30 APRIL 2018



On the morning of March 25th, 1948, the first known tornado forecast was disseminated at Tinker Air Force Base in Oklahoma City by Major Ernest J. Fawbush and Capt. Robert C. Miller. Their successful forecast of a tornado near the Air Force base that afternoon proved to be a turning point in modern day severe weather forecasting.

Severe weather forecasting has come a long way since 1948, but there is room for improvement.

What if, for example, meteorologists could give accurate forecasts for tornadoes and hailstorms two or even three weeks in advance? These phenomena cause more than $10 billion of economic loss every year in the United States, and particularly bad years (such as 2011) can lead to casualties in the thousands.

Long-range forecasts for these events could lead to better mitigation and preparedness strategies for emergency managers. Insurance companies could anticipate periods of large potential losses. Planners and administrators could plan and rehearse strategies for potential upcoming active periods of severe weather.

Scientific knowhow isn’t there quite yet. We scientists cannot say it will storm or be sunny on this day in this city a month from now—but we’re working on it. Pinpointing whether or not a tornado or hailstorm will strike your town (or even county) in Illinois is especially difficult.

My name is Dr. Victor Gensini, and I’m an Assistant Professor in the Department of Geographic and Atmospheric Sciences at Northern Illinois University. I’ve been fascinated by severe weather since I was a child, and first got interested in meteorology after a tornado destroyed my middle school in 2004. Nowadays, I’m teaching NIU students about the mechanics of severe storms and pushing the research envelope on long-range tornado and hail outlooks.

Compared to 70 years ago, the science of meteorology really has made significant advances. Today, day-seven forecasts are as solid as day-three forecasts were back in 1980. Over the past five years, we also have made great strides in the anticipation of severe weather weeks in advance.

I might guess what you’re thinking: How could it be possible to forecast tornado and hailstorms weeks in advance, when the forecast for rain tomorrow can seem so iffy?

The truth is, forecasts for temperature, precipitation and even severe weather are quite good seven to 10 days in advance. It’s human nature, however, to focus on the bad forecasts while forgetting about all the good ones.

Our research focuses on the North Pacific jet stream, a very fast narrow ribbon of wind found at the cruising altitude of commercial aircraft. First discovered during World-War II, jet streams can cause wind speed and direction to change with altitude. This phenomenon is known as wind shear, which is an ingredient necessary for supercell thunderstorms that can spawn tornadoes. Wind shear causes the updraft of a thunderstorm to be tilted in nature. This tilt causes a separation in the updraft and downdraft, leading to a stronger and longer-lived storm. Without wind shear, garden variety thunderstorms occur which generally produce lightning and copious rainfall.

How can meteorologists forecast where a thunderstorm is going to occur?

It’s all related to the atmospheric environment. Forecasters use an ingredients-based checklist (not unlike a recipe for apple pie) to look for wind shear, instability, lift, and moisture. If these ingredients are expected to be present on any given day, expect thunderstorms in the forecast. Pinpointing the exact time and location of these storms is still difficult. Thunderstorms are relatively small phenomenon and last only a short period of time. However, recent advances in computer modeling have made it possible to predict thunderstorms at the county and even street level. These forecasts are generally confined to the next 24-48 hours due to the chaotic nature of thunderstorms, but are being tested now as many as 8 days in advance.

Research has shown that the most important ingredient for tornadoes and hail is wind shear. Thus, we’ve begun looking at ways to track, analyze, and forecast locations of Jetstream patterns in order to better pinpoint when severe storms may be favored.Using a complex blend of statistical and dynamical models rooted in physics and mathematics, we’ve had some success in two- to three-week forecasts for severe weather in the United States. These long-term forecasts are dependent on identifying the type of jet-stream patterns over the Pacific Ocean that produce severe weather. Thunderstorms in the tropical areas of the Pacific Ocean cause dramatic shifts in the strength and placement of the jet-stream. These patterns are typically classified into zonal (flat; east-to-west oriented) or meridional (wavy; north-to-south oriented wind flow). Wavy, roller coaster like, jet-stream patterns are the most likely to produce severe weather across the United States and are used in our model to help aid prediction.

But weather forecasting is an inexact science because of the assumptions we must make about the atmosphere. Our biggest challenge comes from limited atmospheric observations, especially over the vast oceans, which can introduce errors into a forecast that are compounded over time. Our hope is that techniques such as deep-machine learning and pattern recognition might allow us to more skillfully forecast further into the future. There is no doubt in my mind that artificial intelligence will make its way into the forecasting process in coming years. In addition, recent technological advances such as the new GOES satellite series and Dual-Polarization RADAR have greatly enhanced our ability to monitor Earth’s weather conditions.

It’s likely we will never be able to say for certain that a hailstorm or tornado will hit your town in Illinois in two weeks. But, we are striving to get to the point where we will be able to skillfully forecast a higher or lower chance of that happening. With every passing year, severe weather season adds new data points to our research, and allows us to test and refine our methods.

You can find forecasts from our research group at http://atlas.niu.edu

I think Major Fawbush and Capt. Miller would be impressed.

By reading this post, I can already tell you have a situational awareness for severe storms and/or are fully amazed by the tornadoes and hailstones that they can produce (like I am!). You are in good hands receiving weather information from ISC. I fully endorse Illinois Storm Chasers and their mission. I’ve worked closely with this team and can attest to their expertise and professionalism. Stay weather savvy!