Veterans: Last chase year similar to 2015?

[Brett Roberts]

As someone who started chasing in 2006, this season (thus far) has been an eye-opener for me. In the nine seasons I chased prior to this, the total number of days I saw totally ruined by early/morning convection probably doesn't match the number I've seen this year just in April and May. Overnight MCSs and early initiation are both issues that, from experience chasing 2006-2014, I previously regarded as factors likely to modulate the location and upside of a chase day, but unlikely to decimate it the way we've seen many times this year (most prominently 5/7-5/9).

The dominance and orientation of the subtropical jet seems to be the largest culprit for this year's perpetual failure mode, perhaps augmented by relatively wet conditions in the typical EML source region upstream. Can any longtime chasers recall a year remotely similar to this, where numerous good troughs resulted in only marginal chase days that likely would've been high-end in the absence of early convection and widespread warm sector storms? The most similar year I've witnessed personally was 2007, pattern-wise, but it wasn't really even close to this. It was a wet year with lots of MCSs throughout the spring, but on most of the big days (e.g., 28 March, 21 April, 23 April, 4 May), the convective evolution was still prototypical of the Plains: the dryline was clear of convection by noon at the latest, instability built, and storms exploded by 4-6pm (without continuous, widespread warm sector convection initiating all day from lunchtime on).

I'm wondering if other years featuring relatively strong El Ninos during the spring, such as 1983, 1992, and 1998, might have had similar issues. Interestingly, though, it appears this is the first year since at least 1950 where ENSO 3.4 is >=1.0°C in May and on the rise, rather than subsiding after a cold season peak. Combined with the record +PDO, there are certain aspects of the background climate forcings that make this year very unique. Unfortunately, the results of this regime don't seem very conducive to quality chase setups (but do seem conducive to a large quantity of "needle-in-the-haystack" tornado days).

 

[Jeff Duda]

I certainly haven't been chasing long enough to be able to supply any direct observations to answer your question. However, it certainly seems we are in a unique planetary scale weather pattern right now, one that favors a strong sub-tropical jet, lots of meridional flow over the southern plains, and, resultingly, lots of heavy precipitation over the same areas. I suspect this pattern is related to the strengthening El Nino (which, by the way, is forecast to strengthen through the spring and summer and into the fall, and spring/summer ENSO forecasts are never known for their accuracy, but there seems to be a little extra confidence in this forecast), but I'm sure there are other factors, too, such as the +PDO that persists.

I'm starting to wonder/doubt if we will see the typical seasonal pattern of severe weather where the jet gradually shifts north as we get into June and take all the severe weather events north with it. The GFS and CFS, for example, seem to indicate that, but given the sheer amount of water sitting around in the soil and standing in fields, ponds, and filling lakes across the southern plains, and given the tendency for weak, if even existent EMLs and caps, I'm wondering if we may see high-CAPE, moderate shear setups persist well into June in the southern plains. I doubt we'll continue to see the chances for widespread outbreaks, but mesoscale events may end up giving many more severe weather and tornado days across TX and OK well later than expected this year.

May be a wild prediction, but we shall see.

 

[Jeff Snyder]

My first chase was in 1999 (August in MN, not May 3rd in OK), so I'm not sure how "veteran" that makes me. However, I'm having a tough time coming up with a good analog year for this year. We've had springs plagued by east coast troughs and terrible moisture (think 2005 and, IIRC, 2006). We've had springs with a lot of capping issues (think 2002). We've had springs with suboptimal moisture and no flow aloft (think 2009). We've had springs in which all the pieces fell into place event after event (think 2004 and May 2013, though 2007 was also quite good). (All of the above apply mainly to my experience chasing between I80 and I20 in S NE, KS, OK, and N TX).

This year, though, we haven't really had any issues with moisture. In fact, in terms of potential events with good moisture, I think we've had an incredible year. High LCLs haven't been a persistent issue this year, and we haven't had many issues with getting southwest flow aloft over the Plains. As such, there have been a *lot* of chasing opportunities this year. In fact, if not for family commitments, I probably could have chased this year the most I've even chased in my career year-to-date. Even with my "threshold" to chase being higher than it had been before I had a child, I've chased quite a bit this year already. We've had a good number of non-junky chase setups (at least as determined before the morning of the potential event).

In my opinion (one shared with many chasers, no doubt), the primary issue we've repeatedly had this year has been warm sector contamination by late-morning convection. The result has generally been relatively suboptimal juxtaposition of good instability (i.e., high CAPE) and strong shear. Many of the events have seen the best storms south of where we'd usually like to see them as outflow from early-day convection and lingering clouds inhibited robust destabilization. The early convection probably has been driven by early-day short-wave troughs and weak EMLs. Little capping to the west, lots of moisture, and some forcing aloft for early convection has done a number on most of the potential setups. In my 15-16 years of chasing, I'm not sure I can come up with a good analog year to this year.

 

[John Olexa]

I started chasing in the late 1990's but for me it's almost always been lightning. Of course there are seasons with more thunderstorms than others but I always get my chances.

 

[Derek Weston]

I'd probably choose hail, but then again, I've always been a fan of cold temperatures. . . and this penguin does fly!