Similar to 4/14/12?

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By Scott Roberts

TLDR: Yes, but mostly no

We’re getting into the heart of the busy part of storm season as we approach April 15th. Tomorrow (the 13th) is the 34th anniversary of the 1990 Hesston tornado; Sunday (the 14th) is the 12th anniversary of the tornado outbreak that produced the Marquette and Haysville/Wichita tornadoes along with a huge double vortex tornado near Manchester, OK that fortunately dissipated before hitting Argonia.

With a significant weather event forecast for Monday (the 15th) I decided to look at similarities between that big day in 2012, because some of the early SPC outlooks had the same degree of longer-term certainty,

 

First, let’s look back at that day:

Wedge crossing the OK/Kansas line near Manchester (credit: Brandon Sullivan)
Oaklawn Tornado seen from 47th/Hydraulic in Wichita. (Credit: Brandon Ivey)
Central Kansas Tornado Tracks, Map prepared by NWS Wichita

For us it was a busy day, as we were on three tornadic storms. The first started near Macksville around mid-day and is shown at the green place points in the lower left corner on the map above. The second was a weaker storm near Pretty Prairie, where we watched a thin columnar tornado cross a county road not far in front of us (you could see through it, and it wasn’t even enough to leave a track that could be surveyed. We we encountered the two-mile line of cars near Haven and saw it was the groupies following the Dominator, we broke off and reset south for the nighttime storm round (that is the storm that chased us from Haysville to near Oaklawn).

Similarities of this event to that one

Really, they come down to timing and SPC forecaster certainty on the forecast. Here are the links to the SPC outlooks in the days leading up to the outbreak:

Some samples of wording for those outlooks:

  • Tuesday
    “VERTICALLY VEERING WIND PROFILES WILL PROMOTE THE POTENTIAL FOR TORNADIC SUPERCELLS ALSO PRODUCING LARGE HAIL AND DAMAGING WINDS.”
  • Wednesday
    “TORNADIC SUPERCELLS ALONG WITH VERY LARGE HAIL AND DAMAGING WINDS CAN BE EXPECTED ACROSS THIS REGION”
  • Thursday
    [MULTIPLE] FACTORS COMBINED WITH FAST STORM MOTIONS SUGGEST THE POTENTIAL FOR LONG-TRACKED…STRONG TORNADOES OCCURRING FROM THE AFTERNOON THROUGH THE EVENING /INCLUDING AFTER DARK/
  • Friday
    “AN IMPRESSIVE UPPER-LEVEL LOW WILL MOVE ACROSS [THE] FOUR CORNERS REGION SATURDAY AS A POWERFUL 90 TO 110 KT MID-LEVEL JET [MOVES] INTO THE SRN AND CNTRL PLAINS. AHEAD OF THE SYSTEM…A CORRIDOR OF MODERATE TO STRONG INSTABILITY IS FORECAST ACROSS ECNTRL KS…CNTRL OK INTO NW TX. THIS COMBINED WITH STEEP MID-LEVEL LAPSE RATES AND STRONG LOW-LEVEL SHEAR WILL BE VERY FAVORABLE FOR SEVERE STORMS AND A TORNADO OUTBREAK WILL BE LIKELY ACROSS THE SRN AND CNTRL PLAINS FROM LATE SATURDAY AFTERNOON LASTING THROUGH THE EVENING AND INTO THE OVERNIGHT PERIOD.”

Even 5-6 days out the wording was pretty strong. Compare to the outlooks so far in this sequence — for matching, they would be the equivalent of the Monday (not shown), Tuesday and Wednesday outlooks from the April 14, 2012 event.

