Wednesday, April 13, 2011

April 9, 2011 Chase - Iowa

Good forecasting and planning put us in Council Bluff, Iowa around noon to begin the wait for initiation. By around 3pm the warm front, as planned started its surge north of us and into northern Nebraska and Iowa. We moved north to meet some friends and what for convection to fire. Shortly around 5pm a cumulus field was observed in Nebraska moving northeast with several towers trying to go. Eventually a storm went up and headed right for us. As the storm crossed into Iowa it became severe warned and began to take on supercell characteristics. Shortly thereafter, it became tornado warned. This was our first view of the base as it was crossing the Nebraska border.

We, like nearly every chaser in Iowa, observed two massive fires break out in a city as a funnel tried to reach the ground. The two fires rotated counter-clockwise underneath the mesocyclone, a prime example of wind fields around a tornadic storm. The funnel never made it to the ground and although someone did report it as a tornado, it wasn't.

We then went east and followed it into the rolling hills of the Missouri River valley edge and started to trek north towards the storm. We decided that the storm was organizing way to fast and we didn't like our road options so we dropped back south a little ways further from the storm and took a different east option. This caused us to miss the only tornado it dropped during the daylight hours in Mapleton. We got back on the storm right afterwards and were able to observe good structure and a wall cloud.

Once we were headed back east, we pretty much ignored where we were on the map and just kept going east and north with the grid pattern roads and followed the storm. This would cost us knowledge of knowing where everything we observed took place. The wall cloud above lost its structure a bit, but another RFD cut was observed as the storm began to pick up steam. Everytime the storm really started to ramp up again, extremely strong southerly inflow winds would kick up, sometimes (a guestimation) up to 60+ mph. This was almost always a prequel to a new cycle of the storm and another wall cloud and many times a tornado. Here is the new RFD cut.

About ten minutes later, a very large wedge tornado dropped out of the wall cloud and was on the ground for a good 15 minutes. The first tornado of 2011! And the night! Here is tornado #1 with debris under it.

The tornado then lifted and the still present wall cloud was illuminated with lightning.

Only minutes later, yet another RFD cut was observed and then soon followed tornado #2, a pretty cone/stovepipe tornado. Tornado is just left of the telephone pole in the second photo.

Tornado #3 occured about 10-15 minutes later and was on the ground for quite some time. It began as a wedge and developed into a stovepipe.

A new meso formed on the back side of the storm and dropped tornado #4 to the left of #3. It is right behind my name on the image.

Both tornadoes got skinny as they began to die. #4 is on the left and #3 in the back. Debris from the once wedge #3 is still in the air circulating around it. About this time, there was also tornado #5 to the far right. It was a quick rope tornado right in front of us on the road and was to quick for me to get a photograph of it.

Some time went by as the storm cycled after having 3 on the ground at once. Inflow winds greatly picked up and right after, tornado #6 was observed to our northwest on the horizon. It was yet another pretty cone tornado.

That tornado lifted quite soon, and a few minutes later it dropped yet another, this one an elephant trunk looking tornado. This could have been the precursor to the massive wedge west of Pocahontas, however we are pretty sure it picked up. Here are a few photos of tornado #7.

The above photo is the tornado appearing to begin to rope out. We lost visibility of it within the rain and never saw it again.

Now this is when alot of speculation comes in. There was a very large tornado that went through Varina and was on the ground for a very long time. We were south of that city and southwest of Pocahontas and had decent visibility to the meso that dropped this tornado.

This is the timeline of photos and I will narrate what I think happened. If anyone has any other theories on what you are seeing, please let me know.

The storm became the best it had looked all night with a beautifully sculpted meso and rotating updraft into the upper atmosphere.

When the base came into view, we saw what appeared to be a small tornado in the center, tornado #8, with very, very low condensation forming at the base of the updraft to its left. This much and this low hints at an extremely large tornado likely developing.

The following next few images are very difficult to depict what is going on. Condensation wraps around the meso hiding the tornado and developing what was labeled as the 2-3 mile wide wedge that traveled over 30 miles, directly hitting Varina.

At this time I believe we were on CR N28, with the storm to our SW these were taken as were were traveling north. Just before we turned east onto 3 to go into Pocahontas and get much needed gas, these were the last two shots I got of what appeared to be a very massive wedge on the ground. The left side can clearly be seen in what I will call tornado #9.

We got into Pocahontas and of course there was no gas to be had. The workers were extremely upset and told us Varina took a direct hit. We dropped south of the city as another storm that had latched onto the boundary from the main supercell was getting ready to pass directly over the city. As soon as we left the towns power went out. We stopped on a side road and observed the meso of the the second storm come right at us.

The storm tried very hard to drop a tornado in front of us, but had no luck.

We quickly dodged out of there before the RFD slammed us and/or we got stuck in the mud. Took the hour drive back to Ames and called it a night.

Very successful chase! Documented at least 8, but most likely 9 tornadoes! All at night! Hopefully 2011 has much more to offer later this storm season.