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April 2011

Chasecation Day 0 – Departure from MD

Jason, Ian and I will leave Maryland this evening to head into the LA/AR/MS area to try to catch some storms tomorrow afternoon/evening. It looks like there’s some viable chase territory in there, so we’re going for it. The setup looks slightly better than marginal, and we might as well start our chasecation with a chase day before we hit a lull Monday-Wednesday. There will be plenty of instability and directional shear near the warm front, but upper-level dynamics appear to be lagging in the target area.

A system could bring some severe weather into the Central/Northern Plains on the 5th-6th, so we’ve got some time to travel/kill between setups.

Here’s the SPC outlook for tomorrow:

April 28, 2011 Chase Pictures

Just the one quick upload for now… will add more to this post as I get through footage. Finishing up the final prep. for the Plains chase!

Got in a tornado-warned cell just SW of Elizabeth City along Rt. 17. It looked like it could be fun, but aside from some vivid lightning and a non-rotating wall cloud it wasn’t much to see.

This one was the last cell of the day for me… I think it was severe-warned but definitely not tornado-warned. I was in a tornado warning in an earlier cell and was in perfect position along Rt. 17, but it didn’t produce. Lots of lightning, and even a double rainbow at the conclusion of the last cell. It was a long 14-hour chase by myself, but it was fun and I had a good day despite the lack of tornadoes.

Tornado Watch up for most of the Mid-Atlantic

PA and Delmarva are missing out (for now) UPDATE: New tornado watch includes most of PA and western NY!

I’m ready to drop what I’m doing to go chase local cells should they pop up. Jason is quite busy today, but if something happens close by I think he’ll join me for an hour or two.

A lot of weather fanatics and forecasters will not be getting sleep tonight.

A Most Epic System

Keep an eye on the severe weather today, folks. You may not see another system like this one for quite a long time.

Back-to-back High Risk days. Six PDS Tornado Watches since the 25th, with the likelihood that we’ll see 1-2 more before the day is done.

We’ve had three High Risk days in 2011, and we’re still in April! This is truly an amazing month and an amazing year for severe weather.

We leave on May 1st

After some deliberation, Jason, Ian and I have decided to leave Sunday, May 1st (returning on the 15th). Jason and I picked up a few chase items for the trip, and everything’s on schedule as of now.

The models are still trying to decipher the pattern going into the first week of May, but things are trending in our favor. Six days left!

I’ve been kind of ignoring my Sunday/Monday regular updates in recent weeks… I’ll get back on those once the Plains Chase is complete.

A tenative look at the first week of Plains chasing

If we are able to leave on the 30th or really early on May 1st, it looks like we could hit up a potent storm system in the Midwest on the 1st-2nd before making it all the way into the Plains. After that, a progressive upper-level ridge in the West could bring a lull in the action until another system tries to push it east and break it down going into May 6th.

On the flip side, let’s see what the models have been doing wrong lately. Past the day+7 lead time (starting in week two), the models have struggled to capture the effects of the soil moisture across the South and Southeast, which has helped to keep temperatures above normal in the Southern Plains, Southeast and southern Mid-Atlantic. Conversely, the below normal temperatures in the northern and western areas have come in cooler than forecast, which would lead me to think that the -PNA influence and soil moisture could alter the storm track that is presented by the models. While not negating the transient ridge in the West during the first week of May, it could definitely verify weaker than anticipated, which would allow the ridge to break down more at the end of the first week of May when a storm system moves in off of the Pacific. This will hopefully reset the pattern and push us into an active severe weather pattern as we head into the second week of May.

Planning and Forecast for the Storm Chase Expedition

The start date for chasing is being finalized as I type this, but it looks like Jason, Ian (will be bio’ed later) and I will head out from Maryland on April 30th, with the plan to start actively chasing on May 2nd (so long as there are storms on that day). We be out chasing through the 13th, which will give us 12 full potential chase days before we have to start heading back to Maryland.

There’s a few things still left to buy, like a sleeping bag and duffel bag, but other than that there’s just prepping Jason’s car and finalizing the itinerary.

I will be posting a daily blog from start to finish for everyone to follow along and enjoy. It should be an interesting two weeks!

Looking at the climatological statistics and the teleconnection forecasts, it appears as though early May could be quite active in the Central Plains, Midwest and Tennessee Valley regions.

The NAO and PNA are forecast to be either negative or trending negative as we head into early May:


 
Below are the loading patterns (ridges/troughs) that correlate with the NAO and PNA in spring:


(The height anomaly maps are from the Climate Prediction Center)

 
The images are the positive phase correlations of the NAO and PNA. Warm colors indicate positive height anomalies, and the opposite is true for the cooler colors. If you invert the colors for the negative phase, you can see that the -NAO induces a trough over the Rockies and that the -PNA induces a ridge over the Southeast. Together, they help steer the storm track through the Central Plains and into the Midwest, as seen with the red arrows that are added to the images on the right-hand side. This track is quite favorable for severe weather.
 
Here is the latest U.S. Drought Monitor map:

 
It shows dry conditions over the Southern Plains and parts of the Southeast. I won’t go into it much, but I’ll quickly just say “drought breeds drought” in that the drier areas on the map will have a tendency to stay dry, which would indicate that most of the storms will form further north in the Central Plains and the Midwest/Tennessee Valley regions. In a hand-waiving manner, the drought conditions will help keep the storm tracks further north, which will help support the -PNA pattern.

We are also coming out of a strong La Niña winter into a weak Niña or neutral ENSO state, which is climatologically-favored to produce more active severe weather seasons.

The U.S. has been quite active with low pressure systems in recent months as pockets of upper-level energy that form these systems continually move onshore into the West every 2-4 days. All together, this should provide us with an active May pattern, with plenty of severe weather in the Central Plains and Midwest.

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