Sunday, March 29, 2009

2009 Storm Chase III Brief - March 21st

Click any images below for a much larger view!

So there I was on the afternoon of Friday, March 20th, taking a break at lunch to forecast for expected severe weather on Sunday & Monday. Everyone was expecting a good severe weather outbreak on Monday and I was going to try and outforecast everyone for Sunday. As the days moved on, however, the Sunday threat diminished. I spent a lot of time pouring over the models, however, and I noticed that the NAM was painting a nice 1,000J/kg CAPE bullseye over Eastern Colorado. Being so early in the season, I almost don't even think to look around here. So, I checked a few other paramters. Shear looked great ... though we didn't have any forcing. Instability was surprisignly good ... though there was some convective inhibition (especially further east). Moisture was scant ... but good for this time of year.

I shot Tony Laubach and Michael Carlson a text that read something like "1,000J/kg CAPE in E CO tomorrow!"

Given the parameters, I figured it would be a good day for a back yard chase. Tony seemed in line with my thinking, so we planned to organize something the next morning.

After morning chores and an oil change, I met Tony at his apartment. Travis Speakman was also there and we picked up Ed Grubb en route to our target for the day: Fort Morgan.

As we drove out on I-76, we sat under a nice cumulus field. In Fort Morgan, we got lunch at Taco John's and watched some really high-based showers form up.

At that point, we mistakenly thought the weather service had dropped mention of thunderstorms for the day. I figured if we were going to bust, best to do it close to home. None of us had any intention of heading back just yet. I wasn't sure what they were seeing (or thought so at the time), but I still liked my forecast ... especially when we already had convection.

There was a storm that seemed to be gaining strength further to the south and since it was entering the axis of better CAPE, we figured that would be a good play. So, we drove south on CO 71. As we approached the storm it was very high based and barely precipitating. It was, however, kicking up a lot of dust.

It's not what it looks like ...

... this isn't what it looks like either.

This is what it looks like if it just looks like blowing dust ...

We finally intercepted the storm and were surprised when it was suddenly severe-warned. We were sitting directly under the core and there were only a few rain drops. So, we got out of the car an joked around a bit. It was nice hearing some thunder (the first for me in Colorado this year).

The power lines above our head seemed to discharge all of the sudden. If you've been under for one of those, you'll know what I'm talking about. We all dove back into the van and laughed heartily.

At this point, we decided to drive back north to intercept some better looking convection. It was already east of the highway and moving slowly. We stopped to admire its back side as it slowly moved away, us not in any real hurry for anything.

Our (severe-warned) storm to the south started to strengthen again, and though this nice cb was going up to the north ...

... we decided to drop south to our original storm. When we arrived, we found that it had been precipitating while we had left it. We found the ground covered in 0.75" hail, which we called in and reported. (The local WFO is still under the 0.75"+ hail severe criteria ... at least until April 1st)

2330 75 10 N LAST CHANCE WASHINGTON CO 3987 10358 (BOU)

The storm was actually starting to look a little better as it was now in a much more unstable environment. The base was still high due to the lack of moisture (closest ASOS had a 39ºF Td!), but we had us a nice storm! We got on dirt and tried to follow it but soon found the hail swath again. ... and it was a muddy mess!

The hail was a little larger here, so I called in another report:


We realized that following the storm through the mud was a bad option, so we got back on CO 71 and went north to US 34 where we turned east. At Akron, we turned south on CO 63 and punched through a brief core when all of the sudden the weather radio started sounding the warning tone. The storm was only half way through the severe warning polygon and wasn't set to expire for a while. None of the other storms in the CWA exhibited severe characteristics.

So, imagine our surprise when the storm we were on was suddenly tornado-warned! At this point, we could see the entire base of the storm and couldn't believe our eyes. We were under a beautiful super-high-based mesocyclone!

Back in the van, I noticed I had a missed call from the Weather Service and they called me back as I was holding my phone. They asked if we were still on the storm and what we could see. I told them we were in position and could see a very high-based mesocyclone. I doubted that it was a tornadic threat and related that to them before hanging up.

We got back in the van and drove a little further down the road for a better view. For the next half hour or so, we sat in a light rain watching this beautiful, naked beast come right toward us. It was breathtaking. I basically laid down on the berm of the road and tried to shoot lightning, using my cupped hand to keep my camera dry. I don't think I would have rather been anywhere else in the world.

Here are some shots:

As night fell and the storm began to wind down, we drove north and tried to shoot some lightning north of Brush. I spent a lot of time trying but couldn't get any real good shots. The wind was in my face and that was shaking my tripod which didn't make things any easier. All in all, we were satisfied with this chase and packed up, heading back to Denver.


Chase stats:
Mileage: 388
Largest Hail: 0.88"
Rotating Storm Intercepts: 1
Chase Partners: Tony Laubach, Ed Grubb, Travis Speakman
Nowcast Support: Michael Carlson


No comments: