Sunday, June 15, 2008

Father's day or son's Day?

Father's day is usually all about Dad's, but this one certainly seemed like it was a gift to me instead of my father! The day started off with a bang as I was awoke early to a small elevated MCS traversing through Illinois that produced a beautiful shelf cloud according to Tavis's pictures. The MCS quickly exited allowing for rapid destabilization from late morning till early afternoon before a large thunderstorm complex quickly blew up right over top of us. This storm produced the largest hail I have seen to date in Illinois!
Anvil shield from the early afternoon convection to the west

Penny to walnut size hail!
Posing with a handful of small hail
Little did we know, the storms were not done yet! Yet another round of storms initiated off to our west with some surprising structure. These storms were very intense and very short lived. My guess is that they relieved any of the instability that the early afternoon convection missed...
This storm fired and quickly produced a wall cloud type lowering before quickly dissipating...The images were taken with my phone and are not of the best quality...One thing to observe is the northwest flow nature of the storm and the "reflection view" of a typical southwesterly flow supercell.

Notice the precip core on the left side of the storm rather than the right...
Things quickly settled down after this exciting storm to a normal father's day. We were treated to a beautiful sunset and some hard to photograph hummingbirds!
Breathtaking sunset
Reflection of CB off of the lake

Dad posing next to his pride and joy
Curly enjoys the evening
This guy was hard to photograph!

6/11--Deadly Iowa HP's

The day after my birthday was shaping up to be an interesting day for tornadic supercells in western IA. After picking up Dustin in Oglesby and Travis (another NIU chaser) near Princeton, IL, we headed for our initial target of Council Bluffs, IA. After passing through the Quad Cities, I noticed that the right front tire was shaking violently and that it was going to need to be replaced. Luckily for us, a tire center in Des Moines was able to get us right in and after about an hour of labor, we were back on our way to western IA. We arrived to our target a little behind schedule, but were excited to see the rapidly strengthening storms off to our SW.
Shot of an initial supercell forming to our west
Unfortunately for everyone involved, these storms quickly what meteorologists call HP or High Precipitation. These storms are often very hazardous to many for lots of reasons...Storm chasers and others in the path of the storm because it is very hard to find and identify where circulations are in the storm; National Weather Service forecasters because they rarely have ground truth of these circulations until after they have wreaked havoc on their targets; and their obvious title of very heavy rain producers that causes flash flooding in a matter of minuets.
HP storm that quickly "wrapped up" and passed over the Boy Scout camp...
These sort of situations are always a blow to the stomach to everyone involved and no chaser ever wants to see anyone injured while chasing after mother nature...One chaser even had to bail out of his vehicle after realizing that a circulation was passing right over him! This day was certainly a dangerous chase day, and my thoughts and prayers go out to everyone that had their lives changed due to this event. After staying ahead of the HP blob, it started to coalesce with other HP monsters into a large MCS. We stayed ahead of this mess of convection on I-80, stopping frequently to sample the shelf and lightning.
Typical view of the shelf along I-80 just west of Des Moines
CG bolt near Des Moines

Monday, June 9, 2008

6/4-6/5 Bust and Realization

Everything seemed to be falling into place for a two day severe weather episode, so Dustin and I decided to head to the NE, IA border to catch some action. Initially, Wednesday seemed to be the day that was going to an appetizer as the orientation of the upper level trough was still positive and less progressive than the progged upper level flow for Thursday. We basically figured that any convection we could catch Wednesday would be icing to the cake. In summary, Wednesday turned out to be better than Thursday despite the better looking atmospheric conditions on Thursday (more on this later).
After reviewing some data while stopping at Sonic in Des Moines, IA, our initial target was Aurora, NE. While driving to our target we noticed many storms firing of to the west of Aurora near Kearney and Grand Island. We still decided to keep our target due to the very agitated nature of the cumulus clouds outside our windows between Lincoln and Aurora. To our liking, a pair of supercells fired along this northward lifting boundary and put us in the perfect position to chase.
Initial storm north of Aurora, NE, lacking strong low-level inflow
The TIV (Tornado Intercept Vehicle) contemplates on a target

Storms seemed to be lacking a low-level inflow, and with darkness approaching we decided to call it quits near Lincoln, NE. While checking into our hotel, many mexican men were standing outside of the entrance to the hotel amazed by the wind, rain and lightning from the leftover convection. Did I also mention that they were downing 24 oz. beers? Sure enough, we found one of them with a phone up to his ear passed out on the steps leading up to the room.
Yes hunny, I'll make it home for breakfast tomorrow.

After a few laughs, we noticed that the lightning on the backside of the convection we were following was amazing. Must say that it was the best display of anvil zit lighting that I have seen to date.
"Anvil Zits" outside of Lincoln, NE

Dessert after the main course.

After returning to the room, attention quickly turned to Thursday's chasing prospects. After waking up to the largest Storm Prediction Center high risk that I have ever chased, I was anxiously awaiting the afternoon convection. Even though the morning high risk was primarily for a threat of damaging wind, it was apparent that a small area in E central NE was becoming ripe for tornadic supercells (see MD below).
Mesoscale Discussion issued shortly after we left Lincoln

I will now go into quite a bit of detail about Thursday's bust...

After choosing York, NE as a target we noticed some convection starting to fire on radar to our west near Grand Island and we immediately traveled west to scope out the action. It was obvious that these storms were not tapping the uncapped surfaced based instability that the SPC mesoanalysis was showing (see below).

17 Z Surface Based CAPE

Notice the lackluster appearance of the convection along the boundary in S central NE

What was happening? You can clearly see that the storms in northwestern KS were thriving in an environment that seemed much less favorable for supercellular convection. After a few minuets of watching this convection moving out of CO and into KS, we decided to try to intercept these quickly moving supercells, with a flying V appearance on radar, as they would hopefully move near the Red Cloud, NE area. The pair of supercells was moving into a very favorable environment rich with extreme theta-e and backing winds along a N-S oriented pseudo dryline. All I could keep thinking is that this was it, these were going to be the storms that we have been waiting for... We made it to Red Cloud, NE with time to spare and fueled up while watching radar. We were very curious to see what was going to happen when these storms hit the boundary and moved into a much better conceptual severe storm environment. The radar scan after the storm hit the boundary, and I mean right after, the storm immediately lost all of its rotation and started to dissipate into a non-severe shelf cloud. WHAT? Hmm...You would THINK that this storm was moving into a much more favorable environment. What was wrong with the airmass on the east side of this boundary? It was clearly having trouble sustaining any sort of an updraft the entire day. One hypothesis could be that the airmass to the east of this boundary was capped despite the RUC's analysis in the SPC mesoanalysis. Wouldn't this boundary help break that cap?
What happened when the supercell that looked so good on radar hit the boundary? Boundaries are supposed to be areas of enhanced vorticity and wind shear. Was it the orientation that storm crossed the boundary that made it dissipate and turn into a shelf cloud? So many questions were running through my mind on the long drive back to Illinois...One thing for sure is that we as meteorologists still know very little as far a mesoscale processes in these sorts of situations. Who knows, maybe someone will do a case study for the event, but I find it unlikely due to the lack of 18Z soundings behind this psuedo dryline... Now 0-5 while chasing high risk events and 0-4 inside of PDS tornado watches. I'm becoming more frustrated every time I see a high It always seems like there is just way to much going on!

Disappointingly, the best picture of the day

Time lapse of the shelf cloud