Tornado capital of the world goes quiet. Here's why.
Monday, April 30, 2018, 8:55 - A tornado drought is unfolding in parts of the southern Plains. Normally, the tornado capital of the world has recorded several prominent tornadoes by the end of April, but a much different pattern has developed, suppressing the risk. These tornado-free streaks are already jeopardizing significant, long-standing records. Read on to find out.
TORNADO DROUGHT STATS
- Total tornadoes recorded in the 2018 calendar year for Kansas: 0
- Oklahoma is also experiencing a significant tornado drought, not recording a tornado in 2018
- Lack of severe weather ingredients – very few moderate and high risk days issued by the Storm Prediction Center (SPC)
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Well, as the first third of the year wraps up, something rather significant and unusual has developed – the lack of tornadic activity for the Southern Plains:
The record in jeopardy, goes way, way back. Oklahoma, your latest first tornado occurred back on April 26th, 1962. To potentially go through April without a tornado in the state of Oklahoma would be unprecedented. But why?
There's been a significant and persistent troughing pattern that has limited the amount of mild, unstable southerly flow that has migrated into the region. This primary source of moisture from the Gulf of Mexico is a fundamental ingredient for the majority of the tornado outbreaks for this part of the world. Also, snow cover has been well above normal for the central and northern Plains, and temperatures have been significantly below the April mean. Look back at the temperature anomaly for April:
The image above (courtesy: WeatherBell), shows a significant temperature departure from normal, and it's obvious that the heart of the Continental U.S. has been running a significant negative temperature anomaly. This cool, northwest flow and persistent troughing is far from an ideal setup to develop severe weather in the Plains. Typically, upper troughs in spring will pivot from the Four Corner states and the desert southwest, and allow the mild, moist Gulf of Mexico flow to surge northwards; consequently, this creates a dry line (sharp boundary between dry and moist air) and becomes a focal point for the severe weather season. It's this contrast in dry, desert air and the moist Gulf of Mexico environment that creates this world-renowned tornadic breeding ground.
Tornadoes have been spotted and confirmed in bordering states, including several in Texas, but the streak remains for Oklahoma and Kansas. During the final week of April, most of the forecast convection is suppressed to parts of Texas. Large scale ridging in the southwest portion of the United States is incredibly efficient at mitigating the tornadic risk.
A weak shortwave trough is expected to migrate across Texas this upcoming weekend, but the upper level pattern shows a significant ridge modeled over the Plains and the heart of the Continental U.S. – think of this as a storm shield and a particularly stable environment, rather than rising air parcels and an agitated atmosphere.
But, don't write off the severe weather season just yet. The key is with a significant pattern change in the upper levels of the atmosphere. When this shift eventually occurs, a sharp uptick in tornadoes is likely, and be warned, this pattern can switch relatively quickly as we head into peak tornado season in the Southern Plains.