Here We Go Again

It's about the last thing Oklahomans want to hear after last week's devastating tornadoes, but another prolonged severe weather outbreak for our state is about to begin. In a weather pattern not all that different than last week, storms are expected to fire on a daily basis in a very unstable air mass and overspread much of the region with the threat for hail, high winds, and tornadoes.

After a lull in the action for the last couple days, the all-too-familiar ingredients for severe thunderstorms are coming together for a recipe of dangerous weather. Here are the factors that may lead to the very active weather streak ahead.

1. Instability. A constant fetch of very warm, very moist air at the surface will provide continual fuel for storms when they form. As cooler, drier air aloft overspreads our region – over the warm, moist low-level air mass, the vertical difference in temperatures will allow air to rise very rapidly, leading to explosive storm development.

2. Wind shear. This is a tougher ingredient to explain, but what it essentially means is that the difference of speed and direction of wind over a vertical cross-section of the atmosphere is great. For a classic severe weather scenario like in the days ahead, strong southerly winds (our low-level jet stream) interact with stronger westerly winds in the jet stream higher up. This allows storms to become organized, gain rotation in the interaction of those winds. Without the higher wind speeds aloft, storms would build and then collapse in on themselves, cutting off the low-level wind flow that supplies the storms with energy. Between now and Thursday, the wind speeds aloft grow greater, resulting in a more organized, sustained severe thunderstorms known as supercells. Wind shear in the lowest levels of the atmosphere often leads to the rotation and tornado formation in supercell thunderstorms.

3. Lift. This is the term for a frontal boundary of some sort to be the focus for initial storm development. Often times, low level winds collide at either a dry line or cold front, which lifts the air and allows the storms to get going. The instability and wind shear along with other storm interactions determine how strong and how long-lived the storms become.

All three of those main ingredients are coming together for several days, starting today across far western Oklahoma, of severe storms. Since the weather pattern is slow to change, the threat will persist and grow through late in the week. Wednesday evening will be our first real potential of severe storms for eastern Oklahoma (shown in the attached map). The winds aloft grow even stronger and the focus/lift for the severe storms is closer to our side of the state on Thursday, enhancing our risk even further (next map). Tornadoes are anticipated, and a few of them may be particularly strong. The risk of severe weather ends with the final push of a cold front through the region late Friday into Saturday.

Now is the time to prepare once again for this threat. We may be seasoned Tornado Alley residents, but when the threat isn't always in your backyard, it's easy to let our guard down. Instead, we should be mindful of the continued potential for dangerous weather and not hesitate to take action when a warning is issued for your location. Be safe and we'll keep you up-to-date as this severe weather event evolves. We'll be hoping, like you, that this will pass without much ado.

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