  • Wednesday: (Day 6, only the 9th day 6 30% risk area ever issued…those started in 2014)
    “The actual severe weather setup appears substantial. Air mass modification will ensue northward from the western Gulf on D3, with multiple days to improve the low-level moisture profile amid well above-normal surface temperatures and a pronounced elevated mixed layer. With the likely flow field amplification through the troposphere, all ingredients appear present for a significant severe weather day on D6/Monday. The areal uncertainty of the synoptic features is the primary limiting factor.”
  • Thursday (Day 5)
    “With about 3 days of persistent low-level moisture modification from the western Gulf beneath an extensive elevated mixed layer, the northern extent of mid 60s surface dew points should reach into most of OK east of the dryline by Monday afternoon. Late afternoon thunderstorm initiation along the dryline appears probable in the eastern TX Panhandle/western north TX to western OK vicinity, within a kinematic and thermodynamic profile favorable for strong supercells. Convective development will blossom both south and especially north extent during the evening across the central and southern Great Plains.”
  • Friday: (Day 4)
    “Low-level moisture modification from the northwest Gulf, while sufficient for severe storms, does not appear to be overly rich. As such, the more westward initiation of convection during the late afternoon to early evening Monday may be within a more deeply mixed environment across parts of the dryline. Still, there is consensus that a plume of low to mid 60s surface dew points should be advected ahead of the dryline across much of western OK into western north TX. More widespread convective development will occur during the evening to overnight time frame, especially as the Pacific cold front overtakes the dryline and surges east from parts of KS southward.”

To my reading, while there is much greater than normal certainty there will be storms Monday, there are also a number of factors that will serve to limit this risk.

  1. While sufficient for severe storms, the quality of the moisture will not be as good as one might expect with 3 days of moisture flow ahead of the system. The 2012 system had a thick juicy layer to work with at the surface. Real dewpoints that day were mid and upper 60’s. Forecast dew points Monday are 62-65. The difference of three degrees in dewpoint will make a big difference in storm type and organization this time of year.
  2. Timing, while in decent agreement for this far out, is still a bit suspect. Models are trending slower with each run, as they’ve done all year. The conditions simply will not be in place Monday for an early-day storm risk; it’ll be around or after the typical initiation at peak heating (3-4pm) before any storms get going. Also, this event is expected to start in Oklahoma and expand northward as the warm front lifts. That puts us more like Nebraska than Kansas compared to 12 years ago.
  3. Storm Mode. In Kansas, a messy storm mode in the evening is more likely. The storms of April 14, 2012 maintained their separation and supercellular structure. A messy storm mode may produce more total severe events, but they will tend to be less severe. Isolated supercells tend to create their own microclimate and are therefore normally stronger.

My bottom line is this: if we continue to see a trend toward a messy storm mode I beleive we’ll have a bunch of lower-end severe weather observed. If the moisture is better than forecast (it’s been worse than forecast in every event so far this season) we could see a cleaner, more isolated storm mode that would lend itself more toward nighttime tornadoes as the low-level jet kicks in around and after sunset.

Good factors I see Monday that also existed April 14, 2012: a retreating (westward-moving) dryline around and after 7pm. Often a retreating dryline can help initiate storms. The reason is that the retreat is being caused by the low-level moisture piling up against it. So in the environment just east of the retreating dryline, you have locally-higher moisture, and generally backed (more southeast than south) winds. This would potentially indicate a higher risk of tornadoes around sunset from near Woodward to the Medicine Lodge/Harper vicinity. The north-moving warm front normally means elevated storms (not coupled to the surface, as they are riding above the colder air) which present a hail risk. But that’s not always the case, they can enhance the tornado risk if conditions are just right (see Andover 1991).

I may revisit this over the weekend. My deepest model dive of this cycle will be Saturday afternoon after the parent system comes ashore and is sampled by the dense grid in the US. I’ll also have a Day3 SPC outlook to compare with 2012. But my sense is, the risk values will be lower, and the area shifted south, compared to the outbreak day of April 14, 2012.

Safety Information

Regardless, now is the time to prepare for storm season, as we endter the historically most-active two months of the year in Kansas. Tonight and tomorrow I will be posting video interviews with Butler County Emergency Management about what we need in our go bags, along with posting lists you can use to shop for and stock yours.

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