Monday, April 27, 2009

04/26/09 Linear MCS in Iowa

Linear MCS rolling through central and southern Iowa

Sunday, I decided to chase in south central Iowa playing the warm front instead of biting on the HIGH risk in the plains. It turned out to be the right call with only about a dozen tornado reports. What was frustrating is that one storm did form and produce a tornado along the warm front, but well away from most of us storm chasers up in northeast Iowa in Linn County. However, I managed to chase a stout linear MCS (Mesoscale Convective System) across Iowa for a few hours to my liking. I chose yet again on this day to take the more marginal setup in Iowa to stay away from the crowded "convergence" and to save some dough for my chasecation coming up in a few weeks.

As I come across Des Moines, IA the MCS begins to overtake me before I can get east on I-80
Whale's mouth with apparent chaotic motion
Very nice whales mouth from this MCS
Shelf cloud more pronounced now as the cold pool is established
Shelf cloud at sunset as I head home for the day

Today, ended up how I thought it would have. I was just happy I got anything out of it to be honest. Short drives to chase these setups I enjoy. Once when you have the weeks available to stay in the plains and chase the big events it's wise to settle for these types of chases. The good news chasecation is almost here so lets hope the pattern remains active...

04/24/09 Iowa Breaks the CAP

Parkersburg, IA the site of last years E-F5 tornado Friday evening

Friday, was a great day to storm chase. In fact, it was one of my favorites in quite sometime that didn't manage to be a "tornado day". Almost every storm was picturesque and slow-moving leading to many opportunities to sit back and enjoy some nice convection. Despite the high-bases (LCL's) that limited any chance of tornadoes it was a pleasing day for myself. My target area of Fort Dodge, IA was a great area to chase. I'll remember this for future chases too. The SPC forecasted my target area in a SLGT risk. Most chasers instead of chasing this setup drove to Oklahoma and Kansas to get a head start for the MDT risk the next day. I would have headed there too, but my chasecation doesn't start for a few weeks so I decided to make the best of it and take what I could get. Bright blue skies all morning in north central Iowa lead to CAPE near 3,000J/kg by late-afternoon. A cold front was just northwest of my target area and was very slowly progressing south through the day. The question was would the CAP break or not with temperatures surging to near 90ºF in most of Iowa. It felt more like summer (July) than late-April. However, thanks to moistening through the afternoon the lid on the atmosphere finally got blown off by early evening. All the instability was quickly released. This was one of the easiest boundaries to find on visible satellite as well as CU started popping near 3:00pm with convergence along the front.

Morning sunrise as I pack up the chasing gearThe earliest rainbow I've ever seen as I caught this one at 6:00am
Cb's beginning to form as initiation is about to begin
Severe thunderstorm develops near Thornton, IA crossing I-35
Cloud bases a tad too high on this day for tornadoes and a more unidirectional wind profile
I-35 once again as the storm produces quarter inch hail to my north
Supercell characteristics at this point, but notice the lack of strong inflow to the left (Click to enlarge)...
After looking supercellular for a time the strong forcing along the cold front cuts off the best cell of the day
Another photo illustrating the high-bases on these storms
I decide to punch through the cold front to get a taste of the lower humidity
U.S. 20 as a new convective tower forms and also notice the fairly erratic jet contrail as pilots try to navigate and punch through the line

Not a great day for tornadoes, but an excellent day for photographing severe thunderstorms. I'll take it for the relatively short drive to north central Iowa.

04/23/09 MCV's Lightning Show

A MCV responsible for an evening of intense CG lightning

Well here is the first of many posts after some opportunities presented themselves over the past few days as I headed home for some obligations I needed to attend to. It actually, worked out quite well as convection seemed to find me each day since Thursday. Finally tonight, I have some time to sit down and shift through 3 days of events. Let's get started shall we? Thursday, a MCV (Mesoscale Convective Vortex) was moving into central Illinois during the late-afternoon and evening hours requiring the SPC (Storm Prediction Center) to issue a SLGT risk by 3:00pm. As this MCV was moving in an area with moderate instability thunderstorms began to develop to my southwest moving northeast. I noticed this MCV on visible satellite imagery around noon-ish and it peaked my interest for later in the day. I chose to stay at my home base of Kewanee, IL on this day since I wasn't in a bad spot to watch the show.

Thunderstorms near severe-criteria moving in from the west (notice apparent hail shaft)
Storm moving overhead at this point as I wait patiently for the "lightning show"

That's all for this event. Spring is definitely here and it was nice to see a good lightning show after months being cooped up indoors to say the least. More to come...