been showing up in the last few runs of the models.

We'll reevaluate as we travel. Meanwhile, we are planning to see Carlsbad Caverns...the bat flight tonight, and the caverns themselves tomorrow morning before all the tourists overun it.

Here's another picture of the fabulous rotating storm we witnessed yesterday.

5/24/09: Viva Las Vegas....

...New Mexico, that is. Which is where Scott Landolt and I are overnighting. We left Thom off at Denver Airport but decided to stay in the area. A Denver Convergence Zone was developing again, basically a reprise of yesterday. And, this decision paid off for us all.

It turns out that we ended up chasing right to Denver Airport. Thom's flight was in the late afternoon, so while we were chasing and he was waiting, a supercell developed west of Denver Airport. The radar development was spectacular, and the storm ended up producing a marvelously wrapped wedding cake, corkscrew updraft area.

Yes, Thom was in the Airport when the tornado warning was issued, the sirens wailed, the klaxons sounded, and all were asked to the tornado shelters and planes were vectored off.

We are not sure if the storm produced a tornado. We did see two funnel clouds with earlier storms, and Cameron Redwine reported a funnel at the time of maximum development. I'll post more when I get my pictures downloaded.

5/23/09-Part B: Denver Cyclone Produces

Well, on Thom's last day, we actually had a traditional chase.

We dropped down to the Palmer Divide by early afternoon. There seemed to be a boundary with ESE flow south of the Divide and northwesterly or northeasterly winds north of the divide. Low to mid 50 dewpoints abounded.

When we got to Limon, a strong set of echoes was between Colorado Springs and Limon. Just after our arrival there, the northern most of the echoes developed a rain free base, and then, somewhat to my amazement, a fairly good looking wall cloud. We dropped south and noticed that at least at the base of the wall cloud there was decent, but not strong, cyclonic motion.

As the storm moved over us, the wall cloud became outflowish, but left behind on its eastern periphery was the high based funnel, nearly tilted horizontally. All in all, this was a very satisfying chase day. We salvaged an actual chase out of this wreck of a pattern. It also goes to show that what meteorologists call "mesoscale"accidents can produce bounty. A "mesoscale accident" is something that cannot be assessed by looking at computerized weather forecasts, but changes conditions favorable to those for rotating storms by some local effects that are difficult to assess, if not impossible (topography, boundaries from neighboring thunderstorms etc.) True, we did not see a tornado. But others reported brief tornadoes. Our high-based funnel is consistent with those reports.